I see what you mean. Another thing that I do is to load the 727 Cold-n-Dark, then move it to the airport of my choice and save it there. I think that because it was just a change of location, the 727 was set correctly for the Cold-n-Dark situation. It sounds like that is definitely the difference. The only thing it doesn't explain is, why, when I do start mine from the C172 default flight situation, the avionics still don't cut out after 15 minutes or so. It's really weird.

Mark