Elusive radio / intercom problems

My son and I have a factory-built "certified" 2014 RV-12 S-LSA with Dynon avionics on leaseback to a local flight school. The plane has a persistent problem with radio and/or intercom static and popping. It seems to be worse during hot weather. We've tried everything we can think of, including replacing the headset plugs. Here's a report from one of the instructors yesterday and today:

From Alan's evening flight in N259VA yesterday:

In 259VA right now, radio started popping and squealing during runup when everything heated up. Will keep you posted on if it gets better during the flight.

Cruised at 5500’, 62 degrees F at that altitude. After about 20min at cruise we heard some popping and then the radio returned to normal and was clear with no squealing. Will keep you posted on what happens during the return leg to CHA.

About to land, cruised home at 6500’ 60 degrees F outside air temp, no radio issues coming home. No radio issues on the taxi back either.

From Alan's flight today, 7/9, in N259VA -

1230p startup, 88 degrees F on the ground. Radio/intercom started squealing during taxi, remained that way until through runup, departure, climb. After about 20min at cruise (6500' 60 degrees F) the squealing stopped and radio/intercom returned to normal. Normal radio/intercom during climb out and cruise back to CHA. Touch and go at CHA then cruised 3500’ 72 degrees F to Cleveland. After 5min at cruise the radio started popping and then the squealing resumed. Radio/intercom returned to normal during climb out at Cleveland (1500’ and climbing 82 degrees F) and remained normal operation the rest of the flight home and during taxi back to the hanger. It surprised me when it got better on climb out after landing at Cleveland because it was still hot outside at that altitude

Help! Any ideas would be appreciated. We have the first MOSAIC RV-12iST being delivered at Oshkosh and we need to sell this plane to make room for the new one. N250VA is currently advertised on Barnstormers and we need to get this problem solved for the next owner. Thank you!

Tom Snow, Chattanooga, TN, 423-364-5377, [email protected]

Tom, this won’t solve your problem but I’d suggest swapping radios between your planes to see if the issue follows the ratio or stays with the airframe. A radio problem would be the easiest to address.

Here are some of the things we have already done (after reading other threads here on VAF):

- swapped the AV-50000A box for a factory new one
- swapped radios (garmin factory service exchange)
- swapped headset jacks on both sides with new harness from vans
- Swapped voltage regulators
- swapped engines! (well, that was because we hit 2000 hr tbo)
- added an extra ground at the radio stack
- Tried adding the rotax blue capacitor.
- checked the antenna, and antenna wiring on both ends.

Are the headset jacks mounted with insulating washers so that they are only grounded at the instrument panel end?
Check all of the D-Sub connectors for poor crimps and for pins that are not seated properly.

It would help if you could determine if the problem is with the intercom or with the radio.

Try this: the Dynon intercom has a fail-safe built in: if power is lost, the #1 com goes directly to the left seat pilot (possibly just one ear if stereo phones are in use). Next time you hear the squeal, or static, turn off the intercom (volume control full counter clockwise iirc). If the left seat pilot reports the noise has gone away, then you know the issue is in the intercom.

I would disconnect the connector from the COMM radio while leaving the intercom connected. If the issue persists, the intercom module or its wiring is most likely the cause.

You might ask for help here..... https://vansairforce.net/forums/comm.38/

My local EAA chapter's Teen Flight program has a 12 kit that is per plans as far as I know. There's a fancy wing QD electrical connector that was somehow causing a loud squeal. I think the left wing connector wiring was pretty close to the pilot's mic jack. But since the mic/headphone jacks on both seats are buried in the canted deck panel with no access, it was hard to see exactly what was causing it. I heard from another member that it appears to be fixed now.