---------------------------------------------------------- AeroElectric-List Digest Archive --- Total Messages Posted Thu 07/04/13: 10 ---------------------------------------------------------- Today's Message Index: ---------------------- 1. 05:32 AM - Re: Boeing switches (Eric M. Jones) 2. 06:20 AM - Re: Re: Master Switch/Contactor and Starter Questions (Robert L. Nuckolls, III) 3. 07:29 AM - Re: Re: Boeing switches (Robert L. Nuckolls, III) 4. 11:00 AM - Narco Transponder Tray Coax Connector () 5. 11:05 AM - Re: Re: Boeing switches (Jay Hyde) 6. 12:17 PM - Master/Battery/Alt Field vs. Master/Battery and Alt Field... (Michael Burbidge) 7. 02:48 PM - Low voltage indicator with dual alternators (donjohnston) 8. 02:57 PM - Re: Narco Transponder Tray Coax Connector (Bill Putney) 9. 03:22 PM - Re: Re: Boeing switches (Robert L. Nuckolls, III) 10. 03:42 PM - Re: Narco Transponder Tray Coax Connector () ________________________________ Message 1 _____________________________________ Time: 05:32:21 AM PST US Subject: AeroElectric-List: Re: Boeing switches From: "Eric M. Jones" My two cents: Using two parallel switches to prevent trim runaway seems boneheaded, and wouldn't stand a thorough engineering fault-tree review. Furthermore I'd bet that it never prevented ANY problem from occurring. Sure, I understand the intention, but I don't think it's good engineering. -------- Eric M. Jones www.PerihelionDesign.com 113 Brentwood Drive Southbridge, MA 01550 (508) 764-2072 emjones(at)charter.net Read this topic online here: http://forums.matronics.com/viewtopic.php?p=403912#403912 ________________________________ Message 2 _____________________________________ Time: 06:20:29 AM PST US From: "Robert L. Nuckolls, III" Subject: Re: AeroElectric-List: Re: Master Switch/Contactor and Starter Questions At 07:13 PM 7/3/2013, you wrote: > > >I agree. It seems pointless to have 2 solenoids operating at the >same time. The other issue is that I believe the Subaru solenoid >moves the gear before the contactor part puts juice to the motor >brushes. An aircraft type contactor would do both at the same time >rather than sequentially. Have not dismantled one so I may be in error. None of applications of an external contactor proposed for modern starters "bypasses" functionality of the built in solenoid/contactor. The starter's built in solenoids do engage the pinion gear before closing electrical connection for the starter motor. Variants to select from when using these modern starters causes the builder to decide whether the built in contactor is energized by the panel mounted, START switch -OR- energized through a more robust device. There is a problem to be solved when the panel mounted starter control is used to energize the starter's built in contactor. Unlike legacy 'starter solenoids' controlling starters with Bendix drives, the modern pinion engagement solenoids have a very high coil current demand during the first few milliseconds of being energized. See: http://tinyurl.com/op5cs2g Failure to recognize this difference in solenoid/contator performance caused a kerfuffle over burned start switch contacts on the ACS-510 key swicch (clone of legacy Bendix/Gerdes). ACS now sells a diode with two terminals applied. Emacs! A critical need to install this diode across the starter contactor engagement coil arose from the alarming rate at which start contacts in the key switch were destroyed by overstress when the legacy starter/external contactor combo was replaced with a light weight version with combination solenoid/ contactors. Many cars suffered similar failure modes in their key-start switches. SB92-01 from ACS originally place thier diode across the switch contacts . . . wrong place. It was corrected in a subsequent revision. See http://tinyurl.com/nva2xdy B&C adopted the philosophy of jumpering the starter solenoid coil right to the fat-wire terminal on the starter . . . and controlling power to the starter though a modern, starter contactor WITH built in coil suppression diode. The external contactor's inrush demands on the start switch are a small fraction of that for direct control. This philosophy posed a new problem when PM motor starters began to show up on the airplane. PM motors have a pronounced counter-emf during spin-down after the power is removed. This would delay disengagement of the pinion gear and was commonly called "starter run on" . . . in fact it was better called "delayed disengagement". Starters with wound fields (B&C and some others) do not suffer this indignity and function well with the engagement solenoid jumpered directly to the starter's fat-wire terminal. In ANY case, the builder's design goals should include providing a source of solenoid engagement power that (1) is supplied through a low impedance source (short and fatter than usual wires) and (2) avoid running this power through the panel mounted start switch. If the starter is a PM version, the builder can take advantage of the "I" terminal on many modern starter cotactors and use it to SUPPLY current to the engagement solenoid. This provides for instant removal of coil power when the starter switch is opened and prevents 'delayed disengagement'. In this case, the builder would do well to have diode coil suppression on BOTH the external contactor coil AND the solenoid/contactor coil on the starter. Bob . . . ________________________________ Message 3 _____________________________________ Time: 07:29:28 AM PST US From: "Robert L. Nuckolls, III" Subject: Re: AeroElectric-List: Re: Boeing switches At 07:29 AM 7/4/2013, you wrote: > >My two cents: > >Using two parallel switches to prevent trim runaway seems >boneheaded, and wouldn't stand a thorough engineering fault-tree >review. Furthermore I'd bet that it never prevented ANY problem from occurring. Whether or not a problem was demonstrably prevented is irrelevant to the reliability study. Good FMEA mitigation assumes that the part WILL fail. Working out a logical means by which single failures might go undetected for no more than a single tank full of fuel has been a time-honored legacy design goal. >Sure, I understand the intention, but I don't think it's good engineering. they are not used in PARALLEL. In the Boeing case, they are in series with one side controlling direction, the other side in SERIES controlling power. Each side can be explored for functionality in pre-flight, neither side capable of causing a runaway-by-sticking. Beech (and many others) uses the two spdt switches to handle one half of a PM motor UP-OFF- DN switching duty. Again, both sides easily evaluated in pre-flight, neither side capable of causing a runaway-by-sticking. Lear (and many others) uses the 'coolie hat' to drive relays that DID offer a possibility for runaway-by- sticking. But their systems architecture included a wheel-master-disconnect that removed power from all trim systems along with the autopilot. I AM aware of trim runaways in aircraft fitted with wheel master disconnects that would not have happened if the airplane had been fitted with the split trim switch where the WMD switch provided the mitigation. Bob . . . ________________________________ Message 4 _____________________________________ Time: 11:00:48 AM PST US From: Subject: AeroElectric-List: Narco Transponder Tray Coax Connector Can someone point me to the part number/source for a replacement 90-degree, bulkhead, slide-on, coax connector used on the Narco AT-150 transponder tray? Any of the usual suspects (Mouser, Digi-Key, Allied, etc) carry them? Thanks, James ________________________________ Message 5 _____________________________________ Time: 11:05:43 AM PST US From: "Jay Hyde" Subject: RE: AeroElectric-List: Re: Boeing switches Good argument Bob.... I use a switch on the panel to power the trim, but that may be a bit far away for a quick reaction, before the trim lurks all the way to the end. Jay -----Original Message----- From: owner-aeroelectric-list-server@matronics.com [mailto:owner-aeroelectric-list-server@matronics.com] On Behalf Of Robert L. Nuckolls, III Sent: 04 July 2013 04:29 PM Subject: Re: AeroElectric-List: Re: Boeing switches --> At 07:29 AM 7/4/2013, you wrote: >--> > >My two cents: > >Using two parallel switches to prevent trim runaway seems boneheaded, >and wouldn't stand a thorough engineering fault-tree review. >Furthermore I'd bet that it never prevented ANY problem from occurring. Whether or not a problem was demonstrably prevented is irrelevant to the reliability study. Good FMEA mitigation assumes that the part WILL fail. Working out a logical means by which single failures might go undetected for no more than a single tank full of fuel has been a time-honored legacy design goal. >Sure, I understand the intention, but I don't think it's good engineering. they are not used in PARALLEL. In the Boeing case, they are in series with one side controlling direction, the other side in SERIES controlling power. Each side can be explored for functionality in pre-flight, neither side capable of causing a runaway-by-sticking. Beech (and many others) uses the two spdt switches to handle one half of a PM motor UP-OFF- DN switching duty. Again, both sides easily evaluated in pre-flight, neither side capable of causing a runaway-by-sticking. Lear (and many others) uses the 'coolie hat' to drive relays that DID offer a possibility for runaway-by- sticking. But their systems architecture included a wheel-master-disconnect that removed power from all trim systems along with the autopilot. I AM aware of trim runaways in aircraft fitted with wheel master disconnects that would not have happened if the airplane had been fitted with the split trim switch where the WMD switch provided the mitigation. Bob . . . ________________________________ Message 6 _____________________________________ Time: 12:17:10 PM PST US From: Michael Burbidge Subject: AeroElectric-List: Master/Battery/Alt Field vs. Master/Battery and Alt Field... I'm sure I read a discussion of this question somewhere but can't find it. I'm building an RV-9A, basic day/night VFR. I'm using the Basic Day/Night VFR system diagram available from B&C website. It is almost identical to the Z-11 diagram in Bob's book. One difference is that the Z-11 uses a 2 poll 3-throw switch (2-10) for the master, so that the alternator can be switched on after start. The Basic VFR diagram from B&C uses a 2 poll 2 throw switch (2-3) so that the alternator field is on during start. What are the advantages of isolating the alternator field during startup? My airplane has a B&C 40 amp alternator. Which approach would you recommend? Thanks, Michael- ________________________________ Message 7 _____________________________________ Time: 02:48:19 PM PST US Subject: AeroElectric-List: Low voltage indicator with dual alternators From: "donjohnston" I'm going to have a 60a primary and a 20a secondary alternator with B&C LR3C and LS1A voltage regulators respectively. If in the event of a primary alternator failure, and I switch to the secondary, will the primary low voltage warning light (off of LR3C, pin 5) remain illuminated? Or will switching off that alternator open the low voltage circuit? Read this topic online here: http://forums.matronics.com/viewtopic.php?p=403960#403960 ________________________________ Message 8 _____________________________________ Time: 02:57:44 PM PST US From: Bill Putney Subject: Re: AeroElectric-List: Narco Transponder Tray Coax Connector It's TED 9-30-10 connector. These are solder on connectors and have the lowest profile (depth-wise). http://hangar-10.com/products/Tray-Mount-Rf-Antenna-Connect.html You should check with them to make sure a snap ring is included or you may have to buy it separately. There's also a DBA-600 that is a connector like you want with a female BNC so you don't have a cable attached to your tray. You put a BNC on the cable and connect it to this adapter. About the same price as the 9-30-10 but of course you have to do the BNC too. http://hangar-10.com/products/Bnc-Tray-Adapter-W%7B47%7DSnap-Ring.html Bill On 7/4/13 10:59 AM, berkut13@berkut13.com wrote: > Can someone point me to the part number/source for a replacement > 90-degree, > bulkhead, slide-on, coax connector used on the Narco AT-150 transponder > tray? Any of the usual suspects (Mouser, Digi-Key, Allied, etc) carry > them? > > Thanks, > James > * > > > * ________________________________ Message 9 _____________________________________ Time: 03:22:42 PM PST US From: "Robert L. Nuckolls, III" Subject: RE: AeroElectric-List: Re: Boeing switches At 01:05 PM 7/4/2013, you wrote: > >Good argument Bob.... I use a switch on the panel to power the trim, but >that may be a bit far away for a quick reaction, before the trim lurks all >the way to the end. You would do well to deduce the severity of a trim runaway. Is the airplane controllable with full trim either up or down? How fast does the trim run with respect to pilot reaction times needed to deal with a runaway? Are there stops or limits to trim excursion necessary for the full range of CG envelopes or will the system produce more pitch authority than would ever be necessary for normal operations? In a Lear, at Mach cruise, the system is manually failed and the pilot is obligated to keep hands in the lap for 3 seconds. Only then can he move to deal with the situation. After achieving a stable, safe condition, recorded data is analyzed for busting limits on attitude, altitude and airspeed excursions. The exercise is repeated and trim speeds then adjusted until a sweat-free, runaway recovery is assured. The trim systems I've seen in some TC aircraft are so slow that unexpected trims under worst case conditions are no big deal. But what's the story for YOUR airplane? Yes, if trim speeds are brisk, trim authority high and you have good reason for not reducing them, then some form of inarguable override is indicated. Instructing the pilot to pull a breaker for taming a trim runaway is generally not acceptable . . . even panel mounted switche situated amongst other switches will get you frowns from the human factors guys. At the same time, find out just how much risk is associated with an uncontrolled trim event and see if that can be engineered out as opposed to stacking emergency ops hardware on top of the design. Bob . . . ________________________________ Message 10 ____________________________________ Time: 03:42:25 PM PST US From: Subject: Re: AeroElectric-List: Narco Transponder Tray Coax Connector Excellent! Exactly what I needed. Thanks. From: Bill Putney Sent: Thursday, July 04, 2013 4:57 PM Subject: Re: AeroElectric-List: Narco Transponder Tray Coax Connector It's TED 9-30-10 connector. These are solder on connectors and have the lowest profile (depth-wise). http://hangar-10.com/products/Tray-Mount-Rf-Antenna-Connect.html You should check with them to make sure a snap ring is included or you may have to buy it separately. There's also a DBA-600 that is a connector like you want with a female BNC so you don't have a cable attached to your tray. You put a BNC on the cable and connect it to this adapter. About the same price as the 9-30-10 but of course you have to do the BNC too. http://hangar-10.com/products/Bnc-Tray-Adapter-W%7B47%7DSnap-Ring.html Bill On 7/4/13 10:59 AM, berkut13@berkut13.com wrote: Can someone point me to the part number/source for a replacement 90-degree, bulkhead, slide-on, coax connector used on the Narco AT-150 transponder tray? Any of the usual suspects (Mouser, Digi-Key, Allied, etc) carry them? Thanks, James ------------------------------------------------------------------------------------- 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.