X-Mozilla-Keys:                                                                                 

Ken Powell wrote:

The alternator on my car caught fire this morning on the drive in to
work.  By the time that I got stopped and the hood raised, the
alternator (and the wiring around it) was gloriously aflame!  I have a
battery disconnect on the battery so I was able to cut off the power
and put the flames out.  I haven't had chance to evaluate the damage
to the electrical system, but otherwise the car was not damaged.

However, this was a real wakeup call for me; what if this had been at
10,000 ft.  I readily admit that electrical systems are not my strong
point, but I need to address this failure mode for my airplane.  I
will probably follow Tracy's design, but I also need to study Bob
Nucholls' book for guidance.  BTW, I think that I favor the dual
alternator rather than the dual battery approach to redundancy, but

I'm open to other arguments.  I think that either Tracy or Bill
Freeman mentioned using an alternator that can be shut down if a
runaway voltage condition exits.   I remember these 2 guys discussing
some of this stuff a few months back, along with other guidance from
of the rest of you - thanks.  Gotta go to the CD to see if I can find
those posts.  Also, I think maybe a Halon system is a good idea
afterall.

This is just a note to remind everyone that this stuff really can
happen.  We have to be careful and learn from each other.  Thanks to
everyone for trying to keep each other safe.

Ken Powell

Bill Freeman wrote:

Bob Nucholls has a neat
system he recommends to protect you from a runaway alternator.
Basically it forces the main alt fuse to blow, protecting you and your
wiring and your butt.  It is important to have the ability to manually
shut down your alternator, AND an automatic overload device
- big fuse or (in my case) 60 amp circuit breaker.  When your
regulator fails "on", the alt output goes essentially unlimited
and will fry everything in the system, and needs to be shut down
PRONTO.

Smart thing to have a battery disconnect.  I have "been there, done that"
on a friend's car when the (unfused) ammeter wire shorted.  Yikes!
Hard to pry those terminals off in a hurry.  And we could just pull over
and hop out.

Bill

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