Octaplane uncommanded pitch & lost control

Hey Ardu team!

My Octaplane observed an uncommanded pitch and eventually lost control. I have been studying the logs but cant seem to find out what went wrong. Hoping some kind souls here would offer some insights into what happened.

In the short 30 second flight, the octaplane loses control after transitioning to FWBA. There were some uncommanded pitch, and the octa VTOL motors suddenly spin down[13:17:53] and spin up [13:17:56], and the aircraft literally fell out of the skies.

octaplane setup with 2 pusher motors at the rear.
Octa X config; the odd numbered motors are in front and the even numbered motors are at the back.
2 modes - QHOVER and FBWA.
q_assist with the assist speed set to 0.


  1. immediately after switching to FWBA mode, there is quite an error between CTUN.Pitch and CTUN.NavPitch
  2. PIQP.Tar shows the diverging oscillating pitch behaviour. Does this mean that my the autopilot wanted the oscillating pitch? as it is the pitch target of the controller…
  3. octa VTOL motors suddenly spin down[13:17:53] and spin up [13:17:56]

I have included the log file and a video of the flight below.
Greatly appreciate any input and hope to hear from you folks soon!!

Video: https://www.youtube.com/watch?v=DYjh7BDH7l4
Log file: https://u.pcloud.link/publink/show?code=XZLGnBXZmP1RBSHi6rbro4Dm42Apk86VhRKV