I'm not an ArduPlane expert, I'm on the ArduCopter side but I think the radio trims are all set when you do the Radio Calibration through the mission planner. I think gyro offsets are captured at start-up but everything else (i.e. radio trims, accelerometer offsets) are done when you configure the board.
Hi Randy, someone wrote something in issue 792. Maybe it regards to my issue?
I commented on this here: http://diydrones.com/forum/topics/apm2-pid-settings-reset-after-pow...
You need to comment out this line in the ArduPlane firmware:
// read the radio to set trims
trim_radio(); // This was commented out as a HACK. Why? I don't find a problem.
Compile and upload and your trim values will stay as what you set them
From Tridge: That is controlled by the TRIM_AUTO parameter. It defaults to zero, meaning it does not copy trim values when you switch out of manual. That default was chosen because if you don't know it will happen and you have some elevator or aileron stick applied when you change out of manual you get very bad trim.
So when TRIM_AUTO is 1 then every time you switch out of manual the trim values will be used for the other modes but your sticks must be at neutral when you switch.