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0. 06:33 AM - Please Make a Contribution to Support Your Lists... (Matt Dralle)
1. 03:53 PM - Re: YOU BETTER HAVE A PLAN! (Robert L. Nuckolls, III)
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| Subject: | Please Make a Contribution to Support Your Lists... |
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| Subject: | Re: YOU BETTER HAVE A PLAN! |
At 04:23 PM 11/18/2019, you wrote:
>
>I value SIMPLICITY!
>
>While Bob & Stein are absolutely correct in the previous discussion
>about aircraft electrical architecture, I would like to share my perspective.
>Say you actually have an electrical shorting problem and get smoke
>in the cockpit - WHADDAYA' DO NOW?
>
>YOU BETTER HAVE a PLAN! My plan is, one motion, KILL MASTER
>SWITCH; turning off all electrical power. And do anything necessary
>in order to breath some fresh air, including sticking head outside
>window. Often, you only have a very few seconds react and figure
>it all out, or.... GAME OVER!
While smoke (or any untoward smells) in the cockpit
are never a good thing. But the idea that a failing
conductor's noxious output risks become an olfactory
tsunami cries out for an FMEA.
Years ago I did appliance service work from a van that some yahoo had
wired in a burglar alarm by twisting wires together. While driving
down the road at about 40 mph, the darned wiring shorted out and it
was all I could do to get the van stopped and roll out onto the
roadway coughing my brains out; completely oblivious to oncoming
traffic. I was totally incapacitated in mere seconds due to PVC fumes
from melted wiring. The interior of that van had a whole lot more
room to disperse fumes than a typical homebuilt airplane or even my 172.
I'm pleased that your experience had a
happy resolution. But let's do our
FMEA thingy as follows:
How was the failing wire situated in the
vehicle such that an overload of ANY size
would produce smoke? The PRIME DIRECTIVE
all circuit protective devices is: prevent
smoke.
>While I am on this subject, please do not wire your airplane with
>anything but certified aircraft wire (MIL-W-22759). PVC insulated
>crap from the auto store will incapacitate you MUCH sooner. Be
>aware that power cables from accessories and devices never meant to
>be panel installed in certified aircraft have the same danger.
Actually, there is no such thing as 'certified
aircraft wire'. There's a very long list of
wire types flying in T/C aircraft that are
considered flightworthy because they are
part of the ship's type certificate.
It is perfectly acceptable to repair a vintage
aircraft with the same wire that was installed
at the factory . . . this is true all the way
back to uncle Clyde's C-140A that was wired with
cotton over rubber. You used to be able to
buy that stuff (people restoring old cars
were BIG customers). In the 1960s tens of
thousands of s.e. Cessnas were wired with
M19868 type BN (Nylon over PVC). You can
still buy that stuff. Then about 1980
there were about a dozen variations on
'insulation of the day' used throughout
the heavier-than-air industries and yeah,
the Wichita crowd came down on the side
of Tefzel.
But I can assure you, if you 'smoke' a
Tefzel wire in your airplane, you're
not going to find it any more pleasant
than a smoking cotton over rubber wire
in your nice ol' C140 or a nylon over
PVC in your vintage C172,
>As I said, I value simplicity.
>What electrical devices do I need to get my airplane safely back on
>the ground? Answer: ABSOLUTELY NOTHING!
>Can I safely land without flaps or radio or anything else
>electrical? Answer: YES - magneto ignition and flying VFR only.
>Would I rather be flying a homebuilt Van's RV? Answer: You better
>believe it; but I am too darned old now and consider myself very
>lucky to keep what I already have (wife included).
May I suggest an alternative . . . don't
allow any wire a potential to make smoke.
I.e. offer proper protection based
on artful FMEA.
>If you have an electrically dependent airplane.... Good luck with that!
>You had better make those systems very robust and completely
>isolated from the rest as much as humanly possible.
Yup, that's what battery busses are for.
>AND, electronic ignition is great and can offer advantages as long
>as you retain ONE stock magneto. Don't be fooled by marketeer
>nonsense that can kill you. Yeah, I know that I am going to take
>some heat from this; especially since all GA is headed toward EFI
>and total electrical dependency, but I stand my ground.
>
>Keep the odds on your side.
There are electronic ignitions that come with
their own, built in power supplies. There are
also ways to architecture buss-powered ignition
systems to function independent of each other.
It's a decades old technology with a track-record.
Bottom line is that the 'better plan' is not
difficult to put in place . . . it's been
done for over a century with great success.
Bob . . .
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