I lost my favorite plane today. A Midwest SuperHots with an Irvine .72 in her. A problem with my 9C trainer setup caused the problem and we can't fix it or figure it out.

Here is the deal. I have two 9C connected with a trainer cord and flying my Super Hots on several flights with no problem at all. The freq module was out and the power was off on the buddy radio. The trainer function was INH in the buddy unit. The primary unit was setup with all channels set to normal. One the last flight when the student got into trouble and I tried to take the plane back I did not have control and she went stright into the ground at full throttle. Subsequent examination showed that even though the trainer switch was indicating that it was turning off and on, it was not turning off the buddy radio. I esentially had two radios flying the plane no matter what position the trainer switch was in.

The only other factor is that the voltage upon landing (picking up the pieces) was 9.8v. It was the last flight of the day.

Does anyone have any idea what happened or what I should check.