nuckolls.bob(at)aeroelect
Guest
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 Posted: Thu Jun 18, 2009 7:24 pm Post subject: Tyco Breakers (Image corrected) |
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| Quote: |
Felt Bob would take umbrage at the phrase the moment I
pressed the send button. Okay, replace "does not approve
of" with "discourages use of". Semantics anywhere but in a
government bureaucracy. |
You put words in my mouth still . . . my offering
of simple ideas for the use of switch breakers
pointed out that fact that switch breakers force
the builder to fabricate a distribution bus on
the panel . . . not unlike the breaker panels typical
of TC aircraft even today.
If one is favorably impressed with fuse blocks,
then the fabrication of bus bars is already
accomplished with a purchased part . . . and
can be mounted remotely from the panel. If one
has fuse blocks, then the only panel real
estate devoted to control/protection are the
necessary switches. All protected circuits
not requiring switches require no panel space.
If one chooses to use a combination of switch/breakers
and circuit/breakers, then the real estate budget
is affected. I prefer and RECOMMEND the low real
estate, low labor, low cost approach but I would
not discourage anyone from wiring their airplane
any way they wish that does not introduce hazardous
failure modes. Certainly choices of breakers, switch-
breakers and/or fuses do not offer great risks.
| Quote: |
<< These are indeed Cadillac breaker/switches . . . with
a price to match. >>
Just went and looked. Airpax style R11-1-[amp] are
available under $15. This is half the AS&S price of the
Tyco thermal circuit breakers used in type certified
aircraft. |
The breakers in common to TC aircraft are mil-spec
devices with price tags commensurate with
their pedigree. There are other commercial/
industrial breakers to be had for less money . . .
the Airpax line you cited is but one.
| Quote: | < But if your system design goals
include achievement of failure tolerant design
then the $extra$ cost only buys you a style
of device and adds nothing to system reliability
for the airplane.>>
Here, Bob and I have disagreed before. To me, the probable
reliability of this life rated switch/circuit breaker and
two connections is not automatically worse than the switch,
wire across the panel to a circuit breaker array and 4
connections setup typical of most aircraft. |
Breakers that assuage concerns for aircraft designers
have terminal bosses compatible with bus bars that
tie multiple devices together. Like . . .
[img]cid:7.1.0.9.0.20090618222044.01c66008(at)aeroelectric.com.2[/img]
The R11 has fast-on tabs that do not lend themselves
to direct connection to bus bars.
[img]cid:7.1.0.9.0.20090618222044.01c66008(at)aeroelectric.com.3[/img]
| Quote: | As I said, my
experience has been good, I'm confident in the reliability
of the device, I like the simplified wiring and also like
the reduced panel usage. |
As to absolute reliability, the numbers are
inversely proportional to parts count and without
a doubt, the breaker/switch is more complex than
the plain switch. Reliability is inarguable.
Bonanza and Baron owners are presently saddled
with some parts-count issues in the utilization
of this breaker/switch . . .
[img]cid:7.1.0.9.0.20090618222044.01c66008(at)aeroelectric.com.4[/img]
It's a sure bet that they're wishing we'd not
strayed from the simple breaker-panel, switch-
panel architecture common to most other airplanes.
This albatross involves about 80,000 fielded
breaker/switches.
But had you chosen fuse blocks and rocker
switches with fast-on tabs, you would be no
greater parts count than using toggle switches
with fast-on tabs. Further, you would not have
to wrestle with the bus-bar connection issues
presented by fast-on tabs.
| Quote: |
<< I've not seen this class of breaker used
anywhere on a TC aircraft of any size or
price. >>
Which is one of the reasons we build experimental aircraft,
so we can use stuff the TC world doesn't. |
Absolutely! An if you're pleased with the outcome
of your choices, I'm pleased for you. But kindly
refrain from mis-representing my mission here on the List.
When I offer a particular recipe for success, it's
supported by an analysis of design goals that
I'm willing to share and explain. There are certainly
other recipes that have met the builder's design goals . . .
yours included.
Bob . . .
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