---------------------------------------------------------- AeroElectric-List Digest Archive --- Total Messages Posted Mon 02/08/10: 9 ---------------------------------------------------------- Today's Message Index: ---------------------- 1. 07:58 AM - Re: Stuck starter contactor . . . (Robert L. Nuckolls, III) 2. 10:42 AM - Question on switch wiring () 3. 12:09 PM - Re: Re: Starter engaged light, was Starter and contactor (John Burnaby) 4. 12:09 PM - Re: Question on switch wiring (Robert L. Nuckolls, III) 5. 01:51 PM - Re: Re: Starter engaged light, was Starter and contactor (BobsV35B@aol.com) 6. 02:47 PM - Re: Question on switch wiring () 7. 03:31 PM - Re: Question on switch wiring (Robert L. Nuckolls, III) 8. 08:28 PM - GNS 430 no comm (Brooks Wolfe) 9. 09:02 PM - Re: Starter engaged light (Robert L. Nuckolls, III) ________________________________ Message 1 _____________________________________ Time: 07:58:43 AM PST US From: "Robert L. Nuckolls, III" Subject: AeroElectric-List: Re: Stuck starter contactor . . . At 02:00 PM 2/7/2010, you wrote: > > >Hi Bob- > >I was able to find this: > >http://www.ntsb.gov/ntsb/GenPDF.asp?id=FTW90DRA10&rpt=fi > >Some of the physical description of the airframe may be a bit misleading, >but teh fundamental process seems to be accurate. Hmmmm . . . interesting. I'm wondering how the operator 'knew' that the starter contactor had stuck when the FAA inspection could not identify a source of the fire. If somebody 'knew' the starter contactor was stuck or still energized, I'm mystified as to why the aircraft ever left the parking place. A starter feeder should have been protected from destructive overload by some means . . . c/b, current limiter, etc. Since the fire apparently didn't originate under the cowl (from a self-destructing starter) then components that failed to the point of starting a fire had to be things like unprotected wires, failed insulation, failed contactor, etc. It's quite possible that the starter contactor on this airplane looked something like this when new . . . http://www.aeroelectric.com/Pictures/Contactors/6041_Contactor.jpg and may well have degenerated to something like this when failed . . . http://aeroelectric.com/Pictures/Failures/6041_Contactor_Failure.jpg A contactor that is "stuck" is generally turned on 'hard' and is not generating a lot of heat. On the other hand, this style of contactor (mounted in the wheel-well j-box?) needs to be inspected (note removable cover) periodically for degraded contacts or signs of heating off the moving contact carrier. When these contactors experience a high- resistance overheat, they can fail rather spectacularly. The failed contactor I showed came out of a j-box that routes power to a 130A a/c compressor motor. These contactors have a relatively high failure rate . . . but being inside a metal enclosure keeps things from getting out of hand. It's also interesting that re-ignition was attributed to "hot" metal. Things that ignite from hot metal are liquids with easily ignited vapors . . . it doesn't sound like this fire went on long enough and with sufficient fuel to heat aluminum structure or steel landing gear parts to the point where they become re-ignition hazards. On the other hand, things that are combustible within the j-box may have been supporting some glowing coals and been shielded from the extinguisher. . . or it may be that power was still present in the j-box. In any case, it seems unlikely that the real chain of events for this unfortunate demise of an otherwise perfectly good airplane are known. Given its age, it was certainly subject to the effects of time on electrical system materials that were the best-we-knew- how-to-do in 1940. One needs to spend an extra effort to track these materials for continued airworthiness. Calling this one a "stuck starter contactor" incident is a WAG. Bob . . . ________________________________ Message 2 _____________________________________ Time: 10:42:31 AM PST US Subject: AeroElectric-List: Question on switch wiring From: I bought a SPST 12 volt lighted switch from digi-key which I would like to use as a fuel pump indicator switch. SWITCH TOGGLE ILLUM SPST 20A GRN SCHED B: 853650 ECCN: EAR99 LEAD: LEAD ALL ROHS: ROHS NONC CH652-ND Assumptions: My fuel pump runs via a relay switch (20 amp B & C S704-1 job). Question: The switch is provided with a third 1/4" tab on the top (on position) of the switch. Normal use is to add a jumper from the on position to the top tab to illuminate light when turned on. The switch works great when used with standard power/ground connection, e.g. landing light. When I use it in conjunction with the relay switch, the light comes on when the switch is in the off position. Ideas appreciated. Glenn ________________________________ Message 3 _____________________________________ Time: 12:09:18 PM PST US From: "John Burnaby" Subject: Re: AeroElectric-List: RE: Starter engaged light, was Starter and contactor Hello Old Bob, Thanks for giving this some thought. The purpose of the lamp going on when I depress the starter is as a test of the lamp. John ________________________________ Message 4 _____________________________________ Time: 12:09:53 PM PST US From: "Robert L. Nuckolls, III" Subject: Re: AeroElectric-List: Question on switch wiring At 12:33 PM 2/8/2010, you wrote: >I bought a SPST 12 volt lighted switch from digi-key which I would >like to use as a fuel pump indicator switch. > >SWITCH TOGGLE ILLUM SPST 20A GRN >SCHED B: 853650 >ECCN: EAR99 >LEAD: LEAD ALL >ROHS: >ROHS NONC >CH652-ND > >Assumptions: My fuel pump runs via a relay switch (20 amp B & C S704-1 job). > > >Question: The switch is provided with a third 1/4" tab on the top >(on position) of the switch. Normal use is to add a jumper from the >on position to the top tab to illuminate light when turned on. > >The switch works great when used with standard power/ground >connection, e.g. landing light. When I use it in conjunction with >the relay switch, the light comes on when the switch is in the off position. First, why the relay? The switch is rated for 20A . . . probably enough to control the pump directly. The third terminal is for grounding the internal LED/Resistor combination so that the lamp lights when the switch is closed. For this switch to be "relay augmented" you'll have to wire the pump as shown here: Emacs! . . . and this is not a very elegant approach. Unfortunately the switch you have (like most of it's cousins) doesn't bring BOTH lamp leads out for independent excitation of the lamp. One end of the lamp is tied to the "power output" terminal in the assumption that one ALWAYS uses the switch barefoot to control power in the +supply lead. Bob . . . ________________________________ Message 5 _____________________________________ Time: 01:51:43 PM PST US From: BobsV35B@aol.com Subject: Re: AeroElectric-List: RE: Starter engaged light, was Starter and contactor Good Afternoon John, That sounds good, but if the starter works, won't that give you a check of the lamp? The way Beech handled the test function was to present a current from a dedicated lamp test switch to the starter warning lamp. To keep the lamp current from trying to drive the starter, they added a diode that only allows current from the starter to the light and blocks the flow from the lamp to the starter. That way we can check the light without closing the starter relay I did the same thing when I wired my warning lights. Since my factory warning lights were wired a bit differently, I used a double pole, single throw, switch to isolate the starter warning light circuit from the other warning circuits. Works great! Happy Skies, Old Bob In a message dated 2/8/2010 2:11:39 P.M. Central Standard Time, jonlaury@impulse.net writes: Hello Old Bob, Thanks for giving this some thought. The purpose of the lamp going on when I depress the starter is as a test of the lamp. John ________________________________ Message 6 _____________________________________ Time: 02:47:28 PM PST US Subject: RE: AeroElectric-List: Question on switch wiring From: Thanks Bob, Yes, the switch is overkill (or in reality, perhaps the relay is), but the switch matches the others if underutilized. I did not look hard and long enough for a 1 amp or lower with the same size/style. The pump shipped with 12 ga. wire leads and I really did not want to run a 12 ga. wire to the switch, thus the relay. The FP is rated for 7-10 amps. The FP is on the checklist but it's one of the easy to forget items that sometimes gets left on or off. Therefore an pilot light of some kind is a nice feature. Glenn E. Long From: owner-aeroelectric-list-server@matronics.com [mailto:owner-aeroelectric-list-server@matronics.com] On Behalf Of Robert L. Nuckolls, III Sent: Monday, February 08, 2010 3:02 PM Subject: Re: AeroElectric-List: Question on switch wiring At 12:33 PM 2/8/2010, you wrote: I bought a SPST 12 volt lighted switch from digi-key which I would like to use as a fuel pump indicator switch. SWITCH TOGGLE ILLUM SPST 20A GRN SCHED B: 853650 ECCN: EAR99 LEAD: LEAD ALL ROHS: ROHS NONC CH652-ND Assumptions: My fuel pump runs via a relay switch (20 amp B & C S704-1 job). Question: The switch is provided with a third 1/4" tab on the top (on position) of the switch. Normal use is to add a jumper from the on position to the top tab to illuminate light when turned on. The switch works great when used with standard power/ground connection, e.g. landing light. When I use it in conjunction with the relay switch, the light comes on when the switch is in the off position. First, why the relay? The switch is rated for 20A . . . probably enough to control the pump directly. The third terminal is for grounding the internal LED/Resistor combination so that the lamp lights when the switch is closed. For this switch to be "relay augmented" you'll have to wire the pump as shown here: . . . and this is not a very elegant approach. Unfortunately the switch you have (like most of it's cousins) doesn't bring BOTH lamp leads out for independent excitation of the lamp. One end of the lamp is tied to the "power output" terminal in the assumption that one ALWAYS uses the switch barefoot to control power in the +supply lead. Bob . . . ________________________________ Message 7 _____________________________________ Time: 03:31:09 PM PST US From: "Robert L. Nuckolls, III" Subject: RE: AeroElectric-List: Question on switch wiring At 04:44 PM 2/8/2010, you wrote: >Thanks Bob, > >Yes, the switch is overkill (or in reality, perhaps the relay is), >but the switch matches the others if underutilized. I did not look >hard and long enough for a 1 amp or lower with the same size/style. >The pump shipped with 12 ga. wire leads and I really did not want to >run a 12 ga. wire to the switch, thus the relay. The FP is rated for 7-10 amps. Do you have real world current values for what the pump needs in normal operations? Is this a flight pump or an aux/boost pump that is seldom used/needed? 7A (100 watts) is a LOT of power for the pumping of fuel. While your pump may be capable of drawing that much current at rated maximum volume and pressure, I've found that most real-world installations are much less demanding. I think it likely that you can simply wire the pump system with 16 awg wires through the un-aided switch protected by a 10A fuse/breaker. But you need to get some real numbers from somebody who's flying the system or the folks who engineered the system and have numbers. Alternatively, wire it all with 14AWG, 15A breaker and leave the relay out. MUCH simpler and more reliable. The built in lamp can be used as defined in original design goals. Bob. . . ________________________________ Message 8 _____________________________________ Time: 08:28:30 PM PST US From: "Brooks Wolfe" Subject: AeroElectric-List: GNS 430 no comm I'm just wrapping up my 430 installation, and was hoping to hear somethin g (anything) through my headphones.. Nada. I have a used GNS 430 from Wentworth installed. New Sigtronics intercom (at least *this* works). The Garmin is plugged into the intercom with the 50 0 Ohm Audio Hi output. The 500 Ohm Audio Lo is grounded. The Garmin insta ll manual shows a paired "Audio 1" Hi and Low on P4001, but I can't find any other use for it mentioned anywhere, so it's not connected. Pressing the squelch button also makes no noise, as I would have expected =2E One issue that has me concerned is an incident in my hangar a few weeks a go -- A particularly long and bizarre chain of events led to the GNS430 dropping from table to concrete floor. Not far, but enough to give the c ase a tiny bit of wrinkle at the back end. While the unit seems to power up just fine, I can't help but wonder if there might have been some physical damage, causing this inability to get audio. Brooks ________________________________ Message 9 _____________________________________ Time: 09:02:03 PM PST US From: "Robert L. Nuckolls, III" Subject: AeroElectric-List: Re: Starter engaged light At 02:01 PM 2/8/2010, you wrote: >Hello Old Bob, > >Thanks for giving this some thought. > >The purpose of the lamp going on when I depress the starter is as a >test of the lamp. The rule of thumb for lights that routinely illuminate during the process of getting ready for flight don't need press-to-test features. For example, the low volts warning light should be flashing at you before the engine starts and go out when the alternator comes on line. The starter engaged light should be illuminated while you're cranking and go out when you release the button. The criteria for "pre-flight-detectable" are satisfied. 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.