---------------------------------------------------------- AeroElectric-List Digest Archive --- Total Messages Posted Tue 07/10/18: 7 ---------------------------------------------------------- Today's Message Index: ---------------------- 1. 08:02 AM - Re: Re: Z-* Question (Robert L. Nuckolls, III) 2. 09:10 AM - Re: Z-* Question (BMC_Dave) 3. 11:06 AM - Re: Re: Z-* Question (Robert L. Nuckolls, III) 4. 03:25 PM - Re: Z-* Question (BMC_Dave) 5. 04:44 PM - Re: Re: Z-* Question (C&K) 6. 05:09 PM - Re: Re: Z-* Question (Robert L. Nuckolls, III) 7. 07:28 PM - Re: Z-* Question (BMC_Dave) ________________________________ Message 1 _____________________________________ Time: 08:02:35 AM PST US From: "Robert L. Nuckolls, III" Subject: Re: AeroElectric-List: Re: Z-* Question At 11:38 AM 7/7/2018, you wrote: > > >That was my thought, too. If the contactor were to fail OPEN, the >alternator would still be able to feed the battery. The battery >buss would then be powered as long as the engine was running. > >You also retain the ability to isolated the battery from the >alternator using the field switch. I advise caution about 'tweaking' the z-figures based on some notions of dealing with failures, especially rare ones, that require crew to (1) notice that a failure has occurred, (2) diagnose the failure and (3) take low risk remedial action. Be especially wary of the possibility that a tweak may create a new, unconsidered failure mode. The first duty of crew is fly the airplane, navigate to a low risk termination of flight, communicate in your 'spare' time and LEAVE THE TOOLBOX on the ground. The Z-figures evolved out of nearly a century of lessons learned. In 20 years of sifting and adapting here on the List, the architectures have demonstrated low risk performance while minimizing the need to diagnose in flight . . . I recall how a perfectly good L1011 full of passengers was flown into the Florida swamps by a crew distracted with diagnosis on a burned out light bulb while warning squawks and beeps were going on all around them. These discussions are GOOD exercises that go to achieving understanding of how a system works along with confidence in having minimized risk while REDUCING pilot workload when things do go TU. Bob . . . ________________________________ Message 2 _____________________________________ Time: 09:10:02 AM PST US Subject: AeroElectric-List: Re: Z-* Question From: "BMC_Dave" Appears to be the same question I raised here: http://forum.matronics.com/viewtopic.php?t=16770059 I get the cautions about making changes, but would this one not be prudent? I understand contactor failures are rare, but it is also said they wear pretty rough in-service. So why not remove a possible failure mode where you don't realize something is wrong until your engine quits? Read this topic online here: http://forums.matronics.com/viewtopic.php?p=481520#481520 ________________________________ Message 3 _____________________________________ Time: 11:06:55 AM PST US From: "Robert L. Nuckolls, III" Subject: Re: AeroElectric-List: Re: Z-* Question At 11:09 AM 7/10/2018, you wrote: > >Appears to be the same question I raised here: >http://forum.matronics.com/viewtopic.php?t=16770059 > >I get the cautions about making changes, but would this one not be prudent? > >I understand contactor failures are rare, but it is also said they >wear pretty rough in-service. So why not remove a possible failure >mode where you don't realize something is wrong until your engine quits? Okay, recite the narrative for any particular failure. I presume we're talking about Z-14. How would any single failure put engine ops at risk? Bob . . . ________________________________ Message 4 _____________________________________ Time: 03:25:16 PM PST US Subject: AeroElectric-List: Re: Z-* Question From: "BMC_Dave" nuckolls.bob(at)aeroelect wrote: > At 11:09 AM 7/10/2018, you wrote: > > > > > Appears to be the same question I raised here: http://forum.matronics.com/viewtopic.php?t=16770059 (http://forum.matronics.com/viewtopic.php?t=16770059) > > > > I get the cautions about making changes, but would this one not be prudent? > > > > I understand contactor failures are rare, but it is also said they wear pretty rough in-service. So why not remove a possible failure mode where you don't realize something is wrong until your engine quits? > > Okay, recite the narrative for any particular failure. > I presume we're talking about Z-14. How would any > single failure put engine ops at risk? > > > Bob . . . I amended that because while I may have been thinking about it in my post I didn't actually discuss it. In any case, referring to Z-14 say the battery contactor opens in flight. Now the main battery bus is disconnected from the alternator, and in this case you have no alternative means to connect it to either alternator, so hopefully flight-critical systems aren't dependent on it. Additionally, you have no warnings that this has occured. Read this topic online here: http://forums.matronics.com/viewtopic.php?p=481526#481526 ________________________________ Message 5 _____________________________________ Time: 04:44:45 PM PST US Subject: Re: AeroElectric-List: Re: Z-* Question From: C&K On 10/07/2018 6:24 PM, BMC_Dave wrote: > > > nuckolls.bob(at)aeroelect wrote: >> At 11:09 AM 7/10/2018, you wrote: >> >>> >>> Appears to be the same question I raised here: http://forum.matronics.com/viewtopic.php?t=16770059 (http://forum.matronics.com/viewtopic.php?t=16770059) >>> >>> I get the cautions about making changes, but would this one not be prudent? >>> >>> I understand contactor failures are rare, but it is also said they wear pretty rough in-service. So why not remove a possible failure mode where you don't realize something is wrong until your engine quits? >> Okay, recite the narrative for any particular failure. >> I presume we're talking about Z-14. How would any >> single failure put engine ops at risk? >> >> >> Bob . . . > > I amended that because while I may have been thinking about it in my post I didn't actually discuss it. In any case, referring to Z-14 say the battery contactor opens in flight. Now the main battery bus is disconnected from the alternator, and in this case you have no alternative means to connect it to either alternator, so hopefully flight-critical systems aren't dependent on it. > > Additionally, you have no warnings that this has occured. Actually the low battery bus warning should activate as soon as the battery stopped charging. However I want the alternator to keep charging even if the battery contactor is opened by accident or intent. And I want the alternator charging voltage and the overvoltage protection to apply to the battery buss with minimal resistance in the sense circuit to the VR circuit. I want the engine to keep running if the battery goes open circuit. So I do consider it prudent (but not essential) to connect the alternator as directly as possible to the battery for my electrically dependent engine. Ken Ken ________________________________ Message 6 _____________________________________ Time: 05:09:53 PM PST US From: "Robert L. Nuckolls, III" Subject: Re: AeroElectric-List: Re: Z-* Question >>> . >> >>I amended that because while I may have been thinking about it in >>my post I didn't actually discuss it. In any case, referring to >>Z-14 say the battery contactor opens in flight. Now the main >>battery bus is disconnected from the alternator, and in this case >>you have no alternative means to connect it to either alternator, >>so hopefully flight-critical systems aren't dependent on it. Z-14's bus loads have quad redundant power sources. Every feeder in the system can get power from multiple sources. Flight critical loads can be shared between two systems such that no single failure puts the flight at risk. >>Additionally, you have no warnings that this has occured. >Actually the low battery bus warning should activate as soon as the >battery stopped charging. > >However I want the alternator to keep charging even if the battery >contactor is opened by accident or intent. And I want the >alternator charging voltage and the overvoltage protection to apply >to the battery buss with minimal resistance in the sense circuit to >the VR circuit. I want the engine to keep running if the battery >goes open circuit. So I do consider it prudent (but not essential) >to connect the alternator as directly as possible to the battery for >my electrically dependent engine. What are your engine loads? Bob . . . ________________________________ Message 7 _____________________________________ Time: 07:28:58 PM PST US Subject: AeroElectric-List: Re: Z-* Question From: "BMC_Dave" yellowduckduo(at)gmail.co wrote: > On 10/07/2018 6:24 PM, BMC_Dave wrote: > > > > > > > > > nuckolls.bob(at)aeroelect wrote: > > > At 11:09 AM 7/10/2018, you wrote: > > > > > >> > > >> > > >> Appears to be the same question I raised here: http://forum.matronics.com/viewtopic.php?t=16770059 (http://forum.matronics.com/viewtopic.php?t=16770059) > > >> > > >> I get the cautions about making changes, but would this one not be prudent? > > >> > > >> I understand contactor failures are rare, but it is also said they wear pretty rough in-service. So why not remove a possible failure mode where you don't realize something is wrong until your engine quits? > > > Okay, recite the narrative for any particular failure. > > > I presume we're talking about Z-14. How would any > > > single failure put engine ops at risk? > > > > > > > > > Bob . . . > > > > I amended that because while I may have been thinking about it in my post I didn't actually discuss it. In any case, referring to Z-14 say the battery contactor opens in flight. Now the main battery bus is disconnected from the alternator, and in this case you have no alternative means to connect it to either alternator, so hopefully flight-critical systems aren't dependent on it. > > > > Additionally, you have no warnings that this has occured. > > Actually the low battery bus warning should activate as soon as the > > > > battery stopped charging. > > However I want the alternator to keep charging even if the battery > contactor is opened by accident or intent. And I want the alternator > charging voltage and the overvoltage protection to apply to the battery > buss with minimal resistance in the sense circuit to the VR circuit. I > want the engine to keep running if the battery goes open circuit. So I > do consider it prudent (but not essential) to connect the alternator as > directly as possible to the battery for my electrically dependent engine. > > Ken > Ken I don't see anything on the architecture drawing that would warn you that the main battery bus has been disconnected from the alternator(s) nuckolls.bob(at)aeroelect wrote: > > Z-14's bus loads have quad redundant > power sources. Every feeder in the > system can get power from multiple > sources. Flight critical loads can be > shared between two systems such that > no single failure puts the flight > at risk. > > > Bob . . . On Z14P, if the battery contactor opens then anything on the main battery bus will run until the 17AH main battery dies, right? If you have things like say, an electronic ignition, or electric fuel pump, that are required for flight you'd chug along completely unaware of the disconnect until your engine died, correct? 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