---------------------------------------------------------- AeroElectric-List Digest Archive --- Total Messages Posted Wed 04/29/15: 5 ---------------------------------------------------------- Today's Message Index: ---------------------- 1. 09:27 AM - Re: Starter Solenoid behavior with low Battery (Robert L. Nuckolls, III) 2. 09:32 AM - Re: Re: Starter Solenoid behavior with low Battery (Robert L. Nuckolls, III) 3. 12:14 PM - Re: Flexible Wire for Pull Out Fuse Tray? (Robert L. Nuckolls, III) 4. 01:17 PM - Re: Flexible Wire for Pull Out Fuse Tray? (Jeff Luckey) 5. 01:55 PM - Re: Flexible Wire for Pull Out Fuse Tray? (Robert L. Nuckolls, III) ________________________________ Message 1 _____________________________________ Time: 09:27:34 AM PST US From: "Robert L. Nuckolls, III" Subject: Re: AeroElectric-List: Starter Solenoid behavior with low Battery At 19:39 2015-04-28, you wrote: Re-sending: What about the proposal to eliminate the starter contactor? I am looking at the Skytec dagram here: http://www.skytecair.com/Wiring_diag.htm The starter barely gets 10 volts after the master contactor and the starter contactor in series. By eliminating the starter contactor, you would have a hot wire to the starter whenever the master is on. Is this a good idea or suicide How do you arrive at that voltage level. What do you believe voltage drop across the starter contactor to be? Actually, when you wire per the configuration recommended by B&C since day-one of the light-weight starters, you will have THREE contactors in series. Battery, starter external, starter internal. SkyTec was in favor of utilizing on the starter's internal contactor hence the wiring diagram you cited. We elected not to recommend that as a general rule based on a lot of history . . . some of which has roots in the legacy Bendix-Style key switches found on 100,000 single engine airplanes. Here is a document I published almost 20 years ago that explains the extra-ordinary stresses placed on the crew-operated, starter switch by modern, two-stage starter solenoid/contactor www.aeroelectric.com/articles/strtctr.pdf In this article I described the electrical forces that are especially hard on slow-motion, wiping contacts characteristic of the legacy key switch. Forces that prompted an abortive AD by the FAA issued first without understanding the physics and corrected later when the 'fix' didn't fix anything. I'm not implying that there are not alternatives based on other system constraints. For example, this image . . . Emacs! . . . is found in figure Z-22 of the book. This was a system driven 'fix' for the starter run-on phenomenon observed when PM motors were becoming popular. In this instance, one was required to use the built-in contactor . . . so a buffer relay was added to isolate the starter switch from solenoid abuse. This approach could be applied for ANY form of starter motor thus eliminating the external contactor. Given that the B&C starters were going into both OBAM and TC aircraft (already fitted with external contactors) we elected to recommend external contactors as a matter of common practice . . . B&C starters did not have PM motors. The switch supplied with B&C starter installation kits was pretty robust but NOT suited to drive the starter's build in solenoid-contactor. So the short answer is, you can certainly eliminate the external contactor . . . but it's a good idea to know how that decision may create ripples in the rest of the system. Bob . . . ________________________________ Message 2 _____________________________________ Time: 09:32:26 AM PST US From: "Robert L. Nuckolls, III" Subject: Re: AeroElectric-List: Re: Starter Solenoid behavior with low Battery At 21:08 2015-04-28, you wrote: Ok, I was worried there for a while thinking that either I burned up my starter solenoid contacts and/or that it was mounted upside down. Like I said in my original post, now that battery voltage is normal, the starter solenoid is operating perfectly. However, I agree that I probably abused it with the low battery situation, probably shortening its expected service life, and I will be on the look out for future problems with it. \ I don't think a one-of sticking event is a predictor of future problems. The welding material between contacts prone to sticking consists of small mounds of low-area metal that get displaced from the contact mass during a low-battery start attempt. Those features will be flashed away during successive good-battery start operations. But we'll be interested in hearing if you observe any contrary experience. Bob . . . ________________________________ Message 3 _____________________________________ Time: 12:14:14 PM PST US From: "Robert L. Nuckolls, III" Subject: Re: AeroElectric-List: Flexible Wire for Pull Out Fuse Tray? At 17:48 2015-04-28, you wrote: Hello Bob, Thanks again for all your help over the years of our (wife and my) Lancair Legacy project. In our electrical system design, weve gone with a pull-out fuse tray that is on the right side of the instrument panel. Its about 4 tall, 2 wide, 24 long and uses blade fuses that light up when theyve blown. All the fuse blocks are easily visible to the pilot when the tray is pulled out. We chose this solution because of its simplicity and minimum real estate on the Legacys small instrument panel. In its implementation, though, Im a bit concerned with the fatigue life of the thick wires running to it with the tray being pulled out and in for each flight with before takeoff checks. The MIL-W-22759 wire in these gauges is fairly stiff There are several since the diodes between buses are on the avionics shelf because of fuse tray space limitations. Is there a very flexible 10 and 8 AWG wire that we could use for the connections between our fuse tray and avionics shelf, that can better handle the fuse tray motion/flexing than the MIL-W-22759, and is air worthy? Check out a big-box store's electrical supplies. You can get a chunk of 10-3 drop cord (SJ, SJO)and cut away the insulation to acquire three, very flexible and robust runs of 10AWG wire. You won't find 8AWG drop cord but a welding shop can sell you 6AWG welding cable that's only a little larger than your 8AWG and probably more flexible than the 8AWG Tefzel. Bob . . . ________________________________ Message 4 _____________________________________ Time: 01:17:32 PM PST US From: Jeff Luckey Subject: Re: AeroElectric-List: Flexible Wire for Pull Out Fuse Tray? You can get a chunk of 10-3 drop =C2- cord (SJ, SJO)and cut away the insulation to =C2- acquire three, very flexible and robust =C2- runs of 10AWG wire. Bob, is that insulation "kosher" with respect to combustion by-products. I thought that was the reason that Tefzel was the recommended wire/insulat ion type. -Jeff On Wednesday, April 29, 2015 12:24 PM, "Robert L. Nuckolls, III" wrote: ls.bob@aeroelectric.com> At 17:48 2015-04-28, you wrote: Hello Bob, Thanks again for all your help over the years of our (wife and my) Lancair Legacy project. In our electrical system design, we=99ve gone with a pull-out fuse tray that is on the right side of the instrument panel.=C2- It=99s about 4 =9C tall, 2=9D wide, 24=9D long and uses blade fuses that light up when they=99ve blown.=C2- All the fuse blocks are easily visible to the pilot when the tray is pulled out. We chose this solution because of its simplicity and minimum real estate on the Legacy=99s small instrument panel.=C2- In its implementation, though, I=99m a bit concerned with the fatigue life of the thick wires running to it with the tray being pulled out and in for each flight with before takeoff checks.=C2- The MIL-W-22759 wire in these gauges is fairly stiff=C2- There are several since the diodes between buses are on the avionics shelf because of fuse tray space limitations. Is there a very flexible 10 and 8 AWG wire that we could use for the connections between our fuse tray and avionics shelf, that can better handle the fuse tray motion/flexing than the MIL-W-22759, and is air worthy? =C2- Check out a big-box store's electrical =C2- supplies. You can get a chunk of 10-3 drop =C2- cord (SJ, SJO)and cut away the insulation to =C2- acquire three, very flexible and robust =C2- runs of 10AWG wire. =C2- You won't find 8AWG drop cord but a welding =C2- shop can sell you 6AWG welding cable that's =C2- only a little larger than your 8AWG and probably =C2- more flexible than the 8AWG Tefzel. =C2- Bob . . . - S - - =C2- =C2- =C2- =C2- =C2- -Matt Dralle, List Admin. ________________________________ Message 5 _____________________________________ Time: 01:55:45 PM PST US From: "Robert L. Nuckolls, III" Subject: Re: AeroElectric-List: Flexible Wire for Pull Out Fuse Tray? At 15:16 2015-04-29, you wrote: You can get a chunk of 10-3 drop cord (SJ, SJO)and cut away the insulation to acquire three, very flexible and robust runs of 10AWG wire. Bob, is that insulation "kosher" with respect to combustion by-products. I thought that was the reason that Tefzel was the recommended wire/insulation type. It depends on who you talk too. There's one well meaning and vocal faction out there that thinks Tefzel is spawn of the devil . . . http://tinyurl.com/2f8uz After you've spent some time in the test lab letting the smoke out of things, you come to realize that the flavor of smoke from any combustible becomes a rather moot point. Yeah, they do flame tests on insulation . . . by plying it with a torch! After it appears sufficiently antagonized that it should burn, you take away the flame. If I recall the reasoning with any accuracy, the flaming insulation should not propagate along the wire, it should self extinguish in so many seconds, it should not drip flaming globs of insulation and . . . oh yeah . . . should be minimally obnoxious to respiratory system . . . the flavor of a fine pipe tobacco being a design goal. I've been present when wires were burned either by accident or test. I've seen and smelled lots of smoke . . . and there were no reminders of grandpa's favorite pipe. Most the flaming materials wienies seem to think that there is increased risks for having materials that will PROPAGATE or PROMOTE a fire from any/un-named source . . . not many pilots I know fly around with propane torches. Getting a wire lit up by hard faulting to a battery is exceedingly problematic unless the insulation is VERY flammable . . . but wait, seems like those fuses and circuit breakers are supposed to keep things from going that far in the first place. No . . .? Airplanes have been wired with everything from cotton covered rubber to super-exotic- unobtanium for over a century. Yet in the annals of aviation accidents, I'm aware of no incident that was blamed on flammability of the insulation. There may be some out there but they're a vanishingly small proportion of totality of incidents. INTEGRITY of insulation, yes. Swissair 111 wiring sparked and set the airplane's cabin insulation on fire. Look at the pictures of the 777 that belly flopped in SFO. LOTS of stuff throughout the cabin burned with some vigor . . . and I doubt that anyone was reminded of their grandpa's pipe in that incident either. If the flaming materials wienies were really taking their jobs seriously, then every new requirement that strives for happy fires in the cabin would have grounded the existing fleet until sub-standard materials were replaced. Hundreds of thousands of miles of 'sub-standard' wire are airborne someplace over the planet as we speak . . . I suggest that the lowest risk path to personal flight is grounded in good FMEA, craftsmanship, and plan-b for highest risk failures. If you've got serious smoke in the cockpit that doesn't quit when you turn of the master switch . . . well . . . the flavor of that smoke is the least of your worries. I prefer to design for no-fire as opposed to designing for friendly fire. Bob . . . ------------------------------------------------------------------------------------- Other Matronics Email List Services ------------------------------------------------------------------------------------- Post A New Message aeroelectric-list@matronics.com UN/SUBSCRIBE http://www.matronics.com/subscription List FAQ http://www.matronics.com/FAQ/AeroElectric-List.htm Web Forum Interface To Lists http://forums.matronics.com Matronics List Wiki http://wiki.matronics.com Full Archive Search Engine http://www.matronics.com/search 7-Day List Browse http://www.matronics.com/browse/aeroelectric-list Browse Digests http://www.matronics.com/digest/aeroelectric-list Browse Other Lists http://www.matronics.com/browse Live Online Chat! http://www.matronics.com/chat Archive Downloading http://www.matronics.com/archives Photo Share http://www.matronics.com/photoshare Other Email Lists http://www.matronics.com/emaillists Contributions http://www.matronics.com/contribution ------------------------------------------------------------------------------------- These Email List Services are sponsored solely by Matronics and through the generous Contributions of its members.