Thanks for your response.

We flew it with the alternator field turned off, no change, which I
think rules out the charging system. I'll get him to do an in-flight
mag check when he gets it out of annual to see if it goes away on one
set or the other, good idea.

The noise is an impulse noise, could be ignition noise except it doesn't
seem to change at all with RPM. It does seem to be related to vibration
however, so I suppose a marginal ignition lead could do it. It comes
across as bursts of static. Not sure really how to describe it.


nrp wrote:

Ray -

What type A/C and engine? If you have a belt driven alternator, drive
it with an hand held electric motor & see if you can get the noise.
Might it be a mechanical voltage regulator points chattering (which
they do all the time), but without any of the arc suppression ballast
resistors having continuity on the back side of the regulator, in
which case they could radiate a lot of noise.

A better description of the noise would really help. Can I assume it
is not magneto related? (i. e. have you tried operation on each
mag?)