Today's Message Index:
----------------------
1. 08:43 AM - Switch-Breakers (Neal George)
2. 11:41 AM - Re: Switch-Breakers (Robert L. Nuckolls, III)
3. 11:57 AM - Re: Switch-Breakers (Charlie England)
4. 12:42 PM - Re: Switch-Breakers (Robert L. Nuckolls, III)
5. 01:06 PM - Re: Switch-Breakers (Neal George)
6. 03:54 PM - Re: Switch-Breakers (Robert L. Nuckolls, III)
Message 1
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Bob -
What are your thoughts on using switch-breakers for items that are switched frequently,
such as landing lights?
Im under the impression that they should be reserved for occasional use items,
such as Pitot Heat.
Neal
Message 2
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| Subject: | Re: Switch-Breakers |
At 10:42 AM 1/6/2023, you wrote:
Bob -
What are your thoughts on using switch-breakers
for items that are switched frequently, such as landing lights?
I=99m under the impression that they should be
reserved for occasional use items, such as Pitot Heat.
There was a HUGE kerfuffle at Beech during my tenure
there concerning failures of W31 series switch-breakers
in Bonanzas and Barons. These ships used W31 switch
breakers for ALL of pilot operated switches.
It seems that SOMETIME during the Beech incorporation
of these breakers, a change was made that removed
a tiny bit of insulating material from under a
spring.
This was a new layer of 'swiss cheese' in the
potential for generating a hazardous condition.
Here are documents I've saved from the work
product I generated for the failure investigation.
https://tinyurl.com/2zttqpqt
I thought I had a copy of the failure analysis
narrative but that seems not to be in the library.
Nonetheless, it seems that failure of all the jumper
'cable' strands preceded loading the spring with
the current being carried in the switch. For light
loads, this didn't seem to generate an alarming
event. ONE of these switches in the Bonanza carried
prop de-ice current. This switch would not be a
high duty cycle device . . . none the less, one
fielded aircraft suffered a failure of jumper
strands followed by a catastrophic heating event
in the spring that resulted in much smoke and
bad smells in the cockpit.
So . . . lots of slices of cheese had to line up
to bring this difficulty to the forefront. But given
that there were probably 80,000 switches out there
in Beech products (Not to mention Cessnas too), This
was not a trivial concern . . . ESPECIALLY since
the existence of the insulator could not be
verified by inspection.
So, the short answer to your question is: "Probably
no big deal. All new switches have the insulator."
HOWEVER, keep in mind that when the pilot control
device is combined with the fault protection for that
branch, ship's BUS structure is extended to the
hot side of each control . . . not unlike the special
hat dance we do for the 5A crowbar breaker in fuseblock
fitted airplanes.
Bob . . .
Un impeachable logic: George Carlin asked, "If black boxes
survive crashes, why don't they make the whole airplane
out of that stuff?"
Message 3
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| Subject: | Re: Switch-Breakers |
On Fri, Jan 6, 2023 at 1:44 PM Robert L. Nuckolls, III <
nuckolls.bob@aeroelectric.com> wrote:
> At 10:42 AM 1/6/2023, you wrote:
> neal.george@gmail.com>
>
> Bob -
> What are your thoughts on using switch-breakers for items that are
> switched frequently, such as landing lights?
>
> I=C3=A2=82=AC=84=A2m under the impression that they should be reser
ved for occasional use
> items, such as Pitot Heat.
>
>
> There was a HUGE kerfuffle at Beech during my tenure
> there concerning failures of W31 series switch-breakers
> in Bonanzas and Barons. These ships used W31 switch
> breakers for ALL of pilot operated switches.
>
> It seems that SOMETIME during the Beech incorporation
> of these breakers, a change was made that removed
> a tiny bit of insulating material from under a
> spring.
>
> This was a new layer of 'swiss cheese' in the
> potential for generating a hazardous condition.
> Here are documents I've saved from the work
> product I generated for the failure investigation.
>
> https://tinyurl.com/2zttqpqt
>
> I thought I had a copy of the failure analysis
> narrative but that seems not to be in the library.
> Nonetheless, it seems that failure of all the jumper
> 'cable' strands preceded loading the spring with
> the current being carried in the switch. For light
> loads, this didn't seem to generate an alarming
> event. ONE of these switches in the Bonanza carried
> prop de-ice current. This switch would not be a
> high duty cycle device . . . none the less, one
> fielded aircraft suffered a failure of jumper
> strands followed by a catastrophic heating event
> in the spring that resulted in much smoke and
> bad smells in the cockpit.
>
> So . . . lots of slices of cheese had to line up
> to bring this difficulty to the forefront. But given
> that there were probably 80,000 switches out there
> in Beech products (Not to mention Cessnas too), This
> was not a trivial concern . . . ESPECIALLY since
> the existence of the insulator could not be
> verified by inspection.
>
> So, the short answer to your question is: "Probably
> no big deal. All new switches have the insulator."
>
> HOWEVER, keep in mind that when the pilot control
> device is combined with the fault protection for that
> branch, ship's BUS structure is extended to the
> hot side of each control . . . not unlike the special
> hat dance we do for the 5A crowbar breaker in fuseblock
> fitted airplanes.
>
>
> Bob . . .
>
Not to mention the fact that two or three of them will pay for just about
all the fuseblocks & fuses (and maybe some of the wire) we'd need to wire a
decent panel...
Charlie
Message 4
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| Subject: | Re: Switch-Breakers |
>
>Not to mention the fact that two or three of
>them will pay for just about all the fuseblocks=C2
>& fuses (and maybe some of the wire) we'd need to wire a decent panel...
>
>Charlie
And there IS that!
Bob . . .
Un impeachable logic: George Carlin asked, "If black boxes
survive crashes, why don't they make the whole airplane
out of that stuff?"
Message 5
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| Subject: | Re: Switch-Breakers |
Thanks Gentlemen =93
I don=99t disagree, but since I=99m refitting a Bonanza, I don=99t think I
can go quite that far
Neal George
Not to mention the fact that two or three of them will pay for just about a
ll the fuseblocks=C3=82 & fuses (and maybe some of the wire) we'd need to wire
a
decent panel...
Charlie
And there IS that!
Bob . . .
Un impeachable logic: George Carlin asked, "If black boxes
survive crashes, why don't they make the whole airplane
out of that stuff?"
Message 6
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| Subject: | Re: Switch-Breakers |
At 03:06 PM 1/6/2023, you wrote:
>Thanks Gentlemen '
>
>I don't disagree, but since I'm refitting a Bonanza, I don't
>think I can go quite that far=85
Hmmmm . . . yeah . . . that T/C parts list
can be a real drag.
Bob . . .
Un impeachable logic: George Carlin asked, "If black boxes
survive crashes, why don't they make the whole airplane
out of that stuff?"
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