We’ve had a recurring snag on one of the airplanes for the last week. The pilots keep snagging the radio’s as they seem to be cutting in and out whenever they feel like it. We have never been able to duplicate the problem on the ground so we keep sending it back up, “no fault found”. After 3 tries at this it was time to change…something. It was decided to change out the wiring from the PTT switch (Push To Talk) to the radio head and see what happens.
Once the wiring was out we could see that it had been fixed numerous times over the years from the 8 or so butt-splice connectors. But that still didn’t show what the true problem was. After looking really closely at the wiring that was removed I noticed the actual problem:
You can see that a single strand of wire had pushed through this heat shrink butt-splice and was grounding out the switch. Although its easy to see in the picture, you need to remember that this is 28 gauge wire and that single strand poking out is very difficult to see with the naked eye. There was no chance of finding this while it was still in the aircraft hidden amongst the mess of stuff under the dash.