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That would be interesting to delve into. What is the LG motor rated at? And the CB that tripped? If the CB was, say, twice the rating of the motor, and it still blew (and reset successfully) then I may very well have to revisit my premises. Also if there is evidence that (gawd forbid) fuel pumps get hot enough to draw way over their rated current and trip breakers while still capable of working.
Let's look into this ... Jim S.
sqpilot@bellsouth.net wrote:
Hi, Jim....I'm thinking that the landing gear motor is also not a delicate item, but once it overheated, it tripped the circuit breaker. After the motor cooled, the reset circuit breaker allowed the gear to be cycled to the down position. Can a fuel pump also overheat and trip a breaker or blow a fuse? I don't know the answer to that question. Paul Conner
----- Original Message -----
*From:* Jim Sower <mailto:canarder@frontiernet.net>
*To:* Rotary motors in aircraft <mailto:flyrotary@lancaironline.net>
*Sent:* Sunday, May 01, 2005 10:46 PM
*Subject:* [FlyRotary] Re: Ed's new rotor housings
I'm not convinced of the utility of Circuit Breakers for flight
critical systems. I would put each of my fuel pumps, the EFIs and
what have you on dedicated circuits, each protected with a HEAVY
fuse. My objective is not to protect my fuel pump in case of a
surge. It's a flight critical component, so I'm going to allow it
to go while it can. The fuse is waaaay heavier than the pump (or
whatever) draws, and is meant to protect the wire going to the
mechanism rather than the mechanism itself. I do not regard fuel
pumps as delicate items, so I don't intend to protect them from
transient surges and the like. I will ride it 'till it drops, and
the fuse will blow shortly before the wire melts.
Delicate avionics I might very well protect with CBs. These might
need to be protected from transient surges/voltage spikes (from
whence I cannot say since I have OV protection on my alternator)
and the like.
Heavy duty, robust components like fuel pumps need no such
coddling IMO ... Jim S.
WALTER B KERR wrote:
John Slade wrote:
My understanding is that the pumps, at least the ones I'm using
(or at least WAS using when I used to be able to fly this #@#$ing
<mailto:#@#$ing> thing, long ago), are designed to run
continuously. I have one Walbro Inline fuel pump-GSL393 (from
Tracy) and one Walbro Inline fuel pump-GSL394 from Lightning
Motorsports. Both have metal screw in connectors which fit AN
adapters. They're fused at 20 amps.
----------------------------------------------------------------------
OK, I'll stir the pot some more. I am not an electrical engineer,
but I do understand the power of redunancy!
I will take two separately fused circuits over 1 circuit breaker
every day of the week. If there is a short in my one device or in
the power supply lines, I do not wish to be starting a fire by
resetting circuit breakers while looking for a glider port. I
know there are rotary powered airplanes out there that depend on
one circuit breaker for the entire electrical engine power source
that have many, many more hours of rotary time than me, but I
sleep better have two parallel circuits bringing electrical power
to my fused engine buss and then reduntant pumps on entirely
separate fused circuits. My pumps are both checked during run up
and both on during T/O and landing.
Bernie
Homepage: http://www.flyrotary.com/
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