Today's Message Index:
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1. 09:05 AM - Re: Re: Switch Question (Robert L. Nuckolls, III)
2. 09:38 AM - Re: Switch Question (user9253)
3. 10:31 AM - Re: Re: Switch Question (Robert L. Nuckolls, III)
4. 12:50 PM - Re: Switch Question (farmrjohn)
5. 04:03 PM - Re: Re: Switch Question (Robert L. Nuckolls, III)
Message 1
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| Subject: | Re: Switch Question |
At 06:14 PM 12/14/2023, you wrote:
>
>Reviving an old thread, when the original generator was swapped out
>for an alternator they utilizedg only one pole of the two pole
>switch to connect the batter to the bus, leaving the other side unused.
>Would it be possible to utilize the unused poles to control a master
>contractor leaving the heavy wiring from the batter to the switch
>in place? That way when the switch was closed it would energize the
>contractor and allow the connection to the bus, and provide a backup
>method of disconnecting the battery should the contractor fail
>closed for any reason. This is in anticipation of pursuing a
>field approval for a contacor. Thanks, John
Have you engaged an IA to assist in fabricating
an Form 337 likely to be summarily approved?
Find the maintenance manual drawings for the first
airplane of the series that replaced the
battery switch with a contactor. This is 'approved
data'. Duplicate the architecture of that
drawing in support of your 337 goes along way
to getting it approved.
Your risk of contactor-failure-by-sticking-
closed is more remote now than it was 70
years ago. I've never heard of a 'back up
battery disconnect' in any aircraft.
Imitation is a demonstrated form of flattery . . .
it's also a demonstrated prophylactic
against bureaucratic disapproval. What
airplane are we talking about? I may
have the drawings you need in my library.
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.
Message 2
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| Subject: | Re: Switch Question |
His airplane is an Alon Aircoupe that Univair now has the TCSD for.
--------
Joe Gores
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=512789#512789
Message 3
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| Subject: | Re: Switch Question |
At 11:37 AM 12/15/2023, you wrote:
>
>His airplane is an Alon Aircoupe that Univair now has the TCSD for.
>
>--------
>Joe Gores
Okay, thanks Joe.
It' been 20 years since I was last involved in any
'certifiable' field work on a TC aircraft so I dug
back into some old files.
There were individuals certificated by the FAA
to accomplish various tasks. There are also
various levels of documentation needed to support
the project implementation.
As I recall, there are 'repairs' and 'alterations.'
They're also divided into 'major' and 'minor'
classifications. Minor alternations are those
that do not change performance of the airplane.
This generally defined as less than 1 pound
difference in empty weight of the aircraft
(hence no change to w/b). No changes needed
to the pilot's operating handbook. No alterations
to any structural component of the airframe
(like holes thru a spar).
The proposed swap from manual battery switch
to battery contactor could certainly fall in
the minor category (unless you want to drill
the spar carrythru to mount the contactor!)
Check with your local FAA certified talent
but waaayyy back when, I believe such a change
could be accomplished with a log book entry
by an appropriately qualified practitioner.
No 337 necessary.
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.
Message 4
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| Subject: | Re: Switch Question |
Here is the original wiring diagram from the Alon maintenance manual (if I successfully
added the attachment). The wiring has changed with the addition of an
alternator in place of a battery. The circuit for field "F" on the regulator
now comes via the alternator rather than the top pole of the switch as depicted.
Looking at the current definition for minor alteration the question is does the
addition of a contractor constitute a change to the basic design of the system.
My IA and myself don't think so but I'm a bit concerned looking forward to
a pre-sale inspection and the buyer's inspector thinking otherwise. A 337 field
approval should eliminate any doubt in that case. John
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=512791#512791
Attachments:
http://forums.matronics.com//files/aircoupe_electrical_system_213.pdf
Message 5
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| Subject: | Re: Switch Question |
At 02:49 PM 12/15/2023, you wrote:
>
>Here is the original wiring diagram from the Alon maintenance manual
>(if I successfully added the attachment). The wiring has changed
>with the addition of an alternator in place of a battery. The
>circuit for field "F" on the regulator now comes via the alternator
>rather than the top pole of the switch as depicted.
That's an architecture 'cartoon' common to most
pilot's operating handbook for light aircraft.
Drew up lots of them at Cessna. 'Approved data'
would be from any 'hammer-n-tongs' document.
At Cessna, our factory wirebook drawings were
published in the maintenance manuals.
Aircraft of this era may not have enjoyed this
kind of documentation. I only have first hand
knowledge of Beech, Cessna and Lear . . . places
I've worked. That airplane may not ever
have been graced with a factory battery
contactor installation. It just means you don't
have an 'approved' factory document . . . doesn't
mean the drawing you attach to your 337 would
not be approved. An alternator swap would
always require a 337; it changes
weight and balance and might be need to be
tested for adequate cooling at best angle
of climb (depending on mood of the approving
authority).
Swapping a switch for a contactor is zero
risk and doesn't impact performance, w/b or
operating instructions i.e. MINOR . . .
no change of functionality.
>Looking at the current definition for minor alteration the question
>is does the addition of a contractor constitute a change to the
>basic design of the system. My IA and myself don't think so but I'm
>a bit concerned looking forward to a pre-sale inspection and the
>buyer's inspector thinking otherwise. A 337 field approval should
>eliminate any doubt in that case. John
You're asking 'hair dressers' about 'heart
surgery'. The authority resides with the
individual who signs off the installation.
If uncertain, that individual should/would
consult with the local FSDO.
A 337 adds to the FSDO workload . . . the
gotta file the thing. Have your IA check
it out with them . . . THEY are the
'surgeons'.
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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