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                           AeroElectric-List Digest Archive
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                     Total Messages Posted Tue 10/24/23: 1
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Today's Message Index:
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     1. 08:42 AM - Re: Pilot accessible B lead CB  (Robert L. Nuckolls, III)
 
 
 
________________________________  Message 1  _____________________________________


Time: 08:42:05 AM PST US
From: "Robert L. Nuckolls, III" <nuckolls.bob@aeroelectric.com>
Subject: Re: AeroElectric-List: Pilot accessible B lead CB

At 12:50 PM 10/23/2023, you wrote:
>Thanks Bob.
>
>I can believe AFS policy of Quick Panels having a B lead CB by 
>default is as much legal CYA as technical. In their defense they 
>cannot control electrical power system implementation or changes on 
>OBAM aircraft.

    To be sure, throughout history of
    electrical systems in aviation, there
    are probably more airplanes with a
    panel mounted breaker to the generator/
    alternator feed than airplanes without.

    There were a couple hundred thousand
    airplanes built with breakers like those
    pictured in the attachment. Non-pullable.

    The 'policy' was to provide mandated
    branch circuit protection from severe
    overload . . . being able to pull a breaker
    to mitigate a runaway alternator condition
    was never a design goal.

    The voltage ratings on breakers, relays
    and switches are based on the ability of
    the device to OPEN a circuit when experiencing
    a specified fault current. A device rated
    (and qualified) at 30 volts DC would
    probably be in deep doo-doo attempting to
    break a runaway alternator's b-lead.

    In many instances policy has more to do
    with tradition than with carefully considered
    failure analysis or design rules for
    accessories. In spite of the fact that
    avionics master switches haven't been
    a real thing for over 50 years, they're
    still a feature on a lot of modern
    airplanes.

    The voltage ratings on breakers, relays
    and switches are based on the ability of
    the device to OPEN a circuit when experiencing
    a specified fault current. A device rated
    (and qualified) at 30 volts DC would
    probably be in deep doo-doo attempting to
    break a runaway alternator's b-lead.


   Bob . . .

                    ////
                   (o o)
    ===========o00o=(_)=o00o========
    < Go ahead, make my day . . .   >
    < show me where I'm wrong.      >
    ================================

    In the interest of creative evolution
    of the-best-we-know-how-to-do based
    on physics and good practice.

 

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