Hey Tom,
Out of reach? Why would you have them out
of reach? Would that be poor design? Not really.
It sounds like your only concern is not whether
to use breakers or fuses from a performance perspective but that the fuses
would be out of reach.
Once a breaker “pops/breaks” in
the air, should the pilot know something is wrong and perhaps shouldn’t
push the breaker again only to make it do its job again? Once maybe. If a fuse
blows should you replace it in flight? Maybe – once.
Fuses weight much less. Cost much less.
Cost/performance goes to the fuse. Do the same job with caveats. Both are
overload protectors.
CBs do a better job when the load is widely
variable. They are comparatively complex – an electromechanical device. They
can be designed to trip quickly – quicker than fuses. When the load is
constant from start to finish, on to off, fuses may be a better choice. If a
breaker fails, the cost (physical replacement and cost replacement) is enormous
compared to a fuse.
Aircraft interiors experience extreme
variables in temperature, humidity and mechanical vibration degrading breakers.
Fuses win out there.
Investigate the options ad infinitum. Pay
your money and take your chances.
Jim
From: Lancair Mailing
List [mailto:lml@lancaironline.net] On Behalf
Of Tom & Beth Sullivan
Sent: Sunday, April 28, 2013 8:19
AM
To: lml@lancaironline.net
Subject: [LML] Circuit Breakers
vs. fuses
Returning from Sun & Fun a few weeks ago, I
had stopped in Asheville NC to pick up my wife and see my dad. It had
rained really hard while I was in Lakeland and I suspect some water
penetrated the TKS panels on the wings (Mooney Rocket). Flew back to the
U.P. of MI non-stop at FL 180 until about Lake Michigan where I needed FL 220
to stay out of clouds and significant icing. (N1017L for those Flight
Aware addicts).
About 10 minutes before penetrating the precip
I turned the TKS on to high mode and after a couple minutes, no fluid?
Looked at the control panel and no lights; looked at the circuit breaker and it
had popped. I tried it again and it popped after about 30 seconds.
Oh crap! Reset breaker and tried de-ice on low mode, and it ran
fine. Luckily it ran enough fluid to keep the ice off through the 30
minute decent. When I was a couple minutes from breaking out (based
on my home bas KIMT AWOS report), I tried high mode again and it
worked fine. As noted above, I suspect a bit of water in the panels had
froze up in the flight levels, and the "low" TKS power setting must
have done the trick.
Now, what if I had "fuses" located out of reach??
Will be wiring up the IVPT soon and using breakers. It
is still up to the operator to use enough common sense to keep a breaker system
safe.