---------------------------------------------------------- AeroElectric-List Digest Archive --- Total Messages Posted Wed 12/02/09: 17 ---------------------------------------------------------- Today's Message Index: ---------------------- 1. 06:55 AM - Re: AeroElectric-List Digest: 19 Msgs - 12/01/09 (Speedy11@aol.com) 2. 07:16 AM - Re: glide slope anenna (user9253) 3. 07:21 AM - Re: 2 wires a little springy on my panel channel tray (user9253) 4. 07:54 AM - Re: Lamp polarity and unpluggability (user9253) 5. 08:09 AM - Re: 2 wires a little springy on my panel channel tray (messydeer) 6. 08:44 AM - Re: Contactor Failure (Robert L. Nuckolls, III) 7. 08:47 AM - Re: glide slope anenna (Robert L. Nuckolls, III) 8. 08:52 AM - Re: Re: Lamp polarity and unpluggability (Robert L. Nuckolls, III) 9. 09:35 AM - Re: glide slope anenna (Bill Hibbing) 10. 10:10 AM - DIY VHF Comm antenna (Robert L. Nuckolls, III) 11. 10:18 AM - Re: Lamp polarity and unpluggability (messydeer) 12. 11:09 AM - Re: Re: Lamp polarity and unpluggability (Bill Mauledriver Watson) 13. 11:30 AM - Re: DIY VHF Comm antenna (Ernest Christley) 14. 11:44 AM - Avionics Master Switch (Wade Roe) 15. 12:46 PM - Re: DIY VHF Comm antenna (Bill Boyd) 16. 01:10 PM - Re: DIY VHF Comm antenna (Matt Prather) 17. 03:19 PM - Re: Avionics Master Switch (Robert L. Nuckolls, III) ________________________________ Message 1 _____________________________________ Time: 06:55:10 AM PST US From: Speedy11@aol.com Subject: AeroElectric-List: Re: AeroElectric-List Digest: 19 Msgs - 12/01/09 The continuous duty contactor I have installed is temporary. I will replace it with an intermittent duty one. I installed the Skytec starter as it arrived from the manufacturer - that is, with the jumper from the contactor's control line to the main terminal installed. I left the jumper installed because Skytec recommend it - see _http://www.skytecair.com/images/Certified%20LS%20Wiring_1100.jpg_ (http://www.skytecair.com/images/Certified%20LS%20Wiring_1100.jpg) . My error, of course, was that I left out what they call the master solenoid. This is Van's recommended wiring _http://www.skytecair.com/images/Van's%20Starter%20Wiring%20Lg.jpg_ (http://www.skytecair.com/images/Van's%20Starter%20Wiring%20Lg.jpg) , but Skytec recommends against wiring this way. Bob, are you implying that I should have removed the jumper wire from the starter? I will refer to Z-22 as I rewire. Stan Sutterfield At 01:01 PM 12/1/2009, you wrote: >The contactor in question is a B&C S702-1. I talked to Bill >Bainbridge at B&C and he suggested trying the contactor again. I >will bench test it (actually already have but will do it again) and >rewire according to B&C diagram with battery switch between battery >and starter contactor. That way I can remove power to the contactor if needed. That particular design has been applied in the gazillions in automotive applications and is well proven. There are so many clones of the concept I'd be hard pressed to identify the original any more. I don't know where B&C buys their inventory now. At one time, they were offering two versions of that form factor in intermittent duty contactors. One version was qualified onto his first STC'd starter installations. The second came with the inventory I sold him and included a built in coil collapse suppression diode. Yes, it's a lowly diode. > Right now I have installed a continuous duty contactor that I had > lying on the shelf, but it doesn't fit into my space as well as the > B&C contactor. A continuous duty contactor is never a suitable substitute for controlling starter motors. >I did consider using only the starter-fitted contactor, but was >trying to follow Aeroelectric advice so inserted the additional >contactor. It would take additional wiring effort now to change. The "AeroElectric advice" has foundations in a lot of discussion threads involving starters, styles of motors, and system characteristics. If you're running a Skytec PM starter and have jumpered the built in contactor's control line to the main terminal, then it's almost a certainty that your starter suffers from what we've calls "starter run on" . . . a delayed disengagement of the pinion gear due to counter-EMF generated by a motor's armature spinning down in a permanent magnet field. Ideas discovered and recipes developed from those discussions spawned Figure Z-22. >The B&C S702-1 contactor has an internal diode so the starter switch >was connected to the S terminal with no external diode. I did not >install a starter engaged light, but plan to add one as I rewire things. >Rewiring will consist of adding #2 welding cable from the battery to >the battery switch and then to the contactor. Also I'll wire up a >starter engaged light. Please rewire per Z-22. This is important for several reasons: (1) You have a PM starter motor and the change will improve the life of your starter motor, pinion gear and ring gear. (2) You'll eliminate the potential for sticking the contactor again. (3) This also reduces the number of metallic joints and contact sets in series with the starter. All of these are good things. Bob ________________________________ Message 2 _____________________________________ Time: 07:16:41 AM PST US Subject: AeroElectric-List: Re: glide slope anenna From: "user9253" According to my calculations, a quarter wave glideslope antenna should be 21.9cm long. I believe it is horizontally polarized. A temporary antenna can be a length of copper tape stuck onto the windscreen and soldered to the coax center conductor. Attach the coax shield to the adjacent windscreen metal frame. Joe -------- Joe Gores Read this topic online here: http://forums.matronics.com/viewtopic.php?p=275745#275745 ________________________________ Message 3 _____________________________________ Time: 07:21:07 AM PST US Subject: AeroElectric-List: Re: 2 wires a little springy on my panel channel tray From: "user9253" How about something like this for metal edge protection for wires. Joe http://www.jcwhitney.com/FLEXIBLE_EDGE_TRIM_50?ID=12;0;0;0;100001;ProductName;0;0;0;0;2006725;0;0 > I cutoff the rear flange flush with the web of the channel to make room for the wires. I'm not sure yet how I could dress the cut edge. Ideas? -------- Joe Gores Read this topic online here: http://forums.matronics.com/viewtopic.php?p=275754#275754 ________________________________ Message 4 _____________________________________ Time: 07:54:57 AM PST US Subject: AeroElectric-List: Re: Lamp polarity and unpluggability From: "user9253" LEDs should not work with opposite polarity. So I looked up the Radio Shack part number that you gave: 272-345. At first I thought that it was an LED too. But then I realized that it is a RED lamp, not an LED. So actually you are using incandescent lamps. > I understand it would be good to place a rectifying diode across the leads in spike catcher fashion. I do not think so. A reverse-biased diode would have no affect. A forward-biased diode would blow the fuse. Joe http://www.radioshack.com/product/index.jsp?productId=2103779 -------- Joe Gores Read this topic online here: http://forums.matronics.com/viewtopic.php?p=275761#275761 ________________________________ Message 5 _____________________________________ Time: 08:09:53 AM PST US Subject: AeroElectric-List: Re: 2 wires a little springy on my panel channel tray From: "messydeer" Thanks, Joe :-) Another possibility is to bend the cut edge down a bit. Others have added a piece of angle with the flange pointing down across the cutout area. I'll be putting in a vertical piece of 032 angle on either side of the Enigma for support between the tray and glare shield and may not need that extra angle under the tray. I also moved things around with the wires a little. Seems the two mag leads aren't totally responsible for the springiness. All the other wires are adding a little, even though they don't look like it. And I measured the force to be only 6oz. Having never done this before, I'm very cautious. -------- Dan Read this topic online here: http://forums.matronics.com/viewtopic.php?p=275770#275770 ________________________________ Message 6 _____________________________________ Time: 08:44:20 AM PST US From: "Robert L. Nuckolls, III" Subject: AeroElectric-List: re: Contactor Failure At 08:46 AM 12/2/2009, you wrote: The continuous duty contactor I have installed is temporary. I will replace it with an intermittent duty one. I installed the Skytec starter as it arrived from the manufacturer - that is, with the jumper from the contactor's control line to the main terminal installed. I left the jumper installed because Skytec recommend it - see http://www.skytecair.com/images/Certified%20LS%20Wiring_1100.jpg. My error, of course, was that I left out what they call the master solenoid. I'm just guessing . . . but this configuration was probably crafted to MINIMIZE changes to an existing system in a TC aircraft. Adding the jumper to the starter contactor (a technique adopted by B&C many years earlier) offers three advantages. (1) you get a drop-in replacement of a previously installed starter and (2) buffers existing ship's wiring from experiencing the extra-ordinary inrush offered by the two-stage solenoids as described in my article and (3) the PM motor inrush current doesn't hit the system until BOTH the standard starter and built-in contactors close. Since the standard contactor closes first, there's a potential for improving life of this contactor IF it's contacts are closed and stable when the second set of contacts on the starter get closed a few milliseconds later. The DOWNSIDE is the potential for suffering delayed pinion dis-engagement. This is Van's recommended wiring http://www.skytecair.com/images/Van's%20Starter%20Wiring%20Lg.jpg, but Skytec recommends against wiring this way. This is pretty slick. The diagram suggests using the auxiliary "I" (ignition boost) terminal available on most starter contactors to close the starter-mounted contactor . . . again with the idea of shifting motor inrush currents to the starter's internal contactor. It has the advantage of breaking the internal contactor's coil current when the external starter contactor opens. This accomplishes the same goals as Z-22 but with an external STARTER CONTACTOR as opposed to an external BUFFER RELAY. Bob, are you implying that I should have removed the jumper wire from the starter? Not implying, recommending . . . based on what we learned about (1) delayed disengagement and (2) higher stresses on starter control contactor with substitution of PM motor technology. If you already have an external contactor installed (a la Van's suggestion) then making a simple change to remove the jumper and wire the internal contactor control terminal to the external contactor "I" terminal would be a good move. Van's drawing or Z-22 is the elegant solution for new design in an OBAM aircraft. Skytec's drawing is the less than elegant solution for minimizing changes to a TC aircraft when replacing original starter called out on the ship's certification documents. The way you had it wired ORIGINALLY wasn't all that hard on the external contactor . . . assuming that it's contacts were closed and stable before the internal contactor gets closed. I've not had an opportunity to measure it but I suspect this is the case. THEREFORE, I'm comfortable with suggesting that your original sticking failure was probably an isolated case and not indicative of a system design error. ADDING the battery master contactor in series with cranking currents is the firewall against a future repeat causing you to burn a battery or starter. Adding the wire to conform to Van's suggested configuration would be a good move to take care of the potential for delayed disengagement. Bob . . . //// (o o) ===========o00o=(_)=o00o======== < Go ahead, make my day . . . > < show me where I'm wrong. > ================================ ________________________________ Message 7 _____________________________________ Time: 08:47:05 AM PST US From: "Robert L. Nuckolls, III" Subject: Re: AeroElectric-List: glide slope anenna At 11:28 PM 12/1/2009, you wrote: >I've been thinking about building a glide slope antenna and was >wondering if anyone had done this. If so, any ideas would be >great. Pros and cons are welcome. Thanks in advance. > Do you have a VOR antenna installed? If so, consider using a coupler to tie the GS receiver to the VOR antenna. http://aeroelectric.com/Pictures/Antenna/VOR_GS_Duplexer_CI_507.jpg While a VOR antenna is not the IDEAL GS antenna, the signal from a LOC/GS system is huge . . . the ship's ILS system can tolerate losses introduced by this coupler. Bob . . . //// (o o) ===========o00o=(_)=o00o======== < Go ahead, make my day . . . > < show me where I'm wrong. > ================================= ________________________________ Message 8 _____________________________________ Time: 08:52:58 AM PST US From: "Robert L. Nuckolls, III" Subject: Re: AeroElectric-List: Re: Lamp polarity and unpluggability At 09:52 AM 12/2/2009, you wrote: > >LEDs should not work with opposite polarity. So I looked up the >Radio Shack part number that you gave: 272-345. At first I thought >that it was an LED too. But then I realized that it is a RED lamp, >not an LED. So actually you are using incandescent lamps. Good catch Joe! > > > I understand it would be good to place a rectifying diode across > the leads in spike catcher fashion. > >I do not think so. A reverse-biased diode would have no affect. A >forward-biased diode would blow the fuse. WAaayyyy back when, LEDs were considered to be fragile devices when it came to reverse voltage stresses. Indeed, they ARE less tolerant of reverse voltage than their power rectifying cousins. It was not uncommon for a designer to place a reversed polarity diode across an LED to clamp off POTENTIALLY damaging reverse voltage "spikes". Forward voltage "spikes" were less worrisome because the current limiting resistor in series with most LEDs would mitigate stress on the device. Nowadays, we KNOW that are airplanes are not plagued with such spikes. Hence, the folks who make drop in incandescent replacement LEDs don't include such diodes in their product. Bob . . . //// (o o) ===========o00o=(_)=o00o======== < Go ahead, make my day . . . > < show me where I'm wrong. > ================================ ________________________________ Message 9 _____________________________________ Time: 09:35:10 AM PST US From: "Bill Hibbing" Subject: Re: AeroElectric-List: glide slope anenna Thanks Bob. I hadn't thought about that yet but that sure will save a lot of time and effort. Bill Glasair SIIS-FT ----- Original Message ----- From: Robert L. Nuckolls, III To: aeroelectric-list@matronics.com Sent: Wednesday, December 02, 2009 10:45 AM Subject: Re: AeroElectric-List: glide slope anenna At 11:28 PM 12/1/2009, you wrote: I've been thinking about building a glide slope antenna and was wondering if anyone had done this. If so, any ideas would be great. Pros and cons are welcome. Thanks in advance. Do you have a VOR antenna installed? If so, consider using a coupler to tie the GS receiver to the VOR antenna. http://aeroelectric.com/Pictures/Antenna/VOR_GS_Duplexer_CI_507.jpg While a VOR antenna is not the IDEAL GS antenna, the signal from a LOC/GS system is huge . . . the ship's ILS system can tolerate losses introduced by this coupler. Bob . . . //// (o o) ===========o00o=(_)=o00o======== = < Go ahead, make my day . . . > < show me where I'm wrong. > ======== ------------------------------------------------------------------------- ----- Checked by AVG - www.avg.com 12/02/09 01:33:00 ________________________________ Message 10 ____________________________________ Time: 10:10:40 AM PST US From: "Robert L. Nuckolls, III" Subject: AeroElectric-List: DIY VHF Comm antenna See: http://aeroelectric.com/Pictures/Antenna/DIY_Comm_Antenna.jpg Here's a starting point for any readers who would like to experiment with their own DIY comm antennas: This design starts with a CB radio antenna mounting stud: http://tinyurl.com/yzygjbq The design goal is to add a steel (preferably stainless) antenna rod to the antenna side of the mounting stud, prevent rotation of assembly in the mounting hole, and (optionally) add an adapter that is friendly to the commonly used BNC feedline connectors. In the example illustrated, I silver soldered a piece of 3/16 stainless rod in a hole drilled into a steel hex head 3/8-24 x 1/2" bolt. 10% of thread area on the bolt are "buggered" up to provide an "upset- metal" connection between the bolt and female threads in the mounting stud. Avoid damage to first three threads so that the bolt will start easily. Put upper coupler of antenna stud in vise. Coat threads of antenna rod with a thread-locker . . . or just E-6000 adhesive. This is more for moisture sealing than anything else. Thread the antenna into the coupler. It will go in with some resistance due to "damaged" threads . . . but the goal is to achieve some level of gas-tightness between the bolt and the coupler. Fabricate a piece of .060 or so brass tab and soft-solder with 63/37 alloy. You'll have to clean the plating off the interface surface of the lower half of the coupler to get a good sweat. Avoid excessive heat that will damage the stud's plastic insulator. Add UHF to BNC adapter as shown or plan on using a UHF male connector at the end of your feedline. Cut the overall length of the antenna to 22" (tip to mounting surface). Round tip on grinder to avoid sharp edges at the end. If you like, put a 45 degree or so "rakish" bend in the antenna rod beginning about 6" off the mounting surface. Mount to airplane in a robust skin doubler riveted to the skin and picking up some structure if possible. Brighten the surfaces that come together. Use #8 hardware to ground the anti-rotation tab. Truss head screws are suggested. This is about #3 in a series of designs I've considered writing up in the 'Connection. It has evolved to the stage that it would be good for some of you folks to take a whack at building it. Let me know what problems you encounter with fabrication, installation or service. Bob . . . //// (o o) ===========o00o=(_)=o00o======== < Go ahead, make my day . . . > < show me where I'm wrong. > ================================ ________________________________ Message 11 ____________________________________ Time: 10:18:53 AM PST US Subject: AeroElectric-List: Re: Lamp polarity and unpluggability From: "messydeer" Thanks for clearing these things up, guys :-) I was about to call Radio Shack and ask them to explain this. I would have really confused them. It's only a matter of a few bucks for these lights, but any reason to switch to LED warning lights? I know they last much longer, but I'd think as infrequently as these standard lights would come on (starter engaged, low voltage, and visual alarm for EFIS) they'd never burn out anyway. -------- Dan Read this topic online here: http://forums.matronics.com/viewtopic.php?p=275807#275807 ________________________________ Message 12 ____________________________________ Time: 11:09:11 AM PST US From: Bill Mauledriver Watson Subject: Re: AeroElectric-List: Re: Lamp polarity and unpluggability One might use LEDs for reliability (do you check the operation of all warning lights before each flight?). An incandescent filament is subject to failing due to cycling and vibration I'd guess. A solid state LED is forever (?). I'm using them just because they're neat. messydeer wrote: > > Thanks for clearing these things up, guys :-) I was about to call Radio Shack and ask them to explain this. I would have really confused them. > > It's only a matter of a few bucks for these lights, but any reason to switch to LED warning lights? I know they last much longer, but I'd think as infrequently as these standard lights would come on (starter engaged, low voltage, and visual alarm for EFIS) they'd never burn out anyway. > > -------- > Dan > > > ________________________________ Message 13 ____________________________________ Time: 11:30:46 AM PST US From: Ernest Christley Subject: Re: AeroElectric-List: DIY VHF Comm antenna Robert L. Nuckolls, III wrote: > See: > > http://aeroelectric.com/Pictures/Antenna/DIY_Comm_Antenna.jpg > > Here's a starting point for any readers who would > like to experiment with their own DIY comm antennas: > > This design starts with a CB radio antenna mounting > stud: > > * http://tinyurl.com/yzygjbq* > > The design goal is to add a steel (preferably > stainless) antenna rod to the antenna side of > the mounting stud, prevent rotation of assembly in > the mounting hole, and (optionally) add an adapter > that is friendly to the commonly used BNC feedline > connectors. > > In the example illustrated, I silver soldered a > piece of 3/16 stainless rod in a hole drilled into > a steel hex head 3/8-24 x 1/2" bolt. That's a might steep stress riser, going from a whippy piece of stainless into a bolt. How about slipping a few inches of shrink wrap over the base, so that it comes up the whip a bit, and pack it full of E6000? Just a few seconds with a butane flame to give the heat shrink filled tube a taper toward the tip, allowing excess E6000 to be squeezed out. Now you have a strain relief, and another layer of sealing. ________________________________ Message 14 ____________________________________ Time: 11:44:17 AM PST US From: "Wade Roe" Subject: AeroElectric-List: Avionics Master Switch I am planning the switches for the panel in my RV-7 and wanted to get some opinions about the options. The proposed electrical schematic closely parallels AEC Z-13 (all electric on a budget). The plane will be configured for IFR flight (GNS-430w, SL-40, AFS 4500, etc...). I have noticed that many builders are incorporating avionics master switches in their planes that are exclusive to the DC power master (off-batt-main alt). Unless I'm missing something, it would seem to be beneficial to be able to start the engine then bring up the avionics by way of the "avionics master". Also, I'm trying to decide whether or not to use a designated EFIS (on-off) master for the AFS 4500. Thoughts and/or comments would be appreciated. Thanks! Wade Roe (RV-7 in progress) ________________________________ Message 15 ____________________________________ Time: 12:46:08 PM PST US Subject: Re: AeroElectric-List: DIY VHF Comm antenna From: Bill Boyd Or have this guy make you what you need - it will probably outlast your airframe. http://bellsouthpwp.net/b/r/breedlove1/ Bill N4DLN Not a customer of his (yet) but he has good reviews on the HF mobile groups On Wed, Dec 2, 2009 at 1:05 PM, Robert L. Nuckolls, III < nuckolls.bob@aeroelectric.com> wrote: > See: > > http://aeroelectric.com/Pictures/Antenna/DIY_Comm_Antenna.jpg > > Here's a starting point for any readers who would > like to experiment with their own DIY comm antennas: > > This design starts with a CB radio antenna mounting > stud: > > * http://tinyurl.com/yzygjbq* > > The design goal is to add a steel (preferably > stainless) antenna rod to the antenna side of > the mounting stud, prevent rotation of assembly in > the mounting hole, and (optionally) add an adapter > that is friendly to the commonly used BNC feedline > connectors. > > In the example illustrated, I silver soldered a > piece of 3/16 stainless rod in a hole drilled into > a steel hex head 3/8-24 x 1/2" bolt. 10% of thread > area on the bolt are "buggered" up to provide an "upset- > metal" connection between the bolt and female threads > in the mounting stud. Avoid damage to first three threads > so that the bolt will start easily. > > Put upper coupler of antenna stud in vise. Coat threads of > antenna rod with a thread-locker . . . or just E-6000 > adhesive. This is more for moisture sealing than anything > else. Thread the antenna into the coupler. It will go in with some > resistance due to "damaged" threads . . . but the goal > is to achieve some level of gas-tightness between the > bolt and the coupler. > > Fabricate a piece of .060 or so brass tab and soft-solder > with 63/37 alloy. You'll have to clean the plating off > the interface surface of the lower half of the coupler > to get a good sweat. Avoid excessive heat that will damage > the stud's plastic insulator. > > Add UHF to BNC adapter as shown or plan on using a > UHF male connector at the end of your feedline. > Cut the overall length of the antenna to 22" (tip > to mounting surface). Round tip on grinder to avoid > sharp edges at the end. If you like, put a 45 degree > or so "rakish" bend in the antenna rod beginning about > 6" off the mounting surface. > > Mount to airplane in a robust skin doubler riveted > to the skin and picking up some structure if possible. > Brighten the surfaces that come together. Use #8 hardware > to ground the anti-rotation tab. Truss head screws are > suggested. > > This is about #3 in a series of designs I've considered > writing up in the 'Connection. It has evolved to the > stage that it would be good for some of you folks to take > a whack at building it. Let me know what problems you > encounter with fabrication, installation or service. > > Bob . . . > //// > (o o) > ===========o00o=(_)=o00o======== > < Go ahead, make my day . . . > > < show me where I'm wrong. > > ================================ > > * > > * > > ________________________________ Message 16 ____________________________________ Time: 01:10:37 PM PST US Subject: Re: AeroElectric-List: DIY VHF Comm antenna From: "Matt Prather" > > > Robert L. Nuckolls, III wrote: >> See: >> >> http://aeroelectric.com/Pictures/Antenna/DIY_Comm_Antenna.jpg >> >> Here's a starting point for any readers who would >> like to experiment with their own DIY comm antennas: >> >> This design starts with a CB radio antenna mounting >> stud: >> >> * http://tinyurl.com/yzygjbq* >> >> The design goal is to add a steel (preferably >> stainless) antenna rod to the antenna side of >> the mounting stud, prevent rotation of assembly in >> the mounting hole, and (optionally) add an adapter >> that is friendly to the commonly used BNC feedline >> connectors. >> >> In the example illustrated, I silver soldered a >> piece of 3/16 stainless rod in a hole drilled into >> a steel hex head 3/8-24 x 1/2" bolt. > That's a might steep stress riser, going from a whippy piece of > stainless into a bolt. How about slipping a few inches of shrink wrap > over the base, so that it comes up the whip a bit, and pack it full of > E6000? Just a few seconds with a butane flame to give the heat shrink > filled tube a taper toward the tip, allowing excess E6000 to be squeezed > out. Now you have a strain relief, and another layer of sealing. > This is probably a good idea. However, several years ago I built a 5/8 wave whip for a 2m mobile rig - for my car. I started with a CB whip and used a hardware store bolt (5/16" dia, maybe 10" long) to extend the length enough to tune it (on top of a coil wrapped around a teflon core). The total length was something like 48". I whacked a lot of tree branches and several parking garages with it and it never failed. One of the parking garages hooked it while I was pulling into a parking spot.. I didn't think much of it until backing out of the spot it made an abnormally loud "sproing!" sound. Somehow it had put about a 20deg bend about 8" from the end of the whip - it still functioned fine, routinely allowing me to talk with stations 60mi away. I still have the antenna - very low SWR.. Anecdotal, obviously.. But I think the loads are well within the strength of the stainless wire commonly used for antenna whips. Matt- ________________________________ Message 17 ____________________________________ Time: 03:19:42 PM PST US From: "Robert L. Nuckolls, III" Subject: Re: AeroElectric-List: Avionics Master Switch At 01:38 PM 12/2/2009, you wrote: > >I am planning the switches for the panel in my RV-7 and wanted to get some >opinions about the options. The proposed electrical schematic closely >parallels AEC Z-13 (all electric on a budget). The plane will be configured >for IFR flight (GNS-430w, SL-40, AFS 4500, etc...). I have noticed that >many builders are incorporating avionics master switches in their planes >that are exclusive to the DC power master (off-batt-main alt). Unless I'm >missing something, it would seem to be beneficial to be able to start the >engine then bring up the avionics by way of the "avionics master". > >Also, I'm trying to decide whether or not to use a designated EFIS (on-off) >master for the AFS 4500. > >Thoughts and/or comments would be appreciated. See: http://www.aeroelectric.com/articles/avmaster.pdf http://www.aeroelectric.com/articles/DO-160.pdf I have written to and talked with dozens of avionics equipment designers at big and little companies alike for over 25 years to inquire as to the physics behind any recommendation for an avionics master switch. Most letters/e-mails produced ZERO response. Every conversation produced a somewhat mystified response . . . "Gee, we build these things to stand everything BUT and nuclear EMP and folks are STILL worrying about starter motors?" Interestingly enough, when hydraulic packs with PM pump motors were installed for landing gear systems, the AV Master Switch acolytes didn't insist on killing all the radios before extending or retracting the gear. This in spite of the fact that the PM motors put bigger chunks of trash on the bus than did some starter motors! Bottom line is that the AV Master is a convenience/feel-good feature and has no modern function as a firewall against bus-borne hazards to radios. Bob . . . //// (o o) ===========o00o=(_)=o00o======== < Go ahead, make my day . . . > < show me where I'm wrong. > ================================ ------------------------------------------------------------------------------------- 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.