---------------------------------------------------------- AeroElectric-List Digest Archive --- Total Messages Posted Wed 01/20/16: 11 ---------------------------------------------------------- Today's Message Index: ---------------------- 1. 02:05 AM - Re: Re: Engine mount ground? (Werner Schneider) 2. 07:48 AM - Re: Re: Engine mount ground? (Robert L. Nuckolls, III) 3. 08:04 AM - Re: Carling S700 2-3 switch failure. (Robert L. Nuckolls, III) 4. 11:05 AM - On-the-ground power jack (Carlos Trigo) 5. 11:43 AM - Re: On-the-ground power jack (Robert L. Nuckolls, III) 6. 12:36 PM - Re: On-the-ground power jack (Carlos Trigo) 7. 01:11 PM - Re: On-the-ground power jack (Robert L. Nuckolls, III) 8. 01:12 PM - Re: Schematic for twin PM alternators (user9253) 9. 01:23 PM - Rotax 914 Generator, Alternator, Starting and Fuel Pump Control (Ken Ryan) 10. 01:49 PM - Re: Re: Schematic for twin PM alternators (Charlie England) 11. 05:23 PM - Re: Schematic for twin PM alternators (user9253) ________________________________ Message 1 _____________________________________ Time: 02:05:50 AM PST US Subject: Re: AeroElectric-List: Re: Engine mount ground? From: Werner Schneider taking a different path is valid thinking (ask me how I know!!) But then I rather would prefer to have a 2nd strap as backup as otherwise you would need a bridge strap at the rubbermounts. Cheers Werner On 20.01.2016 02:22, rvdave wrote: > > Sort of what I thought but I've been getting some feedback that there should also be a ground cable to the engine mount in case the firewall ground disconnects? ________________________________ Message 2 _____________________________________ Time: 07:48:34 AM PST US From: "Robert L. Nuckolls, III" Subject: Re: AeroElectric-List: Re: Engine mount ground? At 04:03 AM 1/20/2016, you wrote: > >taking a different path is valid thinking (ask me how I know!!) >But then I rather would prefer to have a 2nd strap as backup as >otherwise you would need a bridge strap at the rubbermounts. As Neal pointed out earlier . . . and I have asserted many times over the years, engine mounts are for holding engines onto airplanes. They should not be pressed into service as any part of the electrical system . . . voltages impressed across structural joints due to large circulating currents exacerbates corrosion. Not that this is a demonstrated hazard but diligent failure mode effects analysis dictates that using the engine mount as part of the electrical system is simply not necessary and elevates an otherwise zero-risk to some non-zero number. Another point of interest is the risk for 'burning ship's wiring' with starter currents should a firewall-to-crankcase bond strap become unhooked. Throughout the 'Connection and here on the List, builders have been cautioned about having ANY pathway grounded in two places on the airplane . . . with p-lead shields being the most common violation of that philosophy. Multiple grounds for engine instrumentation run a close second. These are 'ground loops by design', easy (and sometimes important) to avoid. Lastly, the firewall-to-crankcase bond strap should be as "reliable as prop bolts". The only incident for loss of crankcase grounding I witnessed was a mechanic's slip- up on one of our airplanes at K1K1 . . . and yeah, it burned the p-lead shields wired per Cessna factory drawings. I recommend an flat braid strap from some structural bold on engine to the firewall ground stud. Alternatively, a 2AWG piece of WELDING CABLE with lugs installed per http://tinyurl.com/gm8lqxo . . . and attached with robust hardware will give your prop bolts a serious challenge in the longevity/ reliability race. Bob . . . ________________________________ Message 3 _____________________________________ Time: 08:04:53 AM PST US From: "Robert L. Nuckolls, III" Subject: Re: AeroElectric-List: Carling S700 2-3 switch failure. At 07:38 PM 1/19/2016, you wrote: >This manual switch is in a high (8 amps?) fast switching injector >circuit. I use it to disable the primary or secondary injectors >prior to flight to determine if the engine will run on only one set >of injectors. It failed in flight and the engine went very lean >running on only one set of injectors. >The switch initially had no continuity but made a high resistance >contact after flipping it back and forth a few times. First, I would REALLY like to have that switch for failure analysis. How much time did you have on the switch? How is this switch wired? does the switch carry injector currents in BOTH positions? > >Should I replace this switch with a more robust one and if so, where >would I find a suitable switch? There are many more robust switches suited to the task not the least of which is this device http://tinyurl.com/jhkg6ep . . . but it's not clear to me that the S700-2-3 was not suited to the task either. It would be useful for us to study the circumstance of the failure and the in-flight situatin you encounted when it did. Bob . . . ________________________________ Message 4 _____________________________________ Time: 11:05:07 AM PST US From: Carlos Trigo Subject: AeroElectric-List: On-the-ground power jack Hello group Figure Z-31A of the Connection, which refers to the wiring of a "Military style Ground Power jack", indicates a 22AWG wire connecting the 2nd coil post of the contactor (where the BLK wire of the OVM-14 is also connected), with the "Main Ground Buss", through a 2A circuit breaker. Now forgive my dumb question: what is this wire for? And 2 practical questions: - can I strike this wire from my system? - if not, and since the Ground Buss is in the firewall and the Ground power receptacle and contactor are both in the tail of the RV-10, can I simply connect this wire to the negative terminal of the battery? Regards Carlos Enviado do meu iPhone ________________________________ Message 5 _____________________________________ Time: 11:43:24 AM PST US From: "Robert L. Nuckolls, III" Subject: Re: AeroElectric-List: On-the-ground power jack At 01:01 PM 1/20/2016, you wrote: > >Hello group > >Figure Z-31A of the Connection, which refers to the wiring of a >"Military style Ground Power jack", indicates a 22AWG wire >connecting the 2nd coil post of the contactor (where the BLK wire of >the OVM-14 is also connected), with the "Main Ground Buss", through >a 2A circuit breaker. Emacs! The small, third terminal on the "mil-spec" ground power jack serves a several purposes. First, the pin is small . . . no high current . . . just a sample of the voltage available from the ground power source. Second, the pin is SHORTER which means that nothing happens on this pin until the larger two pins are in good electrical contact wthe sockets in the ground power plug. Using this pin as a source of voltage to energize the ground power contactor prevents the larger pins from trying to CARRY current during the make/break operations. The diode in series with that sense lead prevents the contactor from closing should you be inadvertently connected to a battery cart that has been miss-wired and reverse polarity. the crowbar ov module across the coil will trigger if your ground power jocky has inadvertently place the GPU in the 28V mode . . . it's happened to me twice. The crowbar ov module is designed to work against a circuit breaker. In this case, I suggest a switch-breaker not unlike . . . Emacs! I'm generally not a big fan of breaker-switches. But in this case, the device can serve two purposes . . . (1) as breaker to work in concert with the crowbar ovm and (2) a switch you can have on the panel that gives YOU control over the application/removal of ground power to your airplane. >And 2 practical questions: > - can I strike this wire from my system? Not recommended . . . > - if not, and since the Ground Buss is in the firewall and the > Ground power receptacle and contactor are both in the tail of the > RV-10, can I simply connect this wire to the negative terminal of the battery? That breaker switch should be on your panel . . . or perhaps on a bracket under it . . . hence the the LONG wire is from ground power contactor and the switch-breaker. The wire between ground bus and the switch- breaker is short. Bob . . . ________________________________ Message 6 _____________________________________ Time: 12:36:28 PM PST US From: Carlos Trigo Subject: Re: AeroElectric-List: On-the-ground power jack Thanks Bob For the quick response, and the excellent "instructions manual" that came al ong with the response. A last question, derived from your explanations: - When the ground-power jockey connects the female military jack of the ba ttery cart to the airplane, the electrons will not flow unless that breaker- switch you recommended is On, right? Carlos Enviado do meu iPhone No dia 20/01/2016, =C3-s 19:34, Robert L. Nuckolls, III escreveu: > At 01:01 PM 1/20/2016, you wrote: .pt> >> >> Hello group >> >> Figure Z-31A of the Connection, which refers to the wiring of a "Military style Ground Power jack", indicates a 22AWG wire connecting the 2nd coil po st of the contactor (where the BLK wire of the OVM-14 is also connected), wi th the "Main Ground Buss", through a 2A circuit breaker. > > <2547f72d.jpg> > The small, third terminal on the "mil-spec" > ground power jack serves a several purposes. > > First, the pin is small . . . no high current . . . > just a sample of the voltage available from > the ground power source. Second, the pin is > SHORTER which means that nothing happens on this > pin until the larger two pins are in good > electrical contact wthe sockets in the ground > power plug. Using this pin as a source of > voltage to energize the ground power contactor > prevents the larger pins from trying to CARRY > current during the make/break operations. > > The diode in series with that sense lead > prevents the contactor from closing should > you be inadvertently connected to a battery > cart that has been miss-wired and reverse > polarity. the crowbar ov module across the > coil will trigger if your ground power jocky > has inadvertently place the GPU in the 28V > mode . . . it's happened to me twice. > > The crowbar ov module is designed to work > against a circuit breaker. In this case, I > suggest a switch-breaker not unlike . . . > > <2547f78b.jpg> > > I'm generally not a big fan of breaker-switches. > But in this case, the device can serve two > purposes . . . (1) as breaker to work in concert > with the crowbar ovm and (2) a switch > you can have on the panel that gives YOU > control over the application/removal of > ground power to your airplane. > > >> And 2 practical questions: >> - can I strike this wire from my system? > > Not recommended . . . > >> - if not, and since the Ground Buss is in the firewall and the Ground p ower receptacle and contactor are both in the tail of the RV-10, can I simpl y connect this wire to the negative terminal of the battery? > > That breaker switch should be on your > panel . . . or perhaps on a bracket under > it . . . hence the the LONG wire is from > ground power contactor and the switch-breaker. > The wire between ground bus and the switch- > breaker is short. > > Bob . . . ________________________________ Message 7 _____________________________________ Time: 01:11:47 PM PST US From: "Robert L. Nuckolls, III" Subject: Re: AeroElectric-List: On-the-ground power jack At 02:30 PM 1/20/2016, you wrote: >Thanks Bob > >For the quick response, and the excellent "instructions manual" that >came along with the response. > >A last question, derived from your explanations: > - When the ground-power jockey connects the female military jack > of the battery cart to the airplane, the electrons will not flow > unless that breaker-switch you recommended is On, right? Absolutely. If you have the option, the ground power switch can be included in the DC POWER group of system switches on your panel. When ground power is plugged in, you can have control of it from the pilot's position. Doesn't need to be ON until you're ready, you can turn it OFF as you decide. Some of my readers have added a lamp from the high side of contactor coil to ground. This light will indicate when and if ground power is available. Bob . . . ________________________________ Message 8 _____________________________________ Time: 01:12:19 PM PST US Subject: AeroElectric-List: Re: Schematic for twin PM alternators From: "user9253" I revised my schematic and attached it. The relays now switch the AC. All electrical power can be shut off on the engine side of the firewall. The DC output from each regulator is fused separately so that a fault in one will not disable the other one. -------- Joe Gores Read this topic online here: http://forums.matronics.com/viewtopic.php?p=452147#452147 Attachments: http://forums.matronics.com//files/revmaster5a_214.pdf ________________________________ Message 9 _____________________________________ Time: 01:23:40 PM PST US From: Ken Ryan Subject: AeroElectric-List: Rotax 914 Generator, Alternator, Starting and Fuel Pump Control I developed the attached wiring based on input from a Rotax dealer in British Columbia. It assumes that the optional external alternator (40 amp) is installed in addition to the integrated generator (20 amp). The integrated generator is used only to power the main fuel pump. The 914 requires an operational fuel pump to run. The ignition is independent. I would appreciate input on the attached diagram. Thanks. ________________________________ Message 10 ____________________________________ Time: 01:49:14 PM PST US Subject: Re: AeroElectric-List: Re: Schematic for twin PM alternators From: Charlie England On Wed, Jan 20, 2016 at 3:10 PM, user9253 wrote: > > I revised my schematic and attached it. > The relays now switch the AC. All electrical power can be shut off on the > engine side of the firewall. > The DC output from each regulator is fused separately so that a fault in > one will not disable the other one. > > -------- > Joe Gores > > I wish I had the time/aptitude to knock out nice drawings like that. I'm still scribbling in notebooks. Some thoughts. The path from buss through the alt breaker, SPDT switch contains multiple single points of failure that can take out both alternators. The alternators, as drawn in the original 'cartoon' installation drawing seems to show one leg of each alternator connected to ground. If that's the case, interrupting the 'wrong' leg might not shut that alt down, if there's an internal short to ground. Behavior of the IGN terminal is not known, and even if it does control the alt, there's no guarantee that a failure mode won't keep the alt active. Assuming that the IGN terminal can control the alt, the ganged master is a single point of failure for the alts (though if it goes, the alts may not matter. :-) ). With B leads tied to the buss, a failure to ground in either charging system might try to draw power from the buss (battery & other alt). Some of the above may not be important if it's a purely VFR plane with no electrical dependence, & nav can be handled with eyeballs &/or portable nav/gps units. But it shouldn't be too difficult to make the system truly redundant. (Independent OV modules, separate switches, contactors interrupting the B leads, etc) What do you think? ________________________________ Message 11 ____________________________________ Time: 05:23:34 PM PST US Subject: AeroElectric-List: Re: Schematic for twin PM alternators From: "user9253" > I wish I had the time/aptitude to knock out nice drawings like that. It helps to be retired. You are right about the multiple single points of failure in the relay coil circuit. To eliminate the danger, the circuit would have to be duplicated; 2 breakers, 2 capacitors, and two switches. The builder would have to weigh the danger of a single part failing against the disadvantage of adding more parts. I did not see any documents that indicated the AC winding was grounded. That would be easy to check with an ohmmeter. I assume [I know that is dangerous :-) ] that the MIA881279 regulator terminals have functions the same functions as the Rotax regulator. See this thread: http://www.matronics.com/forums/viewtopic.php?p=305164&sid=53455a09f9026927ea6c15eb6d6e198f > there's no guarantee that a failure mode won't keep the alt active. A regulator can not have an output if there is no AC input. The relays only allow one AC dynamo to be connected at a time. > the ganged master is a single point of failure for the alts Yes, but many airplanes have a master switch that is a single point of failure. > With B leads tied to the buss, a failure to ground in either charging system might try to draw power from the buss (battery & other alt). True, but it would have to be a resistive fault. A direct short to ground would blow the 25 amp fuse with battery current. Yes, the circuit could be made more failure tolerant. But is added complexity warranted for the aircraft mission? This is a hobby for me. I do not want to make it into a full time job. :-) You bring up some interesting points. If it were my plane intended for hard IFR, then I would spend more time honing the schematic. -------- Joe Gores Read this topic online here: http://forums.matronics.com/viewtopic.php?p=452153#452153 ------------------------------------------------------------------------------------- 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.