AeroElectric-Archive.digest.vol-de

May 03, 2004 - May 17, 2004



      4 coils (1 per cyl)
      4 injectors (1 per cyl)
      2 computers
      2 batteries
      1 alternator
      
      I'm thinking it would be nice to have a main bus,
      essential bus (backup), overvoltage protection, and
      the ability to tie the batteries together for a "self
      jump".
      
      I'm also thinking that feeding the injector and coil
      12 volt feeds from both bus's would be a good idea.
      Switching the ground leads via a relay board.
      
      If this has been discussed please point me to an
      approximate date and I will try the archives.
      
      Thanks
      Ken Bauman
      
      
      __________________________________
      http://companion.yahoo.com/
      
      
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________________________________________________________________________________
Date: May 03, 2004
From: klehman(at)albedo.net
Subject: Which side of the firewall
How bad an idea is it to locate circuit breakers for my two alternator output wires forward of the firewall beside the batteries? Some breakers spec a 60 degree C. ambient but both my breakers would be rated 50% higher than the alternator outputs. I would guess there is not a problem as far as the trip point goes. Used breakers are handy/cheap for me but I'm willing to cough up the bucks for both an ANL and a Maxi fuse holder if they are necessary or clearly a better idea. I'm also wondering which side of the firewall to mount the voltage regulator for a John Deere 20 amp PM alternator. I'd like to keep the AC feed from the alternator forward of the firewall instead of bundling it with the other wires coming through the firewall. I have a lot of efi wiring coming through the firewall. OTOH the regulator might live longer on the cool side of the firewall if there is no problem bundling all the wires. Due to high ambient heat after shutdown, I've pretty much dismissed the third option which would locate it on the forward side of the engine. thanks for any comments Ken ________________________________________________________________________________
From: "Fergus Kyle" <VE3LVO(at)rac.ca>
Subject: Pressure altitude and short sparks
Date: May 02, 2004
"As has been discussed on this list before, denser air (a composition of non-conductive gasses) is a better insulator (higher dielectric breakdown capability). As the air gets thinner, its propensity to conduct increases." "You can see that Vacuum will break down at around 20kV with a 1" gap, whereas dense air might hold up to 75kV over the same gap." " A plug that works properly at atmospheric pressure may display shorts when the gap is exposed to pressurized air (which has even higher dielectric strength)." How can it display shorts at higher pressure and still have higher dielectric strength? Ferg Europa A064 ________________________________________________________________________________
From: "Eric M. Jones" <emjones(at)charter.net>
Subject: Re: Circuit Breakers and OVPs
Date: May 03, 2004
When an Over-Voltage Module crowbars the alternator field line to ground, it is extremely important to have a fast blow circuit breaker for the Alternator Field when using a crowbar. This fine point is easy to miss. This really might be a good reason to use non-crowbar OVPs Regards, Eric M. Jones www.PerihelionDesign.com 113 Brentwood Drive Southbridge MA 01550-2705 Phone (508) 764-2072 Email: emjones(at)charter.net " I would have made a good Pope." -- Richard M. Nixon (1913-1994) ________________________________________________________________________________
Date: May 03, 2004
From: klehman(at)albedo.net
Subject: Re: Pressure altitude and short sparks
Ferg I think they mean breakdown outside the combustion chamber. Sometimes poor/wet ignition wires will run the engine fine at low power settings but at high power and high compression the wires break down and the engine misses. The voltage goes higher to fire the spark under higher cylinder pressure. Ken Fergus Kyle wrote: > > "As has been discussed on this list before, denser air (a composition of > non-conductive gasses) is a better insulator (higher dielectric breakdown > capability). As the air gets thinner, its propensity to conduct increases." > > "You can see that Vacuum will break down at around 20kV with a 1" gap, > whereas dense air might hold up to 75kV over the same gap." > > " A plug that works properly at atmospheric pressure may display shorts when > the gap is exposed to pressurized air (which has even higher dielectric > strength)." > > How can it display shorts at higher pressure and still have higher > dielectric strength? > Ferg > Europa A064 > > > > > > > ________________________________________________________________________________
Date: May 03, 2004
From: Brian Lloyd <brianl(at)lloyd.com>
Subject: Re: Pressure altitude and short sparks
Fergus Kyle wrote: > " A plug that works properly at atmospheric pressure may display shorts when > the gap is exposed to pressurized air (which has even higher dielectric > strength)." > > How can it display shorts at higher pressure and still have higher > dielectric strength? When the pressure in the cylinder is higher the increased dielectric strength of the air at the electrodes might cause the plug, wire, or some other place in the ignition chain to break down first. -- Brian Lloyd 6501 Red Hook Plaza brianl(at)lloyd.com Suite 201 http://www.lloyd.com St. Thomas, VI 00802 +1.340.998.9447 (voice) +1.360.838.9669 (fax) There is a time to laud one's country and a time to protest. A good citizen is prepared to do either as the need arises. ________________________________________________________________________________
Date: May 03, 2004
From: echristley(at)nc.rr.com
Subject: Re: Pressure altitude and short sparks
----- Original Message ----- From: Fergus Kyle <VE3LVO(at)rac.ca> Date: Sunday, May 2, 2004 4:00 pm Subject: AeroElectric-List: Pressure altitude and short sparks Kyle" > > "As has been discussed on this list before, denser air (a > composition of > non-conductive gasses) is a better insulator (higher dielectric > breakdowncapability). As the air gets thinner, its propensity to > conduct increases." > > "You can see that Vacuum will break down at around 20kV with a 1" gap, > whereas dense air might hold up to 75kV over the same gap." > > " A plug that works properly at atmospheric pressure may display > shorts when > the gap is exposed to pressurized air (which has even higher > dielectricstrength)." > > How can it display shorts at higher pressure and still have higher > dielectric strength? > Ferg > Europa A064 > I think the answer here is that pressurize air does in fact conduct more than a vacuum, which is the best insulator; however, rarified air is more easily IONIZED. What you have with ionized air is a substance is an very good conductor. The subtle difference can have some profound implications. For instance, get some air moving across those worn wiring harnesses and see if they still arc. ________________________________________________________________________________
From: "Bruce Gray" <Bruce(at)glasair.org>
Subject: Pressure altitude and short sparks
Date: May 03, 2004
Hmmm.... I don't see how the cylinder pressure, before ignition, increases with engine speed. Voltage might go up, as a result of magnito RPM increasing. But these are some of the reasons why sparkplugs should be tested in a pressure tester every time they are cleaned and gaped. Bruce www.glasair.org -----Original Message----- From: owner-aeroelectric-list-server(at)matronics.com [mailto:owner-aeroelectric-list-server(at)matronics.com] On Behalf Of klehman(at)albedo.net Subject: Re: AeroElectric-List: Pressure altitude and short sparks Ferg I think they mean breakdown outside the combustion chamber. Sometimes poor/wet ignition wires will run the engine fine at low power settings but at high power and high compression the wires break down and the engine misses. The voltage goes higher to fire the spark under higher cylinder pressure. Ken ________________________________________________________________________________
From: "Eric M. Jones" <emjones(at)charter.net>
Subject: Re: Pitot Static Sources and Ram sources
Date: May 03, 2004
It would make a great science project for your high school student to determine if there is a size tube that is unattractive to mud wasps (and therefore best for pitot [after Henri Pitot (1695-1771), French physicist] tubes). For bees, it turns out that if a gap (and maybe a hole) is below a certain size, the bee will fill it. If the gap is bigger, the bees will build comb in it, but if it is a certain size (7.5mm +/-1.5 mm) the bees will simply ignore it. Rev. Lorenzo Langstroth (Philadelphia in 1851) was the first person to use the bee space in hive construction. How he determined that bees used the metric system is truly one of the wonders of science. You don't have to search the NTSB very hard to find "wasp-like creature in pitot tube" accidents. And you don't have to talk to many pilots to find hair-raising tales that thankfully didn't end up in an NTSB report. Usually pitot tube clogs are discovered near flying speed, half-way down the runway. For static sources I am convinced (perhaps incorrectly) that too much fuss is made of their position. And yes, you can tee off many instruments to the same static source, and have multiple static sources. Classically static sources have been taken from the supports for or just behind pitot ram sources. For pitot ram sources, you can also tee off many instruments, and furthermore you can have multiple ram sources (several pitot tubes) leading into one line. This seems never to have been done in EAA aircraft. Big planes often use two or more pitot tubes but route them to their own instrument banks. I am designing a spare retractable pitot tube. The prototype will appear on my website shortly. Comments are solicited. Regards, Eric M. Jones www.PerihelionDesign.com 113 Brentwood Drive Southbridge MA 01550-2705 Phone (508) 764-2072 Email: emjones(at)charter.net Ring the bells that still can ring Forget your perfect offering There is a crack in everything That's how the light gets in - - Leonard Cohen ________________________________________________________________________________
Date: May 03, 2004
Subject: Re: Pressure altitude and short sparks
From: "Matt Prather" <mprather(at)spro.net>
Hi Ken, In addition to faults in the rest of the ignition system, spark plugs have a fail mode that causes them to not spark at the electrode, but somewhere within the body of the plug. Often, this kind of fail will only show up when the electrode is exposed to the increased dielectric strength of a compressed chamber - either in the sparkplug tester, or when being run in an engine. I am not sure I understand your last comment about spark voltage. It sounds like you are saying there is a mechanism that adjusts spark voltage based on cylinder pressure - something I have never heard of. Regards, Matt- N34RD > > Ferg > > I think they mean breakdown outside the combustion chamber. Sometimes > poor/wet ignition wires will run the engine fine at low power settings > but at high power and high compression the wires break down and the > engine misses. The voltage goes higher to fire the spark under higher > cylinder pressure. > > Ken > > Fergus Kyle wrote: >> >> "As has been discussed on this list before, denser air (a composition >> of non-conductive gasses) is a better insulator (higher dielectric >> breakdown capability). As the air gets thinner, its propensity to >> conduct increases." >> >> "You can see that Vacuum will break down at around 20kV with a 1" gap, >> whereas dense air might hold up to 75kV over the same gap." >> >> " A plug that works properly at atmospheric pressure may display >> shorts when the gap is exposed to pressurized air (which has even >> higher dielectric strength)." >> >> How can it display shorts at higher pressure and still have higher >> dielectric strength? >> Ferg >> Europa A064 >> >> >> >> >> >> >> > > ________________________________________________________________________________
Date: May 03, 2004
From: Brian Lloyd <brianl(at)lloyd.com>
Subject: Re: Pressure altitude and short sparks
Bruce Gray wrote: > > Hmmm.... I don't see how the cylinder pressure, before ignition, > increases with engine speed. It doesn't but it does increase with MAP. At low power settings the throttle is mostly closed and the cylinder is sucking against the resistance of the throttle valve. The MAP is low, probably 10" to 15" Hg, so the pressure in the cylinder is correspondingly lower too. If the compression ratio is 10:1 (for ease of calculation), the cylinder pressure at TDC with 10" of MAP will be 100" Hg. With the throttle wide open the MAP will be close to 30" and the cylinder pressure will be 300" Hg. This is a simplistic calculation but hopefully it is understandable. -- Brian Lloyd 6501 Red Hook Plaza brianl(at)lloyd.com Suite 201 http://www.lloyd.com St. Thomas, VI 00802 +1.340.998.9447 (voice) +1.360.838.9669 (fax) There is a time to laud one's country and a time to protest. A good citizen is prepared to do either as the need arises. ________________________________________________________________________________
Date: May 03, 2004
From: klehman(at)albedo.net
Subject: Re: Pressure altitude and short sparks
Ferg I think they mean breakdown outside the combustion chamber. Sometimes poor/wet ignition wires will run the engine fine at low power settings but at high power and high compression the wires break down and the engine misses. The voltage goes higher to fire the spark with higher cylinder pressure. Ken Fergus Kyle wrote: > > "As has been discussed on this list before, denser air (a composition of > non-conductive gasses) is a better insulator (higher dielectric breakdown > capability). As the air gets thinner, its propensity to conduct increases." > > "You can see that Vacuum will break down at around 20kV with a 1" gap, > whereas dense air might hold up to 75kV over the same gap." > > " A plug that works properly at atmospheric pressure may display shorts when > the gap is exposed to pressurized air (which has even higher dielectric > strength)." > > How can it display shorts at higher pressure and still have higher > dielectric strength? > Ferg > Europa A064 ________________________________________________________________________________
Date: May 03, 2004
Subject: Feedback for Bob - Roll your own crowbar module
From: Ralph Ketter <arizonahikers(at)juno.com>
Original posting 4/12/04 >> >>I build my own OV crowbar module and it functions correctly except that >>it operated in the 10-11 volt range. I triple checked the components and >>wiring. I tested the 1N4742A diode and it regulates at 12V. I changed >>the 1.62K ohm resistor specified for a 14 volt system to 6.04K and the >>circuit operates in the correct voltage range of 15.5-17 volts. Has >>anyone else found this? *************************** > With the 1.62K resistor in place, adjust the potentiometer to > approximately mid range. Adjust the power supply to a point just > below the trip point and then measure voltage at (1) + end of > capacitor and (2) junction of zener diode and the 392 ohm > resistor and tell us what you get. > > Bob . . . > > ----------------------------------------- > ( Experience and common sense cannot be ) > ( replaced with policy and procedures. ) > ( R. L. Nuckolls III ) > ----------------------------------------- Thanks for the reply Bob, Sorry I took so long with a response to your suggestion. I did as you suggested. The pot is set to mid range for all of the following voltage readings. Designating Point (1) as the + end of the capacitor, and Point (2) as the junction of the 392 ohm resistor, and GND as the negative lead, I got the following readings: 1.62 K resistor in place for 14 volt operation. - Trip point = 10.4 volts. Point (1) - Point (2) +0.436 volts GND - Point (2) +7.6 volts 6.04K resistor replacing the 1.62K one. - Trip point = 16.22 volts. Point (1) - Point (2) +0.538 volts GND - Point (2) +7.36 volts These readings made me realize the circuit was not letting the zener regulate at 12 volts so I did the following checks. First I disconnected the SCR trigger lead to prevent it from firing. I reinstalled the original 1.62K resistor. Measuring the Zener voltage from GND to Point (2): As I increased the input voltage the voltage across the zener increases linearly to about 8.25 volts and then starts to decrease. The input voltage is about 9 volts when this knee occurs. I then disconnected the 1N4148 diode and repeated the above test with basically the same results. With the 1N4148 diode still disconnected, I also disconnected the NPN collector and PNP base (they remained connected together) from the Point (2) junction. Now only the Zener and 392 ohm resistor are in series across the supply. Again measuring the Zener voltage from GND to Point (2): The zener voltage tracks the input voltage up to about 11.3 volts at which point the zener begins to regulate. With the two transistors still disconnected, I reconnected the 1N4148 diode. Now the voltage across the zener increases linearly up to 9 volts (input voltage is 9.35) when suddenly the voltage drops to 1.87 volts. When I made the statement in my original email that the zener regulates at 12 volts, I neglected to say that I tested it out of the circuit. Ralph Ketter RV-6 Marysville, KS *************************** ________________________________________________________________________________
Date: May 03, 2004
From: klehman(at)albedo.net
Subject: Re: Pressure altitude and short sparks
Matt I'm just saying that the voltage rises until the plug fires at which point the voltage drops. With more cylinder pressure the voltage rises higher before the plug fires. With defective ignition components it can be that the spark gets out somewhere else before the plug fires. Bruce I am suggesting that cylinder pressure (and manifold pressure) rises when one opens the throttle like it would in a manual transmission car. Similarly with a propellor, cylinder pressure generally increases with manifold pressure. Ken ________________________________________________________________________________
Date: May 03, 2004
Subject: Re: Pressure altitude and short sparks
From: "Matt Prather" <mprather(at)spro.net>
Ken, Thanks for the clarification. I hadn't thought about it in the terms you described, but I agree with what you are saying. Regards, Matt- > > Matt > I'm just saying that the voltage rises until the plug fires at which > point the voltage drops. With more cylinder pressure the voltage rises > higher before the plug fires. With defective ignition components it can > be that the spark gets out somewhere else before the plug fires. > > Bruce > I am suggesting that cylinder pressure (and manifold pressure) rises > when one opens the throttle like it would in a manual transmission car. > Similarly with a propellor, cylinder pressure generally increases with > manifold pressure. > > Ken > > ________________________________________________________________________________
From: "Bruce Gray" <Bruce(at)glasair.org>
Subject: Pressure altitude and short sparks
Date: May 03, 2004
Sorry, the engine is just a constant volume air pump. Cylinder pressure will not vary, regardless of RPM, MP, or a constant speed prop. Now cylinder pressure after ignition is a different matter. Bruce www.glasair.org -----Original Message----- From: owner-aeroelectric-list-server(at)matronics.com [mailto:owner-aeroelectric-list-server(at)matronics.com] On Behalf Of klehman(at)albedo.net Subject: Re: AeroElectric-List: Pressure altitude and short sparks Matt I'm just saying that the voltage rises until the plug fires at which point the voltage drops. With more cylinder pressure the voltage rises higher before the plug fires. With defective ignition components it can be that the spark gets out somewhere else before the plug fires. Bruce I am suggesting that cylinder pressure (and manifold pressure) rises when one opens the throttle like it would in a manual transmission car. Similarly with a propellor, cylinder pressure generally increases with manifold pressure. Ken == == == == ________________________________________________________________________________
Date: May 03, 2004
From: Kevin Horton <khorton01(at)rogers.com>
Subject: Re: Pitot Static Sources and Ram sources
> >For static sources I am convinced (perhaps incorrectly) that too much fuss >is made of their position. The ideal static source would be located where the pressure was the same as the ambient air pressure. But, the aircraft forces the air to flow around it, which causes the air to accelerate and decelerate. Bernoulli's law tells us that the static pressure will change as the air accelerates or decelerates. So it is quite hard to find a place on the airframe where the static source will actually be seeing the correct pressure. And even if you find a location that is good at a particular angle of attack, flap angle, etc, the airflow pattern will be different at other conditions. So, if you want accurate altimeter and airspeed readings, then static source location is important. If you think having an accurate static source is only important if you fly IFR, remember that the static source error affects the altitude reported by our transponder, and that affects the response of TCAS equipped aircraft. If the error is small, no problem, but if the error is large you could easily have a TCAS equipped aircraft that would have missed you if he had just kept flying level, instead climb or dive toward you, because your transponder is reporting that you are at the wrong altitude. The transponder checks that are done won't find a problem with static source position error, as static source position error only exists when you have air flowing around the aircraft. You need to do careful flight tests to measure it: http://members.rogers.com/khorton/rvlinks/ssec.html -- Kevin Horton RV-8 (finishing kit) Ottawa, Canada http://go.phpwebhosting.com/~khorton/rv8/ ________________________________________________________________________________
Subject: Pressure altitude and short sparks
Date: May 03, 2004
From: "George Braly" <gwbraly(at)gami.com>
Bruce, The peak cylinder pressure does change with manifold pressure. Regardless of whether or not there is a spark. For a normal 8.5:1 CR engine, if no spark, peak cylinder pressure happens at TDC, at somewhere between about 125PSI and 300 PSI, depending on MP . Regards, George -----Original Message----- From: owner-aeroelectric-list-server(at)matronics.com [mailto:owner-aeroelectric-list-server(at)matronics.com] On Behalf Of Bruce Gray Subject: RE: AeroElectric-List: Pressure altitude and short sparks Sorry, the engine is just a constant volume air pump. Cylinder pressure will not vary, regardless of RPM, MP, or a constant speed prop. Now cylinder pressure after ignition is a different matter. Bruce www.glasair.org -----Original Message----- From: owner-aeroelectric-list-server(at)matronics.com [mailto:owner-aeroelectric-list-server(at)matronics.com] On Behalf Of klehman(at)albedo.net Subject: Re: AeroElectric-List: Pressure altitude and short sparks Matt I'm just saying that the voltage rises until the plug fires at which point the voltage drops. With more cylinder pressure the voltage rises higher before the plug fires. With defective ignition components it can be that the spark gets out somewhere else before the plug fires. Bruce I am suggesting that cylinder pressure (and manifold pressure) rises when one opens the throttle like it would in a manual transmission car. Similarly with a propellor, cylinder pressure generally increases with manifold pressure. Ken == == == == == == == == ________________________________________________________________________________
Date: May 03, 2004
Subject: Pressure altitude and short sparks
From: "Matt Prather" <mprather(at)spro.net>
Bruce, I respectfully disagree. I am not sure how an engine being a constant volume air pump has any bearing on what the pre-ignition cylinder pressure is.... Air is compressible. As the throttle position is varied, a varying mass of the fuel-air mixture is allowed to enter the cylinder each time the intake valve spends some time open. If the throttle is fully open, a larger mass of fuel-air is drawn into the cylinder on the piston's intake stroke than when the throttle is closed. This larger mass will cause a relatively higher pressure to be generated when the piston reaches the top of its stroke, achieving its fixed minimum volume. This is true whether fuel-air is ever ignited or not. I think the throttle works by changing the volumetric efficiency of the engine - ie, how much volume of atmospheric pressure fuel-air is drawn into the cylinder as compared to the actual cylinder volume. Maybe I am missing something in your explanation... Regards, Matt- > > > Sorry, the engine is just a constant volume air pump. Cylinder pressure > will not vary, regardless of RPM, MP, or a constant speed prop. > > Now cylinder pressure after ignition is a different matter. > > Bruce > www.glasair.org > > snip > > Bruce > I am suggesting that cylinder pressure (and manifold pressure) rises > when one opens the throttle like it would in a manual transmission car. > Similarly with a propellor, cylinder pressure generally increases with > manifold pressure. > > Ken > > > == ________________________________________________________________________________
From: "Richard Sipp" <rsipp(at)earthlink.net>
Subject: Z-12 Main Alternator Control
Date: May 03, 2004
Bob: With respect to Z-12 (Single Battery, Dual Alternator) the main alternator appears to be controlled by the main battery master switch while the aux alternator has a separate on/off switch. Is there a reason for not having a separate main alternator switch as well? I plan on this system for the RV-10 I have under construction. The aircraft is designed with a battery location aft of the passenger compartment. With an aluminum airframe is the 4AWG ground cable to the instrument panel ground bus still the preferred grounding method? Many thanks. Dick Sipp RV10 #65 ________________________________________________________________________________
From: "Bruce Gray" <Bruce(at)glasair.org>
Subject: Pressure altitude and short sparks
Date: May 04, 2004
I stand corrected. My recognized expert on the subject has spoken. I'll just slink back into my corner. Bruce www.glasair.org -----Original Message----- From: owner-aeroelectric-list-server(at)matronics.com [mailto:owner-aeroelectric-list-server(at)matronics.com] On Behalf Of George Braly Subject: RE: AeroElectric-List: Pressure altitude and short sparks Bruce, The peak cylinder pressure does change with manifold pressure. Regardless of whether or not there is a spark. For a normal 8.5:1 CR engine, if no spark, peak cylinder pressure happens at TDC, at somewhere between about 125PSI and 300 PSI, depending on MP . Regards, George -----Original Message----- From: owner-aeroelectric-list-server(at)matronics.com [mailto:owner-aeroelectric-list-server(at)matronics.com] On Behalf Of Bruce Gray Subject: RE: AeroElectric-List: Pressure altitude and short sparks Sorry, the engine is just a constant volume air pump. Cylinder pressure will not vary, regardless of RPM, MP, or a constant speed prop. Now cylinder pressure after ignition is a different matter. Bruce www.glasair.org -----Original Message----- From: owner-aeroelectric-list-server(at)matronics.com [mailto:owner-aeroelectric-list-server(at)matronics.com] On Behalf Of klehman(at)albedo.net Subject: Re: AeroElectric-List: Pressure altitude and short sparks Matt I'm just saying that the voltage rises until the plug fires at which point the voltage drops. With more cylinder pressure the voltage rises higher before the plug fires. With defective ignition components it can be that the spark gets out somewhere else before the plug fires. Bruce I am suggesting that cylinder pressure (and manifold pressure) rises when one opens the throttle like it would in a manual transmission car. Similarly with a propellor, cylinder pressure generally increases with manifold pressure. Ken == == == == == == == == == == == == ________________________________________________________________________________
Subject: Pressure altitude and short sparks
Date: May 04, 2004
From: "George Braly" <gwbraly(at)gami.com>
-----Original Message----- From: owner-aeroelectric-list-server(at)matronics.com [mailto:owner-aeroelectric-list-server(at)matronics.com] On Behalf Of Bruce Gray Subject: RE: AeroElectric-List: Pressure altitude and short sparks I stand corrected. My recognized expert on the subject has spoken. I'll just slink back into my corner. Bruce www.glasair.org -----Original Message----- From: owner-aeroelectric-list-server(at)matronics.com [mailto:owner-aeroelectric-list-server(at)matronics.com] On Behalf Of George Braly Subject: RE: AeroElectric-List: Pressure altitude and short sparks Bruce, The peak cylinder pressure does change with manifold pressure. Regardless of whether or not there is a spark. For a normal 8.5:1 CR engine, if no spark, peak cylinder pressure happens at TDC, at somewhere between about 125PSI and 300 PSI, depending on MP . Regards, George -----Original Message----- From: owner-aeroelectric-list-server(at)matronics.com [mailto:owner-aeroelectric-list-server(at)matronics.com] On Behalf Of Bruce Gray Subject: RE: AeroElectric-List: Pressure altitude and short sparks Sorry, the engine is just a constant volume air pump. Cylinder pressure will not vary, regardless of RPM, MP, or a constant speed prop. Now cylinder pressure after ignition is a different matter. Bruce www.glasair.org -----Original Message----- From: owner-aeroelectric-list-server(at)matronics.com [mailto:owner-aeroelectric-list-server(at)matronics.com] On Behalf Of klehman(at)albedo.net Subject: Re: AeroElectric-List: Pressure altitude and short sparks Matt I'm just saying that the voltage rises until the plug fires at which point the voltage drops. With more cylinder pressure the voltage rises higher before the plug fires. With defective ignition components it can be that the spark gets out somewhere else before the plug fires. Bruce I am suggesting that cylinder pressure (and manifold pressure) rises when one opens the throttle like it would in a manual transmission car. Similarly with a propellor, cylinder pressure generally increases with manifold pressure. Ken == == == == == == == == == == == == == == == == ________________________________________________________________________________
From: "Trampas" <tstern(at)nc.rr.com>
Subject: Pressure altitude and short sparks
Date: May 04, 2004
To get back to the original topic, which related to altitude and ignition system. The cross firing that happens at higher altitudes is usually due to the air density in the distributor. That is the rotor inside the distributor is moving between tabs on the distributor cap, so the air acts as the dielectric between the plug that you want to fire and the neighboring plug or tab in the distributor. As the altitude increases it is easier for the spark to jump to the neighboring distributor tab. As far as the ignition system goes, basically the spark plug is has two electrodes and the voltage potential required to jump an arc between the two electrodes is proportional to the number of air particles between the two electrodes. That is again the dielectric strength of the air, with cylinder pressure this dielectric strength increases. So when the cylinder has the most pressure, the spark plug requires the highest voltage to start the spark. After the spark is started the voltage required to maintain the spark decreases. So what happens is that when the engine is under a load, like when accelerating in a car, the cylinder pressure is very high. Thus it takes a higher voltage to start the spark in the plug. In most engines with good ignition components it takes about 8-12KV to start the spark on the plug. Now in the distributor cap, at sea level it takes over 20KV to have the spark jump to neighboring plug. Now for example imagine you go up in altitude and now it takes about 15KV to fire neighboring plug. Now also imagine that your ignition wires are old (higher resistance) and maybe your plugs are worn such the gap is a bit wider and now instead of 8-12KV to fire the plug you are looking at 15-18KV. Then at this point it is easier for the arc to jump to the neighboring plug than your plug. Keep in mind the neighboring plug has little compression in it's cylinder, thus the 15KV is mainly used to jump gap in distributor cap. Thus the engine will run perfect at low altitudes and miss or cross fire under a load at high altitudes. Now if we want to get further into the spark plug and ignition system we would notice that a coil is charged with energy and then that energy is released as a spark to the plug. Thus there is only X amount of energy and when your plugs or wires wear such that it takes higher voltages it start the plug arcing, well this basically means it takes more energy to start the arc, thus there is less energy left to maintain the arc. That is the spark duration, amount of time plug is arcing, will decrease. This means that the spark plug may not have enough time to completely ignite the fuel in the cylinder and again you get a miss. The reason being that there is fuel and air in the cylinder, ideally these particles are mixed really well. However the spark plug has to ignite enough fuel particles such that they can in turn ignite other. Thus the more fuel particles the arching of the spark plug can hit the more likely combustion will propagate. Thus on newer car engines they are going to wider spark plug gaps, the problem here is again the coil has to be charged with more energy. Here again if you have one coil for eight cylinders you can only charge it for a short time. Thus automotive manufactures have started going to coil on plug. That is there is one coil per plug. This means they can put more energy into the spark plug and increase the spark plug gap, thus making it more likely you can ignite the fuel, getting fast combustion propagation and also run a leaner mixture, one closer to 14.7:1, and some times even leaner. Trampas www.sterntech.com ________________________________________________________________________________
From: "Gary Casey" <glcasey(at)adelphia.net>
Subject: Re: Pressure altitude and short sparks
Date: May 04, 2004
Lots of interesting comments on this subject, but there were some that played a little loose on the terminology and technical details, possibly contributing to confusion: You can't assume that if the compression ratio is 10:1 that the pressure is 10 times the manifold pressure. The pressure actually rises as the 1.35 to 1.4 power of the volume ratio. The difference depends on leakage and the heat rejection of the air to the cylinder walls and there is less heat rejection at higher speed. Also, volumetric efficiency will generally rise with engine speed, at least from cranking speeds to a mid speed range. Therefore, the peak compression pressure will rise with engine speed. For instance, with a 10:1 compression ratio the peak compression press will be 22 to 25 times the manifold pressure. You can't mix the terms "conductivity" and "dielectric strength." All material is conductive to some degree, but dry air is almost non-conductive. However, if you apply a large voltage gradient across air it will ionize and become very conductive. The voltage gradient at which this happens is dielectric strength and that voltage goes up with pressure. Once the air is ionized it takes much less voltage to maintain current flow, probably less than 1/10 the voltage required for the initial breakdown. If you look at the spark plug voltage with a good scope you will see the initial rise in voltage to a very high value (maybe 10,000 to 20,000 volts) and then it will drop to a very low value of 1,000 to 3,000 volts for the remainder of the "burn." In order to cause this ionization, individual molecules must be ionized. If there is a high air velocity through the gap these ions will be blown away, inhibiting a breakdown. For this reason the required ignition voltage does go up with engine speed as the air velocity in the combustion chamber is essentially directly proportional to engine speed. This effect is not the dominate one, though. I don't know if this clarified the issue or made it more confusing. Gary Casey ________________________________________________________________________________
Date: May 04, 2004
From: Brian Lloyd <brianl(at)lloyd.com>
Subject: Re: Pressure altitude and short sparks
Gary Casey wrote: > You can't assume that if the compression ratio is 10:1 that the pressure is > 10 times the manifold pressure. The pressure actually rises as the 1.35 to > 1.4 power of the volume ratio. I was trying to explain things simply so that people who are not engineers or mathematicians could quickly and easily grasp the concept. But as I recall, the ideal gas law states, PV = nRT If the compression ratio is 10:1 and you have isothermal compression then the final pressure will indeed be 10x the inlet pressure as P varies inversely with V since n, R, and T don't change. I know that this is not totally realistic but delta-T is going to be a lot smaller than you think because the heat of compression will quickly transfer to the head and piston crown. Regardless, you are correct in the details. Sorry I was being too simplistic. > I don't know if this clarified the issue or made it more confusing. I guess it depends on who you talk to. You are certainly more correct than I was in detail. -- Brian Lloyd 6501 Red Hook Plaza brianl(at)lloyd.com Suite 201 http://www.lloyd.com St. Thomas, VI 00802 +1.340.998.9447 (voice) +1.360.838.9669 (fax) There is a time to laud one's country and a time to protest. A good citizen is prepared to do either as the need arises. ________________________________________________________________________________
From: "Ed Anderson" <eanderson(at)carolina.rr.com>
Subject: Re: Pressure altitude and short sparks
Date: May 04, 2004
----- Original Message ----- > > > Sorry, the engine is just a constant volume air pump. Cylinder pressure > will not vary, regardless of RPM, MP, or a constant speed prop. > > Now cylinder pressure after ignition is a different matter. > > Bruce > www.glasair.org > While the engine IS a constant volume air pump (in that the total displacement of volume over a cycle is constant), the pressure generated when the piston reaches TDC does depends on the density of the air volume ingested by the cylinder. At low manifold pressures, the air inside the manifold and therefore ingested by the engine, is lower in density than when at high manifold pressures. This difference in density (not volume) is why your air/fuel mixture needs change as well as the power you produce as you vary the throttle opening. So taking a the same volume, but with air at say twice the density at one intake event vs another intake event and compress the density charge to the same TDC space and the pressure will be greater than for the less dense charge. The engine is a constant volume machine, but the cylinder pressure created does differ due to the different air density in the manifold when the intake valve opens. FWIW. Ed Anderson RV-6A N494BW Rotary Powered Matthews, NC eanderson(at)carolina.rr.com ________________________________________________________________________________
Date: May 04, 2004
From: Bobby Hester <bhester(at)hopkinsville.net>
RV-List
Subject: Internal Regulated Alternator converted to External?
Has anyone had there Van's internal regulated 60amp alternator converted to external and used B&C's LR3C-14 regulator? Does this make since to do? -- Surfing the Web from Hopkinsville, KY Visit my web site at: http://www.geocities.com/hester-hoptown/RVSite/ RV7A Slowbuild wings-QB Fuse :-) ________________________________________________________________________________
From: "Ron Koyich" <Ron(at)Koyich.com>
Subject: Off topic - tracing house wiring
Date: May 05, 2004
Apologies for asking this on the list - but where else can one find electrical-savy people concentrated in one place? First - the home in question is in Hong Kong, and I've got no idea who installed the wiring in the first place, or if I could find them even if I knew. Here's the challenge: We have a concrete ceiling in our living room - with some 'loomex' type wire imbedded in the concrete, terminating in the middle of the ceiling. I've mounted a ceiling fan there, but cannot find where the other end of the wire is located. I'd assumed it was at the large bank of switches near the entrance door, as some of them did nothing. The wire doesn't go to those switches, however, so I still cannot put power to the fan. Somewhere in the dark recesses of my mind I recall seeing a device used to trace wires. One part of the unit sends some kind of pulses down the wires, and the other part is a detector for those pulses. So you clip part a) onto the cable you need to trace, and use part b) to follow the wire through whatever it's hidden behind. Do any of you know what this unit might be called - or who makes them - or where they can be purchased? Or is this another home brew project coming up? Thanks - Ron Koyich ________________________________________________________________________________
Date: May 04, 2004
From: richard(at)riley.net
Subject: Re: Off topic - tracing house wiring
At 09:57 PM 5/4/04, you wrote: >- >Do any of you know what this unit might be called - or who makes them >- or where they can be purchased? > >Or is this another home brew project coming up? This is the one I have http://bkprecision.com/pressrelease/july27.html http://www.testequipmentdepot.com/b+k%20precision/262.htm http://www.tequipment.net/BK262.asp The label says "made in China." No guarantee, of course, but you might be able to get one locally. ________________________________________________________________________________
From: "Ron Koyich" <Ron(at)Koyich.com>
Subject: Off topic - tracing house wiring
Date: May 05, 2004
Thanks, Richard - I found a transmitter/receiver pair in Sham Shui Po today - but after getting them home and connected, I couldn't find the other end of the cable anywhere in our flat! God only knows where it goes - I wandered all over the place, including many unlikely places, like the bath off the master bedroom. Nothing. No warble tones except at the start of the cable. Time for another approach - swagged power cords used to be in fashion in the '70s..... Again, thanks! Ron ________________________________________________________________________________
Date: May 05, 2004
From: "Robert L. Nuckolls, III" <bob.nuckolls(at)cox.net>
Subject: Re: Coax Cable
>Below is the result of your inquiry. It was submitted by >mike speer (m.speer(at)shaw.ca) on Monday, May 3, 2004 at 10:33:36 > >Monday, May 3, 2004 > >mike speer > >, >Email: m.speer(at)shaw.ca >Comments/Questions: Hi.. >I have RG-58/U cable that came with my ELT, it is too short for the >location where I want to place my antenna. I would like to know if it is >possible to use RG-400 cable as a replacement for the supplied cable. >Thanks for all your wonderful advise...Mike Yes. In fact, RG400 or RG142 are the materials of choice for modern aircraft fabrication. I will invite you to join us on the AeroElectric List to continue this and similar discussions. It's useful to share the information with as many folks as possible. A further benefit can be realized with membership on the list. There are lots of technically capable folks on the list who can offer suggestions too. You can join at . . . http://www.matronics.com/subscribe/ Thanks! Bob . . . -------------------------------------------- ( Knowing about a thing is different than ) ( understanding it. One can know a lot ) ( and still understand nothing. ) ( C.F. Kettering ) -------------------------------------------- ________________________________________________________________________________
Date: May 05, 2004
From: "Robert L. Nuckolls, III" <bob.nuckolls(at)cox.net>
Subject: Re: Circuit Breakers and OVPs
> >When an Over-Voltage Module crowbars the alternator field line to ground, it >is extremely important to have a fast blow circuit breaker for the >Alternator Field when using a crowbar. This fine point is easy to miss. Define "fast blow circuit breaker" . . . The fault current that flows in the crowbar module is something on the order of 200-300A when it trips. I'm aware of no 5A breaker that is particularly "slow" when presented with this condition. I can offer no valid "concerns" to anyone who is selecting breakers for their project where the use of crowbar ov protection is anticipated. Bob . . . ----------------------------------------- ( Experience and common sense cannot be ) ( replaced with policy and procedures. ) ( R. L. Nuckolls III ) ----------------------------------------- ________________________________________________________________________________
Date: May 05, 2004
From: Mark Steitle <msteitle(at)mail.utexas.edu>
Subject: Re: Internal Regulated Alternator converted
to External? Bobby, A while back I wrote up an explanation for some on this list on how to convert the ND internally-regulated alternator to external regulation. I don't see where it would matter which external regulator you use, as long as the voltage is correct. A search of the archives should locate the article. Mark S. > > >Has anyone had there Van's internal regulated 60amp alternator converted >to external and used B&C's LR3C-14 regulator? >Does this make since to do? > >-- >Surfing the Web from Hopkinsville, KY >Visit my web site at: http://www.geocities.com/hester-hoptown/RVSite/ >RV7A Slowbuild wings-QB Fuse :-) > > ________________________________________________________________________________
From: "Gary Casey" <glcasey(at)adelphia.net>
Subject: Re: Pressure altitude and short sparks
Date: May 05, 2004
<> You are right in the gas law, but the assumption of constant temperature (isothermal) compression is incorrect. It is very close to adiabatic (no heat transfer) than it is to isothermal. In that case V has an exponent that turns out to be approximately 1.4. Since there is actually some heat transfer the exponent can be assumed to be a little lower than 1.4, so 1.35 might be a better number - the higher the engine speed the closer it is to adiabatic. You're right, it does sound a little picky except that going from isothermal to adiabatic changes the predicted peak pressure from 10X to 24X - it can't be ignored. Another post said: <> Exactly, but only true for turbocharged engines that can maintain a fixed manifold pressure regardless of altitude. For a naturally aspirated engine the compression pressure drops in proportion to atmospheric pressure so there is no more cross-firing problem at altitude than at sea level. Also: <> Typical Coil-On-Plug (COP) systems use coils that actually require SHORTER dwell times that single-coil systems. The reason for this is that with no losses in the plug wires it takes less spark energy to light the fire. A byproduct of that is the voltage rise times are faster, making it more likely that fouled plugs will still fire. But the reason for using COP ignition is mainly to eliminate the least reliable part of the engine - the plug wires (Then why does GM mount the individual coils on the valve cover and use short plug wires? Have to ask them). And, yes, a leaner mixture has a higher dielectric strength than a rich one, requiring higher spark voltages. Automotive engines run 99% of the time at exactly 14.7:1 air/fuel ratio so the push to higher voltages has pretty much stopped. An aircraft engine at peak EGT is running about 15:1 and at 100 LOP is at about 16:1, leaner than an automotive engine mixture. Gary Casey ________________________________________________________________________________
From: "Eric M. Jones" <emjones(at)charter.net>
Subject: RE: Off topic - tracing house wiring
Date: May 05, 2004
>From: Ron Koyich (Ron(at)Koyich.com) Now hold on there Roy! Don't give up. The Aeroelectric list has a combined IQ greater than all of China, even with Bob N on vacation. So here's my suggestion. The tester you have may be the wrong tool. Is it one where you attach leads to wires and then go look for them in a fusebox? Then it won't do this job. We need to know: Since apparently you have access to the ceiling leads only; can you determine anything from them? Are there two leads or three? Are they grounded to each other or ground? Is there resistance from one to the other? Have you opened all fixtures, switches and outlets for inspection? Anything else? Possible approaches: 1) Metal detector. Depending on the construction of the house, might work well. 2) Signal generator/radio method: Attach the output of the signal generator tuned to a radio station frequency to the ceiling wires (assuming they're not live). Use an AM radio tuned to the same frequency. When near the wire, the radio station will be blocked. Some fiddling around may be required. This works well to eliminate annoying radio and TV stations from the local area as well. 3) Call an electrician. 4) Call a better electrician. Regards, Eric M. Jones www.PerihelionDesign.com 113 Brentwood Drive Southbridge MA 01550-2705 Phone (508) 764-2072 Email: emjones(at)charter.net ________________________________________________________________________________
Date: May 05, 2004
From: Wallace Enga <wenga(at)svtv.com>
Subject: Re: Circuit Breakers and OVPs
Bob, On a related subject, do you have a part # / source for a device to handle the Load Dump issue and Internal Voltage Regulators that was discussed here a couple of months ago? Thanks Wally Enga > > > > > > >When an Over-Voltage Module crowbars the alternator field line to ground, it > >is extremely important to have a fast blow circuit breaker for the > >Alternator Field when using a crowbar. This fine point is easy to miss. > > Define "fast blow circuit breaker" . . . > > The fault current that flows in the crowbar module is > something on the order of 200-300A when it trips. I'm aware > of no 5A breaker that is particularly "slow" when > presented with this condition. I can offer no > valid "concerns" to anyone who is selecting breakers for > their project where the use of crowbar ov protection is > anticipated. > > Bob . . . ________________________________________________________________________________
From: "Ron Koyich" <Ron(at)Koyich.com>
Subject: RE: Off topic - tracing house wiring
Date: May 05, 2004
Thanks, Eric - on the one hand you give me confidence that we might get somewhere, then on the other you get my name wrong - ah, lack of confidence creeping in. My name is Ron - not Roy. You're not the first to make this mistake - I think it has to do with the 'Koy' in my family name. >>We need to know: Since apparently you have access to the ceiling leads only; can you determine anything from them?<< >> Are there two leads or three?<< Three leeds. None connected to anything. No voltage and infinite resistance between any two. >> Are they grounded to each other or ground? << No - total open circuit - the other end is floating somewhere. >>Is there resistance from one to the other?<< No. >>Have you opened all fixtures, switches and outlets for inspection?<< Not absolutely every one, Eric. But nearly every one and all close by. And I've put a warble tone on the leads and found the other ends of the wires nowhere, including searching in every room of the apartment, and all wiring fixtures. >> Anything else?<< The wires may terminate in the flat above us. >>Call an electrician<< My bet is he'd want to chisel out the ceiling and run a cable over to the wall - too much mess. Decorating department has ruled out swag cord to the fan. If you're in the neighbourhood, Eric, please drop by and sort it out for us.... Thanks for the suggestions - we're into deep thinking now. Best - Ron ________________________________________________________________________________
From: "Fergus Kyle" <VE3LVO(at)rac.ca>
Subject: Re: Pressure altitude and short sparks
Date: May 05, 2004
Cheers, I had no idea what I stirred up with this topic, but found the byplay very interesting and have archived some extensive text on same. Added some depth to a shallow understanding of how an engine pumps out its guts............ Thanks for the trouble taken! Ferg Europa A064 ________________________________________________________________________________
From: "McFarland, Randy" <Randy.McFarland(at)novellus.com>
Subject: Re: Coax Cable
Date: May 05, 2004
Along the lines of RG 400 use, can anyone tell me why the Garmin 327 Transponder installation manual suggests in their Antenna Cable table 2-1 the max length for the cable is 8.8 feet if using RG 400? Is this length specific to the transponder antenna only? Can I run RG 400 for Com / Nav antennas longer than 8.8 feet? (like about 20' out to the wingtip?) Thx Randy RV7A Panel wiring -----Original Message----- From: Robert L. Nuckolls, III [mailto:bob.nuckolls(at)cox.net] Subject: AeroElectric-List: Re: Coax Cable >Below is the result of your inquiry. It was submitted by >mike speer (m.speer(at)shaw.ca) on Monday, May 3, 2004 at 10:33:36 > >Monday, May 3, 2004 > >mike speer > >, >Email: m.speer(at)shaw.ca >Comments/Questions: Hi.. >I have RG-58/U cable that came with my ELT, it is too short for the >location where I want to place my antenna. I would like to know if it is >possible to use RG-400 cable as a replacement for the supplied cable. >Thanks for all your wonderful advise...Mike Yes. In fact, RG400 or RG142 are the materials of choice for modern aircraft fabrication. I will invite you to join us on the AeroElectric List to continue this and similar discussions. It's useful to share the information with as many folks as possible. A further benefit can be realized with membership on the list. There are lots of technically capable folks on the list who can offer suggestions too. You can join at . . . http://www.matronics.com/subscribe/ Thanks! Bob . . . -------------------------------------------- ( Knowing about a thing is different than ) ( understanding it. One can know a lot ) ( and still understand nothing. ) ( C.F. Kettering ) -------------------------------------------- ________________________________________________________________________________
Date: May 05, 2004
From: Richard Tasker <retasker(at)optonline.net>
Subject: Re: RE: Off topic - tracing house wiring
Ron, we lived in HK for three years and I know what you are going through. We had a similar problem when wires running to an outlet that our heater/air conditioner was connected to burned out (thank goodness for concrete or we may have had more than just burned out wiring). One would have thought that it would have been an easy job to just pull new wires through the embedded conduit... Unfortunately, the conduit had evidently corroded and the old wires were trapped in the conduit. I finally ended up just running surface wiring to the outlet. The joys of HK construction! The fuse box was such a nightmare I didn't even want to open the door! If you haven't already tried, connect the wire tracer to a known set of wires to make sure that it is working and will actually trace wires like you want to do. Most of the tracers available in the US assume that you have typical US wiring - no conduit, no armored cable - so they may not work in HK where the wiring is installed in conduit embedded in concrete with lots of rebar around (and who knows - they may have embedded the wiring directly. And, yes, I am sure that an electrician would do exactly what you suggest - lots of chiseling and lots of dust... Dick Tasker > > ________________________________________________________________________________
Date: May 05, 2004
From: Dennis Haverlah <clouduster(at)austin.rr.com>
Subject: Re: Pitot Static Sources and Ram sources
To keep bugs out of my pitot tube and fuel tank vent tubes on my Bonanza, I crumpled up a small piece of aluminum screen and pushed it into each tube. Keep it within 1/16 to 1/8 inch of the end. No more bugs and the air can move in or out OK. Has worked for over 10 years. Dennis H. Eric M. Jones wrote: > >It would make a great science project for your high school student to >determine if there is a size tube that is unattractive to mud wasps (and >therefore best for pitot [after Henri Pitot (1695-1771), French physicist] >tubes). > >For bees, it turns out that if a gap (and maybe a hole) is below a certain >size, the bee will fill it. If the gap is bigger, the bees will build comb >in it, but if it is a certain size (7.5mm +/-1.5 mm) the bees will simply >ignore it. Rev. Lorenzo Langstroth (Philadelphia in 1851) was the first >person to use the bee space in hive construction. How he determined that >bees used the metric system is truly one of the wonders of science. > >You don't have to search the NTSB very hard to find "wasp-like creature in >pitot tube" accidents. And you don't have to talk to many pilots to find >hair-raising tales that thankfully didn't end up in an NTSB report. Usually >pitot tube clogs are discovered near flying speed, half-way down the runway. > >For static sources I am convinced (perhaps incorrectly) that too much fuss >is made of their position. And yes, you can tee off many instruments to the >same static source, and have multiple static sources. Classically static >sources have been taken from the supports for or just behind pitot ram >sources. > >For pitot ram sources, you can also tee off many instruments, and >furthermore you can have multiple ram sources (several pitot tubes) leading >into one line. This seems never to have been done in EAA aircraft. Big >planes often use two or more pitot tubes but route them to their own >instrument banks. > >I am designing a spare retractable pitot tube. The prototype will appear on >my website shortly. Comments are solicited. > >Regards, >Eric M. Jones >www.PerihelionDesign.com >113 Brentwood Drive >Southbridge MA 01550-2705 >Phone (508) 764-2072 >Email: emjones(at)charter.net > >Ring the bells that still can ring >Forget your perfect offering >There is a crack in everything >That's how the light gets in > - - Leonard Cohen > > > > ________________________________________________________________________________
Date: May 05, 2004
From: Leo Gates <leogates(at)allvantage.com>
Subject: Audio Amplifier
I would like to build an audio amplifier for my Zenith CH601HDS. I want to mount a 3 way bookshelf speaker in the baggage compartment and feed the headset audio to it. The speaker I have will handle 40 watts but I think driving it with 10 -20 watts should be adequate - any thoughts? The amplifier needs 150 Ohm input and 4 - 8 Ohm output, 12 V. DC power. Anyone know of a source, either diagram or ready made? Leo Gates ________________________________________________________________________________
From: "Paul Messinger" <paulm(at)olypen.com>
Subject: Re: Circuit Breakers and OVPs
Date: May 05, 2004
I am one of two that are doing an engineering test characterization and design of a Load dump clamp. I am sorry but that project is way behind but nearing completion of preliminary results. There are other pressing issues (not related to load dump) that is delaying my completing the testing. I (we) fully expect to have one or two proven solutions available as well as purchase info, now estimated late this month. Paul ----- Original Message ----- From: "Wallace Enga" <wenga(at)svtv.com> Subject: Re: AeroElectric-List: Re: Circuit Breakers and OVPs > > Bob, > > On a related subject, do you have a part # / source for a device to handle > the Load Dump issue and Internal Voltage Regulators that was discussed > here a couple of months ago? > > Thanks > Wally Enga > > > > > > > > > > > > >When an Over-Voltage Module crowbars the alternator field line to ground, it > > >is extremely important to have a fast blow circuit breaker for the > > >Alternator Field when using a crowbar. This fine point is easy to miss. > > > > Define "fast blow circuit breaker" . . . > > > > The fault current that flows in the crowbar module is > > something on the order of 200-300A when it trips. I'm aware > > of no 5A breaker that is particularly "slow" when > > presented with this condition. I can offer no > > valid "concerns" to anyone who is selecting breakers for > > their project where the use of crowbar ov protection is > > anticipated. > > > > Bob . . . > > ________________________________________________________________________________
From: "Trampas" <tstern(at)nc.rr.com>
Subject: Re: Pressure altitude and short sparks
Date: May 05, 2004
Gary, <From: "Eric M. Jones" <emjones(at)charter.net>
Subject: RE: RE: Off topic - tracing house wiring
Date: May 05, 2004
Sorry about the name thing Ron. Many good suggestions have bubbled up to the surface. I especially like the smoke thing or the vacuum cleaner thing, if there is a conduit. Carbon dioxide would work well too. On a humid day, CO2 would cause condensation on the concrete where the conduit is. Or if you can establish that the conduit or wiring is not too deep, boring test holes with a diamond hole saw would access the wiring, not make much mess, and could easily be patched. Regards, Eric M. Jones www.PerihelionDesign.com 113 Brentwood Drive Southbridge MA 01550-2705 Phone (508) 764-2072 Email: emjones(at)charter.net "Mankind faces a cross-roads. One path leads to despair and utter hopelessness. The other, to total extinction. Let us pray we have the wisdom to choose correctly." --Woody Allen ________________________________________________________________________________
From: KITFOXZ(at)aol.com
Date: May 05, 2004
Subject: Re: Audio Amplifier
In a message dated 5/5/2004 3:50:18 PM Eastern Standard Time, emjones(at)charter.net writes: http://www.allelectronics.com/cgi-bin/category.cgi?category=937&item=AMP-30&ty pe=store Eric M. Jones Eric, Leo, This amp calls for an AC power input not DC. But, not to worry, you may be able to bypass internal power supply rectifier and run on DC. John P. Marzluf Columbus, Ohio Kitfox Outback (out back in the garage) ________________________________________________________________________________
From: "Bob Miller" <drmiller(at)cvillepsychology.net>
Subject: Inrush current protection for lights
Date: May 05, 2004
I've seen little button-size devices that you insert between a standard lightbulb and its socket that supposedly reduces the shock of inrush current that tends to wear out filaments. A keepwarm circuit would be preferable, but my PM alternator produces only 10 amps continuous and I'm about at that limit. Is there anything like those button devices that might work in an aircraft as an alternative to a keepwarm circuit? I know it won't protect the lamps from vibration damage, but it would at least be better than nothing. Bob Miller ________________________________________________________________________________
Date: May 05, 2004
From: Leo Gates <leogates(at)allvantage.com>
Subject: Re: Audio Amplifier
Eric, John, My thoughts exactly. I ordered one today. Thanks again Eric and thanks John. Leo KITFOXZ(at)aol.com wrote: > >In a message dated 5/5/2004 3:50:18 PM Eastern Standard Time, >emjones(at)charter.net writes: >http://www.allelectronics.com/cgi-bin/category.cgi?category=937&item=AMP-30&ty >pe=store > >Eric M. Jones > >Eric, Leo, > >This amp calls for an AC power input not DC. But, not to worry, you may be >able to bypass internal power supply rectifier and run on DC. > >John P. Marzluf >Columbus, Ohio >Kitfox Outback (out back in the garage) > > > > ________________________________________________________________________________
From: KITFOXZ(at)aol.com
Date: May 05, 2004
Subject: Re: Inrush current protection for lights
In a message dated 5/5/2004 4:34:23 PM Eastern Standard Time, drmiller(at)cvillepsychology.net writes: I've seen little button-size devices that you insert between a standard lightbulb and its socket that supposedly reduces the shock of inrush current that tends to wear out filaments. A keepwarm circuit would be preferable, but my PM alternator produces only 10 amps continuous and I'm about at that limit. Is there anything like those button devices that might work in an aircraft as an alternative to a keepwarm circuit? I know it won't protect the lamps from vibration damage, but it would at least be better than nothing. Bob Miller Bob, The device you have seen I believe is simply a diode that rectifies the voltage supply to a household light bulb. Instead of the bulb's filament dropping the entire 120 volt AC voltage across itself, it only sees a half wave pulsing DC supply at half average voltage. The bulb will last a long time but with less light output. For DC voltage aircraft application I would guess using the lowest wattage bulb that will give the minimum light that you require is best. Keep it cooled and vibration protected and forget about browning out the applied voltage. Why waste power on a filament protection device when you only have 10 amps in the bank? John P. Marzluf Columbus, Ohio Kitfox Outback (out back in the garage) ________________________________________________________________________________
Date: May 05, 2004
From: klehman(at)albedo.net
Subject: Re: Inrush current protection for lights
Keystone also makes a variety of inrush limiters which are just thermistors that have a high cold resistance and less resistance when they heat up. Physically they look like an MOV or a large ceramic disc capacitor. I have tried them on sealed beam lamps and they seem to only dim the lamp very slightly. Personally I think it is not worth the effort for automotive style lamps but it might be worth it for more expensive certified lamps. Ken KITFOXZ(at)aol.com wrote: > > In a message dated 5/5/2004 4:34:23 PM Eastern Standard Time, > drmiller(at)cvillepsychology.net writes: > I've seen little button-size devices that you insert between a standard > lightbulb and its socket that supposedly reduces the shock of inrush current that > tends to wear out filaments. A keepwarm circuit would be preferable, but my PM > alternator produces only 10 amps continuous and I'm about at that limit. > Is there anything like those button devices that might work in an aircraft as > an alternative to a keepwarm circuit? I know it won't protect the lamps from > vibration damage, but it would at least be better than nothing. > > Bob Miller > > Bob, > > The device you have seen I believe is simply a diode that rectifies the > voltage supply to a household light bulb. Instead of the bulb's filament dropping > the entire 120 volt AC voltage across itself, it only sees a half wave pulsing > DC supply at half average voltage. The bulb will last a long time but with > less light output. For DC voltage aircraft application I would guess using the > lowest wattage bulb that will give the minimum light that you require is > best. Keep it cooled and vibration protected and forget about browning out the > applied voltage. Why waste power on a filament protection device when you only > have 10 amps in the bank? > > John P. Marzluf > Columbus, Ohio > Kitfox Outback (out back in the garage) ________________________________________________________________________________
From: KITFOXZ(at)aol.com
Date: May 05, 2004
Subject: Re: Inrush current protection for lights
In a message dated 5/5/2004 7:59:28 PM Eastern Standard Time, klehman(at)albedo.net writes: Keystone also makes a variety of inrush limiters which are just thermistors that have a high cold resistance and less resistance when they heat up. Physically they look like an MOV or a large ceramic disc capacitor. I have tried them on sealed beam lamps and they seem to only dim the lamp very slightly. Personally I think it is not worth the effort for automotive style lamps but it might be worth it for more expensive certified lamps. Ken Hello Ken, There are so many variations to semiconductor devices it is hard to tell exactly what it is without a data sheet. There used to be a device used in television circuits called a VDR (voltage dependent resistor) that looked like an MOV in a black or dark brown disk packaging. They may still be used, I don't know. Upon initial power up the device offers very low resistance in series with the degaussing coil, once full voltage is realized across the coil, the resistance climbs to near infinity, shutting off the current to the coil. Perhaps they are actually temperature transient activated? John P. Marzluf Columbus, Ohio Kitfox Outback (out back in the garage) ________________________________________________________________________________
From: "Patrick Elliott" <pelliott(at)innercite.com>
Subject: Alternator from Mag drive.
Date: May 05, 2004
Just bought a VariEze and need a power source. I'm putting two LSE Plasma 3 systems on it and will have two empty mag holes. Does anyone know of a light weight alternator that is driven from a magneto drive? before you ask .. It's on a Rotorway Rw-100 which uses standard Slick mags. same mags you'd find on an O-200 _____ Patrick Elliott 541 297 0004 --- ________________________________________________________________________________
From: "Eric M. Jones" <emjones(at)charter.net>
Subject: Re(buttal) Circuit Breakers and OVPs Rebuttal
Date: May 06, 2004
>> >>When an Over-Voltage Module crowbars the alternator field line to ground, it >>is extremely important to have a fast blow circuit breaker for the >>Alternator Field when using a crowbar. This fine point is easy to miss. >>Eric >The fault current that flows in the crowbar module is >something on the order of 200-300A when it trips. I'm aware >of no 5A breaker that is particularly "slow" when >presented with this condition. I can offer no >valid "concerns" to anyone who is selecting breakers for >their project where the use of crowbar ov protection is >anticipated. >Bob . . . Now Bob.... The circuit breaker associated with the OVP crowbar is a unique case among aircraft circuit breakers. Typically circuit breakers used for this purpose ARE fast blow types. I merely observe that this is a good practice to follow. Otherwise why bother with a fast SCR or Mosfet circuit at all when a simple NTC thermistor would do fine. >Define "fast blow circuit breaker" . . . Okay. I looked up "fast blow circuit breaker" in the dictionary and it says: "Circuit interrupting device with faster trip or quicker response than normal." There is a picture of an Eaton 1500. The idea that a circuit breaker will blow faster at higher current is not a linear correlation. Most breakers are simple bimetal types. You choose: Eaton model 700, at 1000% capacity 25 degC, trips from 0.5 second to 1.5 second. Eaton model 1500, same conditions, trips at 0.025 second to 0.2 seconds. My epiphany that this should be--was based on making some smoke and trying to find out why. What I found out is that it is easier to sink hundreds of amps than it is to interrupt it with a slow bimetal circuit breaker. My good suggestion is simply to use a fast circuit breaker in the Alternator Field line when using OVP. Regards, Eric M. Jones www.PerihelionDesign.com 113 Brentwood Drive Southbridge MA 01550-2705 Phone (508) 764-2072 Email: emjones(at)charter.net " I would have made a good Pope." -- Richard M. Nixon (1913-1994) ________________________________________________________________________________
From: "Gary Casey" <glcasey(at)adelphia.net>
Subject: Re: Pressure altitude and short sparks
Date: May 06, 2004
<> <> Trampas, You are right in that at higher altitudes it takes less voltage to jump between tabs in the distributor or to jump a gap from a cracked plug wire. But the condition that creates the voltage level is the pressure in the combustion chamber, so at higher altitude there will be less voltage required to jump the gap in the plug, which is the dominant factor. It should only be a problem at full throttle when combustion pressure is the highest compared to atmospheric. Then why, as Old Bob points out, would a non-supercharged engine have a problem at high altitude? Don't know, but here is a theory: At low altitude the engine is always run rich at full throttle, keeping the voltage requirement down. Only at high altitude is the engine leaned while the throttle is full open. Under lean conditions the voltage requirement rises by some amount and I'm not sure how much - maybe 10 or 20%? The only other explanation I can come up with is that the distributed capacitance of the ignition wires tends to require a higher peak voltage that is actually necessary to jump the gap in the plug. This effect is constant with altitude, creating a coil voltage that does not drop quite as fast as altitude rises. Just a couple of theories. Make sense? Gary Casey ________________________________________________________________________________
Date: May 06, 2004
From: "Robert L. Nuckolls, III" <bob.nuckolls(at)cox.net>
Subject: Re: Re(buttal) Circuit Breakers and OVPs
Rebuttal > > > > > >> > >>When an Over-Voltage Module crowbars the alternator field line to ground, >it > >>is extremely important to have a fast blow circuit breaker for the > >>Alternator Field when using a crowbar. This fine point is easy to miss. > >>Eric > > > >The fault current that flows in the crowbar module is > >something on the order of 200-300A when it trips. I'm aware > >of no 5A breaker that is particularly "slow" when > >presented with this condition. I can offer no > >valid "concerns" to anyone who is selecting breakers for > >their project where the use of crowbar ov protection is > >anticipated. > > >Bob . . . > >Now Bob.... > >The circuit breaker associated with the OVP crowbar is a unique case among >aircraft circuit breakers. How so unique? > Typically circuit breakers used for this purpose >ARE fast blow types. I merely observe that this is a good practice to >follow. There are volumes of "good practice" admonitions published that offer little or no assistance to the reader. For example, AC43-13 has a big table of wire types that may be considered for use in the repair or modification of aircraft. I have yet to meet the A/P that can wade through that pile "good practice" advice and make a considered selection . . . not to mention find a supplier that can sell him 20 feet of his wire-of-choice. The term "fast blow circuit breaker" is non-quantified, and without recommendations for a specific part number, gives the neophyte builder no information upon which he/she can operate. I object to the non-quantified, non-specific recommendations because they raise concerns while offering no specific solutions. Tossing out the "fast blow" tidbit can serve only to raise anxiety levels. > Otherwise why bother with a fast SCR or Mosfet circuit at all when a >simple NTC thermistor would do fine. > > >Define "fast blow circuit breaker" . . . > >Okay. I looked up "fast blow circuit breaker" in the dictionary and it says: >"Circuit interrupting device with faster trip or quicker response than >normal." Luv that term "normal" . . . if you ran a parts house and an RV builder walks in to purchase a "normal" circuit breaker, what would you sell him? >There is a picture of an Eaton 1500. > >The idea that a circuit breaker will blow faster at higher current is not a >linear correlation. Most breakers are simple bimetal types. > >You choose: Eaton model 700, at 1000% capacity 25 degC, trips from 0.5 >second to 1.5 second. > Eaton model 1500, same conditions, trips at 0.025 >second to 0.2 seconds. > >My epiphany that this should be--was based on making some smoke and trying >to find out why. What I found out is that it is easier to sink hundreds of >amps than it is to interrupt it with a slow bimetal circuit breaker. > >My good suggestion is simply to use a fast circuit breaker in the Alternator >Field line when using OVP. . . . without explanations like you offered above, the information is of little value to most of the folks who frequent this list. The question still unanswered is what are the effects/risks for having a model 700 versus a model 1500 breaker installed as the field control breaker? It's an interesting discussion for folks who make careers of sifting the fine points of contact physics and thermodynamics. I'll suggest that in this venue, little jewels of knowledge should be supported by an explanation of physics and considered recommendations for selection of parts and materials. Bob . . . ________________________________________________________________________________
Date: May 06, 2004
From: "Robert L. Nuckolls, III" <bob.nuckolls(at)cox.net>
Subject: Re: short Vans master relay stud length,
again... > >Guys, > >I know this has come up before...I've got the Vans master relay with the >oh-so-short little studs which will barely hold a single terminal let >alone the multiple ones that I need (battery lead, e-bus feed, Lightspeed >#1, and aux battery feed). > >Before I toss it in the useless parts bin and order a manly B&C relay on >Viagra with a stud size worthy of my 21st Century electrical system, I'm >just curious as to why I can't stack the aformentioned terminals directly >on the + battery terminal? Seems I recall hearing somewhere that this is >bad practice, but can't think of how the physics of the connection would >be any different (i.e. less convenient or less secure) this way as >opposed to attaching them all to the master relay stud. But I don't have >my battery yet (planning Odyssey PC680) so I'm not sure if there are >issues I'm unaware of.... Normally, it's not a good idea to fiddle with the assembly hardware on this series of contactors. Improper placement of the stud when tightening the mounting nut for the stud might cause mis-alignment of contact faces within the assembly and reduce life of the contactor. Since replacement of the contactor was already being considered, I thought we might explore the possibility of getting more exposed threads by replacing the existing mounting nut with a jam nut as shown in http://www.aeroelectric.com/Pictures/stud_length.jpg The White-Rogers contactor on the right seemed to have good rotational stability so that replacing the original nut with a thinner one yielded several more threads for terminal stacking. Unfortunatly, the Cole-Hersee part has a SPECIAL nut that cannot simply be replaced with the plain brass jam nut. So, I guess my best recommendation is to get the more user friendly part from B&C - or stack terminals on the battery post. It's a threaded brass terminal so you'd probably get away with it. Personally, I'd go with the longer stud on a contactor. Bob . . . ________________________________________________________________________________
From: "Trampas" <tstern(at)nc.rr.com>
Subject: Re: Pressure altitude and short sparks
Date: May 06, 2004
Gary, How about this for a theory, the air plane requires XX number of horse power to fly at some indicated air speed. This will be regardless of altitude as we are using indicated air speed, assume no wind and same air temperatures. Thus to produce this horse power the pressure in the cylinders will be same at low altitudes and high altitudes. The difference is that at low altitudes the throttle is not opened as wide thus regulating the manifold pressure, then at higher altitudes you have to open the throttle more to get the extra oxygen, which will keep the manifold absolute pressure where it was at lower altitude, again with the assumption air temperature is constant. Thus as mentioned, in previous posts, the pressure in the cylinders is based on manifold air pressure. Thus to produce the same horsepower at higher altitudes you open the throttle more to match manifold pressure to the same level as it was at low altitudes, assuming same mixture adjustment and same air temperature. Regards, Trampas Stern www.sterntech.com -----Original Message----- From: owner-aeroelectric-list-server(at)matronics.com [mailto:owner-aeroelectric-list-server(at)matronics.com] On Behalf Of Gary Casey Subject: AeroElectric-List: Re: Pressure altitude and short sparks <> <> Trampas, You are right in that at higher altitudes it takes less voltage to jump between tabs in the distributor or to jump a gap from a cracked plug wire. But the condition that creates the voltage level is the pressure in the combustion chamber, so at higher altitude there will be less voltage required to jump the gap in the plug, which is the dominant factor. It should only be a problem at full throttle when combustion pressure is the highest compared to atmospheric. Then why, as Old Bob points out, would a non-supercharged engine have a problem at high altitude? Don't know, but here is a theory: At low altitude the engine is always run rich at full throttle, keeping the voltage requirement down. Only at high altitude is the engine leaned while the throttle is full open. Under lean conditions the voltage requirement rises by some amount and I'm not sure how much - maybe 10 or 20%? The only other explanation I can come up with is that the distributed capacitance of the ignition wires tends to require a higher peak voltage that is actually necessary to jump the gap in the plug. This effect is constant with altitude, creating a coil voltage that does not drop quite as fast as altitude rises. Just a couple of theories. Make sense? Gary Casey ________________________________________________________________________________
Date: May 06, 2004
From: Brian Lloyd <brianl(at)lloyd.com>
Subject: Re: Coax Cable
McFarland, Randy wrote: > > Along the lines of RG 400 use, can anyone tell me why the Garmin 327 > Transponder installation manual suggests in their Antenna Cable table 2-1 > the max length for the cable is 8.8 feet if using RG 400? > Is this length specific to the transponder antenna only? Yes. If you have a DME you can consider that it has the same limitation since it runs at approximately the same frequency as the transponder. > Can I run RG 400 > for Com / Nav antennas longer than 8.8 feet? (like about 20' out to the > wingtip?) Yes. When you run a signal through coax some of it is lost in heating the dielectric between the center conductor and the shield. The loss at 1000 MHz (where the transponder signal is) is much higher than the loss at 118 MHz. There should be no problem running VHF comm and nav signals anyplace in the airplane using RG-400. -- Brian Lloyd 6501 Red Hook Plaza brianl(at)lloyd.com Suite 201 http://www.lloyd.com St. Thomas, VI 00802 +1.340.998.9447 (voice) +1.360.838.9669 (fax) There is a time to laud one's country and a time to protest. A good citizen is prepared to do either as the need arises. ________________________________________________________________________________
Date: May 06, 2004
From: Brian Lloyd <brianl(at)lloyd.com>
Subject: Re: Audio Amplifier
Leo Gates wrote: > > I would like to build an audio amplifier for my Zenith CH601HDS. I want > to mount a 3 way bookshelf speaker in the baggage compartment and feed > the headset audio to it. The speaker I have will handle 40 watts but I > think driving it with 10 -20 watts should be adequate - any thoughts? > The amplifier needs 150 Ohm input and 4 - 8 Ohm output, 12 V. DC power. > Anyone know of a source, either diagram or ready made? You can find an entire range of high-power automotive amplifiers that should do the job for you. Get one that has line-level inputs and try that. Get one that has an adjustable input attenuator (volume control). Most can be bridged so that they provide more power to one output, such as a subwoofer. -- Brian Lloyd 6501 Red Hook Plaza brianl(at)lloyd.com Suite 201 http://www.lloyd.com St. Thomas, VI 00802 +1.340.998.9447 (voice) +1.360.838.9669 (fax) There is a time to laud one's country and a time to protest. A good citizen is prepared to do either as the need arises. ________________________________________________________________________________
Date: May 07, 2004
From: "Robert L. Nuckolls, III" <bob.nuckolls(at)cox.net>
Subject: Re: Stobe Noise
>Below is the result of your inquiry. It was submitted by >Barry M. Schulte (FLYaDIVE(at)AOL.COM) on Wednesday, May 5, 2004 at 04:19:06 > >Wednesday, May 5, 2004 > >Barry M. Schulte > >, >Email: FLYaDIVE(at)AOL.COM >Comments/Questions: Hi Bob: > >I have been trying to remove Strobe Whine from my audio system. I found >on your site (GREAT SITE)a circuit using Radio Shack parts. Only problem >is the Radio Shack Part is no longer available (Part Number 270-030, >Filter kit. Would you have the values of the components used (Choke and >Capicator)? I usually attack strobe whine at the source . . . strobe power supply. They are notorious noise sources but generally easy to tame. Try an off-the-shelf filter like these from Radio Shack: http://www.radioshack.com/product.asp?catalog%5Fname=CTLG&product%5Fid=270-051 http://www.radioshack.com/product.asp?catalog%5Fname=CTLG&product%5Fid=270-055 Install at the power supply location. Let us know what you discover. I will invite you to join us on the AeroElectric List to continue this and similar discussions. It's useful to share the information with as many folks as possible. A further benefit can be realized with membership on the list. There are lots of technically capable folks on the list who can offer suggestions too. You can join at . . . http://www.matronics.com/subscribe/ Thanks! Bob . . . -------------------------------------------- ( Knowing about a thing is different than ) ( understanding it. One can know a lot ) ( and still understand nothing. ) ( C.F. Kettering ) -------------------------------------------- ________________________________________________________________________________
Date: May 07, 2004
From: rmickey(at)ix.netcom.com
Subject: Second Com Antenna Placement
I have one Comat bent whip Com antenna mounted just aft of the battery box (next to the firewall) in the midline of my RV6A. I have a second Archer wingtip Com antenna in my right wingtip. The Archer is not performing up to my specifications and I want to put a second bent whip Comat Com antenna somewhere. My first choice would be behind the first on the midline of the belly. If I put it there, how far back do I need to place it? Are there other locations that would be better? My hanger mate has one on the belly and one on the turtledeck. I don't particularly like the idea of putting the antenna on the top. Thanks. Ross Mickey N9PT ________________________________________________________________________________
From: "Troy Scott" <tscott1217(at)bellsouth.net>
Subject: Re: Re Re: Re(buttal) Circuit Breakers and OVPs
Date: May 08, 2004
Eric and Bob, What do you know about these ECBs listed in AS&S? ECB-14-02 THE ALL-ELECTRONIC CIRCUIT BREAKER This circuit breaker has no mechanical parts, except for the reset switch. The power switching and control components are completely solid state. It has the added benefit of over- voltage and under-voltage protection. It will turn off if the input voltage goes too high, protecting valuable avionics or other equipment. The above is a quote from the AS catalog. Even if we utilize the OVP in the B&C VR, I wonder if one of these might be a good choice for a really "FAST" field interrupt CB? Another thought: For the ultimate in fast and cheap, why not just use a fuse for field wire interrupt OVP? The fuse for that one item could be conveniently located for in-flight replacement even if all other fuses are behind the panel somewhere. Regards, Troy ________________________________________________________________________________
Date: May 07, 2004
From: "Robert L. Nuckolls, III" <bob.nuckolls(at)cox.net>
Subject: Re: Coax Cable
> >McFarland, Randy wrote: > > > > > Along the lines of RG 400 use, can anyone tell me why the Garmin 327 > > Transponder installation manual suggests in their Antenna Cable table 2-1 > > the max length for the cable is 8.8 feet if using RG 400? > > Is this length specific to the transponder antenna only? > >Yes. If you have a DME you can consider that it has the same limitation >since it runs at approximately the same frequency as the transponder. > > > Can I run RG 400 > > for Com / Nav antennas longer than 8.8 feet? (like about 20' out to the > > wingtip?) > >Yes. > >When you run a signal through coax some of it is lost in heating the >dielectric between the center conductor and the shield. The loss at 1000 >MHz (where the transponder signal is) is much higher than the loss at 118 >MHz. There should be no problem running VHF comm and nav signals anyplace >in the airplane using RG-400. Something I can add to Brian's explanation is illustrated in a page from our website at: http://www.aeroelectric.com/temp/coaxloss.pdf Referring to this drawing we see that RG-58 coax has about 30 db loss per 100' of length at transponder frequencies. RG-400 (and RG-142) will have about 20 db of loss per 100'. 30 db attentuation means that a transponder signal will loose 99.9% of it's strength while working its way down 100' of RG-58 while 99% of the signal will make it to the other end of RG-400. Not really good figures in any case. The point here is that RG58 has 10x the losses as RG400 at these frequencies. Now, consider a 10' run of coax to the transponder antenna. RG-58 will toss off 3 db of your signal (50%) while RG-400 will toss off 2 db (about 37%). For this hypothetical installation, there is a 12% gain in both outgoing and incoming signal strengths for replacing RG58 with RG400 in the transponder installation for a 10' cable run. At VHF comm frequencies, were looking at .7 db (15%) versus .5 db (11%) for the same 10' run. Bottom line is that EITHER RG-58 or RG-400 will offer adequate functionality for the relatively short runs of coax needed in light aircraft at either comm or transponder frequencies. The biggest advantage of RG-400 and its close cousins are modern, high temperature and stable plastics plus the silver plated, double shield construction. In the case originally cited, Garmin is specifying their equipment to meet published performance with a maximum of (8.8/100)*20 or 1.75 db of attenuation in both transmit and receive paths. If you need a longer run, expect a small (probably imperceptible) degradation or you can go with a whippier coax like RG-223 where the losses are 17 db per 100' so you can use up to 10.3 feet of coax without degrading performance below the published specifications. Bob . . . ________________________________________________________________________________
Date: May 07, 2004
From: Brian Lloyd <brianl(at)lloyd.com>
Subject: Re: Second Com Antenna Placement pts rule
rmickey(at)ix.netcom.com wrote: > > > I have one Comat bent whip Com antenna mounted just aft of the battery box (next to the firewall) in the midline of my RV6A. I have a second Archer wingtip Com antenna in my right wingtip. The Archer is not performing up to my specifications and I want to put a second bent whip Comat Com antenna somewhere. My first choice would be behind the first on the midline of the belly. If I put it there, how far back do I need to place it? Are there other locations that would be better? My hanger mate has one on the belly and one on the turtledeck. I don't particularly like the idea of putting the antenna on the top. The best isolation will come from putting one antenna on the top and one on the bottom. If you do that there is a chance that the receiver in one radio will still work and not become overloaded when the other radio transmits. If you don't care you can place both antennas on the belly. The more distance between them you can manage, the better it will work. Try to keep them at least 1M apart. -- Brian Lloyd 6501 Red Hook Plaza brianl(at)lloyd.com Suite 201 http://www.lloyd.com St. Thomas, VI 00802 +1.340.998.9447 (voice) +1.360.838.9669 (fax) There is a time to laud one's country and a time to protest. A good citizen is prepared to do either as the need arises. ________________________________________________________________________________
Date: May 07, 2004
Subject: Re: Re Re: Re(buttal) Circuit Breakers and OVPs
From: "Matt Prather" <mprather(at)spro.net>
I am still confused about why Eric says that there is a need for a fast breaker in the field line. It seems like the only benefit to it is that it might shorten the duration of the over-voltage event. My impression is that components built to DO160 standards will have no problem surviving the transients associated with time constant required to open a standard breaker.... As has been discussed (view in the archive), the reason not to use the fuse is that there are short-lived bus transients present that may cause nuisance trips of the circuit protection but which will cause no damage to modestly rugged system components. Regards, Matt- N34RD > > > Eric and Bob, > snip > The above is a quote from the AS catalog. Even if we utilize the OVP in > the B&C VR, I wonder if one of these might be a good choice for a really > "FAST" field interrupt CB? > > Another thought: For the ultimate in fast and cheap, why not just use a > fuse for field wire interrupt OVP? The fuse for that one item could be > conveniently located for in-flight replacement even if all other fuses > are behind the panel somewhere. > > Regards, > Troy > > ________________________________________________________________________________
From: ALWAYSPDG(at)aol.com
Date: May 07, 2004
Subject: Labeling of wires
name(at)matronics.com, description(at)matronics.com, ----(at)matronics.com, ----------------------@matronics.com, --------------------------------------------------@matronics.com I would like to ask the group if there is some sort of labeling system that you would recommend when labeling wires. I am not asking what the hardware should be, but, what sort of letters or numbers or combination thereof to use to mark all of the different wires. Thanks, Mike ________________________________________________________________________________
Date: May 07, 2004
From: rmickey(at)ix.netcom.com
description(at)matronics.com, ----(at)matronics.com, ----------------------@matronics.com, --------------------------------------------------@matronics.com
Subject: Re: Second Com Antenna Placement pts rule
name description ---- ---------------------- -------------------------------------------------- Thanks, Brian. When you say 1m apart, what distance are you measuring if they are for and aft of each other? The distance between the mounting blocks or the distance between the aft mounting block and the aft tip of the forward antenna? Thanks again, Ross -----Original Message----- From: Brian Lloyd <brianl(at)lloyd.com> Subject: Re: AeroElectric-List: Second Com Antenna Placement > The more distance between them you can manage, the better it will work. Try to keep them at least >1M apart. ________________________________________________________________________________
From: "Eric M. Jones" <emjones(at)charter.net>
Subject: Re: Re Re: Re(buttal) Circuit Breakers and OVPs
Date: May 07, 2004
>I am still confused about why Eric says that there is a need for a fast >breaker in the field line. It seems like the only benefit to it is that >it might shorten the duration of the over-voltage event. ....As if that weren't reason enough.... The purpose of a fuse or circuit breaker is to interrupt the circuit if something bad happens. It is not always the case that excessive current is what trips breakers. But usually, and in every aeroelectric case except the OVP case, excessive current determines if and when the circuit breaker trips. Now, most circuit breaker designs are designed with thermal stresses in mind; that is, they protect the wire from melting and starting a fire. Speed is hardly essential. If a short circuit causes a wire to overheat, whether you cut off the power instantly or a second later usually makes little difference. Thus most or all other breakers should be delayed trip. In the OVP case, the alternator field circuit breaker is essentially modified to trip on excessive voltage, in addition to excessive current. This is accomplished by adding a device (a crowbar) that activates the circuit breaker. So unlike the current activated circuit breakers, one would certainly like to minimize the dwell time of the over-voltage condition. Is it necessary? You be the judge. Regards, Eric M. Jones www.PerihelionDesign.com 113 Brentwood Drive Southbridge MA 01550-2705 Phone (508) 764-2072 Email: emjones(at)charter.net "I wouldn't want to belong to a club that would accept someone like me as a member." --Groucho Marx. ________________________________________________________________________________
Date: May 07, 2004
From: Brian Lloyd <brianl(at)lloyd.com>
Subject: Re: Re Re: Re(buttal) Circuit Breakers and OVPs
Matt Prather wrote: > > > I am still confused about why Eric says that there is a need for a fast > breaker in the field line. It seems like the only benefit to it is that > it might > shorten the duration of the over-voltage event. I suspect that the time it takes for the output of the alternator to fall off is a lot longer than the time it takes for the field circuit breaker to open. Remember, the output of an alternator doesn't go off instantly when you remove field excitation. Likewise it doesn't come on instantly when you apply field excitation. The armature (field) has its own time constant that is a function of applied voltage and the inductance of the armature. Bob probably knows the typical time constant of an alternator. I am only guessing. -- Brian Lloyd 6501 Red Hook Plaza brianl(at)lloyd.com Suite 201 http://www.lloyd.com St. Thomas, VI 00802 +1.340.998.9447 (voice) +1.360.838.9669 (fax) There is a time to laud one's country and a time to protest. A good citizen is prepared to do either as the need arises. ________________________________________________________________________________
Date: May 07, 2004
From: Walter Tondu <walter(at)tondu.com>
Subject: Re: Coax Cable
On 05/07 11:23, Robert L. Nuckolls, III wrote: [...] > In the case originally cited, Garmin is specifying their > equipment to meet published performance with a maximum > of (8.8/100)*20 or 1.75 db of attenuation in both transmit > and receive paths. If you need a longer run, expect > a small (probably imperceptible) degradation or you can > go with a whippier coax like RG-223 where the losses > are 17 db per 100' so you can use up to 10.3 feet of > coax without degrading performance below the published > specifications. [...] Hi Bob, Now I KNOW I should wait to ask this question during your seminar here in Long Beach next month, but... After reading your post I decided to do some more research via the web, and to try to understand cabling and the various parameters and data provided there, because now it seems that there are more choices than RG400, RG223 for example. Of course, all I ended up doing was confusing myself even more. Several of the data parameters I found interesting to note were; a) Attenuation Ratings - at differing frequencies b) Power Ratings - at varying frequencies c) Cable physical properties - terminals, diameter, shielding, environmental factors, etc. Now I'm sure that each of these is very important when determining which cable to use for a specific purpose as transponders, comms and navs all have different requirements Of couse, I also found that the numbers a) and b) above varied greatly from site to site, some indicating nominal values and some with max values. Outwardly it would seem that you would be able to select a cable based upon all the above and it would be obvious which cable to use, provided you have accurate information. Can you recomment a source for accurate information and possible suggested cables for most applications? See you in a few weeks! -- Walter Tondu http://www.tondu.com/rv7 ________________________________________________________________________________
Date: May 07, 2004
From: Brian Lloyd <brianl(at)lloyd.com>
Subject: Re: Second Com Antenna Placement
rmickey(at)ix.netcom.com wrote: > > Thanks, Brian. > > When you say 1m apart, what distance are you measuring if they are for and aft of each other? The distance between the mounting blocks or the distance between the aft mounting block and the aft tip of the forward antenna? I was thinking about the distance between the mounting bases but more distance is better. Top and bottom is better still. -- Brian Lloyd 6501 Red Hook Plaza brianl(at)lloyd.com Suite 201 http://www.lloyd.com St. Thomas, VI 00802 +1.340.998.9447 (voice) +1.360.838.9669 (fax) There is a time to laud one's country and a time to protest. A good citizen is prepared to do either as the need arises. ________________________________________________________________________________
Date: May 07, 2004
From: Brian Lloyd <brianl(at)lloyd.com>
Subject: Re: Re Re: Re(buttal) Circuit Breakers and
OVPs Eric M. Jones wrote: > In the OVP case, the alternator field circuit breaker is essentially > modified to trip on excessive voltage, in addition to excessive current. > This is accomplished by adding a device (a crowbar) that activates the > circuit breaker. Actually, the crowbar OVP shorts the field circuit to ground cutting off the power to the field right now. At that point it doesn't matter if the breaker takes 1ms or 100ms to open. The field in the alternator is already off. > So unlike the current activated circuit breakers, one would certainly like > to minimize the dwell time of the over-voltage condition. The crowbar OVP circuit ensures that. > Is it necessary? You be the judge. No, it really isn't. -- Brian Lloyd 6501 Red Hook Plaza brianl(at)lloyd.com Suite 201 http://www.lloyd.com St. Thomas, VI 00802 +1.340.998.9447 (voice) +1.360.838.9669 (fax) There is a time to laud one's country and a time to protest. A good citizen is prepared to do either as the need arises. ________________________________________________________________________________
From: "Richard Garforth" <richard(at)hawk.flyer.co.uk>
Subject: RF breakthro on Vans gauges
Date: May 07, 2004
Seen some old postings regarding this issue - Has anyone found a fix yet? My MAP gauge goes full scale using a top antenna but only part full scale using an underside antenna. Richard G-RVIX(RV9A) ________________________________________________________________________________
From: "Alex Peterson" <alexpeterson(at)earthlink.net>
Subject: RF breakthro on Vans gauges
Date: May 07, 2004
> > Seen some old postings regarding this issue - Has anyone > found a fix yet? My MAP gauge goes full scale using a top > antenna but only part full scale using an underside antenna. > > Richard G-RVIX(RV9A) Richard, the fix is to not look at it while transmitting:>) Alex Peterson Maple Grove, MN RV6-A N66AP 463 hours http://www.home.earthlink.net/~alexpeterson/ ________________________________________________________________________________
From: PeterHunt1(at)aol.com
Date: May 07, 2004
Subject: Help with tachometer pickup
rv-list-digest(at)matronics.com.pts.rule.name.description.----.----------------------.-------------------------------------------------- After installing my SD20 alternator on the vacuum pad of my 0-360-A1A, I find there isn't sufficient clearance for Van's tachometer transducer to screw onto the tachometer outlet on the back of my engine. I built my all electric panel around my SD20, so it will stay. Would someone help me understand my other tachometer pickup options? Thanks. Pete Clearwater, FL RV-6, installing the engine ________________________________________________________________________________
Date: May 07, 2004
From: Brian Lloyd <brianl(at)lloyd.com>
Subject: Re: RF breakthro on Vans gauges
Richard Garforth wrote: > > > Seen some old postings regarding this issue - Has anyone found a fix > yet? My MAP gauge goes full scale using a top antenna but only part > full scale using an underside antenna. What have you tried? I am not familiar with Van's MAP gauge but I would not be at all surprised to find it uses an automotive MAP sensor with three leads: power, ground, and an output voltage that is proportional to MAP which may then be read by a meter. Here are the things I would try: 1. Shield the wiring from the MAP sensor to the indicator. Use some two-conductor shielded tefzel cable such as your mic cable with the signal and power leads inside and the shield is ground. 2. Place ferrite beads on the leads at both the sensor and indicator ends. 3. Bypass the signal and ground leads to the shield using .01 uF disc ceramic capacitors at both ends of the wires. -- Brian Lloyd 6501 Red Hook Plaza brianl(at)lloyd.com Suite 201 http://www.lloyd.com St. Thomas, VI 00802 +1.340.998.9447 (voice) +1.360.838.9669 (fax) There is a time to laud one's country and a time to protest. A good citizen is prepared to do either as the need arises. ________________________________________________________________________________
From: "Paul Schattauer" <chasm711(at)msn.com>
Subject: Help with tachometer pickup
Date: May 07, 2004
Pete Other vendors use a hall effect transistor mounted on a mag, some use a strobe affair on the flywheel, light speed uses their timeing mechanism and im sure there are others. I wasn't too happy with Vans cable to a transmitter rig but was able to make it work. Paul Schattauer RV8 N808PS 50 hrs Man with one tach always knows what his RPM is, man with two tachs is never sure. >From: PeterHunt1(at)aol.com >Reply-To: aeroelectric-list(at)matronics.com >To: aeroelectric-list(at)matronics.com, >rv-list-digest(at)matronics.com.pts.rule.name.description.----.----------------------.-------------------------------------------------- >Subject: AeroElectric-List: Help with tachometer pickup >Date: Fri, 7 May 2004 18:22:03 EDT > > >After installing my SD20 alternator on the vacuum pad of my 0-360-A1A, I >find >there isn't sufficient clearance for Van's tachometer transducer to screw >onto the tachometer outlet on the back of my engine. I built my all >electric >panel around my SD20, so it will stay. Would someone help me understand my >other >tachometer pickup options? Thanks. > >Pete >Clearwater, FL >RV-6, installing the engine > > ________________________________________________________________________________
From: "Bill Hibbing" <n744bh(at)bellsouth.net>
Subject: Re: Help with tachometer pickup
Date: May 07, 2004
Pete, Not sure if this will help or not but I had the same problem with the clearance on my vacuum pump. I got an extension cable from Wicks (P/N CEE-1) that took care of the clearance problem. The cable is flexible also. Bill Glasair ----- Original Message ----- From: <PeterHunt1(at)aol.com> Subject: AeroElectric-List: Help with tachometer pickup > > After installing my SD20 alternator on the vacuum pad of my 0-360-A1A, I find > there isn't sufficient clearance for Van's tachometer transducer to screw > onto the tachometer outlet on the back of my engine. I built my all electric > panel around my SD20, so it will stay. Would someone help me understand my other > tachometer pickup options? Thanks. > > Pete > Clearwater, FL > RV-6, installing the engine > > ________________________________________________________________________________
From: Fiveonepw(at)aol.com
Date: May 07, 2004
Subject: Re: Labeling of wires
In a message dated 05/07/2004 11:08:00 AM Central Standard Time, ALWAYSPDG(at)aol.com writes: what sort of letters or numbers or combination thereof to use to mark all of the different wires. >>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>> You could use a look-up table to indicate that wire #213 is the ground wire from the Navaid head to the servo, or you could use a system that incorporates something more intuitive like "M7-4SRV-" which could indicate: "M"(main bus) "7"(circuit 7 on main bus) "4"(fourth wire on separate drawing you have generated for this device) "SRV"(which is either one of the wires going to the servo, or that you are a Stevie Ray fan 8-) "-"(this is the negative or ground wire for the circuit) Having one of the labeling systems is VERY helpful- I used a Brady Lablemaker and it worked well, although there are many out there- do an archive seach for more than you could ever need........ From The PosumWorks in TN Mark -6A - 72 hours so far and what a damn BUTT KICKIN' MACHINE!!!!!! ________________________________________________________________________________
Date: May 07, 2004
From: "jan" <lydiaxa(at)pobox.sk>
Subject: stick it in a cute blonde tonight! 15
________________________________________________________________________________
Date: May 08, 2004
From: Mickey Coggins <mick-matronics(at)rv8.ch>
Subject: AOPA Never Again electrical problem
Hi, http://www.aopa.org/pilot/never_again/2004/na0405.html This article discusses an electrical problem. Here is the conclusion: "That night, a quick check of the aircraft's manual found the problem. Apparently the alternators would not kick in if battery power was depleted below a threshold amperage. This condition was created during static ground checks of the camera equipment, which resulted in alternator shutdown. The ammeter reading was correct but so borderline that its warning was misinterpreted. The battery was charged overnight and the mission continued the next day without further incident." Is this caused by a particular type of alternator? Of course, I'll never have this problem with my Z11+Z30 equipped RV8, but I do still fly our club's aircraft. Thanks, Mickey -- Mickey Coggins http://www.rv8.ch/ #82007 QB Wings/Fuselage ________________________________________________________________________________
From: "Werner Schneider" <wernerschneider(at)compuserve.com>
Subject: Re: AOPA Never Again electrical problem
Date: May 08, 2004
A voltage readout would have shown the problem before they departed Werner ----- Original Message ----- From: "Mickey Coggins" <mick-matronics(at)rv8.ch> Subject: AeroElectric-List: AOPA Never Again electrical problem > > Hi, > > http://www.aopa.org/pilot/never_again/2004/na0405.html > > This article discusses an electrical problem. Here > is the conclusion: > > "That night, a quick check of the aircraft's manual found > the problem. Apparently the alternators would not kick in > if battery power was depleted below a threshold amperage. > This condition was created during static ground checks of > the camera equipment, which resulted in alternator > shutdown. The ammeter reading was correct but so borderline > that its warning was misinterpreted. The battery was charged > overnight and the mission continued the next day without > further incident." > > Is this caused by a particular type of alternator? > > Of course, I'll never have this problem with my Z11+Z30 > equipped RV8, but I do still fly our club's aircraft. > > Thanks, > Mickey > > > -- > Mickey Coggins > http://www.rv8.ch/ > #82007 QB Wings/Fuselage > > ________________________________________________________________________________
Date: May 08, 2004
From: Brian Lloyd <brianl(at)lloyd.com>
Subject: Re: AOPA Never Again electrical problem
Mickey Coggins wrote: > > Hi, > > http://www.aopa.org/pilot/never_again/2004/na0405.html > > This article discusses an electrical problem. Here > is the conclusion: > > "That night, a quick check of the aircraft's manual found > the problem. Apparently the alternators would not kick in > if battery power was depleted below a threshold amperage. > This condition was created during static ground checks of > the camera equipment, which resulted in alternator > shutdown. The ammeter reading was correct but so borderline > that its warning was misinterpreted. The battery was charged > overnight and the mission continued the next day without > further incident." > > Is this caused by a particular type of alternator? I have an Aztec and I have studied its electrical system in detail. My immediate reaction is to quote some of our British bretheren and state, "what rubbish." (Actually I said something else but Matt says I am not to use those words here.) If there is enough power in the battery to start the engines and run the lights and radios, there is more than enough to excite the alternators. The Aztec has two alternators being driven by a single voltage regulator. The alternators are run with both fields and B-leads in parallel. I can find nothing in the system to ensure that they share the load equally but it seems to work just fine anyway. There is a second VR that may be switched into the circuit should the main VR fail. A toggle switch with a red flip-up cover on the lower center console, conveniently out of sight, selects the VR. (The Aztec isn't big on ergonomics and there are several controls that one must locate and operate by feel.) So what could the problem have been? Well, my guess is that they had an overvoltage transient which tripped the overvoltage protection relay. This type of OVP latches and won't release until all power is removed from the buss. I bet dollars to donuts that if they had turned off the alternators (field switch) and then cycled the battery master, the alternators would have come back on-line. It also points out how Bob's crowbar OVP system communicates the problem much more clearly to the pilot. When the field breaker pops you know what is wrong (or have a pretty good idea) and resetting the breaker puts everything to right unless there is really something wrong with the alternator system, at which time you resort to your essential buss and get on the ground. Getting back to the Aztec, it is possible that a weak battery would provide insufficient stabilization on the buss that the bus voltage could have risen too high when the alternators kicked on that the OVP relay was activated. Still, the battery would have to have been so dead as to not be able to power anything for that to be the case. Regardless, cycling the alternator field switch and the battery master should have cleared the problem. -- Brian Lloyd 6501 Red Hook Plaza brian(at)greenflashnetworks.com Suite 201 http://www.greenflashnetworks.com St. Thomas, VI 00802 +1.340.998.9447 (voice) +1.360.838.9669 (fax) -- Brian Lloyd 6501 Red Hook Plaza brianl(at)lloyd.com Suite 201 http://www.lloyd.com St. Thomas, VI 00802 +1.340.998.9447 (voice) +1.360.838.9669 (fax) There is a time to laud one's country and a time to protest. A good citizen is prepared to do either as the need arises. ________________________________________________________________________________
Date: May 08, 2004
From: Brian Lloyd <brianl(at)lloyd.com>
Subject: Re: AOPA Never Again electrical problem
Werner Schneider wrote: > > A voltage readout would have shown the problem before they departed The Aztec has a combined volt/amp meter that has a three-position switch to display bus voltage or load on either alternator. Part of the run up check list is to cycle the switch through all three positions and abort if buss voltage is not correct or if either alternator shows no load (no output). So you can't miss this one. The meter readings are not subtle. As I said in my previous message about this article, "what rubbish." -- Brian Lloyd 6501 Red Hook Plaza brianl(at)lloyd.com Suite 201 http://www.lloyd.com St. Thomas, VI 00802 +1.340.998.9447 (voice) +1.360.838.9669 (fax) There is a time to laud one's country and a time to protest. A good citizen is prepared to do either as the need arises. ________________________________________________________________________________
From: ALWAYSPDG(at)aol.com
Date: May 08, 2004
Subject: Re: Labeling of wires
Mark, thanks for the information. Mike ________________________________________________________________________________
From: "John Slade" <sladerj(at)bellsouth.net>
Subject: Getting oxidization off wires
Date: May 08, 2004
Electric people. The Florida humidity has got through my nicely crimped BNC connectors and attacked all my antenna connections. I'm planning to make one permanent join at the winglet (where I have a 6 inch stub of cable coming out of the fiberglass from the antenna) then run new cable all the way to the panel. I thought I'd solder the inner cores, shrink wrap with RTV, bring the shields together and solder them too. I need to clean off the shielding to get a good solder connection. Currently the shielding has black copper oxidization all the way up under the outside cover as far as I can see. What can I dip the shielding in to get a good join? Other suggestions for how to do this would be welcome. John Slade Flying Turbo Rotary Cozy IV http://canardaviation.com/cozy ________________________________________________________________________________
From: "Eric M. Jones" <emjones(at)charter.net>
Subject: Re: Buttal on OVP and Circuit Breakers.
Date: May 08, 2004
The Aeroelectric OVP uses a Teccor S6025L silicon controlled rectifier. When an overvoltage is sensed, the SCR (thyristor) quickly turns on and shorts the 5A circuit breaker to ground. We want the breaker to open--but how quickly must this happen? Assuming the bus will supply it, the short circuit current will be approximately 15V (16.2V-diode Vf)/(0.07CB ohm+0.01 ohm wiring resistance)=188 Amps. (For these estimates). Teccor's data is mainly for 50-60 Hz applications, not one-shot crowbars, but the following limits single cycle non-repetitive surge capability---350A peak for 8.3 milliSeconds. (Their recommended I 2*T for fusing is 510 Amp 2* Sec, which is 50% of this.). So we can estimate that something less than an I 2*T of 1000 Amp 2* Sec is required. For the thyristor to survive, it must then suffer less than 188 Amps X 28 milliseconds to get an I 2*T under 1000 Amp 2* Sec (or so). Otherwise the crowbar OVP will work maybe only ONCE. Thus, you can clearly see that getting a circuit breaker that will trip in less than 28 milliseconds under the specified short circuit conditions is essential, else the OVP will fry. I wish I could wrap all this up in a mathematically neat package, but the trip time/overload specifications of most aircraft circuit breakers is simply not available for currents over 10X rated load or 50A. But the circuit breakers will trip far larger currents with ease....they just won't specify the time lag. ----This is my experience from trying to discover why my crowbar OVP disappeared in a flash and left a perfectly good thermal circuit breaker untouched. So I stand by what I said, use a fast breaker for the OVP/Alternator Field line. Regards, Eric M. Jones www.PerihelionDesign.com 113 Brentwood Drive Southbridge MA 01550-2705 Phone (508) 764-2072 Email: emjones(at)charter.net "When the Okies moved to California it raised the average IQ of both states." ---Will Rogers ________________________________________________________________________________
From: "Eric M. Jones" <emjones(at)charter.net>
Subject: Re: Reformated--Re: Buttal on OVP and Circuit Breakers.
Date: May 08, 2004
Sorry, This is hard enough without some of the math symbols trashing the formatting... The Aeroelectric OVP uses a Teccor S6025L silicon controlled rectifier. When an overvoltage is sensed, the SCR (thyristor) quickly turns on and shorts the 5A circuit breaker to ground. We want the breaker to open--but how quickly must this happen? Assuming the bus will supply it, the short circuit current will be approximately 15V (16.2V-diode Vf)/(0.07CB ohm+0.01 ohm wiring resistance)=188 Amps. (For these estimates). Teccor's data is mainly for 50-60 Hz applications, not one-shot crowbars, but the following limits single cycle non-repetitive surge capability---350A peak for 8.3 milliSeconds. (Their recommended I sq * T for fusing is 510 Amp sq * Sec, which is 50% of this.). So we can estimate that something less than an I sq * T of 1000 Amp sq * Sec is required. For the thyristor to survive, it must then suffer less than 188 Amps X 28 milliseconds to get an I sq * T under 1000 Amp sq * Sec (or so). Otherwise the crowbar OVP will work maybe only ONCE. Thus, you can clearly see that getting a circuit breaker that will trip in less than 28 milliseconds under the specified short circuit conditions is essential, else the OVP will fry. I wish I could wrap all this up in a mathematically neat package, but the trip time/overload specifications of most aircraft circuit breakers is simply not available for currents over 10X rated load or 50A. But the circuit breakers will trip far larger currents with ease....they just won't specify the time lag. ----This is my experience from trying to discover why my crowbar OVP disappeared in a flash and left a perfectly good thermal circuit breaker untouched. So I stand by what I said, use a fast breaker for the OVP/Alternator Field line. Regards, Eric M. Jones www.PerihelionDesign.com 113 Brentwood Drive Southbridge MA 01550-2705 Phone (508) 764-2072 Email: emjones(at)charter.net "When the Okies moved to California it raised the average IQ of both states." ---Will Rogers ________________________________________________________________________________
Date: May 08, 2004
From: Jim Bean <jim-bean(at)att.net>
Subject: Re: RF breakthro on Vans gauges
hi, My best result was from changing the radio antenna coax to double shielded (RG-400 is good) with crimped connectors. Jim Bean ________________________________________________________________________________
From: "Bob Lee" <bob(at)flyboybob.com>
Subject: Battery Dump
Date: May 09, 2004
Bob, I just checked the FAQ on Aeroelectric.com and did not find any update on the Battery dumping subject that went around a while back. Did I miss your reply or has the testing not been completed? I understood that you had several ideas that you were planning to test that would provide an inexpensive solution to this risk but then the subject went quiet. Regards, Bob Lee mailto:bob(at)flyboybob.com ________________________________________________________________________________
From: "Paul Messinger" <paulm(at)olypen.com>
Subject: Re: LOAD DUMP
Date: May 09, 2004
Testing has been delayed and I have posted several updates on this; the latest not long ago. Other more important (to me) Tasks have kept me off this project. Plus I am still waiting for calibration on one piece of test equipment (being done free in spare time so its taking much longer to do, however its a 40-80 man hour cal so its not trivial to get done free). Yes we have a couple of solutions that appear on paper to completely solve any Load dump issues. However to prove to Bob (and others) the solution works, requires a high power setup with somewhat unusual instrumentation (at least for me). I am not setup for switching and loading 50 amps at 20 to 80 volts so that has taken some time to get parts for and setup such power testing and associated instrumentation and get it calibrated so the results are meaningful and design margins can be determined. My aircraft already has one solution implimentated (actually done several years ago) based on reading extensive industry info on the subject. Thus the planned testing is not something I need for my own design. In the automotive design, damaging Load Dump's only can occur when there is a failure as the battery is hard wired to the alternator "B" lead. There is a small load dump when you turn off your headlights but the battery absorbs the dump transient current pulse and keeps the voltage under normal levels. The issue in aircraft is different where the battery can be disconnected when the alternator is providing power. This can be either a design where its a simple switch function (pilot error :-) ) or the battery contactor failing open. Also if the OVP is used to open the "B" lead with an internally regulated alternator any opening of the "B" lead during alternator operation can overvoltage the alternator regulator and if that regulator/alternator is not designed to survive load dumps it/they will fail. The current continues for a very short time and the voltages rises until some load path dissipates the current. The voltage rises as needed to provide this load path and voltages can rise to very high levels. The way a IGN coil produces the spark is similar where the primary coil voltage rises from 12V to 350-400V where it is clamped if the spark plug has not fired and dumped the load into the spark. This MAY be the reason for the "reported" failures of the rebuilt ND alternators being sold by Vans for the RV market. I do not know of ANY proof of this however, that is "Vans alternators are inferior" to any other source as has been suggested by some on this list. Testing is more complex than it might seem however to be sure the solution has proper design margin. Consider that the industry has a simple product that is specifically designed for this issue and one poster said that product failed for him (I have an equivalent part and will be trying it also, however its clamping voltage is higher than aircraft avionics can tolerate). Thus the need for careful testing of a somewhat complex issue of transient energy etc. Hopefully the testing will not damage the regulators in my test alternators as I do not have a limitless supply. Regardless its not possible to test all possible alternators and regulator combinations so any solution must have a somewhat large design margin which is hard to determine when the alternator/regulator(s) I have to test are not necessarily worst case etc. For example I do not have any ND alternators nor any of Bob's regulators to test. The peak current capability of the alternator as well as the response time of the regulator are major factors. I have never called it anything but Load dump as that has been the industry term for decades. Bob, as I recall, did want to rename it (do not recall that name) so looking for anything but Load dump will not flag any note from me. Regardless the testing will not be exhaustive and no warrenty it will result in a 100% solution for everyone. The best design solution is one where its not possible to switch into a load dump condition with pilot errors. Thus our solution is not to try to protect the alternator/regulator but the avionics etc on the acft by clamping the spike to levels the avionics can survive. The OVP circuit will NOT protect from load dump as shutting off the regulator is too late. Opening the "B" lead contactor is not a solution either as the contactor takes a long time to open compared to the load dump pulse. Paul ----- Original Message ----- From: "Bob Lee" <bob(at)flyboybob.com> Subject: AeroElectric-List: Battery Dump > > Bob, > > I just checked the FAQ on Aeroelectric.com and did not find any update on > the Battery dumping subject that went around a while back. Did I miss your > reply or has the testing not been completed? I understood that you had > several ideas that you were planning to test that would provide an > inexpensive solution to this risk but then the subject went quiet. > > Regards, > > Bob Lee > mailto:bob(at)flyboybob.com > > ________________________________________________________________________________
From: "Gerry Clabots" <gclabots(at)execpc.com>
Subject: BNC Connector
Date: May 09, 2004
Does someone have a part number and a source for a 90 degree BNC connector that I could use where I connect the coax to the antenna.I will be mounting the antenna under the baggage compartment floor. Thanks Gerry 7A 70188 ________________________________________________________________________________
Date: May 09, 2004
From: "Richard E. Tasker" <retasker(at)optonline.net>
Subject: Re: BNC Connector
I don't have a part number, but unless you just do not have the room, you would be better off (financially and signal strength) to use a regular straight connector and bend the cable. Dick Tasker Gerry Clabots wrote: > >Does someone have a part number and a source for a 90 degree BNC connector that I could use where I connect the coax to the antenna.I will be mounting the antenna under the baggage compartment floor. >Thanks >Gerry 7A 70188 > > ________________________________________________________________________________
From: "Richard Garforth" <richard(at)hawk.flyer.co.uk>
Subject: RF breakthrough on Vans gauges
Date: May 09, 2004
Brian & Jim, Thanks for the suggestions. Taking the easiest first both antennas are already cabled in RG400 - thanks Jim. I explored the situation further today and found that a handheld ICOM xmitter produced the same result - this confirmed it is RF breaking into the gauge or the wiring and not some strange earthing issue. I next removed the gauge and MAP sensor and cable from the aircraft and set up a simple bench test. This showed that the RF is getting into the circuit board in the gauge (even through the glass front). I stripped the gauge down and found there is no HF decoupling to be seen. Also it seems the moving coil meter is centre wound ( 3 terminals) and works on a differential output from the driver chip. The MAP sensor appears to be a 4 arm bridge sensor with a built in regulator. I finished up fitting five 10nF disc caps (thanks Brian) on the meter circuit board. One across each meter coil, one across the two signal arms of the bridge input and one from each signal input to ground. Immediately the interference was reduced considerably. Final fix was to take the MAP sensor out of its plastic box and fit it directly to the rear of the meter and fit ferrite beads to the two signal leads and the power input. The end result is a gauge that only moves a needle width with the ICOM xmitter ant held against the meter front. My guess is that the Vans gauge that gives similar problems, the ammeter, being centre zero has a similar internal configuration and may respond to a similar fix. As I am a committed Voltmeter believer I can only speculate. Richard(G-RVIX) ________________________________________________________________________________
Date: May 09, 2004
From: Wallace Enga <wenga(at)svtv.com>
Subject: Re: LOAD DUMP
Paul I appreciate the efforts you are doing to investigate and resolve this Load Dump anomaly. I have more than a passing interest, as I am using this combination of an Alternator with Internal V.R. and Bob's O.V. Module. When the O.V Disconnect ("B" lead) Contactor opens, I can understand the transient current pulse caused by the now open circuit on the Alternator side, but I fail to see, how this could cause an O.V. spike on the bus side, which is now isolated from the Alternator in the Load Dump scenario. Why doesn't the bus voltage just drop to the Main Batt level or in the case of the pilot mistakenly opening the BATT Contactor, drop to zero? Isn't the very condition which causes the transient current pulse, (the Open "B" lead Contactor) , the result of the busses/batt no longer being connected to the Alternator? What am I missing here? Wally Enga RV7 ________________________________________________________________________________
From: "Rob W M Shipley" <rob(at)robsglass.com>
Subject: Smoke in wires.
Date: May 09, 2004
I received this in my mail the other day and felt that it might contribute much to the erudite discussions we enjoy so much in this list. As an English ex-pat I am intimately aware of the excellence of Lucas products and their contribution to reliability of the fine automobiles made in the British Isles. > << "A Treatise on the Importance of Smoke" by Joseph Lucas > All electrical components and wiring harnesses depend on proper > circuit functioning, which is the transmission of charged ions by > retention of the visible spectral manifestation known as "smoke". > Smoke is the thing that makes electrical circuits work. Don't be > fooled by scientists and engineers talking about excited electrons > and the like. Smoke is the key to all things electrical. > > We know this to be true because every time one lets the smoke out of > an electrical circuit, it stops working. This can be verified > repeatedly through empirical testing. For example, if one places a > large copper bar across the terminals of a battery, prodigious > quantities of smoke are liberated and the battery shortly ceases to > function. In addition, if one observes smoke escaping from an > electrical component such as a Lucas voltage regulator, it will also > be observed that the component no longer functions. > > The logic is elementary and inescapable! The function of the wiring > harness is to conduct the smoke from one device to another. When the > wiring harness springs a leak and lets all the smoke out of the > system, nothing works right afterward. > > Starter motors were considered unsuitable for British motorcycles for > some time largely because they regularly released large quantities of > smoke from the electrical system. > > It has been reported that Lucas electrical components are possibly > more prone to electrical leakage than their Bosch, Japanese or > American counterparts. Experts point out that this is because Lucas > is British, and all things British leak. British engines leak oil, > British shock absorbers, hydraulic forks, and disk brake systems leak > fluid, British tires leak air and British Intelligence leaks national > defense secrets. > > Therefore, it follows that British electrical systems must leak > smoke. Once again, the logic is clear and inescapable. > > Sometimes you may miss the component releasing the smoke that makes > your electrical system function correctly, but if you sniff around > you can often find the faulty component by the undeniable and > telltale smoke smell. Sometimes this is a better indicator than > standard electrical tests performed with a volt-ohm meter. > > In conclusion, the basic concept of transmission of electrical energy > in the form of smoke provides a clear and logical explanation of the > mysteries of electrical components and why they fail. > > "A gentleman does not motor about after dark." > - Joeseph Lucas, 1842 - 1903 I learned a long time ago that once you let the "Factory Smoke" out of any electrical device, it is next to impossible to replenish it. ________________________________________________________________________________
Date: May 09, 2004
From: "Robert L. Nuckolls, III" <bob.nuckolls(at)cox.net>
Subject: Re: BNC Connector
> > >I don't have a part number, but unless you just do not have the room, >you would be better off (financially and signal strength) to use a >regular straight connector and bend the cable. > >Dick Tasker > >Gerry Clabots wrote: > > > > > >Does someone have a part number and a source for a 90 degree BNC > connector that I could use where I connect the coax to the antenna.I will > be mounting the antenna under the baggage compartment floor. > >Thanks > >Gerry 7A 70188 Right angle connectors do exist . . . but are comparatively expensive and not in everybody's catalog. Here's a new article on a low cost but rugged alternative to a one-piece, solderless right-angle connector. http://www.aeroelectric.com/articles/BNC_Rt_Angle/BNC_Rt_Angle.html Bob . . . ----------------------------------------- ( Experience and common sense cannot be ) ( replaced with policy and procedures. ) ( R. L. Nuckolls III ) ----------------------------------------- ________________________________________________________________________________
Date: May 09, 2004
From: "Robert L. Nuckolls, III" <bob.nuckolls(at)cox.net>
Subject: Re: LOAD DUMP
> >Paul > >I appreciate the efforts you are doing to investigate and resolve this Load >Dump anomaly. > >I have more than a passing interest, as I am using this combination of an >Alternator with >Internal V.R. and Bob's O.V. Module. > >When the O.V Disconnect ("B" lead) Contactor opens, I can understand the >transient current pulse caused > by the now open circuit on the Alternator side, but I fail to see, how >this could cause an O.V. spike on the >bus side, which is now isolated from the Alternator in the Load Dump scenario. It doesn't. The issue came to light when a number of folks having alternators wired per figure Z-24 cycled them OFF and ON when the engine was running and the alternator was probably carrying moderate to high loads. The resulting load dump transient was confined to the alternator side of the alternator disconnect contactor and only the alternator's internal voltage regulator was damaged. >Why doesn't the bus voltage just drop to the Main Batt level or in the case >of the pilot mistakenly >opening the BATT Contactor, drop to zero? > >Isn't the very condition which causes the transient current pulse, (the >Open "B" lead Contactor) , >the result of the busses/batt no longer being connected to the Alternator? > >What am I missing here? Not a thing. Bob . . . ----------------------------------------- ( Experience and common sense cannot be ) ( replaced with policy and procedures. ) ( R. L. Nuckolls III ) ----------------------------------------- ________________________________________________________________________________
Date: May 09, 2004
From: "Robert L. Nuckolls, III" <bob.nuckolls(at)cox.net>
Subject: RF interference to Vans gauges
> > > > > > > Seen some old postings regarding this issue - Has anyone > > found a fix yet? My MAP gauge goes full scale using a top > > antenna but only part full scale using an underside antenna. > > > > Richard G-RVIX(RV9A) > >Richard, the fix is to not look at it while transmitting:>) That's one alternative. This is a down-side of some hardware supplied to the OBAM aircraft community. Some products are brought to the marketplace by folks who either don't understand the value of making products perform equal to or better than "certified" stuff -OR- they don't understand the environment in which they are working. There is no excuse for not having fixed this problem by now. I've been hearing about it off-and-on for at least a year. As consumers you have several choices: (1) return the hardware for refund as "not suited to the intended task", (2) work out and implement fixes at your own time and expense, (3) work with the original manufacturer to see if he/she is willing to upgrade your purchase to operate in the real world or (4) just live with it. It doesn't hurt anything as long as you understand the condition and can believe the instrument all times other than transmitting. As always, if anyone does put the wrenches to the manufacturer, tell them I'll offer suggestions for modifying their design . . . perhaps even at no cost. But since I don't own any of this stuff, it's up to those to do own it to be responsible consumers and squeeze these folks into useful action. There's an old adage that suggests "If you continue to do as you've always done, you will continue to be as you've always been." A corollary to this adage says, "Until you convince a supplier that their product has unsatisfactory design flaws and insist on responsible adjustments, they'll continue selling it warts and all to your fellow builders . . . and your's won't get fixed either. Bob . . . ----------------------------------------- ( Experience and common sense cannot be ) ( replaced with policy and procedures. ) ( R. L. Nuckolls III ) ----------------------------------------- ________________________________________________________________________________
From: HCRV6(at)aol.com
Date: May 09, 2004
Subject: Re: BNC Connector
In a message dated 5/9/04 8:36:50 AM Pacific Daylight Time, gclabots(at)execpc.com writes: << Does someone have a part number and a source for a 90 degree BNC connector that I could use where I connect the coax to the antenna. I will be mounting the antenna under the baggage compartment floor. >> I used a 90 degree BNC adapter from Radio Shack for the same installation, hope it works. Harry Crosby Pleasanton, California RV-6, final assembly ________________________________________________________________________________
Date: May 10, 2004
From: "Robert L. Nuckolls, III" <bob.nuckolls(at)cox.net>
Subject: Re: 11394 Barnes
> >Email: skytop(at)megsinet.net >Comments/Questions: Bob, >I want to report to you on the performance of my B&C SD-8 because I almost >called you to report a problem - that wasn't. On the initial system >testing, I was unable to get the SD-8 to stay online. While switching >between primary and alternate, I would see charging of 14A (primary) >{switch to alt} 4A (SD-8 for about 1 second), then it would drop to zero >(0A). These tests were done on the ground and it wasn't until I tested it >again at cruise RPM that it worked okay. Now it stays at 7A. Soon, I >will test it again to find out at what RPM it drops out after being online >for a while. Thank you for taking the time to share your experience with the SD-8. You have discovered the major shortcoming for driving alternators from the vacuum pump pad. At ramp idle and taxi speeds, the pad is under 2,000 rpm. The SD-8 will deliver no useful output at these speeds. At cruise rpm, the vacuum pump pad runs at about 4,000 rpm and even this speed is lower than required for maximum performance from the SD-8. The 200G alternator is the gear driven version of the SD-8 and turns much faster on the generator drive pad of an O-200 . . . in this situation, the alternator is rated at 12A. You can conduct a reasonable pre flight test of the SD-8 by turning it on during mag checks when the engine is running relatively fast. Turn the main alternator OFF (at idle and with minimum loads) and turn the auxiliary alternator ON. Before bringing rpm back down at the end of your mag check, observe that the alternator does come up and produce some output current . . . but it will never be close to rated output. >You'll never know how much I appreciate your book and help on the >"list". I'm currently unssubscribed, else I would post this for others to >consider. Thanks. Hope to see you back on the list on day. Bob . . . ----------------------------------------- ( Experience and common sense cannot be ) ( replaced with policy and procedures. ) ( R. L. Nuckolls III ) ----------------------------------------- ________________________________________________________________________________
From: "Paul Messinger" <paulm(at)olypen.com>
Subject: Re: LOAD DUMP
Date: May 10, 2004
With due respect I disagree, MY testing is designed to cover the several load dump conditions not just internal regulator failure. Its your request that specific results be done properly and documented so others could repeat the test that has taken the time to get proper equipment setup and calibrated. Please read my reply to his post just sent to the group for further comments. While opening the "B" lead contactor can cause a "local load dump" that is not the primary load dump of concern in my opinion and in any case only one of several related design conditions related to load dump and its mitigation. Paul ----- Original Message ----- From: "Robert L. Nuckolls, III" <bob.nuckolls(at)cox.net> Subject: Re: AeroElectric-List: Re: LOAD DUMP > > > > >Paul > > > >I appreciate the efforts you are doing to investigate and resolve this Load > >Dump anomaly. > > > >I have more than a passing interest, as I am using this combination of an > >Alternator with > >Internal V.R. and Bob's O.V. Module. > > > >When the O.V Disconnect ("B" lead) Contactor opens, I can understand the > >transient current pulse caused > > by the now open circuit on the Alternator side, but I fail to see, how > >this could cause an O.V. spike on the > >bus side, which is now isolated from the Alternator in the Load Dump scenario. > > It doesn't. The issue came to light when a number of folks > having alternators wired per figure Z-24 cycled them OFF and ON > when the engine was running and the alternator was probably carrying > moderate to high loads. The resulting load dump transient was > confined to the alternator side of the alternator disconnect contactor > and only the alternator's internal voltage regulator was damaged. > > > >Why doesn't the bus voltage just drop to the Main Batt level or in the case > >of the pilot mistakenly > >opening the BATT Contactor, drop to zero? > > > >Isn't the very condition which causes the transient current pulse, (the > >Open "B" lead Contactor) , > >the result of the busses/batt no longer being connected to the Alternator? > > > >What am I missing here? > > Not a thing. > > Bob . . . > > ________________________________________________________________________________
From: "Paul Messinger" <paulm(at)olypen.com>
Subject: Re: LOAD DUMP
Date: May 10, 2004
Yes you are missing something, at least in the general case. The time it takes for the "B" lead contactor to open is long enough to pass some or all of the load dump pulse to the rest of the circuit. Depending on the equipment and its load at the time the load dump pulse has the potential to raise the bus voltage to very values and exceed the rating of some equipment. Alternator damage is also a consideration. Internal and external regulators are different cases with different time constants with regard to load dump effects. The OVP's location and physical wiring resistances etc all are part of the circuit. Then there is the blowing of the CB. After the CB blows the contactor (in the case of internal regulator alternators) takes time to open and the load dump is still in process or can be. Thus we are concerned about the time between the start of the load dump and the time the "B" lead contactor opens in your case. Also consider in your case that OVP trip from OV normally is due to the failure of the internal regulator so the regulator is already failed. The purpose of my (and my associate) test/investigation is to determine what one or more typical cases really look like as to the various time durations and currents with various load dumping currents from 10 to 40 amps. That is, the sudden loss of the battery as a load capacitor when the alternator is generating current. I am doing the physical testing and my partner is providing technical analysis support as well as design analysis. Its sure not clear to me (us) that the effect of the OVP circuit time constant VS the start of the load dump and the "B" lead contactor time to open results currently unknown amounts of energy past and into the main acft buss. I maintain there are two concerns here. One is damage to avionics due to overvoltage; the other is damage to the alternator. Then there are internal and external regulated alternators with associated OVP circuit designs. Thus several different tests are needed to verify just what is needed and how much energy must be safely dissipated. Some of the group have equipment that is specified to have 20V max input voltage and under 30v max is common. There is a lot of equipment NOT meeting DO-160 and I want to design a protective circuit that protects it. Limiting the electrical system design so that only equipment designed to DO-160 may be nice in theory but in the real world foolish and far too restrictive to many in the group. In addition I have interspersed comments below. > > When the O.V Disconnect ("B" lead) Contactor opens, I can understand the > transient current pulse caused > by the now open circuit on the Alternator side, but I fail to see, how > this could cause an O.V. spike on the > bus side, which is now isolated from the Alternator in the Load Dump scenario. > > Why doesn't the bus voltage just drop to the Main Batt level or in the case > of the pilot mistakenly > opening the BATT Contactor, drop to zero? The load dump starts when the battery is disconnected and that is a long time before the "B" lead (in your case) actually opens compared to the pulse length. When you remove the battery and the alternator is generating battery charging current that current MUST go somewhere. It raises the Bus voltage and potentially can trip the OVP circuit which blows the circuit breaker and allows the "B" lead contactor to open. This is not zero time and while this is happening the acft bus can reach high voltages depending on many factors. > > Isn't the very condition which causes the transient current pulse, (the > Open "B" lead Contactor) , > the result of the busses/batt no longer being connected to the Alternator? The cause of the initial load dump is NOT the opening of the "B" lead contactor but the loss of the battery as a "load leveler". Sure the "B" lead contactor will cause a local to the alternator load dump and that is a different but important concern. We do not want failure propagation in out design. Pilot caused failure in opening the battery when the alternator is in operation or failure of the OVP to cause alternator damage. To me there needed to be a study of the entire load dump issue not just protecting internal regulated alternators from damage from the actions of the OVP circuit. Paul > > What am I missing here? > > Wally Enga > RV7 ________________________________________________________________________________
From: "Tom Roberts" <tom.roberts(at)pioneermachinery.com>
Subject: Re: AeroElectric-List Digest: 11 Msgs - 05/09/04
Date: May 10, 2004
Please unsubscribe me. ----- Original Message ----- From: "AeroElectric-List Digest Server" Subject: AeroElectric-List Digest: 11 Msgs - 05/09/04 > * > > ================================================== > Online Versions of Today's List Digest Archive > ================================================== > > Today's complete AeroElectric-List Digest can be also be found in either > of the two Web Links listed below. The .html file includes the Digest > formatted in HTML for viewing with a web browser and features Hyperlinked > Indexes and Message Navigation. The .txt file includes the plain ASCII > version of the AeroElectric-List Digest and can be viewed with a generic > text editor such as Notepad or with a web browser. > > HTML Version: > > http://www.matronics.com/digest/aeroelectric-list/Digest.AeroElectric-List.2004-05-09.html > > Text Version: > > http://www.matronics.com/digest/aeroelectric-list/Digest.AeroElectric-List.2004-05-09.txt > > > ================================================ > EMail Version of Today's List Digest Archive > ================================================ > > > AeroElectric-List Digest Archive > --- > Total Messages Posted Sun 05/09/04: 11 > > > Today's Message Index: > ---------------------- > > 1. 12:21 AM - Battery Dump (Bob Lee) > 2. 06:22 AM - Re: LOAD DUMP (Paul Messinger) > 3. 08:35 AM - BNC Connector (Gerry Clabots) > 4. 09:32 AM - Re: BNC Connector (Richard E. Tasker) > 5. 12:23 PM - RF breakthrough on Vans gauges (Richard Garforth) > 6. 12:41 PM - Re: Re: LOAD DUMP (Wallace Enga) > 7. 05:00 PM - Smoke in wires. (Rob W M Shipley) > 8. 05:00 PM - Re: BNC Connector (Robert L. Nuckolls, III) > 9. 05:03 PM - Re: Re: LOAD DUMP (Robert L. Nuckolls, III) > 10. 05:28 PM - RF interference to Vans gauges (Robert L. Nuckolls, III) > 11. 06:56 PM - Re: BNC Connector (HCRV6(at)aol.com) > > > ________________________________ Message 1 _____________________________________ > > > From: "Bob Lee" <bob(at)flyboybob.com> > Subject: AeroElectric-List: Battery Dump > > > Bob, > > I just checked the FAQ on Aeroelectric.com and did not find any update on > the Battery dumping subject that went around a while back. Did I miss your > reply or has the testing not been completed? I understood that you had > several ideas that you were planning to test that would provide an > inexpensive solution to this risk but then the subject went quiet. > > Regards, > > Bob Lee > mailto:bob(at)flyboybob.com > > > ________________________________ Message 2 _____________________________________ > > > From: "Paul Messinger" <paulm(at)olypen.com> > Subject: AeroElectric-List: Re: LOAD DUMP > > > Testing has been delayed and I have posted several updates on this; the > latest not long ago. > > Other more important (to me) Tasks have kept me off this project. Plus I am > still waiting for calibration on one piece of test equipment (being done > free in spare time so its taking much longer to do, however its a 40-80 man > hour cal so its not trivial to get done free). > > Yes we have a couple of solutions that appear on paper to completely solve > any Load dump issues. However to prove to Bob (and others) the solution > works, requires a high power setup with somewhat unusual instrumentation (at > least for me). I am not setup for switching and loading 50 amps at 20 to 80 > volts so that has taken some time to get parts for and setup such power > testing and associated instrumentation and get it calibrated so the results > are meaningful and design margins can be determined. > > My aircraft already has one solution implimentated (actually done several > years ago) based on reading extensive industry info on the subject. Thus the > planned testing is not something I need for my own design. > > In the automotive design, damaging Load Dump's only can occur when there is > a failure as the battery is hard wired to the alternator "B" lead. There is > a small load dump when you turn off your headlights but the battery absorbs > the dump transient current pulse and keeps the voltage under normal levels. > > The issue in aircraft is different where the battery can be disconnected > when the alternator is providing power. This can be either a design where > its a simple switch function (pilot error :-) ) or the battery contactor > failing open. Also if the OVP is used to open the "B" lead with an > internally regulated alternator any opening of the "B" lead during > alternator operation can overvoltage the alternator regulator and if that > regulator/alternator is not designed to survive load dumps it/they will > fail. The current continues for a very short time and the voltages rises > until some load path dissipates the current. The voltage rises as needed to > provide this load path and voltages can rise to very high levels. The way a > IGN coil produces the spark is similar where the primary coil voltage rises > from 12V to 350-400V where it is clamped if the spark plug has not fired and > dumped the load into the spark. > > This MAY be the reason for the "reported" failures of the rebuilt ND > alternators being sold by Vans for the RV market. I do not know of ANY proof > of this however, that is "Vans alternators are inferior" to any other source > as has been suggested by some on this list. > > Testing is more complex than it might seem however to be sure the solution > has proper design margin. > > Consider that the industry has a simple product that is specifically > designed for this issue and one poster said that product failed for him (I > have an equivalent part and will be trying it also, however its clamping > voltage is higher than aircraft avionics can tolerate). Thus the need for > careful testing of a somewhat complex issue of transient energy etc. > > Hopefully the testing will not damage the regulators in my test alternators > as I do not have a limitless supply. > > Regardless its not possible to test all possible alternators and regulator > combinations so any solution must have a somewhat large design margin which > is hard to determine when the alternator/regulator(s) I have to test are not > necessarily worst case etc. For example I do not have any ND alternators nor > any of Bob's regulators to test. The peak current capability of the > alternator as well as the response time of the regulator are major factors. > > I have never called it anything but Load dump as that has been the industry > term for decades. Bob, as I recall, did want to rename it (do not recall > that name) so looking for anything but Load dump will not flag any note from > me. > > Regardless the testing will not be exhaustive and no warrenty it will result > in a 100% solution for everyone. The best design solution is one where its > not possible to switch into a load dump condition with pilot errors. > > Thus our solution is not to try to protect the alternator/regulator but the > avionics etc on the acft by clamping the spike to levels the avionics can > survive. The OVP circuit will NOT protect from load dump as shutting off the > regulator is too late. Opening the "B" lead contactor is not a solution > either as the contactor takes a long time to open compared to the load dump > pulse. > > Paul > > > ----- Original Message ----- > From: "Bob Lee" <bob(at)flyboybob.com> > Subject: AeroElectric-List: Battery Dump > > > > > > Bob, > > > > I just checked the FAQ on Aeroelectric.com and did not find any update on > > the Battery dumping subject that went around a while back. Did I miss > your > > reply or has the testing not been completed? I understood that you had > > several ideas that you were planning to test that would provide an > > inexpensive solution to this risk but then the subject went quiet. > > > > Regards, > > > > Bob Lee > > mailto:bob(at)flyboybob.com > > > > > > > ________________________________ Message 3 _____________________________________ > > > From: "Gerry Clabots" <gclabots(at)execpc.com> > Subject: AeroElectric-List: BNC Connector > > > Does someone have a part number and a source for a 90 degree BNC connector that > I could use where I connect the coax to the antenna.I will be mounting the antenna > under the baggage compartment floor. > Thanks > Gerry 7A 70188 > > > ________________________________ Message 4 _____________________________________ > > > From: "Richard E. Tasker" <retasker(at)optonline.net> > Subject: Re: AeroElectric-List: BNC Connector > > > I don't have a part number, but unless you just do not have the room, > you would be better off (financially and signal strength) to use a > regular straight connector and bend the cable. > > Dick Tasker > > Gerry Clabots wrote: > > > > >Does someone have a part number and a source for a 90 degree BNC connector that > I could use where I connect the coax to the antenna.I will be mounting the antenna > under the baggage compartment floor. > >Thanks > >Gerry 7A 70188 > > > > > > > ________________________________ Message 5 _____________________________________ > > > From: "Richard Garforth" <richard(at)hawk.flyer.co.uk> > Subject: AeroElectric-List: RF breakthrough on Vans gauges > > > Brian & Jim, > > Thanks for the suggestions. > > Taking the easiest first both antennas are already cabled in RG400 - thanks Jim. > > I explored the situation further today and found that a handheld ICOM xmitter produced > the same result - this confirmed it is RF breaking into the gauge or the > wiring and not some strange earthing issue. I next removed the gauge and MAP > sensor and cable from the aircraft and set up a simple bench test. This showed > that the RF is getting into the circuit board in the gauge (even through the > glass front). I stripped the gauge down and found there is no HF decoupling > to be seen. Also it seems the moving coil meter is centre wound ( 3 terminals) > and works on a differential output from the driver chip. The MAP sensor appears > to be a 4 arm bridge sensor with a built in regulator. I finished up fitting > five 10nF disc caps (thanks Brian) on the meter circuit board. > One across each meter coil, one across the two signal arms of the bridge input > and one from each signal input to ground. Immediately the interference was reduced > considerably. Final fix was to take the MAP sensor out of its plastic box > and fit it directly to the rear of the meter and fit ferrite beads to the two > signal leads and the power input. > The end result is a gauge that only moves a needle width with the ICOM xmitter > ant held against the meter front. > My guess is that the Vans gauge that gives similar problems, the ammeter, being > centre zero has a similar internal configuration and may respond to a similar > fix. As I am a committed Voltmeter believer I can only speculate. > > > Richard(G-RVIX) > > > ________________________________ Message 6 _____________________________________ > > > From: Wallace Enga <wenga(at)svtv.com> > Subject: Re: AeroElectric-List: Re: LOAD DUMP > > > Paul > > I appreciate the efforts you are doing to investigate and resolve this Load > Dump anomaly. > > I have more than a passing interest, as I am using this combination of an > Alternator with > Internal V.R. and Bob's O.V. Module. > > When the O.V Disconnect ("B" lead) Contactor opens, I can understand the > transient current pulse caused > by the now open circuit on the Alternator side, but I fail to see, how > this could cause an O.V. spike on the > bus side, which is now isolated from the Alternator in the Load Dump scenario. > > Why doesn't the bus voltage just drop to the Main Batt level or in the case > of the pilot mistakenly > opening the BATT Contactor, drop to zero? > > Isn't the very condition which causes the transient current pulse, (the > Open "B" lead Contactor) , > the result of the busses/batt no longer being connected to the Alternator? > > What am I missing here? > > Wally Enga > RV7 > > > ________________________________ Message 7 _____________________________________ > > > From: "Rob W M Shipley" <rob(at)robsglass.com> > Subject: AeroElectric-List: Smoke in wires. > > > I received this in my mail the other day and felt that it might contribute much > to the erudite discussions we enjoy so much in this list. As an English ex-pat > I am intimately aware of the excellence of Lucas products and their contribution > to reliability of the fine automobiles made in the British Isles. > > > << "A Treatise on the Importance of Smoke" by Joseph Lucas > > All electrical components and wiring harnesses depend on proper > > circuit functioning, which is the transmission of charged ions by > > retention of the visible spectral manifestation known as "smoke". > > Smoke is the thing that makes electrical circuits work. Don't be > > fooled by scientists and engineers talking about excited electrons > > and the like. Smoke is the key to all things electrical. > > > > We know this to be true because every time one lets the smoke out of > > an electrical circuit, it stops working. This can be verified > > repeatedly through empirical testing. For example, if one places a > > large copper bar across the terminals of a battery, prodigious > > quantities of smoke are liberated and the battery shortly ceases to > > function. In addition, if one observes smoke escaping from an > > electrical component such as a Lucas voltage regulator, it will also > > be observed that the component no longer functions. > > > > The logic is elementary and inescapable! The function of the wiring > > harness is to conduct the smoke from one device to another. When the > > wiring harness springs a leak and lets all the smoke out of the > > system, nothing works right afterward. > > > > Starter motors were considered unsuitable for British motorcycles for > > some time largely because they regularly released large quantities of > > smoke from the electrical system. > > > > It has been reported that Lucas electrical components are possibly > > more prone to electrical leakage than their Bosch, Japanese or > > American counterparts. Experts point out that this is because Lucas > > is British, and all things British leak. British engines leak oil, > > British shock absorbers, hydraulic forks, and disk brake systems leak > > fluid, British tires leak air and British Intelligence leaks national > > defense secrets. > > > > Therefore, it follows that British electrical systems must leak > > smoke. Once again, the logic is clear and inescapable. > > > > Sometimes you may miss the component releasing the smoke that makes > > your electrical system function correctly, but if you sniff around > > you can often find the faulty component by the undeniable and > > telltale smoke smell. Sometimes this is a better indicator than > > standard electrical tests performed with a volt-ohm meter. > > > > In conclusion, the basic concept of transmission of electrical energy > > in the form of smoke provides a clear and logical explanation of the > > mysteries of electrical components and why they fail. > > > > "A gentleman does not motor about after dark." > > - Joeseph Lucas, 1842 - 1903 > > I learned a long time ago that once you let the "Factory Smoke" out of any electrical > device, it is next to impossible to replenish it. > > > ________________________________ Message 8 _____________________________________ > > > From: "Robert L. Nuckolls, III" <bob.nuckolls(at)cox.net> > Subject: Re: AeroElectric-List: BNC Connector > > > > > > > >I don't have a part number, but unless you just do not have the room, > >you would be better off (financially and signal strength) to use a > >regular straight connector and bend the cable. > > > >Dick Tasker > > > >Gerry Clabots wrote: > > > > > > > > > >Does someone have a part number and a source for a 90 degree BNC > > connector that I could use where I connect the coax to the antenna.I will > > be mounting the antenna under the baggage compartment floor. > > >Thanks > > >Gerry 7A 70188 > > Right angle connectors do exist . . . but are comparatively > expensive and not in everybody's catalog. Here's a new article > on a low cost but rugged alternative to a one-piece, solderless > right-angle connector. > > http://www.aeroelectric.com/articles/BNC_Rt_Angle/BNC_Rt_Angle.html > > Bob . . . > > ----------------------------------------- > ( Experience and common sense cannot be ) > ( replaced with policy and procedures. ) > ( R. L. Nuckolls III ) > ----------------------------------------- > > > ________________________________ Message 9 _____________________________________ > > > From: "Robert L. Nuckolls, III" <bob.nuckolls(at)cox.net> > Subject: Re: AeroElectric-List: Re: LOAD DUMP > > > > > >Paul > > > >I appreciate the efforts you are doing to investigate and resolve this Load > >Dump anomaly. > > > >I have more than a passing interest, as I am using this combination of an > >Alternator with > >Internal V.R. and Bob's O.V. Module. > > > >When the O.V Disconnect ("B" lead) Contactor opens, I can understand the > >transient current pulse caused > > by the now open circuit on the Alternator side, but I fail to see, how > >this could cause an O.V. spike on the > >bus side, which is now isolated from the Alternator in the Load Dump scenario. > > It doesn't. The issue came to light when a number of folks > having alternators wired per figure Z-24 cycled them OFF and ON > when the engine was running and the alternator was probably carrying > moderate to high loads. The resulting load dump transient was > confined to the alternator side of the alternator disconnect contactor > and only the alternator's internal voltage regulator was damaged. > > > >Why doesn't the bus voltage just drop to the Main Batt level or in the case > >of the pilot mistakenly > >opening the BATT Contactor, drop to zero? > > > >Isn't the very condition which causes the transient current pulse, (the > >Open "B" lead Contactor) , > >the result of the busses/batt no longer being connected to the Alternator? > > > >What am I missing here? > > Not a thing. > > Bob . . . > > > ----------------------------------------- > ( Experience and common sense cannot be ) > ( replaced with policy and procedures. ) > ( R. L. Nuckolls III ) > ----------------------------------------- > > > ________________________________ Message 10 ____________________________________ > > > From: "Robert L. Nuckolls, III" <bob.nuckolls(at)cox.net> > Subject: AeroElectric-List: RF interference to Vans gauges > > > > > > > > > > > > > > Seen some old postings regarding this issue - Has anyone > > > found a fix yet? My MAP gauge goes full scale using a top > > > antenna but only part full scale using an underside antenna. > > > > > > Richard G-RVIX(RV9A) > > > >Richard, the fix is to not look at it while transmitting:>) > > That's one alternative. This is a down-side of some > hardware supplied to the OBAM aircraft community. Some > products are brought to the marketplace by folks who > either don't understand the value of making products > perform equal to or better than "certified" stuff -OR- > they don't understand the environment in which they > are working. > > There is no excuse for not having fixed this > problem by now. I've been hearing about it off-and-on > for at least a year. As consumers you have several > choices: (1) return the hardware for refund as > "not suited to the intended task", (2) work out > and implement fixes at your own time and expense, > (3) work with the original manufacturer to see if > he/she is willing to upgrade your purchase to operate > in the real world or (4) just live with it. It > doesn't hurt anything as long as you understand > the condition and can believe the instrument all > times other than transmitting. > > As always, if anyone does put the wrenches to the > manufacturer, tell them I'll offer suggestions for > modifying their design . . . perhaps even at no > cost. But since I don't own any of this stuff, > it's up to those to do own it to be responsible > consumers and squeeze these folks into useful > action. > > There's an old adage that suggests "If > you continue to do as you've always done, > you will continue to be as you've always been." > > A corollary to this adage says, "Until you convince > a supplier that their product has unsatisfactory > design flaws and insist on responsible adjustments, > they'll continue selling it warts and all to your > fellow builders . . . and your's won't get fixed either. > > Bob . . . > > ----------------------------------------- > ( Experience and common sense cannot be ) > ( replaced with policy and procedures. ) > ( R. L. Nuckolls III ) > ----------------------------------------- > > > ________________________________ Message 11 ____________________________________ > > > From: HCRV6(at)aol.com > Subject: Re: AeroElectric-List: BNC Connector > > > In a message dated 5/9/04 8:36:50 AM Pacific Daylight Time, > gclabots(at)execpc.com writes: > > << Does someone have a part number and a source for a 90 degree BNC connector > that I could use where I connect the coax to the antenna. I will be mounting > the antenna under the baggage compartment floor. >> > > I used a 90 degree BNC adapter from Radio Shack for the same installation, > hope it works. > > Harry Crosby > Pleasanton, California > RV-6, final assembly > > ________________________________________________________________________________
Date: May 10, 2004
From: Mark Steitle <msteitle(at)mail.utexas.edu>
Subject: ZAP-STOP Alternator Protector
I was searching the web this morning and ran across an item that claims to address the voltage spike problem on boats. When it comes to voltage spikes, it seems that boats have the same potential risk as airplanes. I'll be the first to acknowledge that I'm out of my element here, but thought that Bob, or someone else, may know something about this item. Here is the quote from their website... It happens - someone turns the battery switch to "OFF" while the engine is still running. Even momentarily turning the battery switch to "OFF" can damage the alternator diodes leaving you without a way to charge your battery. Either the e-Marine Alternator Protector or the Zap-Stop will work to prevent that damage to the diodes. The installation is very simple - just connect the red wire with fuse to the alternator positive and the black wire to alternator ground. It is cheap insurance. e-Marine Alternator Protector or ZAP-STOPAlong with the integral 20 amp slow-blow fuse, e-Marine Alternator Protector or ZAP-STOP is an ingenious device that suppresses high voltage transients by conducting them to ground if they rise to unsafe levels. e-Marine Alternator Protector or ZAP-STOP helps protect alternators and electronics from damage when the battery switch is momentarily turned "OFF" while the engine is running. Their URL is http://www.e-marine-inc.com/products/alternators/zapstop.html Mark S. ________________________________________________________________________________
Date: May 10, 2004
From: Wallace Enga <wenga(at)svtv.com>
Subject: Re: LOAD DUMP
Bob, Paul thanks for the info. I really do appreciate the time you guys spend trying to educate us on these elusive electrons. I may have a situation which is somewhat easier to protect, then the norm. It has two Odyssey PC 680 16 AH batteries. The MAIN Batt is connected via the normal BATT Contactor. The AUX Batt is hard wired via a large Schottky Isolation Diode to the BUS Side of the "B Lead" Disconnect Contactor and also feeds an always Hot AUX Bus. So it is not possible to have both batteries disconnected from the "B Lead" Contactor in this case. I think my biggest concern is protecting the Internal V.R. after mistakenly turning OFF the Master SW with the ALT under a load. Would a large TVS like the 24V LPD24A that was discussed here a few months back, usually save the V.R. in that situation? Wally Enga RV7 ________________________________________________________________________________
Date: May 10, 2004
From: "Robert L. Nuckolls, III" <bob.nuckolls(at)cox.net>
Subject: Dark-n-Stormy Night Stories Redux
Micky Coggins brought this story to our attention last week. A number of folks responded. I've compiled the pertinent data points with some critical review at: http://www.aeroelectric.com/articles/neveragain/neveragain_2.html Bob . . . ----------------------------------------- ( Experience and common sense cannot be ) ( replaced with policy and procedures. ) ( R. L. Nuckolls III ) ----------------------------------------- ________________________________________________________________________________
From: "Paul Messinger" <paulm(at)olypen.com>
Date: May 10, 2004
Yes its a simple device, however some of us need specifics as well as just what the clamping voltage is. Generally speaking electronics designed for marine use is similar to automotive use that is they are very rugged, something that many experimental aircraft electronic items are not. A specific device designed for use in alternator load dump supression is available and has been for many many years. The problem is its max clamping voltags is well above what we are looking for to protect all likely components in an experimental aircraft. Also I assume the 20 amp fuse is there to cover a load dump case where the internal regulator has not failed so the alternator current will not be clamped as long as the voltage is reasonable. Something designed only to protect the alternator during a load dump is a sub set of what I am looking into. The above part not counting the CB is available for under $2 at the on level and around $0.40 at the 100 level. Perhaps part of the overall solution for us but not a universal solution even in a non failed case. Paul ----- Original Message -----
From: "Mark Steitle" <msteitle(at)mail.utexas.edu>
Subject: AeroElectric-List: ZAP-STOP Alternator Protector 0.1 > > I was searching the web this morning and ran across an item that claims to > address the voltage spike problem on boats. When it comes to voltage > spikes, it seems that boats have the same potential risk as > airplanes. I'll be the first to acknowledge that I'm out of my element > here, but thought that Bob, or someone else, may know something about this > item. Here is the quote from their website... > > > It happens - someone turns the battery switch to "OFF" while the engine is > still running. > Even momentarily turning the battery switch to "OFF" can damage the > alternator diodes leaving you without a way to charge your battery. Either > the e-Marine Alternator Protector or the Zap-Stop will work to prevent that > damage to the diodes. The installation is very simple - just connect the > red wire with fuse to the alternator positive and the black wire to > alternator ground. It is cheap insurance. > > e-Marine Alternator Protector or ZAP-STOPAlong with the integral 20 amp > slow-blow fuse, e-Marine Alternator Protector or ZAP-STOP is an ingenious > device that suppresses high voltage transients by conducting them to ground > if they rise to unsafe levels. e-Marine Alternator Protector or ZAP-STOP > helps protect alternators and electronics from damage when the battery > switch is momentarily turned "OFF" while the engine is running. > > > Their URL is http://www.e-marine-inc.com/products/alternators/zapstop.html > > Mark S. > > ________________________________________________________________________________
From: "Eric M. Jones" <emjones(at)charter.net>
Subject: Re: Zap Stop
Date: May 10, 2004
The basis of the Zap-Stop is supposedly a Motorola MR2535L Zener diode. This is not a bad way to go, Zeners DO have Vz temperature dependence and, being avalanche devices are not as fast as one might like, but they are pretty good. The manufacturer has a nice website with interesting products: www.xantrex.com/ Regards, Eric M. Jones www.PerihelionDesign.com 113 Brentwood Drive Southbridge MA 01550-2705 Phone (508) 764-2072 Email: emjones(at)charter.net Teamwork: " A lot of people doing exactly what I say." (Marketing exec., Citrix Corp.) ________________________________________________________________________________
Date: May 10, 2004
From: Brian Lloyd <brianl(at)lloyd.com>
Subject: Re: Dark-n-Stormy Night Stories Redux
Robert L. Nuckolls, III wrote: > > Micky Coggins brought this story to our attention last week. A number > of folks responded. I've compiled the pertinent data points with > some critical review at: > > http://www.aeroelectric.com/articles/neveragain/neveragain_2.html A couple more comments on the the Aztec systems. 1. Landing gear and flaps are powered by a hydraulic pump on the left engine (of course one would put the hydraulic pump on the critical engine, right?) so it is possible to raise and lower the gear with a total electrical failure. Backup is provided by a hand-operated hydraulic pump. 2. "Essential" buss vs. "endurance" buss: seems I got the former phrase from you at some point in the dim, dark recesses of the past. When I implemented such a thing in my Comanche 20 years ago I just called it my backup power source. The EB was actually the "avionics buss" to which I cheated and connected my they-must-always-work devices. I can't help it if you change your mind as to the name. ;-) 3. And when the writer of the story talked about "increased drain" I suspect he may have been referring to increased load since a loadmeter cannot show anything but load, e.g. it is either zero or "something" and only "something" can be increased. So I took this to mean that during the run-up, one of the alternators was carrying all the load, which indicates that the other was doing nothing. Since there is a tendency for one alternator to hog the load anyway, the loss of one alternator prior to take-off may have been interpreted as "only slightly abnormal". But I grasp at straws. I wasn't there and from reading the story I can only say that the author was a piss-poor observer. 4. "Instruments and breakers are poor warning devices." I agree. I was not suggesting that meters and/or breakers are good warning devices, I was suggesting that, compared to latching type over-voltage relays, the popped breaker in the crowbar OVP system is a positive indication that the OVP system has activated. With an OVP latching relay you have no indication. I agree that there is no substitute for a positive low-voltage annunciator. BTW, one should be immediately wary when someone else in the cockpit utters the words, "why is it doing that," or, "I've never seen it do that before." -- Brian Lloyd 6501 Red Hook Plaza brianl(at)lloyd.com Suite 201 http://www.lloyd.com St. Thomas, VI 00802 +1.340.998.9447 (voice) +1.360.838.9669 (fax) There is a time to laud one's country and a time to protest. A good citizen is prepared to do either as the need arises. ________________________________________________________________________________
Date: May 10, 2004
Subject: two things
From: royt.or(at)netzero.net
Country Classic person: Sally Cutter (503) 682-2678 Get file folders. ________________________________________________________________________________
From: "Paul Messinger" <paulm(at)olypen.com>
Subject: Re: Zap Stop
Date: May 10, 2004
Zeners are as much as 10,000 times slower than transorbs and typically designed for longer duration, lower peak currents than transorbs. Thankd for the detailed link however. Paul ----- Original Message ----- From: "Eric M. Jones" <emjones(at)charter.net> Subject: AeroElectric-List: Re: Zap Stop > > > > The basis of the Zap-Stop is supposedly a Motorola MR2535L Zener diode. > > This is not a bad way to go, Zeners DO have Vz temperature dependence and, > being avalanche devices are not as fast as one might like, but they are > pretty good. > > The manufacturer has a nice website with interesting products: > www.xantrex.com/ > > Regards, > Eric M. Jones > www.PerihelionDesign.com > 113 Brentwood Drive > Southbridge MA 01550-2705 > Phone (508) 764-2072 > Email: emjones(at)charter.net > > Teamwork: " A lot of people doing exactly what I say." > (Marketing exec., Citrix Corp.) > > ________________________________________________________________________________
Date: May 10, 2004
From: Dj Merrill <deej(at)thayer.dartmouth.edu>
Subject: Re: AeroElectric-List Digest: 11 Msgs - 05/09/04
Tom Roberts wrote: > > Please unsubscribe me. Hi Tom, Point your web broswer at: http://www.matronics.com/subscription to unsubscribe yourself from the mailing lists. fyi -Dj ________________________________________________________________________________
From: "Paul Messinger" <paulm(at)olypen.com>
Subject: Re: LOAD DUMP
Date: May 10, 2004
> I cannot get into recommending a specific device at this time as this would > require significant time to research any suggested part and then make an > educated guess. > > I want to concentrate on defining the electrical load dump pulse first and > then look for solutions with lots of design margin. > > Testing starting this week. (assumming no more unplanned 'emergencies") > > Paul > > As the monkey said after backing into the lawn mower "It will not be long > now" > > > ----- Original Message ----- > From: "Wallace Enga" <wenga(at)svtv.com> > To: > Sent: Monday, May 10, 2004 9:09 AM > Subject: Re: AeroElectric-List: Re: LOAD DUMP > > > > > > > > Bob, Paul thanks for the info. I really do appreciate the time you guys > > spend trying to educate us on these elusive electrons. > > > > I may have a situation which is somewhat easier to protect, then the norm. > > It has two Odyssey PC 680 16 AH batteries. > > > > The MAIN Batt is connected via the normal BATT Contactor. > > > > The AUX Batt is hard wired via a large Schottky Isolation Diode > > to the BUS Side of the "B Lead" Disconnect Contactor and > > also feeds an always Hot AUX Bus. > > > > So it is not possible to have both batteries disconnected > > from the "B Lead" Contactor in this case. > > > > I think my biggest concern is protecting the Internal V.R. after > mistakenly > > turning OFF the Master SW with the ALT under a load. > > > > Would a large TVS like the 24V LPD24A that was discussed here > > a few months back, usually save the V.R. in that situation? > > > > Wally Enga > > RV7 > > > > > > > > > > > > > > > > > > > > > > > ________________________________________________________________________________
Date: May 11, 2004
From: "Robert L. Nuckolls, III" <bob.nuckolls(at)cox.net>
Subject: Re: LOAD DUMP
> >Yes you are missing something, at least in the general case. > >The time it takes for the "B" lead contactor to open is long enough to pass >some or all of the load dump pulse to the rest of the circuit. Depending on >the equipment and its load at the time the load dump pulse has the potential >to raise the bus voltage to very values and exceed the rating of some >equipment. Alternator damage is also a consideration. Internal and external >regulators are different cases with different time constants with regard to >load dump effects. > >The OVP's location and physical wiring resistances etc all are part of the >circuit. Then there is the blowing of the CB. After the CB blows the >contactor (in the case of internal regulator alternators) takes time to open >and the load dump is still in process or can be. > >Thus we are concerned about the time between the start of the load dump and >the time the "B" lead contactor opens in your case. Also consider in your >case that OVP trip from OV normally is due to the failure of the internal >regulator so the regulator is already failed. The overvoltage protection system was never intended to address the load dump scenario. This is true of both internal and externally regulated alternators. I don't understand how/why characteristics of the OV protection system figure into your study of load-dump mitigation. >The purpose of my (and my associate) test/investigation is to determine what >one or more typical cases really look like as to the various time durations >and currents with various load dumping currents from 10 to 40 amps. That is, >the sudden loss of the battery as a load capacitor when the alternator is >generating current. > >I am doing the physical testing and my partner is providing technical >analysis support as well as design analysis. > >Its sure not clear to me (us) that the effect of the OVP circuit time >constant VS the start of the load dump and the "B" lead contactor time to >open results currently unknown amounts of energy past and into the main acft >buss. > >I maintain there are two concerns here. One is damage to avionics due to >overvoltage; the other is damage to the alternator. > >Then there are internal and external regulated alternators with associated >OVP circuit designs. Thus several different tests are needed to verify just >what is needed and how much energy must be safely dissipated. > >Some of the group have equipment that is specified to have 20V max input >voltage and under 30v max is common. There is a lot of equipment NOT meeting >DO-160 and I want to design a protective circuit that protects it. Limiting >the electrical system design so that only equipment designed to DO-160 may >be nice in theory but in the real world foolish and far too restrictive to >many in the group. Absolute elephant hocky . . . I've been designing to DO-160 Input Voltage recommendations for over 30 years and they are neither foolish or restrictive to the competent designer. I just responded to a thread where folks are out looking for Band-Aids to paste on instruments that wander off into the weeds when comm transmitter is keyed. Is it "too restrictive" or "foolish" to expect these instruments function as advertised under all normal operations of the aircraft? DO-160 is not a "theory" but a minimum standard of performance based on easy-to-achieve, real-world performance that will help anyone provide good products and services to the aviation community . . . it matters not if it's a certified ship or an OBAM aircraft. Suppose I were to offer a new "avgas" for $1.00 a gallon. Would it be "foolish" or "restrictive" to expect that I show the product capable of 100 octane performance and had no characteristics that make it incompatible with everyone's engines? Shucks, there are bins of bolts in hardware stores that will hold pieces of my airplane together. Is it too "restrictive" or "foolish" to concern myself with compatibility of this hardware to the intended task? If it's not okay for fuel or wing bolts, why is it okay for transistors? I don't understand the special case for electrics wherein substandard performance is tolerated to the extent that a user must accommodate it with a super-clean electrical system. I don't know which "group" you're citing. The folks I work with are building the finest aircraft to have ever flown. I'll help Van's instrument house bootstrap their products into the real world if they're the least bit interested. If the manufacturer of a 20V limited device wants to play in the same sandbox with big boys, I'd be pleased to assist them too. However, adding shielded wire, ferrite beads, transorbs, or relocating antennas, etc, to mitigate supplier disinterest or incompetence does not fit my mission. I sincerely hope it's not a component of anyone else's mission here on the list. >In addition I have interspersed comments below. > > > > > > When the O.V Disconnect ("B" lead) Contactor opens, I can understand the > > transient current pulse caused > > by the now open circuit on the Alternator side, but I fail to see, how > > this could cause an O.V. spike on the > > bus side, which is now isolated from the Alternator in the Load Dump >scenario. > > > > Why doesn't the bus voltage just drop to the Main Batt level or in the >case > > of the pilot mistakenly > > opening the BATT Contactor, drop to zero? > >The load dump starts when the battery is disconnected and that is a long >time before the "B" lead (in your case) actually opens compared to the pulse >length. > >When you remove the battery and the alternator is generating battery >charging current that current MUST go somewhere. It raises the Bus voltage >and potentially can trip the OVP circuit which blows the circuit breaker and >allows the "B" lead contactor to open. This is not zero time and while this >is happening the acft bus can reach high voltages depending on many factors. . . . the most significant factor being that OV protection is not designed for load dump mitigation. The output current transient shown in data cited below says to expect peak alternator output current about 15 milliseconds after initiation of the load dump . . . this simply cannot be fielded by hardware designed to protect the system from a failed regulator. > > > > Isn't the very condition which causes the transient current pulse, (the > > Open "B" lead Contactor) , > > the result of the busses/batt no longer being connected to the Alternator? > >The cause of the initial load dump is NOT the opening of the "B" lead >contactor but the loss of the battery as a "load leveler". Sure the "B" lead >contactor will cause a local to the alternator load dump and that is a >different but important concern. We do not want failure propagation in out >design. Pilot caused failure in opening the battery when the alternator is >in operation or failure of the OVP to cause alternator damage. > >To me there needed to be a study of the entire load dump issue not just >protecting internal regulated alternators from damage from the actions of >the OVP circuit. If you can accommodate a full load shutdown event of Figure Z-24 then you can accommodate a load dump of any other variety as well. In response to Eric's comments about the Zap-Stop, the MR2535L device by ON Semiconductor (was Motorola) is not a zener but a true transient suppressor. You can see the data sheet at: http://www.aeroelectric.com/Mfgr_Data/MR2535L-D.pdf Figure 13 is of particular interest. If I interpret this correctly, the exemplar load dump scenario has a time constant of 100 mS. Peak current to be expected will be alternator rated current plus perhaps a 20% safety factor for cold conditions. The data table says worst case Vbr is 40v at 150 degrees C and 90 amps. Sounds like this gizmo was made with DO-160 in mind and would work fine with alternators rated up to 60A or so. The 40 V absolute limit would also accommodate all the built-in regulator chips for which I've seen data. There are a bunch of products in the 1500W peak power range that would substitute for the MR2535. If your repeatable experiment shows that an alternator's output current curve is indeed shaped like Figure 13 during the load-dump event, then sizing a clamp-off device for any voltage is pretty straight forward. However, to accommodate equipment limited to 20V max, you'll probably need an active clamp . . . perhaps a TL431 teamed with a honker P-channel power fet for a power voltage clamp with a corner on the conduction "knee" than the typical transient suppressor. A 20V clamp on a 60A machine would not have to grunt more than 70 joules or so . . . Bob . . . ________________________________________________________________________________
From: "Richard Sipp" <rsipp(at)earthlink.net>
Subject: Fw: Z-12 Main Alternator Control
Date: May 11, 2004
Bob: With respect to Z-12 (Single Battery, Dual Alternator) the main alternator appears to be controlled by the main battery master switch while the aux alternator has a separate on/off switch. Is there a reason for not having a separate main alternator switch as well? I plan on this system for the RV-10 I have under construction. The aircraft is designed with a battery location aft of the passenger compartment. With an aluminum airframe is the 4AWG ground cable to the instrument panel ground bus still the preferred grounding method? Many thanks. Dick Sipp RV10 #65 ________________________________________________________________________________
From: "Paul Messinger" <paulm(at)olypen.com>
Subject: Re: LOAD DUMP
Date: May 11, 2004
Snipped for size. > > > The overvoltage protection system was never intended to address > the load dump scenario. This is true of both internal and externally > regulated alternators. I don't understand how/why characteristics > of the OV protection system figure into your study of load-dump > mitigation. Because I am trying to define a system problem. During the start of the load dump the system bus voltage is expected to trip the OVP and thus its part of the circuit. The physical circuit resistances are important when considering the currents in the shorting elements IE the OVP and what ever is used for the load dump its self. This, along with wiring resistances are major players with a hi current surge that is not limited by the alternator ratings but the internal resistance of the alternator windings as well as the external wiring resistances. Also you state your OVP design ignored load dump but load dump is real and likely in many acft electrical designs where its possible to remove the battery from the system with the alternator in use. Surely any OVP design must address that condition if only to survive as well as provide protection. I agree the OVP is intended to protect from a failed hi voltage regulator but load dump is in effect the same condition but very short in duration. > >Some of the group have equipment that is specified to have 20V max input > >voltage and under 30v max is common. There is a lot of equipment NOT meeting > >DO-160 and I want to design a protective circuit that protects it. Limiting > >the electrical system design so that only equipment designed to DO-160 may > >be nice in theory but in the real world foolish and far too restrictive to > >many in the group. > > Absolute elephant hocky . . . > > I've been designing to DO-160 Input Voltage recommendations > for over 30 years and they are neither foolish or restrictive to the > competent designer. In the REAL work its not hockey, perhaps in the ideal world everyone builds to every aspect of DO-160 or even better, designs to the standards of the automotive world, but its simply not true for some equipment. I have some, and others on this list have, in the past, mentioned other equipment with restrictive voltage limits. Besides, after 40 years I can count on the fingers of one hand the truly competent engineers I have known (out of thousands working in dozens of companies). This based on personal contact and/or the review of subcontractor equipment from major players in the industry in some cases. > I just responded to a thread where folks are out looking > for Band-Aids to paste on instruments that wander > off into the weeds when comm transmitter is keyed. > Is it "too restrictive" or "foolish" to expect these > instruments function as advertised under all normal > operations of the aircraft? No, but in the real world its far too common a case. > Van's instrument house bootstrap their products into the real world > if they're the least bit interested. If the manufacturer of a > 20V limited device wants to play in the same sandbox with big boys, > I'd be pleased to assist them too. However, adding shielded > wire, ferrite beads, transorbs, or relocating antennas, etc, to > mitigate supplier disinterest or incompetence does > not fit my mission. I sincerely hope it's not a component > of anyone else's mission here on the list. SOME Members of THIS group are part of who I am addressing along with many who are unwilling to post directly. Some of us do not have the $$$$ to buy the BIG boys stuff. Not everyone is interested nor can afford a $100,000 acft. Vans is not a small boy and is likely an example of individuals wiring components that work in many cases well and do not work well in others simply based on how the wiring is done. Dynon went thru a year of testing and only after production started found some small number of customers had problems while most did not. Sure there is a radiated noise issue with Dynon (and they are providing a free fix) but after a year of field testing its clear its a problem unique to how the aircraft wiring is physically wired not simply a schematic that works any which way. I have discussed that problem with the chief designer at Dynon and there appears to be a simple wiring approach that is common to the cases of noise and another wiring approach that seems noise free. In any event a series filter fix is free and new production have better internal filtering. My point is there is no way to test all possible conditions. I suspect Van has had no problems with his instruments in aircraft he has wired at his factory. > > > >The load dump starts when the battery is disconnected and that is a long > >time before the "B" lead (in your case) actually opens compared to the pulse > >length. > > > >When you remove the battery and the alternator is generating battery > >charging current that current MUST go somewhere. It raises the Bus voltage > >and potentially can trip the OVP circuit which blows the circuit breaker and > >allows the "B" lead contactor to open. This is not zero time and while this > >is happening the acft bus can reach high voltages depending on many factors. > > > . . . the most significant factor being that OV protection is > not designed for load dump mitigation. The output current transient > shown in data cited below says to expect peak alternator output current > about 15 milliseconds after initiation of the load dump . . . this > simply cannot be fielded by hardware designed to protect the system > from a failed regulator. Astounding statement. You seem to be saying that your OVP design was not designed for and is not expected to survive a load dump, yet we know that load dumps are generated when the alternator load is suddenly reduced. With a battery still connected as in the case of say landing lights being turned off, the battery clamps the load dump. If however, the battery is disconnected when under heavy charge the rest of the system bus must absorb the load dump and its likely the OVP circuit will trip. Thus a system analysis is necessary and all components in the system must be evaluated. > > http://www.aeroelectric.com/Mfgr_Data/MR2535L-D.pdf > > Figure 13 is of particular interest. If I interpret this correctly, > the exemplar load dump scenario has a time constant of 100 mS. > Peak current to be expected will be alternator rated current plus > perhaps a 20% safety factor for cold conditions. The data table > says worst case Vbr is 40v at 150 degrees C and 90 amps. Sounds > like this gizmo was made with DO-160 in mind and would work fine > with alternators rated up to 60A or so. The 40 V absolute limit > would also accommodate all the built-in regulator chips for which > I've seen data. > > There are a bunch of products in the 1500W peak power range > that would substitute for the MR2535. I find the referenced data sheet and Fig 13 specifically of interest in that is so very different from other load dump Mfgrs data test conditions. Dumping a 50 mfd cap here is compared to dumping 150,000 mfd in another case. Who to believe? Well I tend to believe the latter as it comes from a company who has TVS devices as a primary line and is not simply a second source. Remember data sheets are designed to sell product and are typically written by brand new engineers fresh from school.What's not there is more important than what is there in many cases. Regardless I see the need for actual load dump characterization from actual alternators and then consider simulation with a RC circuit for test ease. I have yet to find a data sheet where the RC circuit components are derived from a real alternator to justify the RC value selection. There is no way to determine the relevance of fig 13 to our real world. As for 1.5KW devices this is simply far too small for our needs. 40 V is far too high for me. 5KW devices were suggested months ago and a list member noted they failed for him. (The 5kw device would seem to be an overkill from the data sheet but?? thus the need for system testing). > If your repeatable experiment shows that an alternator's output > current curve is indeed shaped like Figure 13 during the load-dump > event, then sizing a clamp-off device for any voltage is > pretty straight forward. However, to accommodate equipment limited > to 20V max, you'll probably need an active clamp . . . perhaps > a TL431 teamed with a honker P-channel power fet for a power > voltage clamp with a corner on the conduction "knee" than the typical > transient suppressor. A 20V clamp on a 60A machine would not have to grunt > more than 70 joules or so . . . I have already designed and tested a very simple circuit that appears to do the job without any active multi part design. What remains is real world testing. BTW transorbs 'real world knee' is very sharp, at least the many types I have put under test real world test conditions. Spending a lot of time discussing a solution when the problem is not well defined is (to me) foolish. We simply do not have any data, I can find, documentating a load dump from a "real" alternator. I am simply unwilling to use data sheets, conjecture, pilot procedure or "poor regulators" to isolate the approach to the alternator alone when we have an increasing number electrically dependent aircraft being built and ignore the potential system effects of load dump. Paul ________________________________________________________________________________
From: "Troy Scott" <tscott1217(at)bellsouth.net>
Subject: OVP and Load Dump
Date: May 12, 2004
Bob N wrote: << . . . the most significant factor being that OV protection is not designed for load dump mitigation. The output current transient shown in data cited below says to expect peak alternator output current about 15 milliseconds after initiation of the load dump . . . this simply cannot be fielded by hardware designed to protect the system from a failed regulator.>> Bob, An electrical novice like me buys a product based on what the name of the product says it is. In the case of a device labeled "Over Voltage Protection", I expect (reasonably or unreasonably) to get over voltage protection. Until today, I hadn't realized that my B&C VR, which I thought includes OVP, is really only a "most of the time over voltage protector". Isn't a load dump onto the bus an over voltage event? Bob N wrote: << http://www.aeroelectric.com/Mfgr_Data/MR2535L-D.pdf Figure 13 is of particular interest. If I interpret this correctly, the exemplar load dump scenario has a time constant of 100 mS. Peak current to be expected will be alternator rated current plus perhaps a 20% safety factor for cold conditions. The data table says worst case Vbr is 40v at 150 degrees C and 90 amps. Sounds like this gizmo was made with DO-160 in mind and would work fine with alternators rated up to 60A or so. The 40 V absolute limit would also accommodate all the built-in regulator chips for which I've seen data. >> Does this mean I can add one of these to my system to complete the OVP? Respectful Regards, Troy Scott tscott1217(at)bellsouth.net ________________________________________________________________________________
Date: May 11, 2004
From: Wallace Enga <wenga(at)svtv.com>
Subject: Re: OVP and Load Dump
Troy, I think you are confusing two different problems Problem 1 --- A faulty V.R. / ALT putting out over 17 Volts Bob N's O.V. Module is designed to Open the "Field " (control wire to the ALT) and also the "B Lead" thru the Disconnect Contactor --- Isolating the Busses from this malfunctioning charging system. Problem 2 --- Load Dump damage to the Internal Voltage Reg in the ALT, caused by either intentionally or inadvertently Opening this Disconnect Contactor while the ALT is putting out a Normal Charging Current. This problem is going to require some kind of a Transient Voltage Suppressor on the Alternator side of the Contactor to provide a path for this "Energy" to flow to Ground. This is the way I understand it anyway :) Now, I just wish someone would come up with a Part Number that will easily handle this --- I don't care if it costs 49 cents or $49 , I long ago quit keeping track of the amount I am sinking in this project. Hmm, maybe 100 of the 49 cent TVS's will do the job. Wally Enga RV7 >An electrical novice like me buys a product based on what the name of the >product says it is. In the case of a device labeled "Over Voltage >Protection", I expect (reasonably or unreasonably) to get over voltage >protection. Until today, I hadn't realized that my B&C VR, which I thought >includes OVP, is really only a "most of the time over voltage protector". >Isn't a load dump onto the bus an over voltage event? > > >Respectful Regards, >Troy Scott >tscott1217(at)bellsouth.net ________________________________________________________________________________
From: <danobrien(at)cox.net>
Subject: What's all this load dump stuff anyway?
Date: May 11, 2004
You load dump guys have gone way over my head and I suspect the heads of many list readers. A dispassionate explanation of the nature of the debate and its significance would help me and I suspect other readers without any experience in these matters! ________________________________________________________________________________
From: "Paul Messinger" <paulm(at)olypen.com>
Subject: Re: OVP and Load Dump
Date: May 11, 2004
You are missing the larger problem, at least to some of us, and that is a load dump onto the main bus and its likely already done what ever damage it might do before the "B" lead contactor opens and diverts the rest of the dump transient back into the alternator diodes and regulator. Regardless of the reason the alternator we use have been designed to never be disconnected from the battery when charging the battery. With an internal regulator Bob's device can only open a relatively slow to respond contactor. To me its incidental if the alternator fails as the potential of major equyipment failure in the aircfraft is a possibility. Problem is the magnitude of the load dump pulse is dependent on the amount of the load current dumped. 5 amps is approx 8 times smaller than a pulse of 40 amps. Many seem fixated on protecting the alternator regulator when all that results is alternator failure which is less concerting than failure of flight etc equipment from an unprotected transient. Even protecting just the internal regulator seems questionable when the 5,000watt device intended to do just that has been reported to fail in this service. Mfgr data sheets with called load dump simulations vary 100's of times in magnitude. Thus I see no way to get a handle on the problem other than to do tests of real equipment. Besides I want to define the problem and solve all 3 of the issues 2 below and one above. Should have preliminary results by the end of next week. Paul ----- Original Message ----- From: "Wallace Enga" <wenga(at)svtv.com> Subject: Re: AeroElectric-List: OVP and Load Dump > > > Troy, > > I think you are confusing two different problems > > Problem 1 --- A faulty V.R. / ALT putting out over 17 Volts > > Bob N's O.V. Module is designed to Open the "Field " (control wire to the ALT) > and also the "B Lead" thru the Disconnect Contactor --- Isolating the Busses > from this malfunctioning charging system. > > Problem 2 --- Load Dump damage to the Internal Voltage Reg in the ALT, > caused by either intentionally or inadvertently Opening this Disconnect > Contactor while the ALT is putting out a Normal Charging Current. > > This problem is going to require some kind of a Transient Voltage Suppressor > on the Alternator side of the Contactor to provide a path for this "Energy" > to flow to Ground. > > This is the way I understand it anyway :) > > Now, I just wish someone would come up with a Part Number that will easily > handle this --- I don't care if it costs 49 cents or $49 , I long ago quit > keeping > track of the amount I am sinking in this project. > > Hmm, maybe 100 of the 49 cent TVS's will do the job. > > Wally Enga > RV7 > > > >An electrical novice like me buys a product based on what the name of the > >product says it is. In the case of a device labeled "Over Voltage > >Protection", I expect (reasonably or unreasonably) to get over voltage > >protection. Until today, I hadn't realized that my B&C VR, which I thought > >includes OVP, is really only a "most of the time over voltage protector". > >Isn't a load dump onto the bus an over voltage event? > > > > > >Respectful Regards, > >Troy Scott > >tscott1217(at)bellsouth.net > > ________________________________________________________________________________
From: "Eric M. Jones" <emjones(at)charter.net>
Subject: Re: What's all this load dump stuff anyway?
Date: May 11, 2004
>You load dump guys have gone way over my head and I suspect the heads of many list >readers. A dispassionate explanation of the nature of the debate and its >significance would help me and I suspect other readers without any experience >in these matters! Load Dump occurs anytime the alternator/generator sheds its load (like turning something off), because the generator/alternator stator must reduce its magnetic field. This takes a while---almost half-a-second in the worst case. Load Dump is at it's worst when nothing but a flat battery is being honked on by the alternator/ generator and every other load is off---THEN the battery gets disconnected. The Load Dump phenomenon may not have received its proper due in the aviation field and some re-adjustment of "OVP" schemes may (or may not) be advisable. Here's more detail I published earlier (and re-edited)--- The automotive people had this LOAD DUMP stuff figured out a long time ago. The chief document seems to be SAE J1113-11 but you have to pay big bucks to get a look at it, and there's that secret pledge thingy.... But the other guys have published standards which presumably are technically close, and they can be found online. Standard Open-Circuit Volts Rise Time (10%-90%) Pulse duration (10%-10%) SAE J1113-11 ???? ???? ???? Chrysler PF9326 91.5 V 5-10 mS 300 mS Ford CL240 60 V 1-10 mS 300 mS ISO 7637 ???? 5-10 mS 50-400 mS All these standards presume a quick rise from nominal to some higher voltage, then a slower exponential decay back to the nominal base. So they have similar graphs but different values. All these standards also have a particular repetition rate, load impedance, and some minor details, but they are quite similar. Chrysler standard PF9326 (good published information can be found online) presumes there is some load on the system. There is a circuit called the "Load Dump Vehicle Suppression Model" that simulates what one would expect to find in a real-world vehicle (whether or not it keeps its wheels on the ground). According to the Chrysler standard, the peak voltage under these condition is 38 volts for a nominal operating voltage of 13.5V and of course a load given by the LDVSM, about 0.5 ohms. Paul Messinger and Associates (impeccable credentials) are setting up a test to determine what the real numbers are and what approaches are most useful. We await his test results. THEN WE'LL SEE THE FUR FLY! Regards, Eric M. Jones www.PerihelionDesign.com 113 Brentwood Drive Southbridge MA 01550-2705 Phone (508) 764-2072 Email: emjones(at)charter.net "I only regret my economies." --Reynolds Price ________________________________________________________________________________
Date: May 11, 2004
From: Neil Clayton <harvey4(at)earthlink.net>
Subject: Breaker type....will these work?
Bob....would you please look at these P&B breakers (W28) and say if they'll work for a Cozy panel? http://my.execpc.com/~indelect/potter/pbw28.html I like the small footprint, I want to use breakers and I like the idea of being able to run a finger down the row and "feel" if one breaker is out of position (ie tripped). Many thanks Neil ________________________________________________________________________________
From: Nielsen Mark <Mark.Nielsen(at)andritz.com>
Subject: Antenna Placement
Date: May 11, 2004
Bob and Others, I am installing a NAV-COMM (SL-30) in my flying RV-6, and I have some antenna questions. 1. Would the NAV antenna work well if it was installed in the tail cone under the horizontal stabilizer? The balun would be installed inside the fuselage with the "whiskers" sticking out through slots on each side of the fuselage. The fuselage is 9" wide at that point; the antenna would be about 5" below the horizontal stabilizer. 2. Another option would be to mount the NAV antenna on the bottom of the fuselage. The balun would be attached directly to the bottom of the fuselage with the whiskers a 1/2" or so below the skin. How would this work? 3. If the NAV antenna is installed on the bottom of the fuselage, how far must (should) it be away from the COMM antenna? 4. I am also considering a Bob Archer wingtip NAV antenna. (This is not preferred however, because of installation difficulties.) Any comments on reception when using this antenna? 5. I am planning on using a 39" long bare wire for the marker beacon antenna. Is there any reason why this antenna could not be bonded to the inside of the engine cowling? (Again, wingtip installation is difficult.) Is 39" the right length? Any comments would be appreciated. Mark Nielsen RV-6, 909 hours ________________________________________________________________________________
Date: May 12, 2004
From: Brian Lloyd <brianl(at)lloyd.com>
Subject: Re: What's all this load dump stuff anyway?
danobrien(at)cox.net wrote: > > You load dump guys have gone way over my head and I suspect the heads of many list readers. A dispassionate explanation of the nature of the debate and its significance would help me and I suspect other readers without any experience in these matters! I thought someone else might take a stab at this but it seems not. Let me start with how an alternator works. If you vary a magnetic field near a coil of wire, you will cause an electric current to flow in that coil of wire. Likewise, if you pass an electrical current through a coil of wire it will create a magnetic field. You need both of these to make an alternator work. First, there is an armature. This is the part that spins. The armature is really a coil of wire through which current passes to create a magnetic field. When the armature spins it makes a rapidly-reversing magnetic field. Around the inside of the outer frame of the alternator are three coils that don't move. They are called the stators. When the rapidly-rotating magnetic field from the armature passes through the stator coils, the stators produce a rapidly-reversing (alternating) current. This is rectified by the diodes into DC to power the aircraft's electrical system. But the output of the alternator is not constant. If the current in the armature coil (field) is increased, the armature's magnetic field increases and the stators produce a higher voltage. Likewise if the armature is turned faster the output increases. The problem is, we want a constant voltage. This is where the voltage regulator (alternator controller) comes in. The VR is a device that measures the voltage on the bus and varies the armature/field current to keep the voltage constant. If the voltage drops too low, the VR applies more power (current) to the field to cause the output of the alternator to increase. If the voltage goes too high, the VR reduces the power to the field. Imagine now that the VR goes nuts and stops doing its job. In one failure mode it stops providing power to the field and the alternator stops producing electrical power. This is bad but you can limp home on the energy stored in the battery. The other failure mode is that the VR fails and applies full power to the field all the time. Now the voltage goes way up, very likely high enough to fry everything electrical in the aircraft. A runaway alternator can produce an output as high as 100 volts, not exactly healthy for the electrical items in your aircraft. Bob over-voltage protection circuit discovers this high voltage long before it is dangerous to the devices on the bus. It cuts off all power to the field thus turning off the alternator. Now you limp home on the juice left in the battery. No worries. Now on to load dumping. The alternator does not react immediately to the change in field current. It actually takes time for the armature's magnetic field to change thus creating a time-lag in response to the applied power to the field. So when you turn on a big load; e.g. the landing light, pitot heat, etc.; the bus voltage drops momentarily even though the VR detects it and increases the power to the field. Now this is not a problem. But now imagine that you have turned on your 1000W sound system ensuring that the alternator is being called on to deliver maximum power. Assume you turn off the sound system, i.e. "dump the load," so that the bus voltage starts to rise. The VR reduces the current in the field but it takes a finite amount of time for the magnetic field in the armature to change to the new value. In the mean time the bus voltage continues to rise. This sudden, momentary over voltage can cause damage to electrical components. The OVP circuit won't help as the VR has already turned down the current in the field. Brian Lloyd 6501 Red Hook Plaza brianl(at)lloyd.com Suite 201 http://www.lloyd.com St. Thomas, VI 00802 +1.340.998.9447 (voice) +1.360.838.9669 (fax) There is a time to laud one's country and a time to protest. A good citizen is prepared to do either as the need arises. ________________________________________________________________________________
Date: May 12, 2004
From: "Richard E. Tasker" <retasker(at)optonline.net>
Subject: Re: What's all this load dump stuff anyway?
What you have is 100% correct but only 99% of the story. In addition to the scenario of your last paragraph, even if the field current could shut down instantaneously, the output current would still not stop immediately. Since the alternator is an inductive device the energy stored in the stator at the instant that the field goes to zero has to go somewhere. If the battery is still connected it will damp the load dump of both your explanation and this last bit. However, the OVP is intended, as well as interrupt the field current, to open the connection between the alternator output and the battery. When it does this, the stored energy has no where to go so the voltage will rise to whatever it takes until something breaks down and absorbs the energy - probably a diode in the alternator or something in the VR. Dick Tasker Brian Lloyd wrote: > >danobrien(at)cox.net wrote: > > >> >>You load dump guys have gone way over my head and I suspect the heads of many list readers. A dispassionate explanation of the nature of the debate and its significance would help me and I suspect other readers without any experience in these matters! >> >> > >I thought someone else might take a stab at this but it seems not. > >Let me start with how an alternator works. If you vary a magnetic field near a coil of wire, you will cause an electric current to flow in that coil of wire. Likewise, if you pass an electrical current through a coil of wire it will create a magnetic field. You need both of these to make an alternator work. > >First, there is an armature. This is the part that spins. The armature is really a coil of wire through which current passes to create a magnetic field. When the armature spins it makes a rapidly-reversing magnetic field. Around the inside of the outer frame of the alternator are three coils that don't move. They are called the stators. When the rapidly-rotating magnetic field from the armature passes through the stator coils, the stators produce a rapidly-reversing (alternating) current. This is rectified by the diodes into DC to power the aircraft's electrical system. > >But the output of the alternator is not constant. If the current in the armature coil (field) is increased, the armature's magnetic field increases and the stators produce a higher voltage. Likewise if the armature is turned faster the output increases. The problem is, we want a constant voltage. This is where the voltage regulator (alternator controller) comes in. > >The VR is a device that measures the voltage on the bus and varies the armature/field current to keep the voltage constant. If the voltage drops too low, the VR applies more power (current) to the field to cause the output of the alternator to increase. If the voltage goes too high, the VR reduces the power to the field. > >Imagine now that the VR goes nuts and stops doing its job. In one failure mode it stops providing power to the field and the alternator stops producing electrical power. This is bad but you can limp home on the energy stored in the battery. The other failure mode is that the VR fails and applies full power to the field all the time. Now the voltage goes way up, very likely high enough to fry everything electrical in the aircraft. A runaway alternator can produce an output as high as 100 volts, not exactly healthy for the electrical items in your aircraft. > >Bob over-voltage protection circuit discovers this high voltage long before it is dangerous to the devices on the bus. It cuts off all power to the field thus turning off the alternator. Now you limp home on the juice left in the battery. No worries. > >Now on to load dumping. The alternator does not react immediately to the change in field current. It actually takes time for the armature's magnetic field to change thus creating a time-lag in response to the applied power to the field. So when you turn on a big load; e.g. the landing light, pitot heat, etc.; the bus voltage drops momentarily even though the VR detects it and increases the power to the field. Now this is not a problem. > >But now imagine that you have turned on your 1000W sound system ensuring that the alternator is being called on to deliver maximum power. Assume you turn off the sound system, i.e. "dump the load," so that the bus voltage starts to rise. The VR reduces the current in the field but it takes a finite amount of time for the magnetic field in the armature to change to the new value. In the mean time the bus voltage continues to rise. This sudden, momentary over voltage can cause damage to electrical components. The OVP circuit won't help as the VR has already turned down the current in the field. > > >Brian Lloyd 6501 Red Hook Plaza >brianl(at)lloyd.com Suite 201 >http://www.lloyd.com St. Thomas, VI 00802 >+1.340.998.9447 (voice) +1.360.838.9669 (fax) > >There is a time to laud one's country and a time to protest. >A good citizen is prepared to do either as the need arises. > > > > ________________________________________________________________________________
Date: May 12, 2004
Subject: Re: What's all this load dump stuff anyway?
From: Gerry Holland <gnholland(at)onetel.com>
Brian Hi! > > I thought someone else might take a stab at this but it seems not. > Many Thanks for your explanation. It's starting.... I think to make sense. BTW. Great place to live. I've spent time in the past across from you at St Croix. Regards Gerry Europa 384 G-FIZY Trigear with Rotax 912 and Arplast CS Prop. Engine and Prop getting Final fit. Fuel, Oil and Coolant very soon Fuselage painted, Wings almost painted, Flying surfaces painted Airframe Wiring complete, Full Size Panel 70% done . Includes Dynon EFIS, KMD 150, Icom A-200 and SL70 Transponder. AoA Fitted. Activity on Panel, Designing Heater Unit, Shoulder Width Mod completed. http://www.g-fizy.com +44 7808 402404 gnholland(at)onetel.com ________________________________________________________________________________
From: "Jerzy Krasinski" <krasinski(at)provalue.net>
Subject: Re: What's all this load dump stuff anyway?
Date: May 12, 2004
>............... But now imagine that you have turned on your 1000W sound system ensuring that the alternator is being called on to deliver maximum power. Assume you turn off the sound system, i.e. "dump the load," so that the bus voltage starts to rise. The VR reduces the current in the field but it takes a finite amount of time for the magnetic field in the armature to change to the new value. In the mean time the bus voltage continues to rise. This sudden, momentary over voltage can cause damage to electrical components. The OVP circuit won't help as the VR has already turned down the current in the field. > > > Brian Lloyd > > It depends what OVP circuit. A proper OVP circuit is a fast and brutally acting device capable to sink a lot of current from the bus whenever it detects a voltage increase above the norm. In other words it is a device momentarily increasing the load on the bus, absorbing all the excess current caused by the load dump. It absorbs as much current as needed to keep the bus voltage only slightly increased above the norm, far away from damaging voltages. In the mean time the regulator can reduce the field current so the voltage on the bus goes back to normal. That reduces the current through the OVP device which goes idle and the system continues to work in a standard way. Jerzy ________________________________________________________________________________
Date: May 12, 2004
From: echristley(at)nc.rr.com
Subject: Re: What's all this load dump stuff anyway?
> But now imagine that you have turned on your 1000W sound system > ensuring that the alternator is being called on to deliver maximum > power. Assume you turn off the sound system, i.e. "dump the load," > so that the bus voltage starts to rise. The VR reduces the current > in the field but it takes a finite amount of time for the magnetic > field in the armature to change to the new value. In the mean time > the bus voltage continues to rise. This sudden, momentary over > voltage can cause damage to electrical components. The OVP circuit > won't help as the VR has already turned down the current in the field. > > Excellent explanation Brian, but I'd like to add the image that makes it blatantly clear to me. Imagine you're trying to open a door. Really stubborn door. You push with everything you have, and even call in me, Bob and several others from this list. We are all sweating and grunting to get the door open. Suddenly, and without warning, your wife, who is more intelligent than all the rest of us combined, turns the door knob. The resulting explosive release of force can be referred to as a load dump. ________________________________________________________________________________
From: "ronald jagels" <rejnovca(at)hotmail.com>
Subject: LASAR Ignition Wiring
Date: May 12, 2004
Building an RV-8A with battery in the rear, LASAR electronic ignition and planning to use Z-13 as a starting point for electrical systems. The LASAR installation instructions I pulled off the internet apply to a backfit on existing aircraft and indicate use of the conventional O-L-R-Both-Start switch. Power is feed to the LASAR control box and then distributed to the MAG backups with blue wire to the left MAG P lead and green wire to the right MAG P lead. Question - has anyone wired the LASAR ignition using 2-3 switches as described by Bob in the AeroElectric Connection Book? If so how did you wire it? ________________________________________________________________________________
From: "Troy Scott" <tscott1217(at)bellsouth.net>
Subject: Re: OVP and Load Dump
Date: May 13, 2004
Wallace, Thanks for your response. Actually, I do understand the difference in alternator regulator OVP and an OV event caused by Load Dump. I just believe that a device advertised to have "over voltage protection" should include features that provide for common possibilities like Load Dump, which IS a short duration high-voltage-on-the-bus event. The B&C regulator is a separate box with wires going to and coming from it. Would it be a big deal to add the $.49 part and a few wires which would connect to the proper places to absorb a Load Dump? With this and maybe a few other features, maybe then you could legitimately call it a complete OVP system. And it doesn't matter if everybody else makes OVP systems without these features. We're supposed to be better that everybody else, right? Regards, Troy tscott1217(at)bellsouth.net ________________________________________________________________________________
Date: May 12, 2004
From: Wallace Enga <wenga(at)svtv.com>
Subject: Re: What's all this load dump stuff anyway?
Brian, Great explanation on this mysterious electron producer. The one paragraph below, I might quibble with you on, is regarding alternators with Internal Voltage Regulators. These do not have the "classic field wire", but rather a control wire. Cutting off power to this lead may not shut the alternator down in all situations. That is the reason for the addition of a "B Lead" Disconnect Contactor, along with it's Load Dump issues when inadvertently opened. Wally Enga > > >Bob over-voltage protection circuit discovers this high voltage long >before it is dangerous to the devices on the bus. It cuts off all power >to the field thus turning off the alternator. Now you limp home on the >juice left in the battery. No worries. ________________________________________________________________________________
Date: May 12, 2004
From: "Robert L. Nuckolls, III" <bob.nuckolls(at)cox.net>
Subject: Re: What's all this load dump stuff anyway?
> > > > >............... But now imagine that you have turned on your 1000W sound >system ensuring that the alternator is being called on to deliver maximum >power. Assume you turn off the sound system, i.e. "dump the load," so that >the bus voltage starts to rise. The VR reduces the current in the field but >it takes a finite amount of time for the magnetic field in the armature to >change to the new value. In the mean time the bus voltage continues to >rise. This sudden, momentary over voltage can cause damage to electrical >components. The OVP circuit won't help as the VR has already turned down >the current in the field. > > > > > > Brian Lloyd > > > > >It depends what OVP circuit. A proper OVP circuit is a fast and brutally >acting device capable to sink a lot of current from the bus whenever it >detects a voltage increase above the norm. In other words it is a device >momentarily increasing the load on the bus, absorbing all the excess current >caused by the load dump. It absorbs as much current as needed to keep the >bus voltage only slightly increased above the norm, far away from damaging >voltages. In the mean time the regulator can reduce the field current so >the voltage on the bus goes back to normal. That reduces the current through >the OVP device which goes idle and the system continues to work in a >standard way. >Jerzy We're stirring two separate events together in the same pot and blurring sharp distinctions between the two along with consideration of practical remedies. Over Voltage Protection addresses a condition that was largely ignored until alternators were installed on aircraft. It's precipitated by a failure of the voltage regulator failure and the engine driven power source begins pushing an otherwise normal system voltage upward. This is a gross failure of a control device where potential energy available to damage system components is measured in Killowatt-Seconds and the event will proceed with no practical bound on time unless automatic protection (or pilot intervention) steps in to shut off the failed alternator. Voltage settings and time versus voltage operating characteristics have been studied and defined over the past 40 years or so and the result is a large field of offerings in over-voltage relays and, in the AeroElectric case, crowbar OV protection modules. The "load dump" phenomenon is described by simple dynamics of an alternator and it's companion regulator to respond to sudden reduction in load. It doesn't require a 'failure' to initiate the event. A simple operation of the alternator control switch on a Figure Z-24 OV protection system or operation of the battery master in a Bonanza while the alternator is carrying a substantial load is all it takes. This phenomenon is a relative low energy perhaps less than 100 watt-seconds and is self terminating. The classic OV Protection system was not designed for nor should it be expected to deal with this event. The technology of choice is an adaptation of zener voltage regulator diodes especially crafted to provide a temporary but rather robust LOAD to the alternator during the tens of milliseconds that it takes to recover from a sudden drop on demand for its formidable output capabilities. This class of zener is commonly referred to as a TVS or transient voltage suppressor. It's a device rated to soak up large (1500 Watts or more) surges of energy for short (less than 100 milliseconds) periods of time. Load dump is a RARE event in normal operation. Certified aircraft have not been fitted with prophylactic measures because it is so rare. This topic has been stirred numerous times here on the List and elsewhere over the past 5 years or so. It was not until Van's Aircraft noted that flipping the alternator control switch in an aircraft wired per Figure Z-24 might produce a load-dump event (that could damage the alternator only) that the topic bubbled to the surface again. The debate is not whether a load-dump event can happen. We know and accept that its occurs under specific conditions that have become less rare because one can accidently produce the event by flipping switches under otherwise "normal" conditions. The conversation is not so much a debate but a desire to understand and confirm recommendations already circulating throughout the automotive industry for RATING the TVS device. It may well be that a suitable device will surface in the form of this critter: http://www.aeroelectric.com/Mfgr_Data/MR2535L-D.pdf They cost about $3 in low quantity and are installed by simply attaching to the back of the alternator. One wire to the b-lead terminal, other to ground. I've oft cited the value of "repeatable experiments" as the foundation for good engineering decisions. TVS devices come in hundreds of part numbers of which perhaps 20-30 parts are best suited to our task. There's much published literature from the automotive industry that suggests the part cited above will do the trick for 99% of the installations common to OBAM light aircraft. In fact, if any of you are especially concerned about load dump transients, you could acquire one of these critters and install it this afternoon and be 99% assured of having fabricated a firewall against a .001% event. Incidental to the outcome of the proposed repeatable experiments are real debates as to the need for clamping off load-dump transients at voltage levels far below values common in Spam cans. DO-160 cites 40 volt withstand levels for products intended to serve in 14 volt aircraft. Many suppliers to the OBAM community are ignorant of or choose to ignore this simple and easily accommodated recommendation. They offer devices advertised with 20-30 volt limits. Some folk suggest it is in the consumer's best interests to accommodate these products with extra-ordinary efforts found no where else in the aircraft (or automotive) industry. From the perspective of a designer with feet in both buckets, I've suggested that we'll better serve the OBAM aircraft community by insisting potential suppliers educate themselves on the simple techniques proven effective in thousands of products intended for a certified world. OV protection and load dump protection are separate tasks with different requirements. The risks for not installing protection are well documented and not very debatable. I have every expectation that experiments currently proposed will not offer new and startling discoveries . . . the numbers gleaned will allow us to confirm a choice of devices for a well understood task. It's going to be something akin to deciding whether a piece of equipment is held to the airframe with #6 hardware . . . or would #8 be better? There is useful debate to be conducted on how we view ourselves as champions and practitioners of leading edge technology. I prefer to take advantage of 5 decades of knowledge base on electrical system performance upon which we will build an ever expanding leading edge. I don't find it useful and cannot recommend that we step back from the best-we-know-how-to-do just to accommodate the new kids on the block. Let's help them join us at the leading edge instead of spending time and dollars to craft a system especially friendly to sub-standard products. In the hypotheticals I cited yesterday, it would be like putting low compression jugs on an engine to accommodate Nuckolls' cheap 75 octane fuel or drilling half again more holes to install wing attach bolts so one can use hardware store grade 5 fasteners. No doubt some will choose to be accommodating and that's fine too. This is, after all, an OBAM aircraft community. If accommodation does not compromise safety, then I'll be the last to get really excited about anyone's CONSIDERED decisions on configuring their aircraft. I won't recommend accommodation when it's easy to avoid and when the effort is beneficial to the OBAM aircraft community as a whole. This I will happily debate any time . . . it's my job. Bob . . . ________________________________________________________________________________
From: "Eric M. Jones" <emjones(at)charter.net>
Subject: RG142
Date: May 12, 2004
If RG142 is the only coax that is used in an airplane--about how much is used per airplane? (Now please don't say it depends...). I am trying to find out how much weight can be saved by changing to something else, and if RG142 ONLY can be used for everything coaxial. Offline is best: Email: emjones(at)charter.net Regards, Eric M. Jones www.PerihelionDesign.com 113 Brentwood Drive Southbridge MA 01550-2705 Phone (508) 764-2072 ________________________________________________________________________________
From: "David Schaefer" <dschaefer1(at)kc.rr.com>
Subject: Single Ground
Date: May 12, 2004
Bob .. I need your thoughts on a problem I've run up against. I've followed your single ground specifications to a tee. All my grounds are run to the single B&C ground block. However, I have an issue. I have a 'pre-made' harness with 8 power and 8 ground connections all on very short leads coming out of the main cable bundle. All have ring terminals on them. I've cut off the power side ring terminals and replace them with fast-ons to connect to my fuse block. However, I can't decide what to do with the ground side. Do I cut them off and splice longer wires (3') onto the leads to get back across the plane to the ground block? OR can I put the ring terminals on a single bolt and run one larger wire back to the block? OR do I put a couple of bolt-studs by the fuse blocks and ground the ring terminals to the firewall? Will the splices 'degrade' the ground? I'll look forward to your input. Regards DWS ________________________________________________________________________________
From: "LarryRobertHelming" <lhelming(at)sigecom.net>
Subject: Re: RG142
Date: May 12, 2004
If you locate your antennas only in the wing tips it will take considerable more coax than if you locate them in the belly of the plane. * AND* How many antennas will you have? (Now please don't say it depends...). Your answer will not *depend* on anything but your own desires. Indiana Larry ----- Original Message ----- From: "Eric M. Jones" <emjones(at)charter.net> Subject: AeroElectric-List: RG142 > > If RG142 is the only coax that is used in an airplane--about how much is > used per airplane? (Now please don't say it depends...). I am trying to find > out how much weight can be saved by changing to something else, and if > RG142 ONLY can be used for everything coaxial. > > Offline is best: > Email: emjones(at)charter.net > > Regards, > Eric M. Jones > www.PerihelionDesign.com > 113 Brentwood Drive > Southbridge MA 01550-2705 > Phone (508) 764-2072 > > ________________________________________________________________________________
From: <jimk36(at)comcast.net>
Subject: For Bob Nuckolls
Date: May 12, 2004
Bob-- I've been following the load dump thread with some interest, for the plane I'm building and the one I fly. I have had a Beech C33A for 15 years and put about 2000 hours on it. It has a 70A alt. and plenty of equip. to load it up. In all this time I had no idea until this issue came up on the Connection that there was the potential to trash 10s of thousands of dollars of avionics and other equip. There is nothing in the POH about this. In fact the POH says that in the event of an overvoltage condition, [which would be indicated by an O-V warning light], batt and alt switch "off momentarily, then on [this resets the overvoltage relay]". As I understand it this in itself could generate a load dump if the batt were switched off slightly ahead of the alt.. Am I correct? Seems strange that the issue of load dump and operation of the master sw was not included in the POH. Are you aware of any reason for the omission other than that pilots rarely feel the urge to turn off the master while in flight or when on the ground with the engine running? Jim Kaser ________________________________________________________________________________
Date: May 13, 2004
From: "Robert L. Nuckolls, III" <bob.nuckolls(at)cox.net>
Subject: Re: OVP and Load Dump
> > >Wallace, > >Thanks for your response. Actually, I do understand the difference in >alternator regulator OVP and an OV event caused by Load Dump. I just >believe that a device advertised to have "over voltage protection" should >include features that provide for common possibilities like Load Dump, which >IS a short duration high-voltage-on-the-bus event. The B&C regulator is a >separate box with wires going to and coming from it. Would it be a big deal >to add the $.49 part and a few wires which would connect to the proper >places to absorb a Load Dump? With this and maybe a few other features, >maybe then you could legitimately call it a complete OVP system. And it >doesn't matter if everybody else makes OVP systems without these features. >We're supposed to be better that everybody else, right? The LR3 regulator wires to the ship's systems with 20 and 22 awg wires of variable length. The best place to install a TVS is as close to the source (alternator b-lead) as practical with shortest lengths of wire. When the TVS is finally sized, the recommended location would not be inside the LR-3 regulator but right on the back of the alternator. This will allow a single recommended installation to cover all manner of load-dump event in both externally regulated and internally regulated machines wired per Z-24. Bob . . . ________________________________________________________________________________
From: "Troy Scott" <tscott1217(at)bellsouth.net>
Subject: Re: OVP and Load Dump
Date: May 14, 2004
Bob Nuckolls, Thanks!! I'll definitely want to include this feature. I'll stay tuned. Regards, Troy Scott tscott1217(at)bellsouth.net ________________________________________________________________________________
From: "Paul Messinger" <paulm(at)olypen.com>
Subject: Re: What's all this load dump stuff anyway?
Date: May 13, 2004
see embedded ----- Original Message ----- From: "Robert L. Nuckolls, III" <bob.nuckolls(at)cox.net> Subject: AeroElectric-List: Re: What's all this load dump stuff anyway? > > The debate is not whether a load-dump event can happen. > We know and accept that its occurs under specific > conditions that have become less rare because one > can accidently produce the event by flipping switches > under otherwise "normal" conditions. The conversation is > not so much a debate but a desire to understand and > confirm recommendations already circulating throughout > the automotive industry for RATING the TVS device. > It may well be that a suitable device will surface > in the form of this critter: > > http://www.aeroelectric.com/Mfgr_Data/MR2535L-D.pdf > > They cost about $3 in low quantity and are installed > by simply attaching to the back of the alternator. > One wire to the b-lead terminal, other to ground. > I've oft cited the value of "repeatable experiments" > as the foundation for good engineering decisions. > TVS devices come in hundreds of part numbers of which > perhaps 20-30 parts are best suited to our task. > > There's much published literature from the automotive > industry that suggests the part cited above will do > the trick for 99% of the installations common to > OBAM light aircraft. Disagree, the vast majority of devices designed for this purpose by the TVS component industry is for parts many times higher in rating. In fact the ONLY part I can find that is not a 5000W unit is the above referenced part noted by "ON" Semi (not a leader on the TVS field). (This for Alternator Load dump suppression). It might be of interest to point out what the following spec requires. "The DaimlerChrysler Corp EMC spec # PF-9326 change D" states. (Not an exact word by word quote (shortened) but technically factual) 3.5.3 Load Dump Transient test specifies a transient generator that must produce 125 joules of energy to a 0.5 ohm resistive load with an internal source resistance of 0.5 ohms when set to an open source voltage of 105 volts. The waveform must average 45.75v minimum over 95ms duration. Further the test circuit pulse is shown to be above 22.65V for 300ms. The test load used consists of FIVE of the above MR2535 in parallel each with 0.1 individual series resistors. This load results in a suppression of the 90+V pulse to the range of 34-38 volts over the duration of the pulse exceeding this clamped voltage which duration is not specified in numbers but appears to be in the range of 200ms based on waveform charted. The above shows a voltage pulse clamped to close to the DO-160 40 V pulse but as I recall the DO-160 40 V pulse is much shorter than 200ms and thus does not cover maximum load dump conditions, that is, if the above automotive test is max case. In any case it shows the apparent need for much more than one 1500W MR2535 supporting the rest of the industries contention that a 5000watt unit is needed. Bob please restate for us the DO-160 Over voltage tests of one second duration and shorter including the 40v pulse test including pulse peak and duration/pulse shape. To many of us the problem is important, as however unlikely a damaging load dump occurrence is, if you experience one it can damage lots of very expensive equipment. Consider the automobile design. The battery is hard wired to the alternator "B" lead and the rest of the electrical system is connected by the ign switch. Thus in an auto only a mechanical failure can cause a load dump. IE the mechanical connection somehow opens. Then consider automobiles have designed in TVS protection in the dozens of electrical modules and thus have a distributed load dump/transient protection network. In an acft however things are connected differently. The battery is not directly connected to the alternator "B" lead. The system each are individually connected thru power relays to the system bus and thus there are two relays that can cause a load dump if either is opened at the wrong time. The opening of the "B" lead isolates the load dump to the alternator. The opening of the battery relay results in the acft electrical system being exposed to the load dump. It does not matter how or what caused the battery relay to open the result is a system wide load dump. The old spam cans are just as likely to have a load dump as the latest designs in that respect. Its not usually a problem however as the load dump from battery disconnect is not a problem unless the battery is being heavily charged AT that time and normally this is only for a short time after initial startup. Paul ________________________________________________________________________________
Date: May 13, 2004
From: "Robert L. Nuckolls, III" <bob.nuckolls(at)cox.net>
Subject: Re: For Bob Nuckolls
> >Bob-- > >I've been following the load dump thread with some interest, for the plane >I'm building and the one I fly. I have had a Beech C33A for 15 years and >put about 2000 hours on it. It has a 70A alt. and plenty of equip. to load >it up. In all this time I had no idea until this issue came up on the >Connection that there was the potential to trash 10s of thousands of >dollars of avionics and other equip. > >There is nothing in the POH about this. In fact the POH says that in the >event of an overvoltage condition, [which would be indicated by an O-V >warning light], batt and alt switch "off momentarily, then on [this resets >the overvoltage relay]". As I understand it this in itself could generate >a load dump if the batt were switched off slightly ahead of the alt.. Am I >correct? Yes . . . there WILL be a load dump transient but its magnitude is a function of total alternator load, ratio of system loads to battery recharge load, engine rpm, and individual alternator characteristics. Consider further that most if not all of the equipment in your airplane was designed to EXPECT load-dump type transients and survive them. The worst case load dump happens when the battery is deeply discharged and accepting strong recharge current from the alternator while at cruise rpm -AND- minimal system loads. Increasing the amount of stuff running from the bus in comparison to total alternator loads will reduce the magnitude of a potential load dump event. Alternator and battery switches are generally operated on the ground with the engine either stopped or at >Seems strange that the issue of load dump and operation of the master sw >was not included in the POH. Are you aware of any reason for the omission >other than that pilots rarely feel the urge to turn off the master while >in flight or when on the ground with the engine running? No, for the most part, all this discussion is a tempest in a teapot because (1), it's a vary rare event with a huge range of variability depending on system operating conditions and (2) we in the spam can industry have been encouraged to design new products for aircraft with a robust tolerance of the load-dump event. From the perspective of Raytheon Aircraft delivering a new A-36 to a customer, concerns for pilot induced load-dump events causing any damage is completely off the radar screen. We've done the best we know how to do both from regulatory and professional efforts to make this a non-issue with certified aircraft. It only popped up on radar screens in OBAM aircraft because with the special case generated by Figure Z-24 OV protection applied to internally regulated alternators where it's relatively easy to produce a load-dump event that damages the alternator. This happens when the alternator is cycled on and off while the engine is running . . . and again, it probably happened on a Lycoming engine (high alternator drive pulley ratio) and the alternator was working hard to recharge a battery that was just used to crank the engine. If the switch had been flipped on and off a short time later, the event may not have been so high as to zork the regulator. Figure Z-24 has been in publication for about 6 years. Certainly dozens of aircraft are flying this configuration without having to report alternator failures because (1) they operate the switches in the conventional manner and/or (2) load conditions prevalent at the time of switch operation did not produce an event with enough magnitude to damage the alternator's regulator. Don't loose any sleep over this my friend. 99% of what you're seeing discussed here on the list is academic discussion among folk who do this for a living. Like DNA where 95% is chaos which binds together the 5% of what makes us what we are, this voluminous discussion will lead to considered, simple and practical solutions to something that isn't a big problem in the first place. I've had some private e-mails suggesting that we should take this stuff off-list. It "confuses" or "alarms" some folks. Well, the US Congress does a whole lot of confusing or alarming stuff off-list too . . . and we know where that gets us. Just be assured that when all the dust settles, those who are confused or alarmed will be offered simple remedies while those who choose to follow along will be richer in understanding for having taken the time to do it. Bob . . . ________________________________________________________________________________
Date: May 13, 2004
From: Chad Robinson <crobinson(at)rfgonline.com>
Subject: Re: For Bob Nuckolls
Robert L. Nuckolls, III wrote: > The worst case load dump happens when the battery is deeply discharged > and accepting strong recharge current from the alternator while at cruise > rpm -AND- minimal system loads. Increasing the amount of stuff running from > the bus in comparison to total alternator loads will reduce the magnitude > of a potential load dump event. Alternator and battery switches are > generally operated on the ground with the engine either stopped or at Bob, could you please elaborate on this point? I don't understand why minimal system load is part of the worst-case. Is the implication that pre-existing loads other than the battery could help absorb the dump? Or is this simply a percentages thing? > I've had some private e-mails suggesting that we should take > this stuff off-list. It "confuses" or "alarms" some folks. > Well, the US Congress does a whole lot of confusing or alarming > stuff off-list too . . . and we know where that gets us. Just > be assured that when all the dust settles, those who are confused or > alarmed will be offered simple remedies while those who choose > to follow along will be richer in understanding for having > taken the time to do it. It might be nice for you to write up one of your famous articles summarizing the physics of what happens, how to avoid them, and where they actually matter. Regards, Chad ________________________________________________________________________________
Date: May 13, 2004
From: "Robert L. Nuckolls, III" <bob.nuckolls(at)cox.net>
Subject: Re: For Bob Nuckolls
> > >Robert L. Nuckolls, III wrote: > > The worst case load dump happens when the battery is deeply discharged > > and accepting strong recharge current from the alternator while at > cruise > > rpm -AND- minimal system loads. Increasing the amount of stuff > running from > > the bus in comparison to total alternator loads will reduce the > magnitude > > of a potential load dump event. Alternator and battery switches are > > generally operated on the ground with the engine either stopped or at > >Bob, could you please elaborate on this point? I don't understand why minimal >system load is part of the worst-case. Is the implication that pre-existing >loads other than the battery could help absorb the dump? Or is this simply a >percentages thing? It's a ratio . . . or percentage thing. Suppose total load on alternator is 50A, 48A going to things on the bus and 2A to recharging the battery. Now, flip ALL 40A of bus loads off and the alternator will do it's overshoot thing but the battery is still on the bus to soak up the short burst of energy that comes during the load-dump. Now, take the same scenario and turn off the battery. Loads on alternator drop from 50 to 48, not a big dump, no big deal. Reverse the situation. Cold morning, battery in good condition but dead from master being left on. Start with battery cart and turn alternator on. Alternator pegs out at max capability to recharge the dead battery. Say bus has a couple of amps worth of goodies on and you open the battery master contactor. Alternator load drops from max capability (which can be better than label ratings on cold day) down to the couple of amps that the bus powered goodies need. BIG drop in current, BIG overshoot which gets conducted to whatever items are presently powered from the bus. > > I've had some private e-mails suggesting that we should take > > this stuff off-list. It "confuses" or "alarms" some folks. > > Well, the US Congress does a whole lot of confusing or alarming > > stuff off-list too . . . and we know where that gets us. Just > > be assured that when all the dust settles, those who are confused or > > alarmed will be offered simple remedies while those who choose > > to follow along will be richer in understanding for having > > taken the time to do it. > >It might be nice for you to write up one of your famous articles summarizing >the physics of what happens, how to avoid them, and where they actually >matter. It's in the mill. Will be able to complete it when all the data are in from repeatable experiments. Bob . . . ________________________________________________________________________________
From: jmfpublic(at)comcast.net
(Aeroelectric-List)
Subject: Re: What's all this load dump stuff anyway?
Date: May 13, 2004
Paul and Bob, The MR2535 is $1.45, minimum order 10 units from Digikey. Using 5 of them should not be a problem. Jim Foerster ________________________________________________________________________________
From: "Greg Young" <gyoung@cs-sol.com>
Subject: For Bob Nuckolls
Date: May 13, 2004
I had pretty much tuned out the earlier load dump discussions because it was more than my electron challenged brain could handle but I now realize that I recently experienced it and it's practical downside. During maintenance the ammeter line on my Navion got connected to the buss side of the master CB instead of the battery side (don't ask!). That put a 35amp CB in series with the 60amp main breaker from my 50 amp generator. No problem until the engine started and the generator came on line. The 35a blew disconnecting the battery and creating what I now know to be a load dump. That blew all the fuses in my GX-60, SL-30 and SL-70 rendering them useless - twice before we found the problem. The radio shop was able to replace the fuses and the radios appear otherwise undamaged but it wasn't pleasant, easy or convenient (soldered PICO fuses). These are all current generation radios which I assume were built to DO-160. But that gave me no comfort when I was stranded without radios and none now knowing it could happen again if the battery gets disconnected. Oddly, my SL-15/PS7000 audio panel, ACU and various gauges escaped unscathed. Moral - if you have UPSAT radios, carry your own supply of 2a & 7a PICO fuses. I may not be able to change my Navion but I'd sure like to solve/prevent this problem in my RV-6. Regards, Greg Young - Houston (DWH) RV-6 N6GY ...project Phoenix Navion N5221K - just an XXL RV-6A > --> > > > > > > >Robert L. Nuckolls, III wrote: > > > The worst case load dump happens when the battery is > deeply discharged > > > and accepting strong recharge current from the > alternator while > > > at > > cruise > > > rpm -AND- minimal system loads. Increasing the amount of stuff > > running from > > > the bus in comparison to total alternator loads will > reduce the > > magnitude > > > of a potential load dump event. Alternator and > battery switches are > > > generally operated on the ground with the engine > either stopped > > > or at > > > >Bob, could you please elaborate on this point? I don't > understand why > >minimal system load is part of the worst-case. Is the > implication that > >pre-existing loads other than the battery could help absorb > the dump? > >Or is this simply a percentages thing? > > It's a ratio . . . or percentage thing. Suppose total load > on alternator > is 50A, 48A going to things on the bus and 2A to recharging > the battery. > Now, flip ALL 40A of bus loads off and the alternator will do it's > overshoot thing but the battery is still on the bus to soak > up the short > burst of energy that comes during the load-dump. Now, take > the same scenario > and turn off the battery. Loads on alternator drop from 50 > to 48, not a > big dump, no big deal. > > Reverse the situation. Cold morning, battery in good condition but > dead from master being left on. Start with battery cart and turn > alternator on. Alternator pegs out at max capability to recharge > the dead battery. Say bus has a couple of amps worth of goodies > on and you open the battery master contactor. Alternator load drops > from max capability (which can be better than label ratings on > cold day) down to the couple of amps that the bus powered goodies > need. BIG drop in current, BIG overshoot which gets conducted to > whatever items are presently powered from the bus. > > > > > I've had some private e-mails suggesting that we should take > > > this stuff off-list. It "confuses" or "alarms" some folks. > > > Well, the US Congress does a whole lot of confusing > or alarming > > > stuff off-list too . . . and we know where that gets us. Just > > > be assured that when all the dust settles, those who > are confused or > > > alarmed will be offered simple remedies while those who choose > > > to follow along will be richer in understanding for having > > > taken the time to do it. > > > >It might be nice for you to write up one of your famous articles > >summarizing the physics of what happens, how to avoid them, > and where > >they actually matter. > > It's in the mill. Will be able to complete it when all the > data are in from repeatable experiments. > > Bob . . . ________________________________________________________________________________
Date: May 13, 2004
From: Wallace Enga <wenga(at)svtv.com> anyway?
Subject: Re: What's all this load dump stuff
anyway? Jim, The ST BZW50-22 has about the same specs and a little higher Peak Pulse rating of 5000W. Prob get by with 4 of them :) http://www.datasheetcatalog.com/datasheet/B/BZW50-22.shtml Wally Enga > >Paul and Bob, > >The MR2535 is $1.45, minimum order 10 units from Digikey. Using 5 of them >should not be a problem. > >Jim Foerster > ________________________________________________________________________________
From: "Ron Koyich" <Ron(at)Koyich.com>
Subject: For Bob Nuckolls
Date: May 14, 2004
>>Well, the US Congress does a whole lot of confusing or alarming stuff off-list too . . . and we know where that gets us. Just be assured that when all the dust settles, those who are confused or alarmed will be offered simple remedies while those who choose to follow along will be richer in understanding for having taken the time to do it.<< Thanks for the sobering thoughts, Bob. From my years of experience with aircraft electronics and avionics, I believe the practical answer is: load dump problems are not one of the big problems folks need to concern themselves with. Like a spot of dust on an elephant's butt - not a worry. Ron ________________________________________________________________________________
Date: May 13, 2004
Subject: For Bob Nuckolls: Roll your own crowbar module troubles
From: <arizonahikers(at)juno.com>
Bob, This is a resend of previous information I posted but you didn't get. I build my own OV crowbar module and it functions correctly except that it operated in the 10-11 volt range. I triple checked the components and wiring. I changed the 1.62K ohm resistor specified for a 14 volt system to 6.04K and the circuit operates in the correct voltage range of 15.5-17 volts. *************************** Designating Point (1) as the + end of the capacitor, and Point (2) as the junction of the 392 ohm resistor, and GND as the negative lead, with the pot at midrange I got the following readings: ****** 1.62 K resistor in place for 14 volt operation. - Trip point = 10.4 volts. Point (1) - Point (2) +0.436 volts GND - Point (2) +7.6 volts ****** 6.04K resistor replacing the 1.62K one. - Trip point = 16.22 volts. Point (1) - Point (2) +0.538 volts GND - Point (2) +7.36 volts ****** These readings made me realize the circuit was not letting the zener regulate at 12 volts so I did the following checks. First I disconnected the SCR trigger lead to prevent it from firing. I reinstalled the original 1.62K resistor. Measuring the Zener voltage from GND to Point (2): As I increased the input voltage the voltage across the zener increases linearly to about 8.25 volts and then starts to decrease. The input voltage is about 9 volts when this knee occurs. I then disconnected the 1N4148 diode and repeated the above test with basically the same results. With the 1N4148 diode still disconnected, I also disconnected the NPN collector and PNP base (they remained connected together) from the point (2) junction. Now only the Zener and 392 ohm resistor are in series across the supply. Again measuring the Zener voltage from GND to point (2): The zener voltage tracks the input voltage up to about 11.3 volts at which point the zener begins to regulate. With the two transistors still disconnected, I reconnected the 1N4148 diode. Now the voltage across the zener increases linearly up to 9 volts (input voltage is 9.35) when suddenly the voltage drops to 1.87 volts. Do you have any suggestions to help troubleshoot of fix it. Ralph Ketter RV-6 Marysville, KS *************************** ________________________________________________________________________________
From: "KeithHallsten" <KeithHallsten(at)quiknet.com>
Subject: Co-ax splice method
Date: May 13, 2004
I'm about to close up the winglets on the Velocity I'm building, and I need to extend the antenna wire first. The copper-foil type antenna came to me with a short length of RG-58 attached, already glassed into the winglet. I intend to extend it to the instrument panel with RG-400. The area where the splice will be made will be inaccessible once I seal up the winglet, so I want to use the parts and technique that has the lowest probability of a problem for the life of the airframe. I could just install a male connector on one and a female connector on the other, then mate them and cover with some heatshrink. Is this the best approach to this situation? Thanks for your advice! Keith Hallsten, Roseville, CA ________________________________________________________________________________
From: "Ron Koyich" <Ron(at)Koyich.com>
Subject: Co-ax splice method
Date: May 14, 2004
>>I could just install a male connector on one and a female connector on the other, then mate them and cover with some heatshrink. Is this the best approach to this situation? Thanks for your advice!<< That would be good practice, Keith. Using crimp-on connectors and making sure the connectors were installed correctly with low resistance before covered them. Another option, rather than heatshrink, would be the NITO type self vulcanizing tape (rubber with no sticky side - pulling the tape tight over the previous wrap seals the connection). It's good in any harsh environment - keeps moisture out of the connection. If your plane will be kept in a high humidity environment you might consider it. Ron ________________________________________________________________________________
From: "Ron Koyich" <Ron(at)Koyich.com>
Subject: Co-ax splice method
Date: May 14, 2004
>>before covered them<< Edit - Edit ...before you covered them. Of course.... ________________________________________________________________________________
From: "Paul Messinger" <paulm(at)olypen.com>
Subject: Re: What's all this load dump stuff anyway?
Date: May 14, 2004
I know but picking that part is premature as to date. ALL the discussion is based on NO real data just what mfgrs have used for their own purposes. There are much sturdier parts available at much lower cost not that cost is a driver here. Paul ----- Original Message ----- From: <jmfpublic(at)comcast.net> Subject: AeroElectric-List: Re: What's all this load dump stuff anyway? > > Paul and Bob, > > The MR2535 is $1.45, minimum order 10 units from Digikey. Using 5 of them should not be a problem. > > Jim Foerster > ________________________________________________________________________________
From: "Paul Messinger" <paulm(at)olypen.com>
Subject: DO-160
Date: May 14, 2004
Bob, I would like to know the DO-160 requirements associated with transients above say 24V including pulse duration, shape and peak V where the duration is under one second. For example I recall there is a 40V pulse but I do not know its duration or shape. I seem to recall there is a longer pulse at a lower voltage also. Then there is the maximum Voltage steady state level. And perhaps others addressing above normal bus voltage ranges. This info will help me with the load dump testing. Specifically IF I find what appears to be a condition that exceeds DO-160 requirements. In that case I want to further analize the test results and it would also be a factor in any proposed solution which would be a final part of the load dump tests. Paul ________________________________________________________________________________
From: "Paul Messinger" <paulm(at)olypen.com>
Subject: LOAD DUMP TEST START
Date: May 14, 2004
The long waited REAL testing started on 5-13-04. This will take as long as it takes :-) at a rate of a couple of hours per day, but likely completed this month. (Could also be less than a week to preliminary final results, full writeup/documentation may take months.) Its not simple to design a test of this complexity when the results will subject to the likes of Bob :-). I have some preconsived ideas of the results (as do many of us, including Bob, but have set that aside and will let the results stand for themselves. The test conditions are designed to allow others to duplicate with reasonable accuract what I am doing so any or all parts can be setuip in a different lab and the results should be comparable considering the component and test equipment variations. System level Load Dump is not a simple issue as some have tried to make it. That is IF the objective is to detail what happens and how it can effect the other parts of the system. Even the OVP module is part of the system during the time it takes to open the associated 5 amp CB. Only protection of the alternator internal diodes and regulator is one solution and that only takes clamping the voltage to 35-40 volts and that voltage is way too high for some equipment including some of mine. Others will accept the above as enough and TRUST the rest of their system meets DO-160 and that DO-160 is designed to cover load dump and the equipment actually was tested to that specific part of DO-160. Quite a leap of faith in my opinion but perhaps not, as only the test results will tell. It is important to emphasize that damaging Load dumps need very special conditions to occur. Turning off your landing lights produces a load dump but a non failed system clamps it to harmless levels. There are several different tests needed, starting with components, assemblies, and ending up with system tests from alternator to battery with simulated (resistive) equipment loads. Voltage, current, and waveform recordings are included as needed in several parts of the system. The initial test demonstrated very repeatable results and verified the instrumentation approach. The testing is on a very limited set of major components. I do not have the $$ and time to test lots of components costing $$ each. TVS devices I do have in quantity in various types, but alternators and contactors are a different matter. I do not consider this a problem however, as any solution must have a design margin "Built in" of several times the measured data to cover major part variations. I am dismayed at the many recent comments, all apparently based on conjecture (at least I have not seen ANY reference to ANY real data) based on literature and concepts that have widely different conditions assumed. Looking thru the various data sheets and application notes provides a surprising array of examples of simulated load dumps and general comments and NO real alternator test load dump data. Lots of opinions presented as facts to support the authors opinion. I do not plan on any further comments on other load dump posts/comments until the testing is completed as to date its simply an exchange of opinion with no facts and takes time and bandwidth. As to comments that DO-160 equipment being designed to survive any load dump on any aircraft; I question that, but not having the relevant DO-160 test requirements, I have no way to comment. Paul ________________________________________________________________________________
Date: May 14, 2004
From: "Robert L. Nuckolls, III" <bob.nuckolls(at)cox.net>
Subject: Re: Co-ax splice method
> > >I'm about to close up the winglets on the Velocity I'm building, and I >need to extend the antenna wire first. The copper-foil type antenna came >to me with a short length of RG-58 attached, already glassed into the >winglet. I intend to extend it to the instrument panel with RG-400. The >area where the splice will be made will be inaccessible once I seal up the >winglet, so I want to use the parts and technique that has the lowest >probability of a problem for the life of the airframe. I could just >install a male connector on one and a female connector on the other, then >mate them and cover with some heatshrink. Is this the best approach to >this situation? Thanks for your advice! That's what I'd do. There is another suggestion for covering the joint with silicone tape. See S894 at bottom of page at: http://bandc.biz/cgi-bin/ez-catalog/cat_display.cgi?9X358218#S894 This tape is not very robust mechanically so I'd put a layer of heat shrink over it. You don't need much tape . . . one layer stretched tight and 30-50% overlap on turns is sufficient. Alternatively, there are internal melting wall heatshrinks that seal and encapsulate the finished joint. Bob . . . ________________________________________________________________________________
Date: May 14, 2004
From: "Robert L. Nuckolls, III" <bob.nuckolls(at)cox.net> crowbar module troubles
Subject: Re: For Bob Nuckolls: Roll your own
crowbar module troubles crowbar module troubles > >Bob, >This is a resend of previous information I posted but you didn't get. Peter, sorry for the delay on responding to this. Had a really busy week. I've printed your values out. Got a really boring meeting to go to this afternoon. I'll noodle over the data then. Bob . . . >I build my own OV crowbar module and it functions correctly except that >it operated in the 10-11 volt range. I triple checked the components >and wiring. I changed the 1.62K ohm resistor specified for a 14 volt >system to 6.04K and the circuit operates in the correct voltage range of >15.5-17 volts. >*************************** >Designating Point (1) as the + end of the capacitor, and Point (2) as the >junction of the 392 ohm resistor, and GND as the negative lead, with the >pot at midrange I got the >following readings: >****** >1.62 K resistor in place for 14 volt operation. - Trip point = 10.4 >volts. >Point (1) - Point (2) +0.436 volts >GND - Point (2) +7.6 volts >****** >6.04K resistor replacing the 1.62K one. - Trip point = 16.22 volts. >Point (1) - Point (2) +0.538 volts >GND - Point (2) +7.36 volts >****** > >These readings made me realize the circuit was not letting the zener >regulate at 12 volts so I did the following checks. >First I disconnected the SCR trigger lead to prevent it from firing. I >reinstalled the original 1.62K resistor. > >Measuring the Zener voltage from GND to Point (2): >As I increased the input voltage the voltage across the zener increases >linearly to about 8.25 volts and then starts to decrease. The input >voltage is about 9 volts when this knee occurs. > >I then disconnected the 1N4148 diode and repeated the above test with >basically the same results. > >With the 1N4148 diode still disconnected, I also disconnected the NPN >collector and PNP base (they remained connected together) from the point >(2) junction. Now only the Zener and 392 ohm resistor are in series >across the supply. Again measuring the Zener voltage from GND to point >(2): >The zener voltage tracks the input voltage up to about 11.3 volts at >which point the zener begins to regulate. > >With the two transistors still disconnected, I reconnected the 1N4148 >diode. >Now the voltage across the zener increases linearly up to 9 volts (input >voltage is 9.35) when suddenly the voltage drops to 1.87 volts. > >Do you have any suggestions to help troubleshoot of fix it. > >Ralph Ketter >RV-6 >Marysville, KS >*************************** > > Bob . . . ----------------------------------------- ( Experience and common sense cannot be ) ( replaced with policy and procedures. ) ( R. L. Nuckolls III ) ----------------------------------------- ________________________________________________________________________________
Date: May 14, 2004
From: "Robert L. Nuckolls, III" <bob.nuckolls(at)cox.net>
Subject: Re: DO-160
> >Bob, > >I would like to know the DO-160 requirements associated with transients >above say 24V including pulse duration, shape and peak V where the duration >is under one second. > >For example I recall there is a 40V pulse but I do not know its duration or >shape. I seem to recall there is a longer pulse at a lower voltage also. >Then there is the maximum Voltage steady state level. And perhaps others >addressing above normal bus voltage ranges. > >This info will help me with the load dump testing. Specifically IF I find >what appears to be a condition that exceeds DO-160 requirements. In that >case I want to further analize the test results and it would also be a >factor in any proposed solution which would be a final part of the load dump >tests. > >Paul Do you have a fax machine. I'll send you sections 16 and 17 out of the book. I could scan and e-mail them if needs be but it would be a huge file. Bob . . . ________________________________________________________________________________
From: "Paul Messinger" <paulm(at)olypen.com>
Subject: Re: DO-160
Date: May 14, 2004
Your off line response was great thanks a lot. Paul ----- > > Do you have a fax machine. I'll send you sections 16 and 17 out > of the book. I could scan and e-mail them if needs be but it would > be a huge file. > > Bob . . . > ________________________________________________________________________________
Date: May 14, 2004
From: "Robert L. Nuckolls, III" <bob.nuckolls(at)cox.net>
Subject: re: LOAD DUMP TEST START
> >The long waited REAL testing started on 5-13-04. > >This will take as long as it takes :-) at a rate of a couple of hours per >day, but likely completed this month. (Could also be less than a week to >preliminary final results, full writeup/documentation may take months.) > >Its not simple to design a test of this complexity when the results will >subject to the likes of Bob :-). I have some preconsived ideas of the >results (as do many of us, including Bob, but have set that aside and will >let the results stand for themselves. The test conditions are designed to >allow others to duplicate with reasonable accuract what I am doing so any or >all parts can be setuip in a different lab and the results should be >comparable considering the component and test equipment variations. > >System level Load Dump is not a simple issue as some have tried to make it. >That is IF the objective is to detail what happens and how it can effect the >other parts of the system. Even the OVP module is part of the system during >the time it takes to open the associated 5 amp CB. > >Only protection of the alternator internal diodes and regulator is one >solution and that only takes clamping the voltage to 35-40 volts and that >voltage is way too high for some equipment including some of mine. > >Others will accept the above as enough and TRUST the rest of their system >meets DO-160 and that DO-160 is designed to cover load dump and the >equipment actually was tested to that specific part of DO-160. Quite a leap >of faith in my opinion but perhaps not, as only the test results will tell. Anyone who produces a product (not a distributor or dealer) should be expected to KNOW the capabilities of their product. If they beg ignorance in matters of input power variability, then their skills in other matters of the product design are suspect as well. >It is important to emphasize that damaging Load dumps need very special >conditions to occur. Turning off your landing lights produces a load dump >but a non failed system clamps it to harmless levels. > >There are several different tests needed, starting with components, >assemblies, and ending up with system tests from alternator to battery with >simulated (resistive) equipment loads. > >Voltage, current, and waveform recordings are included as needed in several >parts of the system. > >The initial test demonstrated very repeatable results and verified the >instrumentation approach. > >The testing is on a very limited set of major components. I do not have the >$$ and time to test lots of components costing $$ each. TVS devices I do >have in quantity in various types, but alternators and contactors are a >diferrent matter. My mental image derived from your words suggest the task you describe is more complicated than it needs to be. I don't see much value in knowing the middle ground values for load dump events. We know what produces the worst case and we know that some manner of energy sink is needed to grunt the overshoot. See: http://www.aeroelectric.com/temp/loaddumptest.jpg This setup would allow one to take a commercial off-the-shelf alternator (I'd use a new N-D from B&C) or any number of junk-yard takeoffs to plot characteristics of the load dump event as it relates to load and speed of the alternator. You'd have to start out slow and low and work your way up to the conditions that ultimately trash the alternator's built in regulator. Alternatively, once the speed/load conditions are identified that put the regulator at risk (something on the order of 40v) then one could switch to investigation of proposed TVS devices to stand off the load-dump event up to and including full load on alternator at 12,000 rpm. By limiting unprotected testing conditions to those which do not produce regulator killing spikes, one could shift attention to the protection investigation at little risk for needing to repair a test article. A data acquisition system or recording 'scope could capture the voltage/current characteristics of energy dissipated in the TVS during load-dump events. It's would be interesting to explore ALL the variables associated with the various hypothetical situations it seems that the most economical effort is to size the device needed to clamp the worst case scenario at whatever target voltage you choose >I do not plan on any further comments on other load dump posts/comments >until the testing is completed as to date its simply an exchange of opinion >with no facts and takes time and bandwidth. > >As to comments that DO-160 equipment being designed to survive any load dump >on any aircraft; I question that, but not having the relevant DO-160 test >requirements, I have no way to comment. I have made the full text of DO-160 available to you. I cannot speak to the thinking of committee members while this document was being crafted. Don't know if they were considering alternators, generators or both but the values speak for themselves. See paragraph 16.5.4.4 where the worst case (Category Z) for 28v systems cites 80v square pulse (figure 16-4) for 100 milliseconds. and 48 volts for 1 second. This test is intended to characterize resistance to a spectrum of surge voltages described in Figure 16-6. 14V system values are 1/2 the 28v system voltages but with the same times so 40 and 24 volt surges apply. I've been testing to these values for over 30 years . . . it's a no-brainer. It seems to me that selection of a TVS device for clamping alternator load dumps to values LESS than those described in the first 100 milliseconds of figure 16-6 is no big deal. The OVP system takes care of lower voltage events beyond 100 milliseconds. This presumes, of course, that suppliers take the time and effort to recognize the value in building voltage surge immunity into their products as suggested by DO-160. If one wishes to limit load-dump amplitudes to values lower than those suggested by DO-160, then it's simply a engineering and parts selection task with new bounds. With a limited budget for time and dollars, it seems prudent to limit the investigation to conditions specific to the worst case. Bob . . . ________________________________________________________________________________
Date: May 14, 2004
From: richard(at)riley.net
Subject: FS - EGT/CHT probes
I've got 6 each Grand Rapids Technology EGT and CHT probes that I should get rid of - they're extras and have never been installed or used. Hose clamp style EGT, bayonet style CHT. They're $444 new, I'll sell the lot for $350. I'd prefer to sell the whole lot. ________________________________________________________________________________
From: "Paul Messinger" <paulm(at)olypen.com>
Subject: Re: re: LOAD DUMP TEST START
Date: May 14, 2004
----- Original Message ----- From: "Robert L. Nuckolls, III" <bob.nuckolls(at)cox.net> Subject: AeroElectric-List: re: LOAD DUMP TEST START > > > > >The long waited REAL testing started on 5-13-04. > > >> > Anyone who produces a product (not a distributor or dealer) should > be expected to KNOW the capabilities of their product. If they > beg ignorance in matters of input power variability, then their > skills in other matters of the product design are suspect as well. Agreed but then I have found many who seem to know about DO-160 and yet seem to have other product design problems. Also its very hard if not impossible to get thru sales to engineering to determine if the 24V max input V has margin including passage of a specific DO-160 by test or just engineering analysis or wishful thinking. Expect and assume are not something I use frequently as its poor thinking in far too many cases. > > > My mental image derived from your words suggest the task > you describe is more complicated than it needs to be. > I don't see much value in knowing the middle ground values > for load dump events. We know what produces the worst case and > we know that some manner of energy sink is needed to > grunt the overshoot. See: > > http://www.aeroelectric.com/temp/loaddumptest.jpg Interesting but seems to not address what happens before the "B" lead contactor opens to the equipment on the busses. > This setup would allow one to take a commercial off-the-shelf > alternator (I'd use a new N-D from B&C) or any number of junk-yard > takeoffs to plot characteristics of the load dump event as it > relates to load and speed of the alternator. I do not have a B&C or a ND alternator and no reason to know that its nominal much less worst case with regard to load dump. Thus the need for any test results to have design margin added. As for the DO-160 your info will be of great value to me during this testing period and far beyond. This is a low budget test and I do not have either the time or money to get fancy with variable speed drives, specific alternators, and extensive testing. I am not convinced there is all that much difference in alternators with similar current ratings. I do have a 45 and 65 amp (different brands and neither ND) alternator to test so we will see. I am testing what my background and education suggest needs to be tested. However one main concern is how a major load dump interacts in an aircraft system considering internal and external regulators and "B" lead contactors as well as battery contactors and the OVP interaction during the initial part of the load dump before the OVP blows the fuse starting the "B" lead contactor disconnect etc. > By limiting unprotected testing conditions to those which do not > produce regulator killing spikes, one could shift attention to > the protection investigation at little risk for needing to repair > a test article. A data acquisition system or recording 'scope could > capture the voltage/current characteristics of energy dissipated > in the TVS during load-dump events. That is what I have here A digital storage computing O' scope including the built in waveform computer for calculations etc. The delays were in part getting an expensive recal of the equipment for free (IE in spare time at test lab). Paul ________________________________________________________________________________
From: "Ross Mickey" <rmickey(at)ix.netcom.com>
Subject: Antenna Placement
Date: May 14, 2004
-----Original Message----- On Behalf Of Nielsen Mark Subject: AeroElectric-List: Antenna Placement Bob and Others, 2. Another option would be to mount the NAV antenna on the bottom of the fuselage. The balun would be attached directly to the bottom of the fuselage with the whiskers a 1/2" or so below the skin. How would this work? This is how mine is set up. The whiskers are under the horizontal. This setup works great. 3. If the NAV antenna is installed on the bottom of the fuselage, how far must (should) it be away from the COMM antenna? My com is located just aft of the battery box of my 6A on the centerline. There is no interference with the Nav. I am going to install a second Com behind the first that will be closer to the Nav. I will report after this is tested. Ross Mickey N9PT RV6A ________________________________________________________________________________
From: <bakerocb(at)cox.net>
Subject: Weight of RG142
Date: May 15, 2004
AeroElectric-List message previously posted by: "Eric M. Jones" <> 5/12/2004 Hello Eric, Forgive me -- I am going to disregard your requests to respond off line and to not say "It depends". But I will try to put some numbers in my answer. 1) My airplane uses 9 antennas: 2 VHF NAV, 2 VHF COMM, 1 GLIDE SLOPE (not connected), 1 MARKER BEACON, 1 GPS, 1 ELT, and 1 TRANSPONDER. 2) Assume that each box requires 5 feet of coax going to its respective antenna. This is over kill I know -- many of the coax runs are very short. This would be a total of 45 feet of coax (9X5=45). 3) The Belden catalog says that RG 142 weighs 4.3 pounds (68.8 ounces) per 100 feet. Or .688 ounces per foot. 4) 45 feet of coax times .688 ounces per foot gives a total of 30.96 ounces or 1.935 pounds. 5) I don't know of any 50 ohm RG type coax that is significantly lighter than RG142 (which has a solid steel core), but there may be some. There are some versions of RG 58 that are lighter -- and some heavier than RG142. 6) But even if you were to find a 50 ohm RG cable that was only half the weight of RG142 (unlikely) and used that in an airpane like mine you would be saving .9675 pounds. Not a trivial weight saving number, but not one that I would spend hours on trying to accomplish. OC PS: I don't have any weight figure for RG 400, a copper stranded core coax of comparable quality to RG 142. It may be a bit lighter. One can discuss the merits of solid core versus stranded core with some valid arguments on both sides. I've got both in my airplane. PPS: If I were limited to using only one type of RG for everything it would be RG 142. ________________________________________________________________________________
From: "Eric M. Jones" <emjones(at)charter.net>
Subject: Re: Weight of RG142
Date: May 15, 2004
Thanks OC, >>AeroElectric-List message previously posted by: "Eric M. Jones" >>If RG142 is the only coax that is used in an airplane--about how much is used per airplane? (Now please don't say it depends...). I am trying to find out how much weight can be saved by changing to something else, and if RG142 ONLY can be used for everything coaxial. > The Belden catalog says that RG 142 weighs 4.3 pounds (68.8 ounces) per 100 feet. Or .688 ounces per foot. >5) I don't know of any 50 ohm RG type coax that is significantly lighter than RG142 (which has a solid steel core), but there may be some. There are some versions of RG 58 that are lighter -- and some heavier than RG142. >6) But even if you were to find a 50 ohm RG cable that was only half the weight of RG142 (unlikely) and used that in an airplane like mine you would be saving .9675 pounds. Not a trivial weight saving number, but not one that I would spend hours on trying to accomplish. >OC The wire I have found is 0.24 ounces per foot (35% of the weight of standard RG142). Furthermore it has improved characteristics--50% better VSWR, 22% lower insertion loss, reduce phase and attenuation drift, etc. Making even much lighter cable is quite possible. The real question is what is losing a pound worth? Here's my rough estimate: Lets say your aircraft is worth $100,000 and weighs 2,000 pounds. Does this mean your airplane is worth $50/pound? Maybe. A better way to estimate the savings is to look at the total operating cost for the life of the aircraft. In this case lets imagine the aircraft will go 10,000 hours and costs $75 per hour to fly. Thats $750,000. At the end of this time we assume the aircraft will be valueless. So thats $750,000/2000 pounds; or $350/pound. Lets apply the reasonableness test to this: Does $350/pound mean that your old tin barf-bird sitting on the ramp is worth $350/pound? No. This figure says that the cost of moving a pound of airplane all over the sky for 10,000 hours (50 years at 200 hours per year for example) is $350. Thats perfectly reasonable. So how much should you pay to avoid the $350/pound expense? If you invested $35 compounded annually at 8% return with an inflation rate of 3.1%, you would have the $350 in 50 years. So the answer could be $35. (This simple example does not include the increased value in having an airplane that goes a little faster, etc.) (I would like aeroelectric listers opinions on this!). So in summary I really don't know. If the cable costs even nearly the same, certainly get the better and lighter cable. But there are certainly other factors--- A couple weeks ago there was a lister who thought my Super-2-CCA copper clad aluminum FatWire (available in two weeks) was too expensive for the weight saved. I honestly don't know how best to calculate such a thing. I once flew from Van Nuys, Ca to Winslow, Az in a Cessna150 and landed with a pound of usable fuel remaining. I would have paid plenty for that pound of fuel instead of a extra pound of wire. Regards, Eric M. Jones www.PerihelionDesign.com 113 Brentwood Drive Southbridge MA 01550-2705 Phone (508) 764-2072 Email: emjones(at)charter.net ________________________________________________________________________________
Date: May 15, 2004
Subject: Batterys
From: Boddicker <trumanst(at)netins.net>
Listers, and Bob, I know I have read about RG batterys on the list. Searched the archives for an hour and was not rewarded. Will a 17AH panasonic, or the like, turn over an 0-200? It will be wired per Z-11. I think I know the answer, but want confirmation before I order. Thanks, Kevin Boddicker ________________________________________________________________________________
From: "James E. Clark" <james(at)nextupventures.com>
Subject: Batterys
Date: May 15, 2004
The **Odessey PC680" (17AH) turns O-320's and O-360's with no problem. Thus I suspect that an O-200 can be handled. James > -----Original Message----- > From: owner-aeroelectric-list-server(at)matronics.com > [mailto:owner-aeroelectric-list-server(at)matronics.com]On Behalf Of > Boddicker > Sent: Saturday, May 15, 2004 8:50 PM > To: Aeroelectric list > Subject: AeroElectric-List: Batterys > > > Listers, and Bob, > I know I have read about RG batterys on the list. Searched the > archives for > an hour and was not rewarded. > Will a 17AH panasonic, or the like, turn over an 0-200? > It will be wired per Z-11. > I think I know the answer, but want confirmation before I order. > Thanks, > Kevin Boddicker > > ________________________________________________________________________________
Date: May 15, 2004
From: "thomas a. sargent" <sarg314(at)earthlink.net>
Subject: 6A gear weldment fit in a QB kit
I have a 6A quick build. In the QB kit the main gear weldment comes pre-drilled AND the fuselage has been pre-drilled. The problem is the holes in the two parts don't line up very well. How can this be, you say, wasn't it all drilled in place in the fuselage to start with? Apparently not. Bruce at vans tells me that they drill the gear weldment to the spar, but they don't match drill it to the fuselage. They drill those holes in the weldment on the bench somehow. The holes in the gear weldment that lie along the wing spar, look like they match the spar pretty well. But the group of 4 that penetrate the fuselage just forward of the spar appear to be off by at least 1/8" upward. My theory at the moment is that the forward piece that screws to the side of the fuselage (those 2 holes line up rather well) is actually about 1/8" too low. That raises the whole outboard end of the weldment 1/8". I gather many QB builders have similar problems with the gear weldment. What have other people done about it? Thanks, --- Tom Sargent, RV-6A QB ________________________________________________________________________________
Date: May 16, 2004
From: "thomas a. sargent" <sarg314(at)earthlink.net>
Subject: 6A gear weldment fit in a QB kit
OOps! Posted to the wrong list. I'll try to improve my aim. >I have a 6A quick build. In the QB kit the main gear weldment comes >pre-drilled AND the fuselage has been pre-drilled. The problem is the >holes in the two parts don't line up very well. Thanks, --- Tom Sargent, RV-6A QB ________________________________________________________________________________
From: "Paul Messinger" <paulm(at)olypen.com>
Subject: Re: Batterys
Date: May 16, 2004
The PC680 is a vary different battery that the lower cost Panasonic (etc brand) 17AH battery. About the only thing the two have in common are similar AH ratings. The PC680 is designed to have much higher cranking amps, longer life, no need for standby chargers, hundreds of very deep discharge cycles and true multi year life. The real world cost (including shipping) is typically only double the lower cost Panasonic or equivalent ($100 vs. $50 delivered). Sure it depends on where you live. After spending so much ( $$ ) on your aircraft I wonder why so many on this list seem to want to go to the lowest cost battery available when the best is so little more. Just based on specifications the PC680 is double the cranking power of the batteries used on most of the "Spam can" fleet up to and including the O540 etc engines. Given the multi year life, they are actually the same cost if you replace them every other year and more likely there is no need to replace them that frequently. Then there is the advantage of no need for standby chargers. I had a couple of them that were left over the winter and needed less than 1/2AH to top off after 6 months. BTW these batteries are not 2 1/2 years old and still load test to 95% of original capacity. Simple, no brainer, low cost, load testing is possible and I sure dislike replacing batteries just because its a "good idea". On the other hand, I would not fly with the lowest cost batteries in an electrically dependent aircraft. Paul ----- Original Message ----- From: "James E. Clark" <james(at)nextupventures.com> Subject: RE: AeroElectric-List: Batterys > > The **Odessey PC680" (17AH) turns O-320's and O-360's with no > problem. Thus I suspect that an O-200 can be handled. > > James ________________________________________________________________________________
Date: May 16, 2004
From: Walter Tondu <walter(at)tondu.com>
Subject: Re: 6A gear weldment fit in a QB kit
On 05/15 9:48, thomas a. sargent wrote: > I have a 6A quick build. In the QB kit the main gear weldment comes > pre-drilled AND the fuselage has been pre-drilled. The problem is the > holes in the two parts don't line up very well. > > How can this be, you say, wasn't it all drilled in place in the fuselage > to start with? Apparently not. Bruce at vans tells me that they drill > the gear weldment to the spar, but they don't match drill it to the > fuselage. They drill those holes in the weldment on the bench somehow. > > The holes in the gear weldment that lie along the wing spar, look like > they match the spar pretty well. But the group of 4 that penetrate the > fuselage just forward of the spar appear to be off by at least 1/8" > upward. My theory at the moment is that the forward piece that screws > to the side of the fuselage (those 2 holes line up rather well) is > actually about 1/8" too low. That raises the whole outboard end of the > weldment 1/8". > > I gather many QB builders have similar problems with the gear weldment. > What have other people done about it? I had the exact same problem with my 7A. I have a QB wings and SB fuselage. I tried all day to get that damn thing to fit. Called Vans the following monday. Their suggestion started off like this, "get the hydraulic jack from your car, ..." I was flabergasted. No can do. I ordered a new one from Vans, not cheap. Fit like a glove. Apparently they are welded in a jig. Vans indicates that if it's removed from the jig before it cools it may have a tencancy to "slip" a bit. BS. They wouldn't take the original in trade. Now I have a weird looking paperweight. I've detailed the issues on my site. -- Walter Tondu http://www.tondu.com/rv7 ________________________________________________________________________________
From: "Fergus Kyle" <VE3LVO(at)rac.ca>
Subject: Weight of RG-142
Date: May 16, 2004
"(This simple example does not include the increased value in having an airplane that goes a little faster, etc.) (I would like aeroelectric listers opinions on this!). So in summary I really don't know. If the cable costs even nearly the same, certainly get the better and lighter cable. But there are certainly other factors---" Eric, Your arguments are cogent, but I think too complex for the prupose. Having helped rebuild a Yale, Stearman and several other WW II aircraft, and in midst of building a Europa, I would say the most vital statistic for a aircraft destined to fly for 30 years privately - is the reliability factor. The last thing I want to do ever again is re-route coax. It's never out in the open but snaking from one compartment to next, trying to get outside to an antenna. It is ALWAYS bent too tight for the corners to remain central (creeping core which changes impedance) and one needs to know it will be sustained through the ravages of temp and humidity over the years. The connectors are usually poorly attached and protected, and often must be connected in the darkest reaches of the vehicle. For me, weight ain't even "in it". Do it once properly and forget it. Ferg Europa A064 ________________________________________________________________________________
From: "Scott & Leere' Aldrich" <flynski(at)mwutah.com>
Subject: Batterys Cost
Date: May 16, 2004
>The real world cost (including shipping) is typically only double the lower >cost Panasonic or equivalent ($100 vs. $50 delivered). Sure it depends on >where you live. >Paul Ebay search for pc 680, you will find Odyssey world $53.50 plus flat rate $12 shipping anywhere in US. http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&rd=1&item=790221845 6&category=34284 ----- Original Message ----- From: "James E. Clark" <james(at)nextupventures.com> Subject: RE: AeroElectric-List: Batterys > > The **Odessey PC680" (17AH) turns O-320's and O-360's with no > problem. Thus I suspect that an O-200 can be handled. > > James ________________________________________________________________________________
Date: May 16, 2004
From: Mickey Coggins <mick-matronics(at)rv8.ch>
Subject: Re: Batterys
Hi, I have not any research on RG batteries, but I was under the impression that they have pretty much the same specifications and ratings. What kind of things can we use to tell them apart, besides the price? Thanks, Mickey >The PC680 is a vary different battery that the lower cost Panasonic (etc >brand) 17AH battery. About the only thing the two have in common are similar >AH ratings. -- Mickey Coggins http://www.rv8.ch/ #82007 QB Wings/Fuselage ________________________________________________________________________________
Date: May 16, 2004
From: Matt Jurotich <mjurotich(at)hst.nasa.gov>
Subject: ? Pyramid PS-26KX Regulated Adj Voltage 25Amp PowerSupply?
Folks Anybody with experience with Pyramid PS-26KX Regulated Adjustable Voltage 25Amp Power or Pyramid products in general? http://www.etronics.com/product.asp?stk_code=pyrps26kx&store=&catid=4071 This sounds like what I really want for bench testing my new panel. The only alternative being seriously considered is a a much lower output variable supply in parallel with a usable for bench testing battery. Thanks in aadvance Matthew M. Jurotich NASA/Goddard Space Flight Center JWST ISIM Systems Engineer m/c : 443 e-mail mailto: mjurotich(at)hst.nasa.gov phone : 301-286-5919 fax : 301-286-7021 JWST URL: <http://ngst1.gsfc.nasa.gov> ________________________________________________________________________________
From: "Eric M. Jones" <emjones(at)charter.net>
Subject: Re: Weight of RG-142
Date: May 16, 2004
Ferg, I appreciate your wisdom and advice. My interest in this is more to sell product than build an airplane. (Hey, I'm broke, but building a Glastar). RG142 has a steel center conductor so that it can be strung between poles and run up antenna towers. Not very useful in an airplane. Furthermore the bend radius of the wire I am researching is much smaller than standard RG142. Regards, Eric M. Jones www.PerihelionDesign.com 113 Brentwood Drive Southbridge MA 01550-2705 Phone (508) 764-2072 Email: emjones(at)charter.net ________________________________________________________________________________
Date: May 16, 2004
From: "Robert L. Nuckolls, III" <bob.nuckolls(at)cox.net>
Subject: Re: Weight of RG142
> >The wire I have found is 0.24 ounces per foot (35% of the weight of standard >RG142). Furthermore it has improved characteristics--50% better VSWR, 22% >lower insertion loss, reduce phase and attenuation drift, etc. Making even >much lighter cable is quite possible. > >The real question is what is losing a pound worth? Here's my rough estimate: > >Lets say your aircraft is worth $100,000 and weighs 2,000 pounds. Does this >mean your airplane is worth $50/pound? Maybe. > >A better way to estimate the savings is to look at the total operating cost >for the life of the aircraft. In this case lets imagine the aircraft will >go 10,000 hours and costs $75 per hour to fly. Thats $750,000. At the end >of this time we assume the aircraft will be valueless. So thats >$750,000/2000 pounds; or $350/pound. > >Lets apply the reasonableness test to this: Does $350/pound mean that your >old tin barf-bird sitting on the ramp is worth $350/pound? No. This figure >says that the cost of moving a pound of airplane all over the sky for 10,000 >hours (50 years at 200 hours per year for example) is $350. Thats perfectly >reasonable. > >So how much should you pay to avoid the $350/pound expense? If you invested >$35 compounded annually at 8% return with an inflation rate of 3.1%, you >would have the $350 in 50 years. So the answer could be $35. > >(This simple example does not include the increased value in having an >airplane that goes a little faster, etc.) > >(I would like aeroelectric listers opinions on this!). > >So in summary I really don't know. If the cable costs even nearly the same, >certainly get the better and lighter cable. >But there are certainly other factors--- > >A couple weeks ago there was a lister who thought my Super-2-CCA copper clad >aluminum FatWire (available in two weeks) was too expensive for the weight >saved. I honestly don't know how best to calculate such a thing. I once flew >from Van Nuys, Ca to Winslow, Az in a Cessna150 and landed with a pound of >usable fuel remaining. I would have paid plenty for that pound of fuel >instead of a extra pound of wire. > >Regards, >Eric M. Jones Excellent points. I can reinforce those ideas with the following anecdotes from my own experience. In 1964 when I was a tech writer for Cessna, a number commonly circulated around the engineering department suggested "For every pound of emptly weight added to our airplanes, it will cost the owner(s) of that airplane $100 to buy the pound of stuff, maintain it, and purchase fuel to carry it around over the lifetime of the airplane. When I worked at Lear on the Gates-Piaggio GP-180 program, I asked my management how much bonus I could offer my suppliers for weight reduction. That got me a bunch of surprise looks. "Shucks Nuckolls, beat 'em up for every ounce you can get . . . but why should we offer a 'bonus'? I told them about my experience at Cessna. They went off into a huddle and a few days later came back with a figure of $300. I was skeptical that it was truly that low . . . but it did mark a milestone in the way my management thought about the economics of designing, building and operating our products. The fact that they would offer ANY substantial number in dollars for weight reduction was pretty cool. A few days ago, I meet one of RAC's higher engineering management folks in the Denver airport. He had been visiting kids in the Denver area and I was coming back from a consulting trip in Idaho. I bemoaned the state of an important system in one of our products that was too complicated (astounding parts count), too heavy (about 50-60 pounds), terrible service history (been in the #1 trouble reports slot on the airplane since day-one), and about 1.5 to 2x more expensive than more attractive options. I proposed RAC consider of a system that was at least 50 pounds lighter with a demonstrated zero faults performance record for many hours on a flight test aircraft. I asked him what it was worth for weight reduction on this airplane? He didn't think long before he came up with the number of $2,000 per pound. I then described my proposal for replacing the system and suggested that if we could carve 50 pounds out, 1/3 to 1/2 the cost of hardware, 95% of the installation labor and offer system with an impeccable track record then at $100,000 savings to the customer (in ADDITION to good will generated by eliminating a troublesome system), that changing over to the new system was essentially "free" . . . yes, there are some up-front costs on the order of a $million but this would amortize out VERY quickly. He didn't argue with me. The discussion went to other topics but it will be interesting to see what his reaction and support is when I bring this solution up in an upcoming meeting. Eric's observations are accurate and right on point. There are economies of operation, financing, fabrication and parts selection that can argue most energetically with each other. During Voyager's design and construction phases we were told that it takes 5# of fuel to carry 1# of airplane around the world. This means that every pound of empty weight jacks up take off weight by 6 pounds. Here the economies of operation held sway and every effort was made to carve grams out of the airplane sometimes at great expense on an airplane that had a lifetime of a few hundred hours! Each of you needs to make your own decisions as to which economy drives various decisions for purchase and assembly of parts. I've oft used the term "cost of ownership" in discussions where the long term benefit from a larger investment up front pays off. I've also championed the notion of parts-count-reduction where the economies of reliability are perceived as most important. If one can bring multiple benefits to bear (lower parts count, lower weight, lower cost of ownership) while improving performance . . . then I'll suggest this is the very ESSENCE of the OBAM aircraft fabrication philosophy that will never be fully realized in the certified world. While OBAM aircraft have published gross weight limits, I think we can agree that those limits can be pushed under certain conditions (cool air, c.g. well inside limits, etc) and certain times when they cannot. It seems that spending lots of time and dollars on weight reduction for weight reduction's sake may not be the same overpowering economy in OBAM aircraft that it is in certified ships. I'll join Eric in offering the notion that the simple-ideas underlying the really elegant decision are easily obscured by a lot of ol' pilot's tales and hangar wisdom. Bringing questions out to the List is the best place to filter the various ideas in search of the elegant solution. Bob . . . ________________________________________________________________________________
From: <bakerocb(at)cox.net>
Subject: Weight of RG142
Date: May 16, 2004
AeroElectric-List message previously posted by: "Eric M. Jones" <<....skip.....The wire I have found is 0.24 ounces per foot (35% of the weight of standard RG142). Furthermore it has improved characteristics--50% better VSWR, 22% lower insertion loss, reduce phase and attenuation drift, etc.....skip....>> 5/16/2004 Hello Eric, Can you please share with us the identity, source, and cost of this wire? Thanks. OC PS: I found your weight analysis benefit very interesting. Please let me add another sort-of-weight benefit consideration. The situation involved an airplane ditching and subsequent rescue at sea within hours. In debriefing the survivors one spoke of the desperate level of thirst that he experienced shortly after being free of the ditched aircraft. He described the thirst as almost totally mentally debilitating and leaving his mouth and throat so dry that he was unable to transmit over his portable survival radio. He vowed that he would never again fly in an airplane unless he had at least a pint of water personally available. A pint of water weighs one pound. What is that pound worth? ________________________________________________________________________________
Date: May 16, 2004
From: Charlie England <ceengland(at)bellsouth.net>
Subject: Re: ? Pyramid PS-26KX Regulated Adj Voltage 25Amp
PowerSupply? Matt Jurotich wrote: > >Folks > >Anybody with experience with Pyramid PS-26KX Regulated Adjustable Voltage >25Amp Power or Pyramid products in general? > >http://www.etronics.com/product.asp?stk_code=pyrps26kx&store=&catid=4071 > >This sounds like what I really want for bench testing my new panel. The >only alternative being seriously considered is a a much lower output >variable supply in parallel with a usable for bench testing battery. > >Thanks in aadvance > >Matthew M. Jurotich > >NASA/Goddard Space Flight Center >JWST ISIM Systems Engineer > >m/c : 443 >e-mail mailto: mjurotich(at)hst.nasa.gov >phone : 301-286-5919 >fax : 301-286-7021 > >JWST URL: <http://ngst1.gsfc.nasa.gov> > Since you work for NASA, I'm sure you've heard the old urban legend about 0-G writing instruments for NASA & the Soviets. As a corollary, you can buy a 12 V jump start pack from Harbor Freight, WalMart, etc. for under $50 & it will have uses outside of & beyond your a/c project. The only thing you might need adjustable voltage for is checking a low-voltage warning circuit. You can get that by just letting the battery in the jump start pack run down the trip voltage of the detector. 'Better is the enemy of good enough.' Charlie ________________________________________________________________________________
Date: May 16, 2004
From: "Robert L. Nuckolls, III" <bob.nuckolls(at)cox.net>
Subject: Re: Weight of RG142
> >PS: I found your weight analysis benefit very interesting. Please let me >add another sort-of-weight benefit consideration. The situation involved >an airplane ditching and subsequent rescue at sea within hours. In >debriefing the survivors one spoke of the desperate level of thirst that >he experienced shortly after being free of the ditched aircraft. He >described the thirst as almost totally mentally debilitating and leaving >his mouth and throat so dry that he was unable to transmit over his >portable survival radio. He vowed that he would never again fly in an >airplane unless he had at least a pint of water personally available. A >pint of water weighs one pound. What is that pound worth? Aha! The economics of survival. Economics has been often described as the study of scarce resources for which there are multiple uses. Economics isn't just about dollars. Bob . . . ________________________________________________________________________________
Date: May 16, 2004
From: richard(at)riley.net
Subject: Re: Weight of RG142
At 10:37 AM 5/16/04, you wrote: > > > > > > >PS: I found your weight analysis benefit very interesting. Please let me > >add another sort-of-weight benefit consideration. The situation involved > >an airplane ditching and subsequent rescue at sea within hours. In > >debriefing the survivors one spoke of the desperate level of thirst that > >he experienced shortly after being free of the ditched aircraft. He > >described the thirst as almost totally mentally debilitating and leaving > >his mouth and throat so dry that he was unable to transmit over his > >portable survival radio. He vowed that he would never again fly in an > >airplane unless he had at least a pint of water personally available. A > >pint of water weighs one pound. What is that pound worth? > > Aha! The economics of survival. Economics has been > often described as the study of scarce resources for > which there are multiple uses. Economics isn't just about > dollars. Last week I was at a technology expo for my Very Large Aerospace Company. They had a wonderful materials display. Thinwall titanium casting, additive titanium, laser fusing. They had a nose gear strut for a 777 made of silicon carbide fibers in a titanium matrix. They said it save weight at about $1000/lb. At that price, it was worth it to them. ________________________________________________________________________________
From: "William Slaughter" <willslau(at)alumni.rice.edu>
Subject: ? Pyramid PS-26KX Regulated Adj Voltage 25Amp PowerSupply?
Date: May 16, 2004
I have a PS-26KX that has been working well. I've owned it about a year, and it has experienced a very low duty cycle, but it seems to be well made, and judging by the weight, must have a healthy size transformer. No complaints. William Slaughter -----Original Message----- From: owner-aeroelectric-list-server(at)matronics.com [mailto:owner-aeroelectric-list-server(at)matronics.com] On Behalf Of Matt Jurotich Subject: AeroElectric-List: ? Pyramid PS-26KX Regulated Adj Voltage 25Amp PowerSupply? --> Folks Anybody with experience with Pyramid PS-26KX Regulated Adjustable Voltage 25Amp Power or Pyramid products in general? http://www.etronics.com/product.asp?stk_code=pyrps26kx&store=&catid=4071 This sounds like what I really want for bench testing my new panel. The only alternative being seriously considered is a a much lower output variable supply in parallel with a usable for bench testing battery. Thanks in aadvance Matthew M. Jurotich NASA/Goddard Space Flight Center JWST ISIM Systems Engineer m/c : 443 e-mail mailto: mjurotich(at)hst.nasa.gov phone : 301-286-5919 fax : 301-286-7021 JWST URL: <http://ngst1.gsfc.nasa.gov> == direct advertising on the Matronics Forums. == == == ________________________________________________________________________________
From: "David Schaefer" <dschaefer1(at)kc.rr.com>
Subject: Bob - Single Ground question ??
Date: May 16, 2004
Bob .. I need your thoughts on a problem I've run up against. I've followed your single ground specifications to a tee. All my grounds are run to the single B&C ground block. However, I have an issue. I have a 'pre-made' harness with 8 power and 8 ground connections all on very short 6" leads coming out of the main cable bundle which is about 4' long. All had ring terminals on them. I've cut off the power side ring terminals and replaced them with fast-ons to connect to my B&C fuse block. However, I can't decide what to do with the ground side. #1 Do I cut off the ring terminals and splice longer wires (3') onto the leads to get back across the plane to the ground block (3' away)? #2 Do I put the ring terminals on a single bolt and run one larger wire back to the ground block? #3 Do I put a couple of bolt-studs by the fuse blocks and ground the ring terminals to the firewall at the local site? Will the splices 'degrade' the ground? I'll look forward to your input. Regards DWS ________________________________________________________________________________
Date: May 16, 2004
From: "Robert L. Nuckolls, III" <bob.nuckolls(at)cox.net>
Subject: Re: Batteries
> > >Hi, > >I have not any research on RG batteries, but I was under >the impression that they have pretty much the same >specifications and ratings. What kind of things can >we use to tell them apart, besides the price? Their ratings are what they are . . . if you want to compare the nitty-gritty details of one battery against another, then download the data sheets for each battery from the manufacturer. Keep in mind that "ratings" generally don't say much about service life . . . particularly with respect to how you want to use the battery (crank an engine a couple dozen times a year, fly perhaps 50 hours out of a total of 8670 hours/year. The battery sits unattended for 8720 hours per year in a variety of environmental conditions which MAY include the occasional total discharge for having left something turned on. There's just no way any manufacturer can sign up to this task with certainty nor can he compare his product with anyone else's product with accuracy. Therefore, one must resort to marketing hype in an attempt to distinguish his product from the competitors. If you want to get 100% out of an expensive battery, then be prepared to do periodic capacity tests and discard the battery when cap test falls below your e-bus operations requirements (this too can be a huge variable). You may find that the added labor and tools to squeeze an expensive battery dry costs more than buying the cheapest battery you can find and replacing it every year. This goes directly to the thread I responded to earlier about the economics of weight savings, etc. etc. Here we're talking the economics of maintenance to maintain reliability. I suggest the cost of ownership for the lower cost, "disposable" battery is ultimately less than squeezing every last drop from a $high$ battery. Bob . . . ________________________________________________________________________________
Date: May 16, 2004
From: "Robert L. Nuckolls, III" <bob.nuckolls(at)cox.net> 25Amp PowerSupply?
Subject: Re: ? Pyramid PS-26KX Regulated Adj Voltage
25Amp PowerSupply? 25Amp PowerSupply? > > >Folks > >Anybody with experience with Pyramid PS-26KX Regulated Adjustable Voltage >25Amp Power or Pyramid products in general? > >http://www.etronics.com/product.asp?stk_code=pyrps26kx&store=&catid=4071 > >This sounds like what I really want for bench testing my new panel. The >only alternative being seriously considered is a a much lower output >variable supply in parallel with a usable for bench testing battery. > >Thanks in aadvance > >Matthew M. Jurotich This has the right specs. I'd think it was a good value for the task. Bob . . . ________________________________________________________________________________
Date: May 17, 2004
From: Mickey Coggins <mick-matronics(at)rv8.ch>
Subject: Re: Batteries
That's kind of what I thought too. I'll just swap one of my batteries out each year. Sort of like the info you gave in this article: http://www.aeroelectric.com/articles/AA_Bat_Test.pdf Thanks, Mickey > ... I > suggest the cost of ownership for the lower cost, "disposable" > battery is ultimately less than squeezing every last drop > from a $high$ battery. -- Mickey Coggins http://www.rv8.ch/ #82007 QB Wings/Fuselage ________________________________________________________________________________
Date: May 17, 2004
From: "Robert L. Nuckolls, III" <bob.nuckolls(at)cox.net>
Subject: Re: Bob - Single Ground question ??
> > >Bob .. >I need your thoughts on a problem I've run up against. I've followed your >single ground specifications to a tee. All my grounds are run to the single >B&C ground block. > >However, I have an issue. I have a 'pre-made' harness with 8 power and 8 >ground connections all on very short 6" leads coming out of the main cable >bundle which is about 4' long. All had ring terminals on them. I've cut >off the power side ring terminals and replaced them with fast-ons to connect >to my B&C fuse block. > >However, I can't decide what to do with the ground side. > >#1 Do I cut off the ring terminals and splice longer wires (3') onto the >leads to get back across the plane to the ground block (3' away)? > >#2 Do I put the ring terminals on a single bolt and run one larger wire back >to the ground block? > >#3 Do I put a couple of bolt-studs by the fuse blocks and ground the ring >terminals to the firewall at the local site? Give #3 a try. If you don't have an noise problem from the ignition system (and you probably won't), then there's nothing else to do. If push comes to shove and you do get some noise, then extend the individual wires to the ground block. >Will the splices 'degrade' the ground? No. Bob . . . ----------------------------------------- ( Experience and common sense cannot be ) ( replaced with policy and procedures. ) ( R. L. Nuckolls III ) ----------------------------------------- ________________________________________________________________________________
Date: May 17, 2004
From: "Robert L. Nuckolls, III" <bob.nuckolls(at)cox.net>
Subject: Re: Weight of RG-142
Eric Jones wrote: >The wire I have found is 0.24 ounces per foot (35% of the weight of standard >RG142). Furthermore it has improved characteristics--50% better VSWR, 22% >lower insertion loss, reduce phase and attenuation drift, etc. Making even >much lighter cable is quite possible. > >The real question is what is losing a pound worth? Here's my rough estimate: > >Lets say your aircraft is worth $100,000 and weighs 2,000 pounds. Does this >mean your airplane is worth $50/pound? Maybe. > >A better way to estimate the savings is to look at the total operating cost >for the life of the aircraft. In this case lets imagine the aircraft will >go 10,000 hours and costs $75 per hour to fly. Thats $750,000. At the end >of this time we assume the aircraft will be valueless. So thats >$750,000/2000 pounds; or $350/pound. > >Lets apply the reasonableness test to this: Does $350/pound mean that your >old tin barf-bird sitting on the ramp is worth $350/pound? No. This figure >says that the cost of moving a pound of airplane all over the sky for 10,000 >hours (50 years at 200 hours per year for example) is $350. Thats perfectly >reasonable. > >So how much should you pay to avoid the $350/pound expense? If you invested >$35 compounded annually at 8% return with an inflation rate of 3.1%, you >would have the $350 in 50 years. So the answer could be $35. > >(This simple example does not include the increased value in having an >airplane that goes a little faster, etc.) > >(I would like aeroelectric listers opinions on this!). > >So in summary I really don't know. If the cable costs even nearly the same, >certainly get the better and lighter cable. >But there are certainly other factors--- > >A couple weeks ago there was a lister who thought my Super-2-CCA copper clad >aluminum FatWire (available in two weeks) was too expensive for the weight >saved. I honestly don't know how best to calculate such a thing. I once flew >from Van Nuys, Ca to Winslow, Az in a Cessna150 and landed with a pound of >usable fuel remaining. I would have paid plenty for that pound of fuel >instead of a extra pound of wire. > >Regards, >Eric M. Jones Excellent points. I can reinforce those ideas with the following anecdotes from my own experience. In 1964 when I was a tech writer for Cessna, a number commonly circulated around the engineering department suggested "For every pound of emptly weight added to our airplanes, it will cost the owner(s) of that airplane $100 to buy the pound of stuff, maintain it, and purchase fuel to carry it around over the lifetime of the airplane. When I worked at Lear on the Gates-Piaggio GP-180 program, I asked my management how much bonus I could offer my suppliers for weight reduction. That got me a bunch of surprise looks. "Shucks Nuckolls, beat 'em up for every ounce you can get . . . but why should we offer a 'bonus'? I told them about my experience at Cessna. They went off into a huddle and a few days later came back with a figure of $300. I was skeptical that it was truly that low . . . but it did mark a milestone in the way my management thought about the economics of designing, building and operating our products. The fact that they would offer ANY substantial number in dollars for weight reduction was pretty cool. A few days ago, I meet one of RAC's higher engineering management folks in the Denver airport. He had been visiting kids in the Denver area and I was coming back from a consulting trip in Idaho. I bemoaned the state of an important system in one of our products that was too complicated (astounding parts count), too heavy (about 50-60 pounds), terrible service history (been in the #1 trouble reports slot on the airplane since day-one), and about 1.5 to 2x more expensive than more attractive options. I proposed RAC consider of a system that was at least 50 pounds lighter with a demonstrated zero faults performance record for many hours on a flight test aircraft. I asked him what it was worth for weight reduction on this airplane? He didn't think long before he came up with the number of $2,000 per pound. I then described my proposal for replacing the system and suggested that if we could carve 50 pounds out, 1/3 to 1/2 the cost of hardware, 95% of the installation labor and offer system with an impeccable track record then at $100,000 savings to the customer (in ADDITION to good will generated by eliminating a troublesome system), that changing over to the new system was essentially "free" . . . yes, there are some up-front costs on the order of a $million but this would amortize out VERY quickly. He didn't argue with me. The discussion went to other topics but it will be interesting to see what his reaction and support is when I bring this solution up in an upcoming meeting. Eric's observations are accurate and right on point. There are economies of operation, financing, fabrication and parts selection that can argue most energetically with each other. During Voyager's design and construction phases we were told that it takes 5# of fuel to carry 1# of airplane around the world. This means that every pound of empty weight jacks up take off weight by 6 pounds. Here the economies of operation held sway and every effort was made to carve grams out of the airplane sometimes at great expense on an airplane that had a lifetime of a few hundred hours! Each of you needs to make your own decisions as to which economy drives various decisions for purchase and assembly of parts. I've oft used the term "cost of ownership" in discussions where the long term benefit from a larger investment up front pays off. I've also championed the notion of parts-count-reduction where the economies of reliability are perceived as most important. If one can bring multiple benefits to bear (lower parts count, lower weight, lower cost of ownership) while improving performance . . . then I'll suggest this is the very ESSENCE of the OBAM aircraft fabrication philosophy that will never be fully realized in the certified world. While OBAM aircraft have published gross weight limits, I think we can agree that those limits can be pushed under certain conditions (cool air, c.g. well inside limits, etc) and certain times when they cannot. It seems that spending lots of time and dollars on weight reduction for weight reduction's sake may not be the same overpowering economy in OBAM aircraft that it is in certified ships. I'll join Eric in offering the notion that the simple-ideas underlying the really elegant decision are easily obscured by a lot of ol' pilot's tales and hangar wisdom. Bringing questions out to the List is the best place to filter the various ideas in search of the elegant solution. Bob . . . ________________________________________________________________________________
From: "Ron Lee" <rlee468(at)comcast.net>
Subject: Batteries
Date: May 17, 2004
Since I've started using an automatic battery maintainer, my plane and cycle batteries have lasted two to three times as long. ________________________________________________________________________________
Subject: starting-only battery
From: Bob Bittner <rbittner(at)us.ibm.com>
Date: May 17, 2004
05/17/2004 09:48:06 AM, Serialize complete at 05/17/2004 09:48:06 AM Probably not too many people on the list with "no" electrical system in their airplane, but perhaps someone here could offer insight.. A friend with a Parakeet bipe (currently no electrical system) wants to add just a starter & battery to his airplane. He'd like to know about how much capacity one would need to get at least 3-4 starts out of a battery then charge it back up when home. I think it's a Cont O-200. Certainly, it could vary based on how long it takes to start, temperature, etc. But, I'm just probing for him any stories or suggestions from the group. It seems the amp-hour ratings decline as the load current increases, so I don't think one could rely on capacity calculated from the normal Ah rating. Anyone out there with just a battery & starter for wiring demands? Thanks. ---------------------------------------------- >+ Bob Bittner ________________________________________________________________________________
From: Chuck Jensen <cjensen(at)dts9000.com>
Subject: Alarm System
Date: May 17, 2004
Is there an alarm system available for exp. aircraft that has been used. I have a keyed door but, having just installed avionics that has the equivalent value of the GNP of a developing nation, I'd like to give potential thieves a better run for their money than some winky door lock. An audible alarm and potentially activation of strobe and canard flashers would seem to be a minimu. I assume some "good" solutions have been worked out but didn't find it in the archives. Ideas? Chuck, in East Tennessee Velocity XLRG ________________________________________________________________________________
Date: May 17, 2004
From: "David E. Nelson" <david.nelson(at)pobox.com>
Subject: Re: starting-only battery
Hi Bob, Can't help the capacity question but I do have thought here: Might I suggest he carry a small 12 V solar panel (say from JC Whitney) with him just in case no power source for the charger is available. Maybe also rig it so that it charges the battery while in flight since he's resticted to day time only flying. Regards, /\/elson On Mon, 17 May 2004, Bob Bittner wrote: > > Probably not too many people on the list with "no" electrical system in > their airplane, but perhaps someone here could offer insight.. > > A friend with a Parakeet bipe (currently no electrical system) wants to > add just a starter & battery to his airplane. He'd like to know about how > much capacity one would need to get at least 3-4 starts out of a battery > then charge it back up when home. I think it's a Cont O-200. Certainly, > it could vary based on how long it takes to start, temperature, etc. But, > I'm just probing for him any stories or suggestions from the group. > > It seems the amp-hour ratings decline as the load current increases, so I > don't think one could rely on capacity calculated from the normal Ah > rating. > > Anyone out there with just a battery & starter for wiring demands? > > Thanks. > > ---------------------------------------------- >+ > Bob Bittner > > > > > > > -- ~~ ** ~~ If you didn't learn anything when you broke it the 1st ~~ ** ~~ time, then break it again. ________________________________________________________________________________
Date: May 17, 2004
From: Dj Merrill <deej(at)thayer.dartmouth.edu>
Subject: Re: Alarm System
Chuck Jensen wrote: > > Is there an alarm system available for exp. aircraft that has been used. I > have a keyed door but, having just installed avionics that has the > equivalent value of the GNP of a developing nation, I'd like to give > potential thieves a better run for their money than some winky door lock. > An audible alarm and potentially activation of strobe and canard flashers > would seem to be a minimu. I assume some "good" solutions have been worked > out but didn't find it in the archives. Ideas? > > Chuck, in East Tennessee > Velocity XLRG Electrify the door lock for a nice "shocking" surprise? ;-) Seriously, though, you could probably easily adapt a car alarm, although I'd be a little concerned about running the battery dead. -Dj ________________________________________________________________________________
Date: May 17, 2004
From: echristley(at)nc.rr.com
Subject: Re: Weight of RG-142
> > I'll join Eric in offering the notion that the simple-ideas > underlying the really elegant decision are easily obscured by > a lot of ol' pilot's tales and hangar wisdom. I appreciate Eric's analysis so much, that I'm going to order some copper clad aluminum wire even if I end up not using it. I don't necessarily think his analysis is correct, but even the fact that he made an ATTEMPT to justify the weight savings on a dollar savings basis is a watershed event for me. I mean, how often do you see the adds that scream "SAVE .08oz for only $18,000!!" The problem I have with Eric's analysis is that it doesn't seem to seperate out what the effect of adding #1 will have. It just sort of lumps the additional weight in with everything. What I really want to get at is, "How much more will it cost me in the long run to use the radio that is #1 heavier?" I think the best method of analysis would derive from Bob's experience on the Voyager project. #1 requires #5 of fuel to go around the world. I don't see the examples of the more business type planes being as applicable, because by their very nature spec'd out to fly a lot more. But the around the world voyager trip. That is a trip of around 25,000 miles, and five pounds of fuel is around a gallon. The numbers I hear for the average GA pilot flight time is about 100hrs/year, which amounts to a 2hr flight EVERY weekend. With a 200mph plane, that's about 20,000 miles per year. So, saving a pound will save a gallon of gas a year. Or about $3 (I'll run mogas. About $2 for me.) Now, I don't see the typical OBAM aircraft flying for 30 years in its original configuration. Radios, tires possibly even engines change. Not only that, I'm likely to sell it in a decade after my wife gets tired of me and takes half the plane in the divorce. Do I really care that the next guy might have a slightly higher fuel burn? Then there is the high probability of mother nature or an accident taking it out. I don't have actuarial data, but I would put the lifetime of the aircraft at 10 years. So, how much do you spend to save $30 ($3x10years)? Funny how my final number came so close to Eric's. To me, that's a good number. I realize that any analysis of this type is full of maybe's, what if's and mostly speculation. ________________________________________________________________________________
From: "Jim Stone" <jrstone(at)insightbb.com>
Subject: Re: Alarm System
Date: May 17, 2004
Hey Chuck, What avionics did you install, and what is your exact address? JHSF, Jim ----- Original Message ----- From: "Chuck Jensen" <cjensen(at)dts9000.com> Subject: AeroElectric-List: Alarm System > > Is there an alarm system available for exp. aircraft that has been used. I > have a keyed door but, having just installed avionics that has the > equivalent value of the GNP of a developing nation, I'd like to give > potential thieves a better run for their money than some winky door lock. > An audible alarm and potentially activation of strobe and canard flashers > would seem to be a minimu. I assume some "good" solutions have been worked > out but didn't find it in the archives. Ideas? > > Chuck, in East Tennessee > Velocity XLRG > > ________________________________________________________________________________
Date: May 17, 2004
Subject: RG400 Cables
From: Jack <jgh2(at)charter.net>
A few weeks ago I contacted a supplier who had an overstock of 15' RG400 cables with male BNC connectors and molded strain reliefs (see < http://webpages.charter.net/jghkah/cables/cables.html >). I bought more than needed for my plane and sold the extras for $18/cable on the Matronics RV list. Recently some RV list members asked whether more cables were available. The supplier will not be making more but, as of last week, still had some left and was willing to sell in quantities of 12 or more (with a significant shipping charge). If enough members of the RV and AeroElectric would like to purchase these cables at $20 each (plus $5 dollars for shipping up to two cables plus $1 for each additional cable) I'll order another dozen or so. If you are interested please email me directly. I'll post a message to both lists next Monday to let everybody know whether there was sufficient interest to justify the order and, if so, the expected arrival date. Jack H. ________________________________________________________________________________
From: "James Redmon" <james(at)berkut13.com>
Subject: Instrument light dimming
Date: May 17, 2004
All, I am buttoning up my Berkut project for transport to the airport in a few weeks and in the process tried out the night-flight configuration with the newly installed canopies. I am using a single B&C dimmer unit to drive all the instrument and radio lighting. The mostly incandescent lighting in the radios dims down to almost nothing and is not a problem. However, the backup 2 1/4" AS and ALT instruments are powered by the "add-on" glow strip rings that are powered by a DC-AC inverter. The inverter is hooked up to the same panel dimmer and it does dim...but not nearly enough. They are still way-to-bright for night ops, while some radio lights are at about zero illumination. The question is, how can I achieve additional dimming on those instruments without sacrificing too much full-bright range? I can stand a little degradation, but not too much as the blue/green light makes them stand-out from under the long canopy cover. Thanks, James Redmon Berkut #013 N97TX http://www.berkut13.com ________________________________________________________________________________
From: "Eric M. Jones" <emjones(at)charter.net>
Subject: Re: Weight of RG-142
Date: May 17, 2004
NACA published this paper in 1924! Much of this will tease out the changes in performance, range etc. from a weight change. Caution: Not for the mathematically faint-hearted! Reliable formulae for estimating airplane performance and the effects of changes in weight, .....snip... etc. Diehl, Walter S , Bureau of Aeronautics (Navy) (Washington, DC, United States) NACA Report 173, 22 pp. , 1924 Abstract: The derivation and the verification of formulae for predicting the speed range ratio, the initial rate of climb, and the absolute ceiling of an airplane. Curves used in the computation are given in NACA-TR-171. Standard formulae for service ceiling, time of climb, cruising range, and endurance are also given in the conventional forms. http://naca.larc.nasa.gov/reports/1924/naca-report-173/ (everything you ever wanted to know about aviation)! From NACA Technical Note 206: Charles Ward Hall 1924: Structural Weight of Aircraft as Affected by the System of Design: "From one point of view-- the pay load--that is, the weight which is to be transported, whether it be mail or other goods, bombs, or machine gun bullets, represents the only profitable part of the enterprise. A


May 03, 2004 - May 17, 2004

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