Extreme oscillations causing crash

Apologies I don’t have a log to share as this is a complete hull loss over mountainous terrain, and I am not using telemetry. Understand I might never found the root cause, but would really appreciate any inputs after watching the attached short video clip.

This is my second hull loss since early this year. Same plane z84 with omnibusf4pro, same cause, loss of control due to extremely violent oscillations as soon as the “displayed” airspeed drops too low. I don’t have an airspeed sensor. Displayed airspeed can be low for many reasons (bad TECS setup, GPS loss, turning off EKF2 to force arm when AHRS not healthy, especially when using synthetic airspeed) I believe Ardupilot scales the PID/output values based on airspeed, something relating to Scaling_Speed.

Since then I have dial all PID values wayyy down, reducing scaling_speed, limiting TECS_PITCH_MAX to 8 degree and TECS_CLMB_MAX to 3 degree so airspeed will never get low. It flown beautifully in auto mission for 7 minutes, and then it took 2 sec to loose the plane. Lost video signal at the same time so it must have been catastrophic. Any thoughts are much appreciated.


The amp meter goes down, negative even in the last few frames. I’m guessing that isn’t calibrated correctly, but the battery voltage is going up so it’s suggesting that the total current draw is going down. At the same time your throttle (I’m assuming it’s throttle %) is about 47%, so I would expect to see a few amps draw. Is it possible you had a structural failure and the motor came off?