Hi spike,

nobody has really explained why then the instructions say to have trims zeroed in each flight mode. Perhaps it relates to the gyro functioning in heading hold mode, if you are going to use that. With a heli gyro, if you are in HH mode and have trim dialled in, the gyro will interpret that as a desired constant rate tail deflection and it will rotate the tail constantly one way or another, depending on the direction of trim.

I have been trying to answer this question for some time.....