ArduCopter 3.2.1 Auto mode sudden height fluctuation


I am recently testing auto mode of ArduCopter 3.2.1. Days before in a test flight of auto mode, the quadcopter suddenly rose and fell near the target height for a couple of times and eventually got normal.

I checked the dataflash log. The ThrOut, due to certain reason, suddenly raised to 1000 and fell to very small repeatedly which resulting the deviation of attitude.

Could anyone help me find the reason of the sudden full throttle?

Thanks a lot.

Please download log file using this link:

I had the same thing happen today (20mph wind) with my quad (pixhawk), a friends tricopter (apm) and a bixler (no fc).
We put it down to varying air pressure/turbulence as it’s never happened before in calmer winds.

Could you post your dataflash log or send it to me? my email is It will be fantastic if you can provide me some potential reasons for this phonomenon.

I noticed that the baro-err appeared AFTER the sudden throttle change.

So the throttle change led to the attitude deviation. I checked the height error and climb speed error which were all in normal range when the throttle suddenly rose.

The only abnormal thing is that EKF->AX became large when the throttle suddenly rose.