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Well, Jim
We certain will each go in the direction that we
feel best meets our needs. In my opinion, nothing is lost by using a
CB instead of a fuse. Even if its a rare event
- whereby a temporary overload condition exists, once a fuse is blow
- that's it, no second chance. However, if I were going to use
fuses in flight critical components (which I won't) I would certainly make them
"slow-blow" fuses. Like I said nothing against fuses in their place, I do
use fuses in non-critical components.
Ed
----- Original Message -----
Sent: Sunday, May 01, 2005 11:46 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 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
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