---------------------------------------------------------- AeroElectric-List Digest Archive --- Total Messages Posted Fri 01/31/20: 20 ---------------------------------------------------------- Today's Message Index: ---------------------- 1. 10:37 AM - Protecting the fat wires (Randy C-GRPY) 2. 10:58 AM - Re: Proposed Z-14 implementation (Randy C-GRPY) 3. 11:00 AM - Re: Proposed Z-14 implementation (Randy C-GRPY) 4. 11:03 AM - Re: Protecting the fat wires (Randy C-GRPY) 5. 12:01 PM - Re: Protecting the fat wires (user9253) 6. 12:33 PM - Re: Protecting the fat wires (user9253) 7. 12:51 PM - Re: Proposed Z-14 implementation (user9253) 8. 01:49 PM - Re: Protecting the fat wires (Charlie England) 9. 02:05 PM - Re: Protecting the fat wires (Randy C-GRPY) 10. 02:13 PM - Re: Protecting the fat wires (Randy C-GRPY) 11. 03:44 PM - Re: Proposed Z-14 implementation (Randy C-GRPY) 12. 03:51 PM - Re: Z-14 implementation for electrically dependent engine (Randy C-GRPY) 13. 04:41 PM - Re: Protecting the fat wires (johnbright) 14. 05:03 PM - Re: Re: Protecting the fat wires (Charlie England) 15. 06:43 PM - Re: Proposed Z-14 implementation (johnbright) 16. 07:41 PM - Re: Z-14 implementation for electrically dependent engine (johnbright) 17. 07:43 PM - Re: Z-14 implementation for electrically dependent engine (johnbright) 18. 07:46 PM - Re: Z-14 implementation for electrically dependent engine (johnbright) 19. 07:50 PM - Re: Protecting the fat wires (Robert L. Nuckolls, III) 20. 08:40 PM - Re: Re: Proposed Z-14 implementation (Robert L. Nuckolls, III) ________________________________ Message 1 _____________________________________ Time: 10:37:45 AM PST US Subject: AeroElectric-List: Protecting the fat wires From: "Randy C-GRPY" Hello all! This is my first time posting on this list so I'd like to introduce myself and say hello. I also have a question that I posted on Facebook. It was suggested that I post the query here. How do you determine which fat wires need circuit protection of some sort? All of the branch circuits off of a bus get a fuse or a breaker, but what about the wires feeding the busses from the contactors? Mr. Nuckolls diagrams sometimes have protection for the larger wires but most often not. I read Aeroelectric Connection in the past and I think that he addressed this but I cant find it. Ausmans book also only talks specifically about protecting branch circuits. Can anybody school me on this? Somebody pointed out, and I do remember reading, that the fat wires will ground to airframe and burn a hole rather than burning the wire itself. It seems to me that the airframe is the fuse. Why not just use an ANL? Thanks Randy Read this topic online here: http://forums.matronics.com/viewtopic.php?p=494548#494548 ________________________________ Message 2 _____________________________________ Time: 10:58:51 AM PST US Subject: AeroElectric-List: Re: Proposed Z-14 implementation From: "Randy C-GRPY" nuckolls.bob(at)aeroelect wrote: > At 02:33 PM 1/23/2020, you wrote: > > > > > Thanks Bob, > > > > I do understand, as importantly shown in the N811HB accident investigation, that failures that have no effect on the current flight should be detected before the next flight! Those unfamiliar with N811HB may well learn more than one lesson at http://www.aeroelectric.com/Reference_Docs/Accidents/N811HB_Feb2008_LA-IVp/ (http://www.aeroelectric.com/Reference_Docs/Accidents/N811HB_Feb2008_LA-IVp/) > > > > This is an example of a system that was DESIGNED > to fail. The builder attended one of my seminars > out in Eugene OR some years earlier. Had the book. > Was assisted by a degreed engineer neighbor. > > The same neighbor adapted Z-14 as a recommended > architecture for a high performance airplane > carrying a full-up compliment of Garmin glass . . . > but then ignored the advice offered by his > own recommendations by bringing BOTH ignitions > to a common bus with a poorly crafted constellation > of protective devices. > > The whole point of the Z14 philosophy is > independent redundancy . . . but lost in > this airplane by adding a feature that negated > that philosophy in a catastrophic way. The > feature? A dual diode feed common bus for > both ignitions. > > If they had simply subscribed to this List > and run the ideas past the members, the error > would have most certainly been avoided with advice > from numerous members. > > > > I am planning an O-360 with dual SDS ignition and injection. Part of my approach is to develop a detailed schematic of what it takes to keep the engine running, have a radio, and have a "six pack" of instruments long enough to make an alternate airport with the main contactors open (Z-14 derivative). I plan an engine bus with dual feeds, one from each battery via Schottky diodes; loss of one feed is preflight detectable using EFIS voltmeters. > > Why dual feed bus? Run half the engine > goodies from one battery bus, the rest > from the opposite battery bus. > > These busses are already QUAD feed. > either bus has the opportunity to power > up from a total of 4 sources. No single > failure will deprive BOTH busses of > a robust energy source. > > > > > I do a wire by wire failure analysis that informs the preflight checklist: > > Assume only one failure per flight. > > What are the effects of a wire shorted or open? > > Wires, bus bars and most power distribution > components are considered to be exceedingly > low failure rate . . . those kinds of things > are generally never a part of the system > reliability study. > > > > Does the failure affect safety? If so, can the safety effect be designed out?How will the failure be discovered before the next flight? > > This is important for failures that may not be > obvious in flight . . . for example a light > bulb in a warning system, exterior lamps, > back up pumps for the engine driven mechanical > pump, etc. One might suffer a failure that > would go unnoticed unless explored as part > of a pre-flight process. > > > > If the failure affects flight safety, can something be done about it? > > Have an alternative . . . i.e. plan-B . . . > a way to do without that accessory. > > > > How will the crew know what to do? Can they do it immediately by simple predetermined actions? > > You betcha . . . that's what the FEMA and architecture > refinement is all about. The design goal is to be able > to tolerate failure of any LRU (line replaceable unit) > with the least possible work load on crew. Z-14, for all > it's robustness, only has three switches to fiddle with. > They have NO potential for pilot-induced hazard. I.e. > no mis-positioning of switches creates immediate > hazard. > > > > In case of electrical fire can the battery contactor(s) be opened without affecting flight safety? > > Generally yes . . . I've initiated and/or completed > numerous flights in the "J-3" mode . . . ZERO > electrics. With engine feeds as recommended > above, you can shut down all DC power > management switches without affecting > engine ops. > > > > > Some failures not detectable by preflight checks are added to annual inspection: > > There should be no useful/critical accessory that is not > at least pre-flight testable . . . otherwise, > why carry it around? > > > > A fat wire short to sheetmetal that clears itself. > > Redundant grounds for both the computer and the injector driver sections of the ECUs. (Loss of computer ground sends injectors and coils 100% duty cycle.) > > Redundant grounds to voltage regulators. > > > > Some check done twice yearly: > > Ship's batteries and EFIS backup batteries capacity checks. > > Primary and aux alternator crowbar test. > > > > You've got an excellent start on the > task . . . let's keep talking. > > > > Bob . . . Good day Bob. I watched your videos with great interest related to that accident report. It was my understanding that the diode on the the feed between the two sides was what led to the current hogging that happened and which ultimately caused the whole thing to come crashing down. With Z-14, if I am understanding correctly, should not be an issue since the two sides are also isolated. Is this correct? Also, assuming proper fusing and wires, if you had two batteries powering one bus, it would be, and should be, easy to check each power feed during the preflight. I too am using Z-14 to power my SDS ignition. I posted a separate thread on how to properly choose protection for the bigger wires. I will try and post my schematic there. Thanks for being such a good resource. Regards Randy Read this topic online here: http://forums.matronics.com/viewtopic.php?p=494551#494551 ________________________________ Message 3 _____________________________________ Time: 11:00:20 AM PST US Subject: AeroElectric-List: Re: Proposed Z-14 implementation From: "Randy C-GRPY" nuckolls.bob(at)aeroelect wrote: > At 02:33 PM 1/23/2020, you wrote: > > > > > Thanks Bob, > > > > I do understand, as importantly shown in the N811HB accident investigation, that failures that have no effect on the current flight should be detected before the next flight! Those unfamiliar with N811HB may well learn more than one lesson at http://www.aeroelectric.com/Reference_Docs/Accidents/N811HB_Feb2008_LA-IVp/ (http://www.aeroelectric.com/Reference_Docs/Accidents/N811HB_Feb2008_LA-IVp/) > > > > This is an example of a system that was DESIGNED > to fail. The builder attended one of my seminars > out in Eugene OR some years earlier. Had the book. > Was assisted by a degreed engineer neighbor. > > The same neighbor adapted Z-14 as a recommended > architecture for a high performance airplane > carrying a full-up compliment of Garmin glass . . . > but then ignored the advice offered by his > own recommendations by bringing BOTH ignitions > to a common bus with a poorly crafted constellation > of protective devices. > > The whole point of the Z14 philosophy is > independent redundancy . . . but lost in > this airplane by adding a feature that negated > that philosophy in a catastrophic way. The > feature? A dual diode feed common bus for > both ignitions. > > If they had simply subscribed to this List > and run the ideas past the members, the error > would have most certainly been avoided with advice > from numerous members. > > > > I am planning an O-360 with dual SDS ignition and injection. Part of my approach is to develop a detailed schematic of what it takes to keep the engine running, have a radio, and have a "six pack" of instruments long enough to make an alternate airport with the main contactors open (Z-14 derivative). I plan an engine bus with dual feeds, one from each battery via Schottky diodes; loss of one feed is preflight detectable using EFIS voltmeters. > > Why dual feed bus? Run half the engine > goodies from one battery bus, the rest > from the opposite battery bus. > > These busses are already QUAD feed. > either bus has the opportunity to power > up from a total of 4 sources. No single > failure will deprive BOTH busses of > a robust energy source. > > > > > I do a wire by wire failure analysis that informs the preflight checklist: > > Assume only one failure per flight. > > What are the effects of a wire shorted or open? > > Wires, bus bars and most power distribution > components are considered to be exceedingly > low failure rate . . . those kinds of things > are generally never a part of the system > reliability study. > > > > Does the failure affect safety? If so, can the safety effect be designed out?How will the failure be discovered before the next flight? > > This is important for failures that may not be > obvious in flight . . . for example a light > bulb in a warning system, exterior lamps, > back up pumps for the engine driven mechanical > pump, etc. One might suffer a failure that > would go unnoticed unless explored as part > of a pre-flight process. > > > > If the failure affects flight safety, can something be done about it? > > Have an alternative . . . i.e. plan-B . . . > a way to do without that accessory. > > > > How will the crew know what to do? Can they do it immediately by simple predetermined actions? > > You betcha . . . that's what the FEMA and architecture > refinement is all about. The design goal is to be able > to tolerate failure of any LRU (line replaceable unit) > with the least possible work load on crew. Z-14, for all > it's robustness, only has three switches to fiddle with. > They have NO potential for pilot-induced hazard. I.e. > no mis-positioning of switches creates immediate > hazard. > > > > In case of electrical fire can the battery contactor(s) be opened without affecting flight safety? > > Generally yes . . . I've initiated and/or completed > numerous flights in the "J-3" mode . . . ZERO > electrics. With engine feeds as recommended > above, you can shut down all DC power > management switches without affecting > engine ops. > > > > > Some failures not detectable by preflight checks are added to annual inspection: > > There should be no useful/critical accessory that is not > at least pre-flight testable . . . otherwise, > why carry it around? > > > > A fat wire short to sheetmetal that clears itself. > > Redundant grounds for both the computer and the injector driver sections of the ECUs. (Loss of computer ground sends injectors and coils 100% duty cycle.) > > Redundant grounds to voltage regulators. > > > > Some check done twice yearly: > > Ship's batteries and EFIS backup batteries capacity checks. > > Primary and aux alternator crowbar test. > > > > You've got an excellent start on the > task . . . let's keep talking. > > > > Bob . . . Good day Bob. I watched your videos with great interest related to that accident report. It was my understanding that the diode on the the feed between the two sides was what led to the current hogging that happened and which ultimately caused the whole thing to come crashing down. With Z-14, if I am understanding correctly, should not be an issue since the two sides are also isolated. Is this correct? Also, assuming proper fusing and wires, if you had two batteries powering one bus, it would be, and should be, easy to check each power feed during the preflight. I too am using Z-14 to power my SDS ignition. I posted a separate thread on how to properly choose protection for the bigger wires. I will try and post my schematic there. Thanks for being such a good resource. Regards Randy Read this topic online here: http://forums.matronics.com/viewtopic.php?p=494550#494550 ________________________________ Message 4 _____________________________________ Time: 11:03:51 AM PST US Subject: AeroElectric-List: Re: Protecting the fat wires From: "Randy C-GRPY" This is my schematic. I'm looking for guidance on. Read this topic online here: http://forums.matronics.com/viewtopic.php?p=494552#494552 Attachments: http://forums.matronics.com//files/c_grpy_main_power_132.pdf ________________________________ Message 5 _____________________________________ Time: 12:01:04 PM PST US Subject: AeroElectric-List: Re: Protecting the fat wires From: "user9253" Is the electrical system safer or less safe with the fat wire protected with an ANL fuse? Count the ways that fuse can fail. There are two crimps that connect the ring terminals to fat wires. There are two bolts that connect the ring terminals to the fuse. The fuse itself can blow. And there are exposed terminals that can short to ground. So installing an ANL fuse creates about 6 more possible failure modes. Why not just install the fat wire properly so that it is highly unlikely that it will short out? Use fuses instead of a VPX. -------- Joe Gores Read this topic online here: http://forums.matronics.com/viewtopic.php?p=494553#494553 ________________________________ Message 6 _____________________________________ Time: 12:33:12 PM PST US Subject: AeroElectric-List: Re: Protecting the fat wires From: "user9253" The ANL fuse on the downstream side of the aux contactor could blow if the aux battery is used to crank the engine. -------- Joe Gores Read this topic online here: http://forums.matronics.com/viewtopic.php?p=494555#494555 ________________________________ Message 7 _____________________________________ Time: 12:51:41 PM PST US Subject: AeroElectric-List: Re: Proposed Z-14 implementation From: "user9253" The diodes did not cause the failure. The 5 amp fuses did. If 20 amp circuit breakers had been used instead of 5 amp fuses, the whole bus would not have lost power. -------- Joe Gores Read this topic online here: http://forums.matronics.com/viewtopic.php?p=494556#494556 ________________________________ Message 8 _____________________________________ Time: 01:49:44 PM PST US Subject: Re: AeroElectric-List: Protecting the fat wires From: Charlie England On 1/31/2020 12:36 PM, Randy C-GRPY wrote: > > Hello all! This is my first time posting on this list so I'd like to introduce myself and say hello. I also have a question that I posted on Facebook. It was suggested that I post the query here. > > How do you determine which fat wires need circuit protection of some sort? All of the branch circuits off of a bus get a fuse or a breaker, but what about the wires feeding the busses from the contactors? Mr. Nuckolls diagrams sometimes have protection for the larger wires but most often not. I read Aeroelectric Connection in the past and I think that he addressed this but I cant find it. Ausmans book also only talks specifically about protecting branch circuits. Can anybody school me on this? > > Somebody pointed out, and I do remember reading, that the fat wires will ground to airframe and burn a hole rather than burning the wire itself. It seems to me that the airframe is the fuse. Why not just use an ANL? > > Thanks > Randy > As Joe pointed out, you're adding multiple failure points. It's worth mentioning that it's everyday practice for the primary power feeder to be protected only by the master contactor, which is (should be) next to the battery. Tens of thousands of cert. a/c are built that way. Just about all other wires do have some type of circuit protection. I tend to agree with Joe about electronic distribution gadgets. The convenience looks attractive, but some of them have failure modes that can take the whole plane 'dark', and I'm not aware of any that publish every detail of their 'innards'. That means you don't know what you don't know. With a radio or other widget that's a 'black box', you can install a backup, but making an electronic power distribution system redundant would be a monumental task. Charlie ________________________________ Message 9 _____________________________________ Time: 02:05:12 PM PST US Subject: AeroElectric-List: Re: Protecting the fat wires From: "Randy C-GRPY" user9253 wrote: > The ANL fuse on the downstream side of the aux contactor could blow if the aux battery is used to crank the engine. Ahhhh.....good point. The contactors are going to be next to the batteries. With one battery in the tail there would be a large wire running to the firewall. What I am understanding from you is that that wire is protected by the contactor and no further fusing is required. How about the hot wires from the unswitched side of the contactors feeding the engine bus? Would you protect that close to the battery? I appreciate your input. Randy Read this topic online here: http://forums.matronics.com/viewtopic.php?p=494559#494559 ________________________________ Message 10 ____________________________________ Time: 02:13:52 PM PST US Subject: AeroElectric-List: Re: Protecting the fat wires From: "Randy C-GRPY" ceengland7(at)gmail.com wrote: > On 1/31/2020 12:36 PM, Randy C-GRPY wrote: > > > > > > > > > Somebody pointed out, and I do remember reading, that the fat wires will ground to airframe and burn a hole rather than burning the wire itself. It seems to me that the airframe is the fuse. Why not just use an ANL? > > > > ThanksHello all! This is my first time posting on this list so I'd like to introduce myself and say hello. I also have a question that I posted on Facebook. It was suggested that I post the query here. > > > > How do you determine which fat wires need circuit protection of some sort? All of the branch circuits off of a bus get a fuse or a breaker, but what about the wires feeding the busses from the contactors? Mr. Nuckolls diagrams sometimes have protection for the larger wires but most often not. I read Aeroelectric Connection in the past and I think that he addressed this but I cant find it. Ausmans book also only talks specifically about protecting branch circuits. Can anybody school me on this? > > > > Randy > > > > As Joe pointed out, you're adding multiple failure points. It's worth > > > > > I tend to agree with Joe about electronic distribution gadgets. The > convenience looks attractive, but some of them have failure modes that > can take the whole plane 'dark', and I'm not aware of any that publish > every detail of their 'innards'. That means you don't know what you > don't know. With a radio or other widget that's a 'black box', you can > install a backup, but making an electronic power distribution system > redundant would be a monumental task. > > Charlie I appreciate your input. The VPX has a pretty good history so far and it serves as more than just a circuit breaker. I personally like it and it seems like a lot of users are choosing it these days. I will rethink it though. If it were to go offline, say by turning the master off, my backup is one switch that will switch to an essential bus that served by the backup alternator. At least that is what I was hoping for with the layout I designed. My panel does have a G5 with its own backup battery that will stay on even if Master and Aux power is turned off. Read this topic online here: http://forums.matronics.com/viewtopic.php?p=494560#494560 ________________________________ Message 11 ____________________________________ Time: 03:44:30 PM PST US Subject: AeroElectric-List: Re: Proposed Z-14 implementation From: "Randy C-GRPY" user9253 wrote: > The diodes did not cause the failure. The 5 amp fuses did. If 20 amp circuit breakers > had been used instead of 5 amp fuses, the whole bus would not have lost power. Yes, I understand that it wasn't fused with a big enough breaker/fuse. Bob did another video in that series though that poo pooed that design even with properly sized fuses. I didn't understand why he felt it was a bad design since it is easy to check both feeds to the bus during the run up. He championed having the ignitions on two completely independent busses for which I appreciate the reasons. His design doesn't completely transfer over from what I can tell to combined ignition/fuel injection systems like SDS. So I guess the question that I would have is: Is that diode protected double fed single bus still a design waiting to fail if one does his due diligence including checking redundant power to the busses during run up and properly sizing and fusing the wires? Randy Read this topic online here: http://forums.matronics.com/viewtopic.php?p=494561#494561 ________________________________ Message 12 ____________________________________ Time: 03:51:49 PM PST US Subject: AeroElectric-List: Re: Z-14 implementation for electrically dependent engine From: "Randy C-GRPY" nuckolls.bob(at)aeroelect wrote: > > > > > Any other suggestions as to how to provide redundant power to all 6 fuel injectors? > > > > Thanks much! > > This is figure Z-14 . . . both main and > aux busses are already quad redundant > with virtually zero risk for total loss > of power. > > Can you point us to a schematic/wiring > diagram for the engine electrics? > > > > Bob . . . SDS's schematic.... Read this topic online here: http://forums.matronics.com/viewtopic.php?p=494562#494562 Attachments: http://forums.matronics.com//files/engine_bus_382.pdf ________________________________ Message 13 ____________________________________ Time: 04:41:14 PM PST US Subject: AeroElectric-List: Re: Protecting the fat wires From: "johnbright" Fat wire burns thru elevator cable... one of Bob Nuckols' stories: "Bottom line is that you're many, many times more likely to have a bad day in the cockpit for reasons far removed from a hard ground fault on your 6AWG bus feeder wire. . . and THAT because you didn't conduct due diligence in its installation. In the case of the bus feeder, the risks are not so much to the wire as to the thing the wire touches. Case in point: C90 twin turboprop on short final experiences disconnect of elevator cables. Pilot uses trim commands and power to execute go-around, assesses the condition and successfully lands the airplane with rudder, trim and power. Pulling up floorboards in the cockpit revealed a 40A protected feeder to the windshield de-ice inverter had been mis-positioned against the elevator control cable during a maintenance operation. Over what had to be many hours of operation, motion of the cable wore through the insulation bringing the cable into contact with the hot wire. The arcing and sparking was of insufficient intensity to come to attention of crew in spite of the fact that it was going on virtually under their feet. The copper wire was barely damaged. The breaker never popped while the elevator cable eventually eroded through and parted. Compare thermal properties of copper versus steel . . . this explains why the best steel safes have intermediate layers of copper in their construction. It's EASY to burn through steel . . . next to impossible on copper. This narrative explains the high order probability that even if you DID get your 6AWG feeder faulted to ground, it's most likely to be a soft fault that burns a hole in your airplane while doing little damage to the wire . . . and certainly far short of getting it to smoke and/or open a fuse/breaker. Adding 'protection' to this pathway doubles the number of joints in the pathway and adds nothing demonstrable in terms of fault response . . . which is why the spam-can builders don't do it either. ... Bob Nuckolls ..." -------- John Bright, RV-6A, at FWF, O-360, dual SDSEFI EM-5-F Dual Batt Dual Alt RV-6A SDS dual EM-5-F john_s_bright@yahoo.com, Newport News, Va Read this topic online here: http://forums.matronics.com/viewtopic.php?p=494563#494563 ________________________________ Message 14 ____________________________________ Time: 05:03:31 PM PST US Subject: Re: AeroElectric-List: Re: Protecting the fat wires From: Charlie England On 1/31/2020 4:03 PM, Randy C-GRPY wrote: > > > user9253 wrote: >> The ANL fuse on the downstream side of the aux contactor could blow if the aux battery is used to crank the engine. > > Ahhhh.....good point. > > The contactors are going to be next to the batteries. With one battery in the tail there would be a large wire running to the firewall. What I am understanding from you is that that wire is protected by the contactor and no further fusing is required. > > How about the hot wires from the unswitched side of the contactors feeding the engine bus? Would you protect that close to the battery? > > I appreciate your input. > Randy My choice is to use a fuselink soldered & heatshrunk onto the battery end of the wire feeding the engine bus. Fuselinks have been quite common in the automotive world to protect things like alternator B leads. An ANL would achieve the same thing, for more money & extra failure points. Protecting the wire makes good sense; I just wanted the minimum risk of a 'false positive' circuit interruption. Charlie ________________________________ Message 15 ____________________________________ Time: 06:43:23 PM PST US Subject: AeroElectric-List: Re: Proposed Z-14 implementation From: "johnbright" Randy C-GRPY wrote: > I didn't understand why he felt it was a bad design since it is easy to check both feeds to the bus during the run up... > > Randy I don't understand how this can be done. Ref attached bus schematic of N811HB. -------- John Bright, RV-6A, at FWF, O-360, dual SDSEFI EM-5-F Dual Batt Dual Alt RV-6A SDS dual EM-5-F john_s_bright@yahoo.com, Newport News, Va Read this topic online here: http://forums.matronics.com/viewtopic.php?p=494565#494565 Attachments: http://forums.matronics.com//files/n811hb_bus_schematic_108.png ________________________________ Message 16 ____________________________________ Time: 07:41:28 PM PST US Subject: AeroElectric-List: Re: Z-14 implementation for electrically dependent engine From: "johnbright" Randy C-GRPY wrote: > > > SDS's schematic.... Hi Randy, Some thoughts: The SDS schematic leaves out a lot of details. [list=]The ECU select switch is SPDT. If the ECUs are unswitched I don't understand how you can preflight if the injectors are working.[/list] -------- John Bright, RV-6A, at FWF, O-360, dual SDSEFI EM-5-F Dual Batt Dual Alt RV-6A SDS dual EM-5-F john_s_bright@yahoo.com, Newport News, Va Read this topic online here: http://forums.matronics.com/viewtopic.php?p=494566#494566 ________________________________ Message 17 ____________________________________ Time: 07:43:42 PM PST US Subject: AeroElectric-List: Re: Z-14 implementation for electrically dependent engine From: "johnbright" johnbright wrote: > > Randy C-GRPY wrote: > > > > > > SDS's schematic.... > > > Hi Randy, > > Some thoughts: > > The SDS schematic leaves out a lot of details. > The ECU select switch is SPDT. > Since the ECUs are unswitched I don't understand how you can preflight if the injectors relays are working. -------- John Bright, RV-6A, at FWF, O-360, dual SDSEFI EM-5-F Dual Batt Dual Alt RV-6A SDS dual EM-5-F john_s_bright@yahoo.com, Newport News, Va Read this topic online here: http://forums.matronics.com/viewtopic.php?p=494567#494567 ________________________________ Message 18 ____________________________________ Time: 07:46:37 PM PST US Subject: AeroElectric-List: Re: Z-14 implementation for electrically dependent engine From: "johnbright" johnbright wrote: > > johnbright wrote: > > > > Randy C-GRPY wrote: > > > > > > > > > SDS's schematic.... > > > > > > Hi Randy, > > > > Some thoughts: > > > > The SDS schematic leaves out a lot of details. > > The ECU select switch is SPDT. > > Since the ECUs are unswitched I don't understand how you can preflight if the injector relays are working. > -------- John Bright, RV-6A, at FWF, O-360, dual SDSEFI EM-5-F Dual Batt Dual Alt RV-6A SDS dual EM-5-F john_s_bright@yahoo.com, Newport News, Va Read this topic online here: http://forums.matronics.com/viewtopic.php?p=494568#494568 ________________________________ Message 19 ____________________________________ Time: 07:50:30 PM PST US From: "Robert L. Nuckolls, III" Subject: Re: AeroElectric-List: Protecting the fat wires At 12:36 PM 1/31/2020, you wrote: > >Hello all! This is my first time posting on this >list so I'd like to introduce myself and say >hello. I also have a question that I posted on >Facebook. It was suggested that I post the query here. Welcome aboard my friend. This is the intellectual watering hole for a useful contingent of experienced and contemplative thinkers. >How do you determine which fat wires need >circuit protection of some sort? All of the >branch circuits off of a bus get a fuse or a >breaker, but what about the wires feeding the >busses from the contactors? Mr. Nuckolls=99 >diagrams sometimes have protection for the larger wires but most often not. I think you're referring to b-lead protection on alternators . . . this is in recognition of solid state devices (rectifiers) in alternators with a known history of faults albeit a very old one. It's now a exceedingly rate occurrence. Some cars have fusible links in their alternator b-leads. I think my Kia mini-van has several mani-ANL limiters in the battery feeders. But as a general rule, you're on solid ground with the z-figures . . . all descendants of a century of practice in TC aircraft and 30 years experience here on the List. > I read Aeroelectric Connection in the past and > I think that he addressed this but I can=99t > find it. Ausman=99s book also only talks > specifically about protecting branch circuits. Can anybody school me on this? > >Somebody pointed out, and I do remember reading, >that the fat wires will ground to airframe and >burn a hole rather than burning the wire >itself. It seems to me that the airframe is the >fuse. Why not just use an ANL? It simply adds parts count and cost that affords no practical value. A quick review of the power distribution on a couple hundred thousand TC light aircraft will confirm this design philosophy. You can add all the ANL devices that you wish, operationally they will add no risk beyond increased probability of failure due to un-warranted complexity. Bob . . . ________________________________ Message 20 ____________________________________ Time: 08:40:39 PM PST US From: "Robert L. Nuckolls, III" Subject: Re: AeroElectric-List: Re: Proposed Z-14 implementation >Good day Bob. > >I watched your videos with great interest related to that accident >report. It was my understanding that the diode on the the feed >between the two sides was what led to the current hogging that >happened and which ultimately caused the whole thing to come >crashing down. With Z-14, if I am understanding correctly, should >not be an issue since the two sides are also isolated. Is this correct? Z-14 (and all other z-figures depicting dc power feeds to ignition, fuel, injectors, etc.) show INDEPENDENT feeds to all such devices. In other words, redundant accessories never share hardware once the electrons leave the source through single feeder protection. Indeed, the guest-engineer on the project used Z-14 as a basis for a 'recommended' power distribution system that powered a full-up compliment of Garmin glass on the panel. In his published architecture, he replaced the cross-feed contator with a fat diode and ran one ignition from the main battery . . . the second ignition from the aux battery. But he failed to describe a recommended operating protocol for the two alternators. However, in the accident aircraft, fuse protected feeders from each battery was brought through diodes to a common bus whereupon power was distributed out through breakers to the two ignition systems. Bad deal. First, there was no way that loss of one battery bus fuse could be detected in pre-flight . . . which was the case leading up to this accident. Having the aux alternator off line caused the aux battery ignition feeder voltage to be LOWER than the main battery by approx .7 volts. This caused the main battery ignition fuse to carry the load for BOTH ignitions causing failure of the main fuse followed by the aux fuse hours later. Further, a fault in one system would have taken out BOTH fuses and killed both systems. If he had left out the diodes, common bus and the do-nothing breakers . . . that ship would probably be flying okay today. Lessons learned . . . diodes are handy critters for lots of applications but are SELDOM warranted in power distribution systems. I've used them in the normal feed path to an endurance bus in several figures and in Z-19 where a SINGLE ECU and FUEL PUMP configuration are provided two power sources through independent switches. Fiddle the architecture with caution . . . The latest Figure Z-12 . . . http://www.aeroelectric.com/PPS/Adobe_Architecture_Pdfs/Z12NP1.pdf artfully crafted is as robust as anyone should need in an OBAM aircraft . . . if you really gotta have dual batteries, add Z-30. 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.