REFLECTOR:Headset Heartache

Ronnie Brown reflector@tvbf.org
Tue, 23 Sep 2003 15:10:14 -0400


Pulling the alternator field breaker only turns the field voltage off.  The
armature and diodes are still connected to the battery positive.  Some
alternators will still produce some current from residual magnetism even if
the field is shut off.

You have two big batteries on your XL, you should be able to disconnect the
alternator output wire, tape it up good and go fly.

Before you go up, try reseating your avionics.

While you are up there, try cycling everything. Radios, mags, ignition,
intercom, lights, everything!

I had a similar situation on one of my flight tests, it was a humid morning
and I had a loud, bacon frying noise come up on my intercom and radios. I
tried talking to Unicom and they said all they heard was hash.  I turned the
intercom/audio panel off, it went away.  Turned it back on and it came back.
I landed, tried it again and it still was noisy. I attributed it to static
buildup on the glass airframe.  Guess what, it hasn't happened since.  And I
have flown through clouds and rain several times, Hmmmmmm.....  Go figure!!!

Good luck,
Ronnie

----- Original Message -----
From: "Chuck Jensen" <cjensen@dts9000.com>
To: <reflector@tvbf.org>
Sent: Tuesday, September 23, 2003 2:39 PM
Subject: RE: REFLECTOR:Headset Heartache


| When I go to the field later this afternoon, and assuming I can make the
| noise appear again on cue, we'll certainly explore those ideas.  During
the
| test flight, I was real hopefully when I pulled the alternator circuit
| breaker.  The noise died-off almost in snyc with pulling the breaker, was
| quiet for a 5 seconds, then SCP again.  Subsequent cycling showed there
was
| no (dis)connection with the alternator.
|
| However, is it correct to assume that if the alternator breaker is been
| pulled, that that effectively isolates the alternator from the electrical
| system and it would be unable to induce noise to the electrical/audio
| system?
|
| Finally, I've tried to relate hot/cold/humidity/stock market to changes in
| the noise but I find no correlation or commonality.
|
| With that said, I now go forth to slay the electronic dragons.
|
| Chuck Jensen
|
| -----Original Message-----
| From: reflector-admin@tvbf.org [mailto:reflector-admin@tvbf.org]On
| Behalf Of Brian Michalk
| Sent: Tuesday, September 23, 2003 11:38 AM
| To: reflector@tvbf.org
| Subject: RE: REFLECTOR:Headset Heartache
|
|
| > So, this morning, I got the av shop to commit a tech and I agreed
| > to go down
| > to the aerodome so I could run the engine for him to aid in the
| > troubleshooting, since it is quiet running on batteries.  I fired it
|
| Ahh.  There is a clue.
| It is quiet running on batteries, engine not running.
| It is noisy running on batteries, engine running.  -- alternator field off
| It is noisy running on alternator, engine running. -- alternator field on
|
| Perhaps it is the alternator, or something associated with a running
engine.
|
| Check/clean the ground strap to the alternator.
| Check/clean the ground strap to the engine.
| Check/clean the battery ground path (bus).
| --those are easy.
| Remove all electrical cables from the alternator, then run the engine.
See
| if the problem still creeps up.
|
| Unfortunately this seems intermittent, which makes things difficult to
| diagnose.
| Does it get better/worse with humidity, engine temperature or altitude?
|
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