Very unstable XY yaw in loiter with heavy load copter

ArduCopter Copter 3.4
1

Hello all,

This morning we made multiple flights with our heavy load in a very unstable situation in loiter with roll pitch and yaw extremely unstable . Same kind of flight in the afternoon and the copter was pretty stable again. We are very puzzled on why the copter was so unstable in the morning.
in attachment the log of the morning unstable and the log of the afternoon without trouble.
We didn’t change any parameters nor calibrations.

unstable : https://my.pcloud.com/publink/show?code=XZ0Qi3ZBol5OjuxGtbrS0a0IqjXPBsI3m8y
stable : https://my.pcloud.com/publink/show?code=XZzQi3ZWfE4UO2p8dfeaR4ne8bLLYvUFvJ7

Thanks for your help
Doms

2

Looks pretty similar to me. Did the ‘stable’ flight really look that much better?

I think I’d go back to stabilize or althold and look at the attitude tune. Roll looks worse than pitch. The tune appears symmetric for now.