Octocopter Crash, Dev 4.4, strange ration in yaw during autotune

ArduCopter
1

Hi
I need help with investigating why crash happened. Copter was flying without problems several times earlier. That’s new setup with t-motor coax 501x motors and alpha escs integrated in arms, Cube Orange, Here+, 6s, 20" propellers. I changed the propellers from 18" to 20" and started autotune to get better parameters. For few minutes it was ok and suddenly copter started to rotate in yaw. It was in alt hold and I had to disarm during flight because I could not get control over copter. Earlier copter was flying ok the only problem which I sow before flight was duplicate node of can bus. Any idea what happened ? Where should I search for problem ?

My log from that flight is here:
https://drive.google.com/file/d/1OSO5EgUONdluce8qWII5aUM3jJqy5cRI/view?usp=share_link

2

Hi
i need help with this crash! Can someone from Arducopter team can help me ?

3

I don’t see an obvious reason why it Yawed at that moment. Is there a reason you are using 4.4-dev and not the the latest Stable?

1 Like
4

I am using 4.4 because I want to use gimbal DJI RS2. There is possibility that red power cable was loose and because of that copter started to yaw.

5

Two weeks ago I had second crash and again there was no any error in logs or info from telemetry. It happened just after changing propellers from carbon 18" to foldable polymer 20" MF 2009. After many e-mails with T-motor and Kopterworx I get info that T-motor MF foldable propellers are not suitable for coax copters. I bought this foldable propellers in combo with motors and escs! They are even showed on banners of T-motor shop in coaxial setup! It looks like MF Polymer - Folding T-motor propellers are to weak for coax motors and breaks during flight. I wouldn’t use them also in flat multirotors. To be fair there is little note on t-motor shop that they are not recommended for coaxial setups.