nuckolls.bob(at)aeroelect
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 Posted: Wed Jan 06, 2010 8:56 am Post subject: [AeroElectric-List] Questions about circuit protection |
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At 07:00 PM 1/5/2010, you wrote:
| Quote: | Bob
I really don’t want to resuscitate this discussion but, even being aware of the technical advantages of fuses versus circuit breakers, it is indeed almost impossible to convince a pilot that a fuse is better than a circuit breaker. |
It has never been offered as 'better' . . . only
adequate to the task of meeting design goals in
a failure tolerant system.
| Quote: | | In flight, when a fuse blows, the pilot will hardly notice it, and even if some device (whose circuit was protected by that fuse) becomes blank, he will not know if it was the fuse or anything else that caused that device to die. |
Have you read . . .
http://www.aeroelectric.com/articles/fusvbkr2.html
| Quote: | If a circuit breaker pops out, there is a big probability the pilot will immediately notice it, or at least after seeing any device die, he will immediately look to the circuit breakers heads to look for the one that popped out.
Being a pilot trained for so many things, he must also know that he shall not push that particular breaker in, unless he wants to light up the fire which will burn his own ass… |
It's not clear that you embrace/understand the
rationale presented for unreachable fuse-blocks.
Certainly everyone has a choice to make and
in the final analysis it's personal. I did a
power distribution diagram for the BD-10 jet
about 15 years ago. I bounced the idea of fuse-blocks
off the electrical systems wienie. He agreed that
they were adequate to the task but opined that
anyone building a BD-10 wanted that "busy fighter
cockpit look. The more knobs, buttons and switches
the better." But even after the drawing was completed
using breakers throughout, he about had a cow when
I put about a dozen breakers back in the engine
compartment. The architecture called for protection
in these feeders and the sources for those feeders
were in the tail. Further, there was no failure
mode effects analysis that supported any need for
pilot access to these breakers whatsoever. Nonetheless,
he insisted on having all breakers in the cockpit.
I submitted my bill for work accomplished to date
and bowed out of the project. Got a nastygram from
Mr. Bede hisself honking about the fee and stating
that his electro-wienie wasn't authorized to make
contracts. I settled for 50 cents on the dollar
and chalked it up to the fates.
Have you identified errors in the logic offered in many
published pieces on the website and here on the
List that speak to suitability of fuses? If not,
then like the BD-10 episode, it's a matter of preference.
Breakers and their panels are not unsafe. They're
only heavier, more expensive, take up panel space,
require hours of fabrication time, restrict
wire bundle routing options, offer no enhanced level
of safety and MAY be distracting to a pilot who should
be doing more important things.
But if one chooses breakers, they're in good company.
The vast majority of the GA fleet is carrying tons
of them around the sky with a vanishingly small
probability that any single breaker will ever be
called upon to do its job.
Bob . . .
[quote][b]
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