I have 7 CUAV Pixhack v3, but with one I had an interesting finding yesterday.
Everytime I fly this drone I have a big stability problem with the first flight. The drone is drifting or even speeding up in pitch direction when using Alt Hold mode and Stabilize mode , but only at the first flight. After landing the gyro of IMU0 has an offset of 40-70 in y direction. With the following flights after power up calibration no issue anymore.
Yesterday I identified that this is a temperature effect. With the first flight the IMU is cold. With power on calibration it is set to zero. During flight the temperature of the FC increases as well as the offset of IMU0 gyro Y and the instability increases as well. The gyros of the other 2 IMUs are fine.
I attach a picture where you can see the temperature depandancy.
Any idea how to solve that beside switching of IMU0.