I had this problem. My solution was to use the radio to switch between
mic's using the menu system. The first one I tried (KR2) was no good - the
boom mic would break through with the engine on. Then I exchanged that for
an ATR833 and this totally suppressed the unused mic. The trick is to wire
the PTT switch to both Left and Right channels and just use the radio to
select Left (headset mic.) or Right (boom mic.)

I believe that DG use a relay that switches automatically with the engine
circuit. A complication ready to fail if you ask me!

Frankly, I rarely use the boom mic, I just put the headset behind the
headrest and use the headset mic. which is possibly better than the dynamic
boom mic because it is noise cancelling by design (the sound from both
sides cancels out). I am tempted to remove the boom mic. because it is in
the way, except that is a back-up....

End of message...

At 16:03 25 April 2014, Paul Remde wrote:
Hi,

I am trying to help a customer out with a motorglider microphone wiring
question. I'm hoping someone here will have a suggestion.

Motorgliders often have both boom microphones and aviation headsets.
Obviously, the headsets are used when the motor is running and the boom
microphones are used when in gliding mode. It wouldn't work well to leave

the boom microphones live when the aviation headsets are in use because
they
would pickup the engine noise. How are motorgliders wired so that only
the

headset mics are used when the headsets are plugged in?

I suppose that a "boom mic enable" switch could be used to disable the
boom

mics when not in use. But I think there is a way to have the boom
microphones disabled by a switch being opened mechanically when the
headset

mic plug is plugged into the mic jack. Standard aviation mic jacks don't

have any way to accommodate that. Any suggestions?

The goal is to make it intuitive for the pilot - and reliable.

Best Regards,

Paul Remde