---------------------------------------------------------- AeroElectric-List Digest Archive --- Total Messages Posted Sat 09/23/06: 21 ---------------------------------------------------------- Today's Message Index: ---------------------- 1. 12:54 AM - Mogas versus 100LL (DEAN PSIROPOULOS) 2. 04:27 AM - Re: strange electrical failure in flight (FLYaDIVE@aol.com) 3. 04:35 AM - Re: strange electrical failure in flight (Kevin Horton) 4. 04:41 AM - Re: strange electrical failure in flight (Richard Reynolds) 5. 06:24 AM - Ground Power Jack Question (MikeEasley@aol.com) 6. 06:24 AM - Re: Mogas versus 100LL (Gary Casey) 7. 07:17 AM - Re: Eeeeek! Another fear and question. (John Swartout) 8. 07:50 AM - Re: Eeeeek! Another fear and question. (Dave N6030X) 9. 08:08 AM - Re: Eeeeek! Another fear and question. (Robert L. Nuckolls, III) 10. 08:16 AM - Re: Ground Power Jack Question (Robert L. Nuckolls, III) 11. 08:51 AM - Re: Eeeeek! Another fear and question. (Robert L. Nuckolls, III) 12. 11:34 AM - Re: strange electrical failure in flight (Vern Little) 13. 11:36 AM - Re: strange electrical failure in flight (DAVID REEL) 14. 03:38 PM - Re: Re: Mogas versus 100LL (n801bh@netzero.com) 15. 04:36 PM - Re: Re: Mogas versus 100LL (Jim Baker) 16. 04:45 PM - Re: Re: Mogas versus 100LL (Jim Baker) 17. 05:43 PM - Re: strange electrical failure in flight (Robert L. Nuckolls, III) 18. 07:59 PM - Re: Re: Mogas versus 100LL (Kelly McMullen) 19. 07:59 PM - Re: Z13/8 & Z32 Relays (was Eeeeek! Another fear and question) (Larry Rosen) 20. 08:48 PM - Re: Eeeeek! Another fear and question. (John Swartout) 21. 09:52 PM - Eaton Starter Contactor Website () ________________________________ Message 1 _____________________________________ Time: 12:54:27 AM PST US From: "DEAN PSIROPOULOS" Subject: AeroElectric-List: Mogas versus 100LL --> AeroElectric-List message posted by: "DEAN PSIROPOULOS" >Time: 08:24:46 PM PST US >Subject: Re: AeroElectric-List: Mogas versus 100LL >From: >Octane rating is not the only thing one needs to be concerned with when it >comes to fuel. I don't know the technocrat term for it, but the speed at >which the fuel burns is a definite concern. On huge displacement engines >turning low RPMs, if you were to use a racing fuel designed for high RPM >engines of the same octane you would most like run into problems. From >what the locals at the airport say, high octane mogas should not be used >in a O-540s because it burns too fast, and since the cylinders are the >same as a O-360?? I believe you are referring to something called the Cetane rating Ron. The only place I've ever heard this term used is in association with DIESEL engines. Since the fuel is injected directly into the highly heated and compressed air in the diesel's cylinders, it must burn at a certain rate so as not to spontaneously combust and cause detonation (yes diesels can be damaged by detonation too). I've never heard it used in association with gasoline engines but that doesn't mean it's not important. >On the other hand, using 100LL that is a slow burning fuel used in a 73CC >22HP (well over 11K) Yamaha YZ 80 engine that is in my self retrieving >balloon kills performance and probably raises EGT to disheartening levels. I could be wrong but I don't think it's the high octane that is causing your situation here. Tetraethel lead in the fuel effectively increases the resistance of the mixture to spontaneously combusting in the higher temperatures of aircooled engines and higher cylinder pressures of the old 1960s era high performance auto engines (10/11/12 to 1 compression ratios with the old design wedge heads). What may be causing the 100LL to burn slower is the particular mix of aromatic hydrocarbons that make up the composition of av-gas. The av-gas mixture has a much lower volatility than mogas and that may be related to why it burns at a different speed (assuming you are correct here). >On Rotax 4 strokes you can use 100LL, but it does raise the EGTs because >it burns slower than high octane mogas, and some of that burn makes its >way into the exhaust. There may be something to this. The old Ford tractor we used to mow the runway at the soaring club was run on 100LL (always available from our tow plane supply) for many years and although it seemed to run just fine, eventually it needed a valve job. Not sure if that was due to 100LL or just wear and tear. Old piston engines used softer valves and seats and needed the cushioning effect of the lead in the fuel to get reasonable service life from these components (mfgrs went to much harder valves and seats when the lead was phased out many years ago). >A old timer said on old auto engines that didn't use aluminium pistons, >used to loosen the distributor, and run up the engine and begin retarding >the ignition, he said he would get the exhaust glowing, hence carbon would >be burned off. Slow burning fuel does the same in a engine designed for >fast burning fuel. Not sure why you'd want to do that unless the carbon was causing detonation or pre-ignition. But yes, on an engine with severely retarded timing the fuel would still be burning when the exhaust valve opened and EGT would be higher (ala your "slow burning" fuel). >Using a fast burning fuel in a engine designed for a slow burning fuel can >cause detonation. Detonation raises temperatures, let it go and God forbid >pre-ignition begins to occur. First time I've really heard this argument Ron, I don't think the lead is the culprit though, racing engines use lead in the gasoline to this day as far as I know (you just can't get octanes much above 95 with unleaded gasoline so you have to use lead or go to alcohol or some other fuel to get there without the lead). But...it may be the fuel formulation differences, I'll refer this one to Archie (and anyone else who wants to chime in about the subject) on the engines list. There are some very knowledgeable folks over there. >Ron Parigoris Dean Psiropoulos Do not archive on the aeroelectric list ________________________________ Message 2 _____________________________________ Time: 04:27:52 AM PST US From: FLYaDIVE@aol.com Subject: Re: AeroElectric-List: strange electrical failure in flight --> AeroElectric-List message posted by: FLYaDIVE@aol.com In a message dated 9/22/06 11:28:16 PM Eastern Daylight Time, scc_ron@yahoo.com writes: > > Then I pulled the cowl to troubleshoot the problem. the master powered up > the Main bus as if nothing happened. I started the engine and got 13.5 volts > from the ND Alternator regardless of RPM. When I switched on the E Bus, the > charge rate / output from the alternator jumped to 14.3. If I switched it off, > the number again drops back to 13.5 volts. No blown fuses. > > Anybody have an idea of what happened and what I might want to do? Thanks > in advance. > Ron > RV-4 N8ZD ========================== Ron: It sure sounds like a bad GROUND. Second guess would be a bad B+ connection. But, start with the GROUND, that is easy to check just by hooking a ground wire to the battery and bypassing to the other ground connection points. Been there, Done that. And POOF the problem was gone. Barry "Chop'd Liver" "Show them the first time, correct them the second time, kick them the third time." Yamashiada ________________________________ Message 3 _____________________________________ Time: 04:35:28 AM PST US From: Kevin Horton Subject: Re: AeroElectric-List: strange electrical failure in flight --> AeroElectric-List message posted by: Kevin Horton On 22 Sep 2006, at 23:25, Ron Patterson wrote: > Hope someone has some ideas on how to troubleshoot an eletrical > failure that I don't understand. I have Bob's Essential Bus and > Main Bus setup, one battery, new plane (50 hours). In flight today > I had an indication that I had a problem when my main bus connected > items shut down. I turned on the Essential bus, turned off the > Cessna type Master/Battery switch and continued on, landing > uneventfully as planned with Bob's system. > > Then I pulled the cowl to troubleshoot the problem. the master > powered up the Main bus as if nothing happened. I started the > engine and got 13.5 volts from the ND Alternator regardless of RPM. > When I switched on the E Bus, the charge rate / output from the > alternator jumped to 14.3. If I switched it off, the number again > drops back to 13.5 volts. No blown fuses. > > Anybody have an idea of what happened and what I might want to do? > Thanks in advance. Don't worry about the difference in indicated voltage when you switch the E Bus on and off. Your voltmeter is connected to the E Bus, which is normally supplied from the Main Bus, through a diode. The difference in voltages you see when the E Bus is switched on and off is due to the voltage drop through the diode. This is normal. In flight, did all the electrically powered items die at the same time? If so, it looks like something happened that killed the power supply to the Main Bus. Is your system wired so the normal feed to the Main Bus comes from the starter contactor, with the battery contactor and alternator feed also connected to that same bolt on the starter contactor? If so, check the connection there, and at the other end of that cable where it connects to the Main Bus. If the electrically powered items failed one by one, then it sounds like a low voltage condition, due to an alternator problem. Let us know if this was the way things happened and we can work this avenue. Kevin Horton RV-8 (finishing kit) Ottawa, Canada http://www.kilohotel.com/rv8 ________________________________ Message 4 _____________________________________ Time: 04:41:20 AM PST US From: Richard Reynolds Subject: Re: AeroElectric-List: strange electrical failure in flight Because of the diode between the main and essential buses, there will be a lower voltage on the essential bus with the essential bus switch off if voltage is measured on the essential bus.. The best place to measure the charing voltage is at the alternaor side of the starter contactor or the battery contactor or the battery. Where are you measuring the voltage? Richard Reynolds Norfolk VA On Sep 22, 2006, at 11:25 PM, Ron Patterson wrote: > Hope someone has some ideas on how to troubleshoot an eletrical > failure that I don't understand. I have Bob's Essential Bus and > Main Bus setup, one battery, new plane (50 hours). In flight today > I had an indication that I had a problem when my main bus connected > items shut down. I turned on the Essential bus, turned off the > Cessna type Master/Battery switch and continued on, landing > uneventfully as planned with Bob's system. > > Then I pulled the cowl to troubleshoot the problem. the master > powered up the Main bus as if nothing happened. I started the > engine and got 13.5 volts from the ND Alternator regardless of RPM. > When I switched on the E Bus, the charge rate / output from the > alternator jumped to 14.3. If I switched it off, the number again > drops back to 13.5 volts. No blown fuses. > > Anybody have an idea of what happened and what I might want to do? > Thanks in advance. > Ron > RV-4 N8ZD > > ________________________________ Message 5 _____________________________________ Time: 06:24:43 AM PST US From: MikeEasley@aol.com Subject: AeroElectric-List: Ground Power Jack Question I installed the Ground Power Jack according to the article. I built jumper cables from some Harbor Freight "el cheapo" cables and a plug from A/S. I tried to hook up my battery charger to the jumper cables and charge my battery but the contactor won't close. It appears that my charger won't put out any current unless it "senses" a battery is connected. If I hook my jumper cables to a spare car battery, everything works fine. Mike Easley Colorado Springs Lancair ES 12V ________________________________ Message 6 _____________________________________ Time: 06:24:44 AM PST US From: Gary Casey Subject: AeroElectric-List: Re: Mogas versus 100LL Good comments, Ron. Yes, the octane rating is a measure of the resistance of the fuel/air mixture to auto-ignite, or ignite without the presence of an open flame. It's a complex phenomenon and autoignition is a function of time, pressure and temperature. The rating methodology, developed by Ethyl Corporation way back when, compares the resistance to auto-ignition of the test fuel to mixtures of normal heptane to iso-octane. The octane number is the percentage of iso-octane in the mix that behaves like the test fuel (80-octane fuel behaves like a a mixture of 20% n-heptane and 80% iso-octane). Since the actual test is really done by measuring the BMEP of a test engine, numbers over 100 are possible - 110-octane fuel will allow the test engine to operate at 110% of the BMEP allowed by iso-octane (not exactly correct, but close enough). The method isn't exact and if the test engine is operated at different temperatures and loads the observed octane number comes out differently. Running at light load creates an octane rating called the "research octane" number and running at high temperature/high load produces a number called "motor octane". The law says the average octane rating of an automotive fuel must be displayed on the pump and that's why it says (R+M)/2 on the pump. Aviation fuel, because engines are usually operated under conditions more like the the motor method, are typically rated by the motor method - I believe 100LL is more correctly called 100/120 (100 motor octane and 120 research octane). That's why some of the past- history fuels were called 110/130 etc. When the fuel is ignited by an open flame front there is little difference in flame speed between high octane and low octane fuel: Flame speed is NOT the primary difference between the fuels. Detonation is auto-ignition of the "end gases" late in the combustion process. Because of combustion in the cylinder the end gases(the portion of the charge furthest from the ignition source) are compressed to very high pressures, which because of the gas law PV=NRT, raises their temperature. They will only remain unburned for a limited time and if the flame front doesn't arrive soon enough, igniting them progressively, they will auto-ignite all at once, "exploding." This will cause all sorts of problems, but will not usually result in immediate engine failure. As Ron correctly described below, "pre-ignition" is simply ignition of the fuel charge before the spark occurs. Because the charge burns and raises the pressure before the piston fully compresses the charge the temperature and pressure can go to extremely high levels, causing major damage very quickly. For example (George Braly would have the real numbers) normal compression (no ignition) pressure might be 350psi, combustion results in pressures of 800 to 1,000 psi and pre- ignition could result in pressures up to 2,000 psi. Pre-ignition can (likely) result from pre-ignition because of the extremely high pressure and temperature of the end gases. One thing that isn't usually thought about is the rate of heat transfer from a gas to the cylinder, which is proportional to the velocity, temperature difference AND PRESSURE of the gas. Double the pressure and double the temperature and the heat transfer will go up by a factor of 4. Detonation results in sonic shock waves traveling through the combustion chamber, which means locally the hot gases are moving at sonic velocity. Much of the damage from both detonation and pre- ignition is caused by the extremely high heat transfer rates, not just the pressure. Detonation under high loads can increase the local heat transfer rate to the point that after a short time a component (edge of the exhaust valve, carbon deposit, etc) can be heated to the point it causes pre-ignition. This has sometimes been referred to as "runaway detonation." I hope from the above description you get the idea that detonation and pre-ignition can be a real horror story for the engine. The best thing is to maintain a healthy detonation margin. In general, detonation is suppressed by increasing the octane rating, lowering the compression ratio, retarding the ignition timing, lowering the inlet temperature and pressure, lowering the cylinder head temperature, increasing turbulence and reducing the distance from the spark plug to the end gases(by running on both plugs). And you can dilute the charge by adding water, excess fuel or excess air (run LOP). As you can see, most of these things will reduce the power output of the engine and therein lies the conundrum. For a standard unmodified aircraft engine the worst operating case would be a takeoff from Death Valley on a dry, 115-degree day with the carb heat left on, mixture leaned and one of the mags inoperative. As I recall it is just those conditions that the FAA requires to be demonstrated for a certified engine. Sorry about the excessively long non-electric dissertation. Gary Casey > The higher the octane rating, the higher the temperature and > pressure that can be reached before detonation occurs. I am not > positive > on this, but am pretty certain on Mainland USA, the pump octane rating > is > not figured the same as Aviation fuel is, I forget if Avgas is > higher or > lower. Anyway for a short time detonation probably will not cause any > real > harm. Now if you let it go on for long periods of time, things will > begin > to heat up, detonation will become more pronounced. The burning of > fuel > mixture during Detonation begins with a spark at the plug. Preignition > is > the real show stopper. This is where for some reason the mixture > ignites > way too far advanced. Could be a glowing piece of carbon, or > leaving the > helicoil tab stick a bit too much into the cylinder, or just plain too > high a temperature. Piston moving up and fighting pressure now. > > OK comments here?? > > OK so if we are straight that octane rating is the ability for a > fuel to > not detonate, I don't think that is absolute takes into consideration > the > speed at which the flame front will burn in an orderly fashion. > Different > brews can have the same octane rating, but can burn at different > speeds. > Ron Parigoris ________________________________ Message 7 _____________________________________ Time: 07:17:48 AM PST US From: "John Swartout" Subject: RE: AeroElectric-List: Eeeeek! Another fear and question. Well, I'm trying to understand the system I'm going to install, and some things aren't making sense to me. Following your reasoning, since I spent big bucks on a highly reliable L40 main alternator which doesn't rely on any relay to deliver power, and on two P-mags which may not require any ship's power anyway, the highly reliable SD-8 backup alternator is just excess baggage so what difference does it make whether its electrons can get to where they are needed? That doesn't sound like correct design theory to me. I am trying to integrate Z-13/8, Z-32, and an avionics master switch circuit of Bob's design, and am trying to figure out where and whether to use relays which are shown in Z-32 but not in the other drawings. I note that in Z-32, the up-to-8-amp Endurance Bus feeds alternate power through a relay. (Bob has a sketch at www.aeroelectric.com/Pictures/Schematics/E-BusFatFeed.gif which says "for [E-Bus] feeds over 5A consider adding a relay to control power at the Bat Bus.") I seem to recall that the reason for using a relay is to avoid arcing at the switch which would possibly compromise the switch. But in Bob's article "Avionics Master Switches: Really Necessary?," he shows a circuit with the caption "If you really want an avionics master switch, how about doing it this way?" It shows an essential bus/avionics bus powering a transponder, turn coordinator, intercom, instrument flood, gps receiver, Nav/Comm, and fuel boost pump. Both the main feed and the alternate feed are controlled by switches, not relays. I like the idea and want to use it-but my endurance/avionics bus supports more than 5 amps, so I am "considering" the Z-32 Heavy Duty E-Bus, which uses a relay. This made me think, if the alternate feed needs a relay, shouldn't the main feed (avionics master switched) use a relay also? If not, why not? It's doing the same thing normally that the alternate feed does if the main alternator fails-so why doesn't it need a relay, too? But Bob's recent post saying that relays are among the least reliable of components makes me nervous because in the combined schematic I am contemplating my Endurance Bus would be dependent on one relay in normal mode and two relays if I were operating in main-alternator-failed mode. Remember that the "Endurance Bus" used to be named the "Essential Bus" (for a legitimate reason). Should anything "Essential" really be totally dependent on relays? If not, I am looking for assistance in developing a better architecture that gives me a Heavy Duty (up to 8-amp) Essential/Avionics Bus with an avionics master switch. John -----Original Message----- From: owner-aeroelectric-list-server@matronics.com [mailto:owner-aeroelectric-list-server@matronics.com] On Behalf Of Dave N6030X Sent: Friday, September 22, 2006 11:34 PM Subject: RE: AeroElectric-List: Eeeeek! Another fear and question. --> AeroElectric-List message posted by: Dave N6030X I think that's why it's called the Endurance Bus. So what if both relays fail. If you've designed the system correctly, you have sufficient battery to get to your destination, and you don't even break a sweat. Dave Morris At 10:15 PM 9/22/2006, you wrote: >--> AeroElectric-List message posted by: "John Swartout" > > >I *assume* that while relays may be the "least reliable" of components, they >are still "pretty" reliable, else they would not appear in the Z-drawings. >But my point is that when you combine Z13/8 and Z32, the chances of the >E-bus not working in a main-alternator-failure situation are not your >hypothetical 1/10,000 * 1/10,000, rather they are increased to 1/5,000 >because BOTH relays have to work, and if either one fails (1/10,000 * 2) you >are flying on the battery only, even though the SD-8 is fine. Usually Bob >endeavors to minimize the opportunities for a single component failure to >cause an emergency, and I wonder if he considers this daisy chain of "least >reliable components" in the Z13/8 + Z32 to pass muster. > >John > >-----Original Message----- >From: owner-aeroelectric-list-server@matronics.com >[mailto:owner-aeroelectric-list-server@matronics.com] On Behalf Of Matt >Prather >Sent: Friday, September 22, 2006 7:30 PM >To: aeroelectric-list@matronics.com >Subject: Re: AeroElectric-List: Eeeeek! Another fear and question. > >--> AeroElectric-List message posted by: "Matt Prather" > >A couple of thoughts... > > - Relays in some applications are less reliable than some solid state >equivalents in that application. Saying hard/fast that relays are less >reliable is probably not completely accurate. > > - When relays fail, often it's by degraded performance.. You'll notice >that once in a while a relay will fail to snap in, or disconnect. You >exercise the controlling switch a time or two, and it starts to function. > You make the mental note "Hmmm, that xyz relay is getting flakey; better >check it out when I get back to the hangar." And you go on with your >flight. > > - The chances of a having a particular, properly installed/applied relay >failing on any flight might be 1/10,000. The chances of having two >different similar relays fail on the same flight might be 1/10,000 * >1/10,000. A very unlikely possibility. > > >Regards, > >Matt- > > > Bob, your 9/13/06 post regarding LEDs says in part: > > > > > > > > Finally, relays are rated amongst the least reliable of > > > > components. It behooves us to limit their use where ever practical. > > > > > > > > Okay. That brings up a question. I'm planning Z13/8 with Z32. Z32 Heavy > > Duty E-Bus Feed shows the use of a relay to energize the alternate feed > > path. But Z13/8 also relies on a relay to supply the SD-8's output to the > > E-Bus. That's two relays that must work for E-Bus operations independent > > of > > battery power. Is there a practical way to avoid the built-in weakness of > > two relays in the E-Bus circuit? > > > > > > > > John > > > > > > > > > > > > ________________________________ Message 8 _____________________________________ Time: 07:50:13 AM PST US From: Dave N6030X Subject: RE: AeroElectric-List: Eeeeek! Another fear and question. --> AeroElectric-List message posted by: Dave N6030X Well, I'll wait for Bob to justify his own schematics, but I know he is in Kansas at the tandem-wing fly-in today and may not be able to comment for a while. If it were ME, I would not use a relay to power the E-bus. I would use a switch. Switches handle larger current than 5A all the time, and if you're concerned about reliability, just use a switch rated for larger current. The other thing you should do here, since you're discovering you have an unusual e-bus, is to ask yourself whether all of those items really need to be on the e-bus. I had to go through several iterations before I finally pared my e-bus down to what was really going to be necessary to have running ALL THE TIME to complete the flight. Remember you can always power up the Main Bus for a few minutes if you need to, while on battery power. Dave Morris At 09:14 AM 9/23/2006, you wrote: >Well, I'm trying to understand the system I'm >going to install, and some things aren't making sense to me. > >Following your reasoning, since I spent big >bucks on a highly reliable L40 main alternator >which doesn't rely on any relay to deliver >power, and on two P-mags which may not require >any ship's power anyway, the highly reliable >SD-8 backup alternator is just excess baggage so >what difference does it make whether its >electrons can get to where they are >needed? That doesn't sound like correct design theory to me. > >I am trying to integrate Z-13/8, Z-32, and an >avionics master switch circuit of Bobs design, >and am trying to figure out where and whether to >use relays which are shown in Z-32 but not in >the other drawings. I note that in Z-32, the >up-to-8-amp Endurance Bus feeds alternate power >through a relay. (Bob has a sketch at >www.aeroelectric.com/Pictures/Schematics/E-BusFatFeed.gif >which says for [E-Bus] feeds over 5A consider >adding a relay to control power at the Bat >Bus.) I seem to recall that the reason for >using a relay is to avoid arcing at the switch >which would possibly compromise the switch. > >But in Bobs article Avionics Master >Switches: Really Necessary?, he shows a >circuit with the caption If you really want an >avionics master switch, how about doing it this >way? It shows an essential bus/avionics bus >powering a transponder, turn coordinator, >intercom, instrument flood, gps receiver, >Nav/Comm, and fuel boost pump. Both the main >feed and the alternate feed are controlled by >switches, not relays. I like the idea and want >to use itbut my endurance/avionics bus supports >more than 5 amps, so I am considering the Z-32 >Heavy Duty E-Bus, which uses a relay. This made >me think, if the alternate feed needs a relay, >shouldnt the main feed (avionics master >switched) use a relay also? If not, why >not? Its doing the same thing normally that >the alternate feed does if the main alternator >failsso why doesnt it need a relay, too? But >Bobs recent post saying that relays are among >the least reliable of components makes me >nervous because in the combined schematic I am >contemplating my Endurance Bus would be >dependent on one relay in normal mode and two >relays if I were operating in >main-alternator-failed mode. Remember that the >Endurance Bus used to be named the Essential >Bus (for a legitimate reason). Should anything >Essential really be totally dependent on >relays? If not, I am looking for assistance in >developing a better architecture that gives me a >Heavy Duty (up to 8-amp) Essential/Avionics Bus with an avionics master switch. > >John > >-----Original Message----- >From: >owner-aeroelectric-list-server@matronics.com >[mailto:owner-aeroelectric-list-server@matronics.com] On Behalf Of Dave N6030X >Sent: Friday, September 22, 2006 11:34 PM >To: aeroelectric-list@matronics.com >Subject: RE: AeroElectric-List: Eeeeek! Another fear and question. > >--> AeroElectric-List message posted by: Dave N6030X > >I think that's why it's called the Endurance Bus. So what if both >relays fail. If you've designed the system correctly, you have >sufficient battery to get to your destination, and you don't even >break a sweat. > >Dave Morris > >At 10:15 PM 9/22/2006, you wrote: > >--> AeroElectric-List message posted by: "John Swartout" > > > > > >I *assume* that while relays may be the "least reliable" of components, they > >are still "pretty" reliable, else they would not appear in the Z-drawings. > >But my point is that when you combine Z13/8 and Z32, the chances of the > >E-bus not working in a main-alternator-failure situation are not your > >hypothetical 1/10,000 * 1/10,000, rather they are increased to 1/5,000 > >because BOTH relays have to work, and if either one fails (1/10,000 * 2) you > >are flying on the battery only, even though the SD-8 is fine. Usually Bob > >endeavors to minimize the opportunities for a single component failure to > >cause an emergency, and I wonder if he considers this daisy chain of "least > >reliable components" in the Z13/8 + Z32 to pass muster. > > > >John > > > >-----Original Message----- > >From: owner-aeroelectric-list-server@matronics.com > >[mailto:owner-aeroelectric-list-server@matronics.com] On Behalf Of Matt > >Prather > >Sent: Friday, September 22, 2006 7:30 PM > >To: aeroelectric-list@matronics.com > >Subject: Re: AeroElectric-List: Eeeeek! Another fear and question. > > > >--> AeroElectric-List message posted by: "Matt Prather" > > > >A couple of thoughts... > > > > - Relays in some applications are less reliable than some solid state > >equivalents in that application. Saying hard/fast that relays are less > >reliable is probably not completely accurate. > > > > - When relays fail, often it's by degraded performance.. You'll notice > >that once in a while a relay will fail to snap in, or disconnect. You > >exercise the controlling switch a time or two, and it starts to function. > > You make the mental note "Hmmm, that xyz relay is getting flakey; better > >check it out when I get back to the hangar." And you go on with your > >flight. > > > > - The chances of a having a particular, properly installed/applied relay > >failing on any flight might be 1/10,000. The chances of having two > >different similar relays fail on the same flight might be 1/10,000 * > >1/10,000. A very unlikely possibility. > > > > > >Regards, > > > >Matt- > > > > > Bob, your 9/13/06 post regarding LEDs says in part: > > > > > > > > > > > > Finally, relays are rated amongst the least reliable of > > > > > > components. It behooves us to limit their use where ever practical. > > > > > > > > > > > > Okay. That brings up a question. I'm > planning Z13/8 with Z32. Z32 Heavy > > > Duty E-Bus Feed shows the use of a relay to energize the alternate feed > > > path. But Z13/8 also relies on a relay to > supply the SD-8's output to the > > > E-Bus. That's two relays that must work for E-Bus operations independent > > > of > > > battery power. Is there a practical way to > avoid the built-in weakness of > > > two relays in the E-Bus circuit? > > > > > > > > > > > > John > > > > > > > > > > > > > > > > > > > > > > > > ________________________________ Message 9 _____________________________________ Time: 08:08:01 AM PST US From: "Robert L. Nuckolls, III" Subject: Re: AeroElectric-List: Eeeeek! Another fear and question. --> AeroElectric-List message posted by: "Robert L. Nuckolls, III" At 05:43 PM 9/22/2006 -0400, you wrote: >Bob, your 9/13/06 post regarding LEDs says in part: > > >Finally, relays are rated amongst the least reliable of > > components. It behooves us to limit their use where ever practical. > > >Okay. That brings up a question. I m planning Z13/8 with Z32. Z32 Heavy >Duty E-Bus Feed shows the use of a relay to energize the alternate feed >path. But Z13/8 also relies on a relay to supply the SD-8 s output to the >E-Bus. That s two relays that must work for E-Bus operations independent >of battery power. Is there a practical way to avoid the built-in weakness >of two relays in the E-Bus circuit? This thread has expanded into a predictable level of excitement for lack of perspective . . . Note the key word in the quotation above . . . PRACTICAL About 20 years ago, I was designing the first of a series of electronically controlled rate controllers for pitch trim on the Learjets. While conducting a Mil-HBK-217 MTBF study, it was interesting to note that when only the electronic components, wires, solder joints and connectors were factored into the study, MTBF for the device was in the thousands of hours . . . about 7,000 as I recall. When adding the last component, a mil-spec, 4-pole, double throw, hermetically sealed 25A relay to the study, the predicted MTBF fell to 900 hours for the system. Mil-HBK-217 suggests and even accommodates de-rating of parts to decrease stresses with commensurate increases in MTBF. I was able to design the system so that the relay was closed and bounce free before current flowed in the contacts. Further, I was able to shut off all current flow electronically before the relay contacts were opened. Mil-HDK-217 had no prediction formula for my proposed scenario but obviously, it was going to be as high as was PRACTICALLY possible for incorporation of the relay. Twenty years later, inquiries to the overhaul shop for this product tell me that relays have NEVER been replaced in a unit returned for repair. Even as I write these words, I'm designing the next new product to appear in the AeroElectric Connection catalog and the design incorporates a RELAY. Why not replace it electronically? PRACTICALITY - it's technologically possible but costs more . . . makes the product more expensive to build and doesn't make it perform any better. It MIGHT keep the system from needing maintenance attention before the original owner sells the airplane . . . but I doubt it. The decision as to whether a relay or contactor is PRACTICAL involves consideration of much more data than the gross reliability factors. Cost of ownership and FMEA for the SYSTEM figure heavily into the thought process. We still use $25, el-cheeso contactors in our airplanes because in spite of their need for periodic maintenance, we have crafted a Plan-B to deal with those failures. Hence my recommendation to many builders over the years that 'upgrading' to Mil-Spec contactors in their RV is dollars probably not well spent. So before anyone goes of the end of the plank in excitement or fear, know that suggestions for the selection of ANY component need to be considered against your ability to deal sweat-free with a failure of that component. If your Plan-B is solid, then use of that component is PRACTICAL and as free of excitement and concerns as we know how to do. Bob . . . ________________________________ Message 10 ____________________________________ Time: 08:16:31 AM PST US From: "Robert L. Nuckolls, III" Subject: Re: AeroElectric-List: Ground Power Jack Question --> AeroElectric-List message posted by: "Robert L. Nuckolls, III" At 09:21 AM 9/23/2006 -0400, you wrote: >I installed the Ground Power Jack according to the article. I built >jumper cables from some Harbor Freight "el cheapo" cables and a plug from >A/S. I tried to hook up my battery charger to the jumper cables and >charge my battery but the contactor won't close. It appears that my >charger won't put out any current unless it "senses" a battery is >connected. If I hook my jumper cables to a spare car battery, everything >works fine. > >Mike Easley >Colorado Springs >Lancair ES 12V Yup, some chargers are like that. You might need to 'float' a small battery across the charger terminals external to the airplane to wake it up so that you can get power to the ship's battery for charging. Understand further that having a fixed, external power contactor's coil load on a 'smart charger' will probably prevent it from going into the maintenance mode when ship's battery achieves full charge. Smart chargers should be fitted with low current, fused feeders directly to the battery bus. A connector set like http://www.aeroelectric.com/Pictures/Connectors/274-010.jpg http://www.aeroelectric.com/Pictures/Connectors/274-013.jpg might do nicely. These parts are available from Radio Shack. Bob . . . --------------------------------------------------------- < What is so wonderful about scientific truth...is that > < the authority which determines whether there can be > < debate or not does not reside in some fraternity of > < scientists; nor is it divine. The authority rests > < with experiment. > < --Lawrence M. Krauss > --------------------------------------------------------- ________________________________ Message 11 ____________________________________ Time: 08:51:15 AM PST US From: "Robert L. Nuckolls, III" Subject: RE: AeroElectric-List: Eeeeek! Another fear and question. --> AeroElectric-List message posted by: "Robert L. Nuckolls, III" At 09:47 AM 9/23/2006 -0500, you wrote: >--> AeroElectric-List message posted by: Dave N6030X > >Well, I'll wait for Bob to justify his own schematics, but I know he is in >Kansas at the tandem-wing fly-in today and may not be able to comment for >a while. > >If it were ME, I would not use a relay to power the E-bus. I would use a >switch. Switches handle larger current than 5A all the time, and if >you're concerned about reliability, just use a switch rated for larger >current. The other thing you should do here, since you're discovering you >have an unusual e-bus, is to ask yourself whether all of those items >really need to be on the e-bus. I had to go through several iterations >before I finally pared my e-bus down to what was really going to be >necessary to have running ALL THE TIME to complete the flight. Remember >you can always power up the Main Bus for a few minutes if you need to, >while on battery power. > >Dave Morris The suggestion for adding an e-bus relay had nothing to do with current carrying capacity of the e-bus switch. There's be a long standing tradition in TC aircraft to limit the size of always-hot feeders in aircraft to those protected by 5A or smaller breakers. Since the "FAT" e-bus feeder needs to carry more than the few amps originally considered when the e-bus was conceived, the idea for adding a 'mini-contactor' at the e-bus for larger feeders was offered. Now, fuses are much faster than breakers, and for Z-13/8 were a continuous e-bus load of 8A is PRACTICAL, then assuming the e-bus alternate feed is fuse-fed from the battery bus, going up to 10A fuse is a useful thing to consider without thumbing our noses too vigorously at tradition. Too many folks are treating the Z-figures as carved-in- stone recommendations for details of a proposed electrical system. These drawings are STARTING POINTS that illustrate architectures that will in-turn drive your Plan-A/Plan-B thinking. Don't get yourselves wrapped around any axles here based on sizes of wires, sizes of fuses/breakers or which devices are fed from which busses. The drawings were never intended to be a recipe for success, only a tool for development. I get a half-dozen requests a week for "Gee Bob, I like Figure Z-x but it doesn't . . . and I want to . . . Would you please craft me a Z-y that takes care of all my desires/worries?" All these requests get the same reply which is not much different that what I've written above. Nobody promised anyone a decision free solution. One is always on firm footing to clone the system out of a C-172 and drive on. Any variations from that theme WILL require thought, exploration, crafting/answering of questions and finally understanding of the final configuration which WILL be uniquely applicable to YOU and your airplane. Bob . . . ________________________________ Message 12 ____________________________________ Time: 11:34:30 AM PST US From: Vern Little Subject: Re: AeroElectric-List: strange electrical failure in flight --> AeroElectric-List message posted by: Vern Little Ron, did you measure the alternator output voltage directly at the battery, or is your voltmeter connected to the main bus? If you have any isolation diodes involved between the voltmeter and the battery (such as automatic e-bus/main bus switching), this could be the cause of your 13.5 volt reading. Vern Little Ron Patterson wrote: > Hope someone has some ideas on how to troubleshoot an eletrical failure > that I don't understand. I have Bob's Essential Bus and Main Bus setup, > one battery, new plane (50 hours). In flight today I had an indication > that I had a problem when my main bus connected items shut down. I > turned on the Essential bus, turned off the Cessna type Master/Battery > switch and continued on, landing uneventfully as planned with Bob's system. > > Then I pulled the cowl to troubleshoot the problem. the master powered > up the Main bus as if nothing happened. I started the engine and got > 13.5 volts from the ND Alternator regardless of RPM. When I switched on > the E Bus, the charge rate / output from the alternator jumped to 14.3. > If I switched it off, the number again drops back to 13.5 volts. No > blown fuses. > > Anybody have an idea of what happened and what I might want to do? > Thanks in advance. > Ron > RV-4 N8ZD > > * > > > * ________________________________ Message 13 ____________________________________ Time: 11:36:10 AM PST US From: "DAVID REEL" Subject: Re: AeroElectric-List: strange electrical failure in flight --> AeroElectric-List message posted by: "DAVID REEL" The big increase in voltage with load could be due to high resistance in the regulator sense circuit. The more load you add, the higher the current in the alternator field coil. If the sense circuit is also the field coil supply, any resistance in the circuit will cause a voltage drop and the regulator will increase the voltage to make up for the sensed drop in voltage. So, if you add lots of load, you could be getting voltage spikes over 16v which would trip an overvoltage protector which you probably also have. Check to see if your alternator field circuit breaker tripped. I had to reduce the resistance in my field circuit to .02 ohms by removing the fuse and wiring it directly to the buss through a fuse link before I could get reliable operation from my system. Dave Reel - RV8A ________________________________ Message 14 ____________________________________ Time: 03:38:11 PM PST US From: "n801bh@netzero.com" Subject: Re: AeroElectric-List: Re: Mogas versus 100LL Thank you Gary. That is the best explanation of octane and detonation/ p reignition scenerios I have ever read. I was going to try to desrcibe it but you did so much better. The only thing I might add is the fact that in the process of diluting the mixture with extra air there is a point where before it really starts to run lean the engine flame front goes in to a blow torch effect and will melt the top of the piston and or the ex haust valve. If you can transition though this setting fast enough the m otor just lays down and the EGT's show a cooler number, set the air/fuel mixture at around 16-1, depending on the engine of course, and work the motor hard, you will get very high EGT's, low fuel flow numbers and hur t pistons/ valves. The best way to describe it is watch a cutting torch work, one adjusts the mixture till they get a neutral flame and when yo u press the lever the additional O2 will not only add to the velocity of the flame front , it will almost double the temp of the cutting flame i tself. . Ben www.haaspowerair.com Ben Haas N801BH www.haaspowerair.com -- Gary Casey wrote: Good comments, Ron. Yes, the octane rating is a measure of the resistan ce of the fuel/air mixture to auto-ignite, or ignite without the presenc e of an open flame. It's a complex phenomenon and autoignition is a fun ction of time, pressure and temperature. The rating methodology, develo ped by Ethyl Corporation way back when, compares the resistance to auto- ignition of the test fuel to mixtures of normal heptane to iso-octane. The octane number is the percentage of iso-octane in the mix that behave s like the test fuel (80-octane fuel behaves like a a mixture of 20% n-h eptane and 80% iso-octane). Since the actual test is really done by mea suring the BMEP of a test engine, numbers over 100 are possible - 110-oc tane fuel will allow the test engine to operate at 110% of the BMEP allo wed by iso-octane(not exactly correct, but close enough). The method is n't exact and if the test engine is operated at different temperatures a nd loads the observed octane number comes out differently. Running at l ight load creates an octane rating called the "research octane" number a nd running at high temperature/high load produces a number called "motor octane". The law says the average octane rating of an automotive fuel must be displayed on the pump and that's why it says (R+M)/2 on the pump . Aviation fuel, because engines are usually operated under conditions more like the the motor method, are typically rated by the motor method - I believe 100LL is more correctly called 100/120 (100 motor octane and 120 research octane). That's why some of the past-history fuels were c alled 110/130 etc. When the fuel is ignited by an open flame front there is little differen ce in flame speed between high octane and low octane fuel: Flame speed is NOT the primary difference between the fuels. Detonation is auto-ign ition of the "end gases" late in the combustion process. Because of com bustion in the cylinder the end gases(the portion of the charge furthest from the ignition source) are compressed to very high pressures, which because of the gas law PV=NRT, raises their temperature. They will on ly remain unburned for a limited time and if the flame front doesn't arr ive soon enough, igniting them progressively, they will auto-ignite all at once, "exploding." This will cause all sorts of problems, but will n ot usually result in immediate engine failure.As Ron correctly described below, "pre-ignition" is simply ignition of the fuel charge before the spark occurs. Because the charge burns and raises the pressure before t he piston fully compresses the charge the temperature and pressure can g o to extremely high levels, causing major damage very quickly. For exam ple (George Braly would have the real numbers) normal compression (no ig nition) pressure might be 350psi, combustion results in pressures of 800 to 1,000 psi and pre-ignition could result in pressures up to 2,000 psi . Pre-ignition can (likely) result from pre-ignition because of the ext remely high pressure and temperature of the end gases. One thing that i sn't usually thought about is the rate of heat transfer from a gas to th e cylinder, which is proportional to the velocity, temperature differenc e AND PRESSURE of the gas. Double the pressure and double the temperatu re and the heat transfer will go up by a factor of 4. Detonation result s in sonic shock waves traveling through the combustion chamber, which m eans locally the hot gases are moving at sonic velocity. Much of the da mage from both detonation and pre-ignition is caused by the extremely hi gh heat transfer rates, not just the pressure. Detonation under high lo ads can increase the local heat transfer rate to the point that after a short time a component (edge of the exhaust valve, carbon deposit, etc) can be heated to the point it causes pre-ignition. This has sometimes b een referred to as "runaway detonation."I hope from the above descriptio n you get the idea that detonation and pre-ignition can be a real horror story for the engine. The best thing is to maintain a healthy detonati on margin. In general, detonation is suppressed by increasing the octan e rating, lowering the compression ratio, retarding the ignition timing, lowering the inlet temperature and pressure, lowering the cylinder head temperature, increasing turbulence and reducing the distance from the s park plug to the end gases(by running on both plugs). And you can dilut e the charge by adding water, excess fuel or excess air (run LOP). As y ou can see, most of these things will reduce the power output of the eng ine and therein lies the conundrum. For a standard unmodified aircraft engine the worst operating case would be a takeoff from Death Valley on a dry, 115-degree day with the carb heat left on, mixture leaned and one of the mags inoperative. As I recall it is just those conditions that the FAA requires to be demonstrated for a certified engine.Sorry about t he excessively long non-electric dissertation.Gary Casey The higher the octane rating, the higher the temperature and pressure that can be reached before detonation occurs. I am not positive on this, but am pretty certain on Mainland USA, the pump octane rating is not figured the same as Aviation fuel is, I forget if Avgas is higher or lower. Anyway for a short time detonation probably will not cause any real harm. Now if you let it go on for long periods of time, things will begin to heat up, detonation will become more pronounced. The burning of fuel mixture during Detonation begins with a spark at the plug. Preignition is the real show stopper. This is where for some reason the mixture ignites way too far advanced. Could be a glowing piece of carbon, or leaving the helicoil tab stick a bit too much into the cylinder, or just plain too high a temperature. Piston moving up and fighting pressure now. OK comments here?? OK so if we are straight that octane rating is the ability for a fuel to not detonate, I don't think that is absolute takes into consideration the speed at which the flame front will burn in an orderly fashion. Different brews can have the same octane rating, but can burn at different speeds. Ron Parigoris ======================== ======================== ======================== ======================== ======================== ======================== ====================

Thank you Gary. That is the best explanation of octane and deto nation/ preignition scenerios I have ever read. I was going to try to de srcibe it but you did so much better. The only thing I might add is the fact that in the process of diluting the mixture with extra air there is a point where before it really starts to run lean the engine flame fron t goes into a blow torch effect and will melt the top of the piston and or the exhaust valve. If you can transition though this setting fast eno ugh the motor just lays down and the EGT's show a cooler number, set the air/fuel mixture at around 16-1, depending on the engine of course , and work the motor hard, you will get very high EGT's, low fuel f low numbers and hurt pistons/ valves. The best way to describe it is watch a cutting torch work, one  adjusts the mixture till th ey get a neutral flame and when you press the lever the additional O2 will not only add to the velocity of the flame front , it will almost double the temp of the cutting flame itself. .

 

Ben

www.haaspowerair.com


Ben Haas
N801BH
www.haaspo werair.com

-- Gary Casey <glcasey@adelphia.net& gt; wrote:
Good comments, Ron.  Yes, the octane rating is a measure of the resistance of the fuel/air mixture to auto-ignite, or ig nite without the presence of an open flame.  It's a complex phenome non and autoignition is a function of time, pressure and temperature.&nb sp; The rating methodology, developed by Ethyl Corporation way back when , compares the resistance to auto-ignition of the test fuel to mixtures of normal heptane to iso-octane.  The octane number is the percenta ge of iso-octane in the mix that behaves like the test fuel (80-octane f uel behaves like a a mixture of 20% n-heptane and 80% iso-octane).   ;Since the actual test is really done by measuring the BMEP of a test en gine, numbers over 100 are possible - 110-octane fuel will allow the tes t engine to operate at 110% of the BMEP allowed by iso-octane(not exactl y correct, but close enough).  The method isn't exact and if the te st engine is operated at different temperatures and loads the observed o ctane number comes out differently.  Running at light load creates an octane rating called the "research octane" number and running at high temperature/high load produces a number called "motor octane".  Th e law says the average octane rating of an automotive fuel must be displ ayed on the pump and that's why it says (R+M)/2 on the pump.  Aviat ion fuel, because engines are usually operated under conditions more lik e the the motor method, are typically rated by the motor method - I beli eve 100LL is more correctly called 100/120 (100 motor octane and 120 res earch octane).  That's why some of the past-history fuels were call ed 110/130 etc.


When the fuel is ignited by an open flame front there is little dif ference in flame speed between high octane and low octane fuel:  Fl ame speed is NOT the primary difference between the fuels.  Detonat ion is auto-ignition of the "end gases" late in the combustion process.  Because of combustion in the cylinder the end gases(the portion of the charge furthest from the ignition source) are compressed to very hi gh pressures, which because of the gas law PV=NRT, raises their temper ature.  They will only remain unburned for a limited time and if th e flame front doesn't arrive soon enough, igniting them progressively, t hey will auto-ignite all at once, "exploding."  This will cause all sorts of problems, but will not usually result in immediate engine fail ure.

As Ron correctly described below, "pre-ignition" is simply ignition of the fuel charge before the spark occurs.  Because the charge bu rns and raises the pressure before the piston fully compresses the charg e the temperature and pressure can go to extremely high levels, causing major damage very quickly.  For example (George Braly would have th e real numbers) normal compression (no ignition) pressure might be 350ps i, combustion results in pressures of 800 to 1,000 psi and pre-ignition could result in pressures up to 2,000 psi.  Pre-ignition can (likel y) result from pre-ignition because of the extremely high pressure and t emperature of the end gases.  One thing that isn't usually thought about is the rate of heat transfer from a gas to the cylinder, which is proportional to the velocity, temperature difference AND PRESSURE of the gas.  Double the pressure and double the temperature and the heat transfer will go up by a factor of 4.  Detonation results in sonic shock waves traveling through the combustion chamber, which means locall y the hot gases are moving at sonic velocity.  Much of the damage f rom both detonation and pre-ignition is caused by the extremely high hea t transfer rates, not just the pressure.  Detonation under high loa ds can increase the local heat transfer rate to the point that after a s hort time a component (edge of the exhaust valve, carbon deposit, etc) c an be heated to the point it causes pre-ignition.  This has sometim es been referred to as "runaway detonation."

I hope from the above description you get the idea that detonation and pre-ignition can be a real horror story for the engine.  The be st thing is to maintain a healthy detonation margin.  In general, d etonation is suppressed by increasing the octane rating, lowering the co mpression ratio, retarding the ignition timing, lowering the inlet tempe rature and pressure, lowering the cylinder head temperature, increasing turbulence and reducing the distance from the spark plug to the end gase s(by running on both plugs).  And you can dilute the charge by addi ng water, excess fuel or excess air (run LOP).  As you can see, mos t of these things will reduce the power output of the engine and therein lies the conundrum.  For a standard unmodified aircraft engine the worst operating case would be a takeoff from Death Valley on a dry, 115 -degree day with the carb heat left on, mixture leaned and one of the ma gs inoperative.  As I recall it is just those conditions that the F AA requires to be demonstrated for a certified engine.

Sorry about the excessively long non-electric dissertation.

Gary Casey


The higher the octane rating, the higher the temperature and

pressure that can be reached before detonation occurs. I am not positive

on this, but am pretty certain on Mainland USA, the pump octane rating

is

not figured the same as Aviation fuel is, I forget if Av gas is higher or

lower. Anyway for a short time detonation probably will not cause any

real

harm. Now if you let it go on for long periods of time, things will

begin

to heat up, detonation will become more pronounced. The burning of fuel

mixture during Detonation begins with a spark at the plu g. Preignition

is

the real show stopper. This is where for some reason the mixture ignites

way too far advanced. Could be a glowing piece of carbon , or leaving the

helicoil tab stick a bit too much into the cylinder, or just plain too

high a temperature. Piston moving up and fighting pressu re now.


OK comments here??


OK so if we are straight that octane rating is the abili ty for a fuel to

not detonate, I don't think that is absolute takes into consideration

the

speed at which the flame front will burn in an orderly f ashion.

Different

brews can have the same octane rating, but can burn at d ifferent speeds.

Ron Parigoris


======================== =========== c-List">http://www.matronics.com/Navigator?AeroElectric-List ======================== =========== tronics.com ======================== =========== ics.com ======================== =========== www.matronics.com/contribution ======================== ===========
________________________________ Message 15 ____________________________________ Time: 04:36:05 PM PST US From: "Jim Baker" Subject: Re: AeroElectric-List: Re: Mogas versus 100LL X-mailer: Pegasus Mail for Windows (4.41) --> AeroElectric-List message posted by: "Jim Baker" > in the process of diluting the mixture with extra air there is a point > where before it really starts to run lean the engine flame front goes into a blow torch effect and > will melt the top of the piston and or the exhaust valve. I suppose you can prove this? Not anecdotally, but with solid, repeatable science that has already been done? And might want to take this to the Matronics Engines list instead..... Jim Baker 580.788.2779 Elmore City, OK ________________________________ Message 16 ____________________________________ Time: 04:45:20 PM PST US From: "Jim Baker" Subject: Re: AeroElectric-List: Re: Mogas versus 100LL X-mailer: Pegasus Mail for Windows (4.41) --> AeroElectric-List message posted by: "Jim Baker" > The best way to describe it is > watch a cutting torch work, one adjusts the mixture till they get a neutral flameand when you > press the lever the additional O2 will not only add to the velocity of the flame front , it will almost > double the temp of the cutting flame itself. . Oops...too quick on the send..didn't even see this bit of mis-info. Tell ya what you do....take the torch, heat up the metal to start the cut, start the cut with the extra O2 then turn off the fuel gas. Continues to cut, doesn't it. The flame never gets twice as hot, not even close. As a matter of record the temperature stays roughly the same. http://www.welding.org/newsletters/winter2002/oxyfuel.html ________________________________ Message 17 ____________________________________ Time: 05:43:12 PM PST US From: "Robert L. Nuckolls, III" Subject: Re: AeroElectric-List: strange electrical failure in flight --> AeroElectric-List message posted by: "Robert L. Nuckolls, III" At 08:25 PM 9/22/2006 -0700, you wrote: >Hope someone has some ideas on how to troubleshoot an eletrical failure >that I don't understand. I have Bob's Essential Bus and Main Bus setup, >one battery, new plane (50 hours). In flight today I had an indication >that I had a problem when my main bus connected items shut down. I turned >on the Essential bus, turned off the Cessna type Master/Battery switch and >continued on, landing uneventfully as planned with Bob's system. > >Then I pulled the cowl to troubleshoot the problem. the master powered up >the Main bus as if nothing happened. I started the engine and got 13.5 >volts from the ND Alternator regardless of RPM. When I switched on the E >Bus, the charge rate / output from the alternator jumped to 14.3. If I >switched it off, the number again drops back to 13.5 volts. No blown fuses. As others have noted, the approx 0.7 to 0.8 volt jump between e-bus volts with alternate feed closed versus open is explained by the 0.7 volt drop in the normal feed diode. This is normal and is not a big deal . . . Consider that electro-whizzies for aircraft are generally expected to operate hunky-dory from a battery which delivers it's energy over a 12.5 to 11.0 volt domain. So, when the alternator is not working and the e-bus switch is closed, what you see is what the battery is able to deliver which starts out about 12.5 volts at 100% charged and by the time it's down to 11.0 volts, it's 95% used up. Turn on an alternator and the battery jumps up to 14.25 volts (recommended regulator setting for 99.999% of all 14v regulators on the road and in the air. Under this condition, with the e-bus alternate feed switch open, one expects 14.2 - 0.7 or 13.5 volts at the e-bus. If 12.5 and down is okay battery only, then I'll suggest that 13.5 with the alternator running is okay too. If you have only one voltmeter in the airplane, it's a good deal to have it on the e-bus and just KNOW that the alternator is running 0.7 above e-bus reading. When the alternator is running, you don't much care what the voltmeter reads . . . but when the alternator is not running, knowing what the battery is a lot more useful. There is when you find out if your battery maintenance and endurance bus calculations were correct. This explains the observed voltage variations you cited . . . which I'll suggest were predicted, normal and no big deal. This doesn't explain what was going on with your alternator. When you say the main bus stuff "shut down" . . . does this mean the stuff went completely dark? If the e-bus stuff stay up, I presume it was because you were flying with the e-bus alternate feed switch closed. Not a big deal . . . but it's a good idea to preflight the alternate feed path. Use the e-bus alternate feed to get your ATIS/Clearance before cranking up the engine. Then note that the e-bus DOES wiggle by the predicted 0.7 volts as the switch is operated . . . this says the diode is in place and good. What kind of alternator? Regulator? Do you have a low votlage warning light? Bob . . . ________________________________ Message 18 ____________________________________ Time: 07:59:13 PM PST US From: Kelly McMullen Subject: Re: AeroElectric-List: Re: Mogas versus 100LL --> AeroElectric-List message posted by: Kelly McMullen Well, other than promoting serious old wive's tales on a list where subject is way off topic........... by definition, any leaning past peak EGT is in fact COOLER than at peak. Given that the oxygen content is changing less than 1 percent between 50 ROP and 50 LOP, the torch effect you claim violates known laws of physics. n801bh@netzero.com wrote: > > Thank you Gary. That is the best explanation of octane and detonation/ > preignition scenerios I have ever read. I was going to try to desrcibe > it but you did so much better. The only thing I might add is the fact > that in the process of diluting the mixture with extra air there is a > point where before it really starts to run lean the engine flame front > goes into a blow torch effect and will melt the top of the piston and > or the exhaust valve. If you can transition though this setting fast > enough the motor just lays down and the EGT's show a cooler number, > set the air/fuel mixture at around 16-1, depending on the engine of > course, and work the motor hard, you will get very high EGT's, low > fuel flow numbers and hurt pistons/ valves. The best way to describe > it is watch a cutting torch work, one adjusts the mixture till they > get a neutral flame and when you press the lever the additional O2 > will not only add to the velocity of the flame front , it will almost > double the temp of the cutting flame itself. . > > > > Ben > > www.haaspowerair.com > ________________________________ Message 19 ____________________________________ Time: 07:59:13 PM PST US From: Larry Rosen Subject: Re: AeroElectric-List: Z13/8 & Z32 Relays (was Eeeeek! Another fear and question) --> AeroElectric-List message posted by: Larry Rosen Would a solid-state relay, like the power link Jr. provide a more reliable, lower current draw solution to the S-704-1 relays shown on Z13/8 and Z32? What are the disadvantages to this type of relay other than cost? Other than "tradition" what is the rational for wanting a contact in a always hot feed of more than a few amps? Larry Rosen RV-10 N204EN (reserved) Robert L. Nuckolls, III wrote: > --> AeroElectric-List message posted by: "Robert L. Nuckolls, III" > > > At 09:47 AM 9/23/2006 -0500, you wrote: > >> --> AeroElectric-List message posted by: Dave N6030X >> >> >> Well, I'll wait for Bob to justify his own schematics, but I know he >> is in Kansas at the tandem-wing fly-in today and may not be able to >> comment for a while. >> >> If it were ME, I would not use a relay to power the E-bus. I would >> use a switch. Switches handle larger current than 5A all the time, >> and if you're concerned about reliability, just use a switch rated >> for larger current. The other thing you should do here, since you're >> discovering you have an unusual e-bus, is to ask yourself whether all >> of those items really need to be on the e-bus. I had to go through >> several iterations before I finally pared my e-bus down to what was >> really going to be necessary to have running ALL THE TIME to complete >> the flight. Remember you can always power up the Main Bus for a few >> minutes if you need to, while on battery power. >> >> Dave Morris > > The suggestion for adding an e-bus relay had nothing to do > with current carrying capacity of the e-bus switch. There's > be a long standing tradition in TC aircraft to limit the size > of always-hot feeders in aircraft to those protected by 5A or > smaller breakers. > > Since the "FAT" e-bus feeder needs to carry more than the few > amps originally considered when the e-bus was conceived, the > idea for adding a 'mini-contactor' at the e-bus for larger > feeders was offered. > > Now, fuses are much faster than breakers, and for Z-13/8 > were a continuous e-bus load of 8A is PRACTICAL, then > assuming the e-bus alternate feed is fuse-fed from the > battery bus, going up to 10A fuse is a useful thing to > consider without thumbing our noses too vigorously at tradition. > > Too many folks are treating the Z-figures as carved-in- > stone recommendations for details of a proposed electrical > system. These drawings are STARTING POINTS that illustrate > architectures that will in-turn drive your Plan-A/Plan-B > thinking. > > Don't get yourselves wrapped around any axles here based > on sizes of wires, sizes of fuses/breakers or which > devices are fed from which busses. The drawings were > never intended to be a recipe for success, only a tool > for development. I get a half-dozen requests a week for > "Gee Bob, I like Figure Z-x but it doesn't . . . and > I want to . . . Would you please craft me a Z-y that > takes care of all my desires/worries?" > > All these requests get the same reply which is not > much different that what I've written above. Nobody > promised anyone a decision free solution. One is > always on firm footing to clone the system out of > a C-172 and drive on. Any variations from that theme > WILL require thought, exploration, crafting/answering > of questions and finally understanding of the final > configuration which WILL be uniquely applicable to > YOU and your airplane. > > Bob . . . > > ________________________________ Message 20 ____________________________________ Time: 08:48:37 PM PST US From: "John Swartout" Subject: RE: AeroElectric-List: Eeeeek! Another fear and question. --> AeroElectric-List message posted by: "John Swartout" Okay -- I think I get it. First, I forgot the chief reason to use a relay in the first place -- to keep fat wires short and if possible, out of the cockpit. Second, I lost sight of the over-arching fact that just HAVING a back-up alternator on board is a huge leap in reliability, not to mention STILL having the last ditch option of keeping the lights on with the battery for a couple of hours. <:) (smiley face with dunce cap) I think the simple answer to my specific question is YES, use a relay in the H.D. E-Bus normal feed line if that's the only way to keep the run from the Main Bus to the switch and from the switch to the E-Bus under 6 inches or so. It is useful to know, however, that the relays might have a service life short enough to consider replacing them at, say 500-hour intervals. Mine will be living in a pretty benign environment, two of them just fwd of the panel, and two just aft of the firewall. In any conglomeration of components, it's a truism that one of them will be the weakest link. Upgrade or eliminate it, and something else will automatically become the weakest link. Although 900 hours MTBF seems pretty short -- any ONE relay failing during a given flight will not produce a life-threatening emergency in my plane. And I can carry a spare, as Bob suggests in AEC. Thanks Bob. John -----Original Message----- From: owner-aeroelectric-list-server@matronics.com [mailto:owner-aeroelectric-list-server@matronics.com] On Behalf Of Robert L. Nuckolls, III Sent: Saturday, September 23, 2006 11:05 AM Subject: Re: AeroElectric-List: Eeeeek! Another fear and question. --> AeroElectric-List message posted by: "Robert L. Nuckolls, III" At 05:43 PM 9/22/2006 -0400, you wrote: >Bob, your 9/13/06 post regarding LEDs says in part: > > >Finally, relays are rated amongst the least reliable of > > components. It behooves us to limit their use where ever practical. > > >Okay. That brings up a question. I m planning Z13/8 with Z32. Z32 Heavy >Duty E-Bus Feed shows the use of a relay to energize the alternate feed >path. But Z13/8 also relies on a relay to supply the SD-8 s output to the >E-Bus. That s two relays that must work for E-Bus operations independent >of battery power. Is there a practical way to avoid the built-in weakness >of two relays in the E-Bus circuit? This thread has expanded into a predictable level of excitement for lack of perspective . . . Note the key word in the quotation above . . . PRACTICAL About 20 years ago, I was designing the first of a series of electronically controlled rate controllers for pitch trim on the Learjets. While conducting a Mil-HBK-217 MTBF study, it was interesting to note that when only the electronic components, wires, solder joints and connectors were factored into the study, MTBF for the device was in the thousands of hours . . . about 7,000 as I recall. When adding the last component, a mil-spec, 4-pole, double throw, hermetically sealed 25A relay to the study, the predicted MTBF fell to 900 hours for the system. Mil-HBK-217 suggests and even accommodates de-rating of parts to decrease stresses with commensurate increases in MTBF. I was able to design the system so that the relay was closed and bounce free before current flowed in the contacts. Further, I was able to shut off all current flow electronically before the relay contacts were opened. Mil-HDK-217 had no prediction formula for my proposed scenario but obviously, it was going to be as high as was PRACTICALLY possible for incorporation of the relay. Twenty years later, inquiries to the overhaul shop for this product tell me that relays have NEVER been replaced in a unit returned for repair. Even as I write these words, I'm designing the next new product to appear in the AeroElectric Connection catalog and the design incorporates a RELAY. Why not replace it electronically? PRACTICALITY - it's technologically possible but costs more . . . makes the product more expensive to build and doesn't make it perform any better. It MIGHT keep the system from needing maintenance attention before the original owner sells the airplane . . . but I doubt it. The decision as to whether a relay or contactor is PRACTICAL involves consideration of much more data than the gross reliability factors. Cost of ownership and FMEA for the SYSTEM figure heavily into the thought process. We still use $25, el-cheeso contactors in our airplanes because in spite of their need for periodic maintenance, we have crafted a Plan-B to deal with those failures. Hence my recommendation to many builders over the years that 'upgrading' to Mil-Spec contactors in their RV is dollars probably not well spent. So before anyone goes of the end of the plank in excitement or fear, know that suggestions for the selection of ANY component need to be considered against your ability to deal sweat-free with a failure of that component. If your Plan-B is solid, then use of that component is PRACTICAL and as free of excitement and concerns as we know how to do. Bob . . . ________________________________ Message 21 ____________________________________ Time: 09:52:57 PM PST US From: Subject: AeroElectric-List: Eaton Starter Contactor Website --> AeroElectric-List message posted by: Does anyone know the website for the Eaton Starter contactors??. I need one for a Lyc IO-540. Thanks