---------------------------------------------------------- AeroElectric-List Digest Archive --- Total Messages Posted Wed 12/24/03: 15 ---------------------------------------------------------- Today's Message Index: ---------------------- 1. 01:49 AM - Re: Fuel sw? (Steve Hunt) 2. 02:04 AM - Fuel Sw (Steve Hunt) 3. 07:47 AM - Re: Turbo pressure to mags? (Robert L. Nuckolls, III) 4. 08:02 AM - Re: Turbo pressure to mags? (Richard Tasker) 5. 08:31 AM - Re: Fuel sw? (Tore S. Bristol) 6. 08:39 AM - Re: Turbo pressure to mags? (Pete & Farrell Rouse) 7. 08:52 AM - Re: Resistive Fuel Sensors (Trampas) 8. 09:40 AM - Re: Turbo pressure to mags? (Matt Prather) 9. 09:56 AM - Re: Turbo pressure to mags? (Paul A. Franz, P.E.) 10. 10:58 AM - Re: Turbo pressure to mags? () 11. 11:20 AM - Re: [Continues] Intermittent Internet Connectivity Issues to (Matt Dralle) 12. 12:00 PM - Re: Fuel Sw (Robert L. Nuckolls, III) 13. 01:26 PM - Re: Thermocouples (Gary Casey) 14. 01:26 PM - Re: Turbo pressure to mags? (Gary Casey) 15. 02:12 PM - Re: Re: Turbo pressure to mags? (George Braly) ________________________________ Message 1 _____________________________________ Time: 01:49:27 AM PST US From: "Steve Hunt" Subject: Re: AeroElectric-List: Fuel sw? --> AeroElectric-List message posted by: "Steve Hunt" Hi Bob, the background to EFIS in my "8" is as follows. I would never choose to fly IFR or at night with one engine driving the one prop , its not wrong to do this elsewhere,however, I simply dont think it is a good thing for me to do.(despite my 13000 hrs flying...or maybe because of it?!)... My EFIS Lite weighs 520 grammes...about 3.25 Lbs. For this I get all the basic flight insts plus a GPS driven moving map plus a nav system (virt VOR with 360 "compass".) Its a heck of a lot of kit for 500 grammes! We dont have much free airspace on our little Island and we need to be able to either find our way around with great accuracy or accept help with radar headings in order to avoid all the controlled airspace when in our home builds. Yes I like aeros but I also want to tour with my `plane. The set up proposed would be very unwise given the above and our weather when visual can mean "in sight of the ground" but with perhaps no discernable horizon. So this was my logic to having stnd by power available , for at least ten minutes battery operation. This would give me time to get back on the ground in most circumstances that I can imagine when flying over land in UK. The ammeter question is well off my patch hence the dumb question. However, what I was referring was the advice on pages 7-12 and 7-13 of "The Aeroelectric Connection". I wondered if I wired it to the B lead just before my starter relay ....would that be a reasonable thing to do? Is there a better solution? Have I completely miss understood again! rgds Steve ________________________________ Message 2 _____________________________________ Time: 02:04:27 AM PST US From: "Steve Hunt" Subject: AeroElectric-List: Fuel Sw --> AeroElectric-List message posted by: "Steve Hunt" Whoops, just re read my latest dumb question.What I meant to say was....would you recommend I fit a battery ammeter as described on page 7-14, or is there a better solution(less weighty)....or indeed is this me being old fashioned and I simply dont need one? I will try to make the Kansas seminar!!! Steve ________________________________ Message 3 _____________________________________ Time: 07:47:39 AM PST US From: "Robert L. Nuckolls, III" Subject: Re: AeroElectric-List: Turbo pressure to mags? --> AeroElectric-List message posted by: "Robert L. Nuckolls, III" At 02:50 AM 12/24/2003 -0500, you wrote: >--> AeroElectric-List message posted by: "Ronald J. Parigoris" > > >I know that when flying high, that Turbo pressure is sent to mags. > >In WW2 They sent pressure to ignition harnesses as well. > >I am not sure why this suppresses arcing???? > >I think a vacuum is a better insulator than air??? Not at all. Your spark plugs used to be tested by observing the spark gap through a windowed chamber while air pressure was adjusted until the spark would just stop. The better plugs will spark at 150 psi, poorer ones at lesser pressures. Vacuum tubes won't function with even a small amount of air present. >Is it perhaps that it is not just pressurized, but is allowing an airflow >to cool >things down? Turbo C210's and Mooney's have a small pipe that takes pressurized air downstream of turbochargers to the magneto housings. Without such pressurization, they're in danger of internal arc-over. Waveguides in the B-52 radar system are pressurized, without pressurization, the 50 kilowatt pulse of energy going out to the antenna would never make it . . . one would have a little storm of mini-lightning strikes going on somewhere in the feedline. Bob . . . ________________________________ Message 4 _____________________________________ Time: 08:02:02 AM PST US From: Richard Tasker Subject: Re: AeroElectric-List: Turbo pressure to mags? --> AeroElectric-List message posted by: Richard Tasker Air at atmospheric pressure is more resistant to arcing than lower pressure air. If you had a true vacuum then the arcing would be even more suppressed, but at high altitudes you only have lower pressure - not vacuum. As you mentioned, higher pressure air cools better. My $0.02... Dick Tasker Ronald J. Parigoris wrote: >--> AeroElectric-List message posted by: "Ronald J. Parigoris" > >I know that when flying high, that Turbo pressure is sent to mags. > >In WW2 They sent pressure to ignition harnesses as well. > >I am not sure why this suppresses arcing???? > >I think a vacuum is a better insulator than air??? > >Is it perhaps that it is not just pressurized, but is allowing an airflow to cool >things down? > >Thx. >Ron Parigoris > > > > ________________________________ Message 5 _____________________________________ Time: 08:31:16 AM PST US From: "Tore S. Bristol" Subject: Re: AeroElectric-List: Fuel sw? --> AeroElectric-List message posted by: "Tore S. Bristol" ----- Original Message ----- From: "Steve Hunt" Subject: Re: AeroElectric-List: Fuel sw? > --> AeroElectric-List message posted by: "Steve Hunt" > > Hi Bob, > > the background to EFIS in my "8" is as follows. > > I would never choose to fly IFR or at night with one engine driving the one prop , its not wrong to do this elsewhere,however, I simply dont think it is a good thing for me to do.(despite my 13000 hrs flying...or maybe because of it?!)... > > My EFIS Lite weighs 520 grammes...about 3.25 Lbs. For this I get all the basic flight insts plus a GPS driven moving map plus a nav system (virt VOR with 360 "compass".) Its a heck of a lot of kit for 500 grammes! > > We dont have much free airspace on our little Island and we need to be able to either find our way around with great accuracy or accept help with radar headings in order to avoid all the controlled airspace when in our home builds. > > Yes I like aeros but I also want to tour with my `plane. > > The set up proposed would be very unwise given the above and our weather when visual can mean "in sight of the ground" but with perhaps no discernable horizon. > > So this was my logic to having stnd by power available , for at least ten minutes battery operation. This would give me time to get back on the ground in most circumstances that I can imagine when flying over land in UK. > > > The ammeter question is well off my patch hence the dumb question. However, what I was referring was the advice on pages 7-12 and 7-13 of "The Aeroelectric Connection". I wondered if I wired it to the B lead just before my starter relay ....would that be a reasonable thing to do? Is there a better solution? Have I completely miss understood again! > > rgds > > Steve > > Hi! Good news; 520 g is more like 1,15 lbs so you just saved another 2,1 lbs! Regards Tore S Bristol Norway > > ________________________________ Message 6 _____________________________________ Time: 08:39:47 AM PST US From: "Pete & Farrell Rouse" Subject: Re: AeroElectric-List: Turbo pressure to mags? --> AeroElectric-List message posted by: "Pete & Farrell Rouse" Ron, There is something called 'breakdown voltage' that is basically the voltage necessary to ionize the air sufficiently between a gap of a know distance to induce an arc across the gap. The breakdown voltage gets lower as the air density gets lower, thus the breakdown voltage decreases with increasing altitude. There is something called the 'Paschen Curve' that describes this phenomenon. The higher the voltage, the more probability of arcing at altitude. The only reason I am able to comment on this at all, is that I asked a very similar question in the last few days. Well, I just ran out of knowledge, so I'll shut up now..... Happy Holidays, Pete Rouse ----- Original Message ----- From: "Ronald J. Parigoris" Subject: AeroElectric-List: Turbo pressure to mags? > --> AeroElectric-List message posted by: "Ronald J. Parigoris" > > I know that when flying high, that Turbo pressure is sent to mags. > > In WW2 They sent pressure to ignition harnesses as well. > > I am not sure why this suppresses arcing???? > > I think a vacuum is a better insulator than air??? > > Is it perhaps that it is not just pressurized, but is allowing an airflow to cool > things down? > > Thx. > Ron Parigoris > > ________________________________ Message 7 _____________________________________ Time: 08:52:16 AM PST US From: "Trampas" Subject: RE: AeroElectric-List: Resistive Fuel Sensors --> AeroElectric-List message posted by: "Trampas" Some sensors you can put in parallel with multiple gauges. Most sensors which have three wires, like most resistive float senders outputs a voltage on one of the pins which varies. Multiple gauges can be placed in parallel with theses sensors, assuming the gauges have a relative high impedance input. Now with that said you would have to check with EIS to determine if their unit can be put in parallel with an analog gauge. As far as oil pressure if you use a switch it is easy to have multiple devices triggered off the same switch. One of the big things in my mind about using multiple gauges is for the redundancy, however if you are using the same sensor then your redundancy is really not there, since from my experience the sensor is more likely to fail than a gauge. Personally I see a need for a back up oil pressure gauge and a back up voltage gauge, especially with electronic instruments. Let's not forget that your job is to fly the plane, with or with out engine running. As far as knowing how much fuel you have which most people have a reasonable guess based on experience, after all if you are unsure of your fuel level, then you need fuel. Regards, Trampas -----Original Message----- From: owner-aeroelectric-list-server@matronics.com [mailto:owner-aeroelectric-list-server@matronics.com] On Behalf Of John Slade Subject: RE: AeroElectric-List: Resistive Fuel Sensors --> AeroElectric-List message posted by: "John Slade" > Are there any concerns about having more than one gauge attached > to these sensors? Now that's a question I'd like to hear the answer to. My system needs 3 oil pressure sensors (hobbs, gauge and voice annunciator). Can I use the same sensor for all of them? Same's true of oil temp & coolant temp. ________________________________ Message 8 _____________________________________ Time: 09:40:04 AM PST US Subject: Re: AeroElectric-List: Turbo pressure to mags? From: "Matt Prather" --> AeroElectric-List message posted by: "Matt Prather" Here is a chart that lists the dielectric strengths of various common materials. Note that vacuum is one of the lowest (worst) dielectric strengths. Regards, Matt- N34RD Dielectric strengths for insulators Dielectric strength in kilovolts per inch (kV/in): Material* Dielectric strength ========================================= Vacuum --------------------- 20 Air ------------------------ 20 to 75 Porcelain ------------------ 40 to 200 Paraffin Wax --------------- 200 to 300 Transformer Oil ------------ 400 Bakelite ------------------- 300 to 550 Rubber --------------------- 450 to 700 Shellac -------------------- 900 Paper ---------------------- 1250 Teflon --------------------- 1500 Glass ---------------------- 2000 to 3000 Mica ----------------------- 5000 > --> AeroElectric-List message posted by: "Ronald J. Parigoris" > > > I know that when flying high, that Turbo pressure is sent to mags. > > In WW2 They sent pressure to ignition harnesses as well. > > I am not sure why this suppresses arcing???? > > I think a vacuum is a better insulator than air??? > > Is it perhaps that it is not just pressurized, but is allowing an > airflow to cool things down? > > Thx. > Ron Parigoris > > ________________________________ Message 9 _____________________________________ Time: 09:56:05 AM PST US Subject: Re: AeroElectric-List: Turbo pressure to mags? From: "Paul A. Franz, P.E." --> AeroElectric-List message posted by: "Paul A. Franz, P.E." On Wed, 2003-12-24 at 07:59, Richard Tasker wrote: > --> AeroElectric-List message posted by: Richard Tasker > > Air at atmospheric pressure is more resistant to arcing than lower > pressure air. If you had a true vacuum then the arcing would be even > more suppressed, but at high altitudes you only have lower pressure - > not vacuum. As you mentioned, higher pressure air cools better. Voltage required to arc is actually a U shaped curve with the minimum arcing voltage to hop a 1 cm gap occurring at about 150,000 FT DA. Rather than depend on air as an insulator in high flying stuff Reynolds makes elastomer seals that aren't susceptible to this arc length creep. The above link shows Paschen's 19th century results when this was studied. -- PAF Consulting Engineers | 427 - 140th Ave NE (425)641-8202 voice | Bellevue, WA 98005 (425)641-1773 fax | GnuPG Public Key - ________________________________ Message 10 ____________________________________ Time: 10:58:38 AM PST US From: Subject: Re: AeroElectric-List: Turbo pressure to mags? --> AeroElectric-List message posted by: Ron You have it backwards. Air is a relatively poor conductor. It acts as an insulator. Since the air at high altitudes is less dense, it is not as good at insulating spark arcing. Pressurizing the interior of the magnetoes and the wiring harnesses helps suppress arcing by supplying a more dense atmosphere. Charlie Kuss > > From: "Ronald J. Parigoris" > Date: 2003/12/24 Wed AM 02:50:06 EST > To: aeroelectric-list@matronics.com > Subject: AeroElectric-List: Turbo pressure to mags? > > ________________________________ Message 11 ____________________________________ Time: 11:20:42 AM PST US From: Matt Dralle Subject: AeroElectric-List: Re: [Continues] Intermittent Internet Connectivity Issues to Matronics... --> AeroElectric-List message posted by: Matt Dralle Dear Listers, Pacbell is suppose to be working the Matronics connectivity issue this morning. Intermittent connectivity is still a issue although things are better than yesterday. They will probably be doing some intrusive testing on the line later today which will disrupt connections during the test. More information as it becomes available! Thanks for your patience. Matt Dralle Matronics Email List Admin. At 02:59 PM 12/23/2003 Tuesday, you wrote: >Dear Listers, > >Starting at about 1:05pm PDT Matronics starting having intermittent >connectivity issues to the Internet. I've called the ISP and they are >looking into the problem and may do intrusive testing on the line at some >point this afternoon/evening. For the most part, things seem to be >working right now, but the line will drop out every once in a while for 2 >to 3 minutes. > >This problem will effect connections to the Matronics Web server as well >as distribution of List mail. > >I will post a follow up when the problem has been resolved... Hopefully >later today. > >Matt Dralle >Matronics Email List Admin. > >do not archive Matt G Dralle | Matronics | PO Box 347 | Livermore | CA | 94551 925-606-1001 V | 925-606-6281 F | dralle@matronics.com Email http://www.matronics.com/ WWW | Featuring Products For Aircraft ________________________________ Message 12 ____________________________________ Time: 12:00:23 PM PST US From: "Robert L. Nuckolls, III" Subject: Re: AeroElectric-List: Fuel Sw --> AeroElectric-List message posted by: "Robert L. Nuckolls, III" At 10:04 AM 12/24/2003 +0000, you wrote: >--> AeroElectric-List message posted by: "Steve Hunt" > > >Whoops, >just re read my latest dumb question.What I meant to say was....would you >recommend I fit a battery ammeter as described on page 7-14, or is there a >better solution(less weighty)....or indeed is this me being old fashioned >and I simply dont need one? > >I will try to make the Kansas seminar!!! Battery ammeters have some degree of utility for troubleshooting as do alternator loadmeters. The later are easier to install while maintaining a minimize the fat-wires-in-the-cockpit philosophy. I'd recommend a loadmeter if you have any ammeter at all. A low voltage warning light may well suffice for all necessary in-flight electrical system instrumentation. Bob . . . ________________________________ Message 13 ____________________________________ Time: 01:26:15 PM PST US From: "Gary Casey" Subject: AeroElectric-List: RE: Thermocouples --> AeroElectric-List message posted by: "Gary Casey" <then it is conservative to use the same kind of wire from the switch to the >instrument. Caveat: the switch needs to be in the same temperature zone as >the instrument since the 'cold junction' matches are critical to >sensor/instrument accuracy. Anytime one has a connection in the sensor >wire, one creates another cold junction. It's more accurate to say that deleterious effects of any parasitic thermocouples generated when introducing foreign metals can be minimized as long as whatever is done to one side of the thermocouple path is done to the other side but in opposite polarity . . . it's a sorta two-wrongs-can- make-a-right approach.>> Bob is certainly correct here. A long time ago when we were using passive "pyrometers," really just voltmeters, to read thermocouples we even went as far as to use a special selector switch that was made of the right materials. But then I worked at a powerplant one summer and there were thermocouples half a mile away from the instrument. We ran the TC wires to a junction box, connected them to copper and ran the rest of the way in copper. For an aircraft it would work just fine that way. Splice the TC wires under the cowl to copper wires, run the copper wires to an ordinary wafer switch if you like, and then to the instrument. Just make sure you don't make a spice on one side of the circuit at a location that is at a different temperature than the splice on the other side of the circuit. It all works very easily and if there is an error it is so small that you'll never find it. Gary Casey ________________________________ Message 14 ____________________________________ Time: 01:26:15 PM PST US From: "Gary Casey" Subject: AeroElectric-List: RE: Turbo pressure to mags? --> AeroElectric-List message posted by: "Gary Casey" <<--> AeroElectric-List message posted by: "Ronald J. Parigoris" I know that when flying high, that Turbo pressure is sent to mags. In WW2 They sent pressure to ignition harnesses as well. I am not sure why this suppresses arcing???? I think a vacuum is a better insulator than air??? Is it perhaps that it is not just pressurized, but is allowing an airflow to cool things down? Thx. Ron Parigoris>> Vacuum might be a better INSULATOR, but the higher the pressure of the air the higher its DIELECTRIC STRENGTH. In other words it will take a higher voltage to arc when the pressure is higher. And this is why the magnetos are sometimes pressurized. The problem mostly exists at the rotor where at some voltage the current will arc to another post rather than to a plug. A Naturally Aspirated engine doesn't have this problem because the pressure in the cylinder also goes down with higher altitude. A supercharged engine is typically operated at a constant manifold pressure and hence a constant cylinder pressure regardless of altitude. If the magneto is pressurized the potential for cross-firing is minimized. Gary Casey ________________________________ Message 15 ____________________________________ Time: 02:12:45 PM PST US From: George Braly Subject: RE: AeroElectric-List: RE: Turbo pressure to mags? --> AeroElectric-List message posted by: George Braly Re mags: If you use Bendix 1200 mags, they do NOT need to be pressurized until above about 28000 feet. If you use Slick mags, they need to be pressurized above about 12,000'. Very simple. Very predictable. Very repeatable. I have flown an unpressurized set of Bendix 1200 series mags to 33,000'D.A. before they started to arc. Regards, George -----Original Message----- From: owner-aeroelectric-list-server@matronics.com [mailto:owner-aeroelectric-list-server@matronics.com]On Behalf Of Gary Casey Subject: AeroElectric-List: RE: Turbo pressure to mags? --> AeroElectric-List message posted by: "Gary Casey" <<--> AeroElectric-List message posted by: "Ronald J. Parigoris" I know that when flying high, that Turbo pressure is sent to mags. In WW2 They sent pressure to ignition harnesses as well. I am not sure why this suppresses arcing???? I think a vacuum is a better insulator than air??? Is it perhaps that it is not just pressurized, but is allowing an airflow to cool things down? Thx. Ron Parigoris>> Vacuum might be a better INSULATOR, but the higher the pressure of the air the higher its DIELECTRIC STRENGTH. In other words it will take a higher voltage to arc when the pressure is higher. And this is why the magnetos are sometimes pressurized. The problem mostly exists at the rotor where at some voltage the current will arc to another post rather than to a plug. A Naturally Aspirated engine doesn't have this problem because the pressure in the cylinder also goes down with higher altitude. A supercharged engine is typically operated at a constant manifold pressure and hence a constant cylinder pressure regardless of altitude. If the magneto is pressurized the potential for cross-firing is minimized. Gary Casey --- Incoming mail is certified Virus Free. ---