Today's Message Index:
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1. 03:12 AM - Always hot wire to panel (GTH)
2. 06:13 AM - Re: Always hot wire to panel (GTH)
3. 06:54 AM - Re: Always hot wire to panel (user9253)
4. 07:21 AM - Re: Re: Always hot wire to panel (GTH)
5. 08:42 AM - Re: Always hot wire to panel (Robert L. Nuckolls, III)
6. 09:59 AM - Dual Battery design (Hariharan Gopalan)
7. 10:39 AM - Re: Dual Battery design (Hariharan Gopalan)
8. 07:49 PM - Re: Dual Battery design (user9253)
Message 1
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| Subject: | Always hot wire to panel |
Hi all,
Could anyone point me to a text or reference document mentioning the
rule about limiting the rating of always hot battery wires such as the
wire from battery contactor to Master Switch ?
Thanks in advance,
--
Best regards,
Gilles
http://contrails.free.fr
http://lapierre.skunkworks.free.fr
Message 2
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| Subject: | Re: Always hot wire to panel |
>
>
> Could anyone point me to a text or reference document mentioning the
> rule about limiting the rating of always hot battery wires such as the
> wire from battery contactor to Master Switch ? /
Hi again,
I believe I got them :
FAR Part 23-1361 (b)(1)
CS 23.1361 (b)(2)
--
Best regards,
Gilles
http://contrails.free.fr
http://lapierre.skunkworks.free.fr
Message 3
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| Subject: | Re: Always hot wire to panel |
Usually the negative side of the master contactor coil is switched. So there is
no always hot wire running into the cockpit from the master contactor.
--------
Joe Gores
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=465241#465241
Message 4
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| Subject: | Re: Always hot wire to panel |
Le 19/01/2017 15:52, user9253 a crit :
>
> Usually the negative side of the master contactor coil is switched. So there
is no always hot wire running into the cockpit from the master contactor.
>
Joe,
Thank you for your response.
Just to be sure, isn't this wire from the contactor coil to the panel
switch permanently "hot", albeit through the contactor coil ?
--
Best regards,
Gilles
http://contrails.free.fr
http://lapierre.skunkworks.free.fr
Message 5
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| Subject: | Re: Always hot wire to panel |
At 08:10 AM 1/19/2017, you wrote:
>><mailto:gilles.thesee@free.fr><gilles.thesee@free.fr>
>>
>>
>>Could anyone point me to a text or reference document mentioning
>>the rule about limiting the rating of always hot battery wires such
>>as the wire from battery contactor to Master Switch ?
The 'rules' pertain only to those wires which
elevate risks during MAJOR deformation of the
airframe. The contractor-to-master switch
wire is not a 'feeder' in any sense . . . rather
a control wire. Further, current in that wire
is limited by the resistance in the battery
contactor coil.
In this case, an elevation of risk would be
driven by the probability of damage that
takes the wire to ground . . . of course,
this would RE-CLOSE a contactor that the
pilot purposefully OPENED in preparation
for the extra-ordinarily hard landing.
Probability of this being a factor in post
crash scenarios is exceedingly small . . .
if things are so badly munched that the wire
gets grounded, then consequences for having
re-closed the contactor are irrelevant.
The rules are not limited to feeders 'to the
panel' . . . but to anywhere in the airframe.
The 5A limit is more a 'rule of thumb' having
history back as far as I can remember . . . heard
it first at Cessna in '64.
As a matter of demonstrable physics, an artfully
crafted rule would limit ENERGY dissipated in the
fault . . . as opposed to simply limiting current.
I'd feel more comfortable about a 10A fuse off
the battery bus than a 5A breaker. Given that
energy rates are based on Voltage(squared), the
hazards presented by a 5A breaker off a 24 volt
battery are 4x those presented by a 12 volts,
There is a HUGE range of reaction times for electronic
breakers, magnetic breakers, thermal breakers,
fuses, current limiters, etc. etc. Hence, the 5A rule
is a VERY broad brush. This topic is a VERY
tiny concern in the grand scheme of things.
I recall a comment by a greybeard in the accident
investigation world at Beech who once shared the
observation, "If the airplane burns, the battery
is likely to still be in the airplane. If the airplane
did not burn, go look for where the battery landed
after it was ejected."
An interesting anecdote for which I have no
personal knowledge. But it does re-enforce a notion
that risks to airframe and passengers are orders
of magnitude greater for reasons not even
remotely associated with choices of circuit
protection.
Bob . . .
Message 6
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| Subject: | Dual Battery design |
I was originally planning on using the Z19B, but came across a print out of
what looks like a much simpler dual batter design. Not sure where I printed
this from, but this surely looks like an aeroelectric design and can not
find this in the 12th edition book.
could someone please see if they recognize this and enlighten me?
Thanks
Hari
Message 7
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| Subject: | Re: Dual Battery design |
Forgot the attachment.
On Thu, Jan 19, 2017 at 9:55 AM, Hariharan Gopalan <rdu.hari@gmail.com>
wrote:
> I was originally planning on using the Z19B, but came across a print out
> of what looks like a much simpler dual batter design. Not sure where I
> printed this from, but this surely looks like an aeroelectric design and
> can not find this in the 12th edition book.
>
> could someone please see if they recognize this and enlighten me?
>
> Thanks
> Hari
>
Message 8
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| Subject: | Re: Dual Battery design |
That is not one of Bob N's schematics. It has some major flaws.
The starter current goes through the ammeter shunt.
The E-bus relay coil appears to be always grounded but is not.
The 4 pole switch is a single failure point.
The 20 amp circuit breaker for the starter contactor and solenoid seems too big.
The 200 amp ANL alternator current limiter seems way too big.
The 200 amp ANL battery current limiters are unnecessary and should not be in series
with starter motor.
--------
Joe Gores
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=465264#465264
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