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nuckolls.bob(at)aeroelect
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 Posted: Mon May 09, 2022 2:48 am Post subject: The value of FMEA |
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I'll encourage everyone to view this video on youtube.
It's an excellent demonstration of competent flight testing
but a sobering example of hazards to accomplish
a competent FMEA.
Electrical system details are offered at about 44
minutes into the video.
https://youtu.be/4PHTVTw_Y2A
Failure of the engine in this story reminds me of
the LancAir IVP accident where ignition system
was designed to fail.
We don't have enough wiring detail to do an
after action debrief on this incident but I
hope it's strong incentive to get our homework
done before we take the active.
Bob . . .
Un impeachable logic: George Carlin asked, "If black boxes
survive crashes, why don't they make the whole airplane
out of that stuff?"
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user9253
Joined: 28 Mar 2008
Posts: 1921
Location: Riley TWP Michigan
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| Posted: Mon May 09, 2022 9:46 am Post subject: Re: The value of FMEA |
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If the accident aircraft had been wired per Z-101, the engine would not have quit and electrical power to the main
power bus would not have been lost. Of course the plane still would have crashed because the landing gear failed.
If the 30 amp circuit breaker had not been installed to protect the main power bus, then the main power
bus would not have lost electrical power. A fuselink would have been a better choice than a circuit breaker.
Most small planes do not have any short circuit protection for the main bus other than the battery contactor.
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nuckolls.bob(at)aeroelect
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| Posted: Mon May 09, 2022 10:20 am Post subject: The value of FMEA |
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At 12:46 PM 5/9/2022, you wrote:
| Quote: | --> AeroElectric-List message posted by: "user9253" <fransew(at)gmail.com>
If the accident aircraft had been wired per Z-101, the engine would not have quit and electrical power to the main
power bus would not have been lost. Of course the plane still would have crashed because the landing gear failed.
If the 30 amp circuit breaker had not been installed to protect the main power bus, then the main power
bus would not have lost electrical power. A fuselink would have been a better choice than a circuit breaker.
Most small planes do not have any short circuit protection for the main bus other than the battery contactor. |
Precisely. Any circuit protection upstream of
dedicated feeder protection should have been
ROBUST . . . like a current limiter. It would
be interesting to see the gear control/annunciation
logic. I think I would have preferred to shut the
pump off based on pressure . . . not limit switches.
I would power the hydraulic system thru a current
limiter at the battery contactor. Engine
critical devices need their own, dedicated
bus structure with SHORT access to the
well maintained battery.
Do I recall that he experienced engine stoppage
earlier in the flight as well?
Having a properly responding engine might
have mitigated the outcome if he had
more options for energy management during
approach/touchdown . . . but yeah
that gear collapse was a game changer.
Bob . . .
Un impeachable logic: George Carlin asked, "If black boxes
survive crashes, why don't they make the whole airplane
out of that stuff?"
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johnbright
Joined: 14 Dec 2011
Posts: 165
Location: Newport News, VA
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| Posted: Tue May 10, 2022 3:01 pm Post subject: Re: The value of FMEA |
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| nuckolls.bob(at)aeroelect wrote: | | ... Do I recall that he experienced engine stoppage earlier in the flight as well?.... |
Engine stumbled at 36:17 in the video... went from 4k to 1k rpm and back up to 4k twice.
At 42:13 in the video the engine quit.
At 43:00 in the video he mentions checking switches and circuit breakers but it's not clear to me he checked the 30A main bus breaker that is higher up on the right. By this time he had tried to shake the gear down a couple times and he was glide-able to the airport.
Events are tabulated at 50.37 in the video... clip of table attached here. Stumble at flight time 45:46 and quit at 56:11.
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_________________
John Bright, RV-6A, at FWF, O-360
Z-101 single batt dual alt SDS EM-5-F.
john_s_bright@yahoo.com, Newport News, Va
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stuart(at)stuarthutchison
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| Posted: Tue May 10, 2022 7:15 pm Post subject: The value of FMEA |
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He makes the point that he was distracted by various things … we know why. It was interesting that the low voltage idiot light was flashing for so long unnoticed, which ought to be a bold face emergency action item with an electrically dependent engine. It really doesn’t matter much what is fault or design flaw is causing the low voltage at that point (except maybe checking the Alternator switch and field CB hasn’t tripped) because the engine is inevitably about to stop … an obvious priority.
Kind regards, Stu
Sent from my iPhone
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