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1. 10:56 AM - Shorted battery caused crash (user9253)
2. 12:36 PM - Re: Shorted battery caused crash (Robert L. Nuckolls, III)
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| Subject: | Shorted battery caused crash |
There is an article on page 50 of the April 2015 issue of Kitplanes Magazine about
aircraft design risks. The article mentions a 2012 crash of a P-51 replica
that made a forced landing after one of the two batteries shorted, resulting
in the stoppage of the electrically dependent engine.
NTSB Report: http://tinyurl.com/nbso2eg
Quote from Kitplanes, ". . .the design must allow the pilot to disconnect the batteries
from each other to prevent dual-battery depletion. This FEW Mustang's
battery connections didn't include a disconnect feature."
Does anyone know what type of batteries these were, flooded or AGM? If an electrically
dependent aircraft with dual batteries experienced an electrical failure
due to a short circuit, either internal to a battery or external, and the
engine and electronics quit, would there be any other symptoms like battery contactors
chattering? Would the pilot know what action to take? Shutting off
one or both battery contactors might seem counter-intuitive if the pilot had not
previously thought about this scenario.
Joe
--------
Joe Gores
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=439046#439046
Message 2
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| Subject: | Re: Shorted battery caused crash |
At 12:55 2015-03-04, you wrote:
>
>There is an article on page 50 of the April 2015 issue of Kitplanes
>Magazine about aircraft design risks. The article mentions a 2012
>crash of a P-51 replica that made a forced landing after one of the
>two batteries shorted, resulting in the stoppage of the electrically
>dependent engine.
>NTSB Report: http://tinyurl.com/nbso2eg
Yeah, read that. Not enough information. The
NTSB assertions MIGHT be correct but even if
so, there is little to be gained from this
event-narrative other than "Be careful out there,
what you don't know might prevent you from
ever knowing further . . ."
I've read perhaps 100 of what I call, "dark-n-stormy
night stories" over the years. I don't recall reading
a single narrative that offered an analysis of
root cause and potential remedy for a design
deficiency. The author's assertions could not
go beyond, "Be attentive and ask around . . .
particularly from informed sources."
From the NTSB probable cause statement:
The pilot reported that there was an electrical system failure during
the cruise portion of the test flight, which resulted in insufficient
voltage to maintain engine operation using either the primary or
secondary battery circuits. Following the total loss of engine power,
the pilot elected to perform a wheels-up landing on a gravel road.
The non-certificated automobile engine that was installed in the
airplane was equipped with a computer-controlled electronic ignition
system and high-pressure fuel pumps. According to the pilot/builder,
the airplane incorporated two 12-volt batteries wired in parallel to
supply voltage to the main power bus to power the engine systems.
Post accident examination revealed that the primary battery had an
internal short and would not take a charge. The secondary battery was
found below normal service voltage, but could be recharged.
Postaccident testing revealed that the two batteries were not
isolated from each other; as a result, an internal short of one of
the two batteries could drain the other battery's charge. No
anomalies were found with the remaining electrical system components
or wiring paths.
The National Transportation Safety Board determines the probable
cause(s) of this accident as follows:
* An internal failure of one of the electrical system's two
batteries combined with the inadequate electrical system design,
which resulted in a total loss of engine power.
Clearly, this system did not benefit from
an artfully conducted FMEA. This had
nothing to do with selection of batteries
but upon how the batteries were implemented.
Just between you and me, I'm skeptical of
the shorted battery thingy . . . if one cell
shorts, it becomes a 10v battery. The alternator
goes into full-bore output in an attempt to
bring it's terminal voltage back to 14+
volts but in any case, system voltage does
not drop below 11 volts.
What was the alternator doing all this time?
Was there any provisions for annunciation
of low voltage?
If his system was not designed to function
at 11+ volts (well short of battery
depletion) then there were probably additional
design features/limits that stacked on top of
each other to ruin his day.
Without seeing the architecture, reading
a narrative of design goals capped off
with tests conducted to verify that the goals were
achieved . . . the article is of little value
beyond that "Be careful" thingy.
Bob . . .
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