Hi everyone,
we’re looking for advice or insight regarding the crash of our MFE Believer built during its short maiden flight. Its not our first built plane and we
Hardware
- Airframe https://en.makeflyeasy.com/index.php/believer/
- 2x 6S3P LiIon Battery
- 2x T-motor MN4012 KV480 + 12x12 prop
- Holybro Tekko ESC with bdshot
- Speedybee F405 Wing with Arduplane 4.6.0
- No airspeed sensor used (but connected and disabled by Parameters)
- Takeoffweight ~5kg
The weather conditions were suboptimal, with steady winds North-East Wind around 25 km/h and gusts (up to 25km/h). The takeoff itself was smooth and uneventful. However, shortly takeoff was completed, the plane suddenly performed a almost 360° unintended roll in AUTO mode. After that the pilot took over in FBWA mode, but the aircraft remained unstable and ultimately crashed.
Link to the log: Nextcloud | HSA
Looking at the logs, we noticed a few things:
- Switches to DCM and back to EKF3
- Two times there seems some position discontinuity
- EKF position variance began increasing soon after takeoff and again before the crash for unknown reasons
- We had some EKF-GPS-Glitch flags a few times but the GPS seemed pretty stable - saw that this is also set if EKF doesnt fit to GPS but still dont understand why EKF gets inaccurate then
- ROLL_LIMIT_DEG set to 45° but plane did roll angles > 45°
- Desired Pitch and Roll is hardly met by the controller
Could a gust or wind cause such roll behaviour ?
Could a possibly vibrating FCU cause such roll behaviour?
Is it possible there was basically too less airspeed and the plane stalled and crashed?
Any input or suggestions would be highly appreciated. We really want to understand the issue before we take off with the next one.
Thanks a lot !