XUAV crash

Flight Testing & Log Analysis
1

Hi everyone,

We are trying to diagnose a repeated crash issue with our XUAV Talon, and we would appreciate any help with reviewing the flight logs.

We have three logs:

  1. A successful flight log

  2. First crash log

  3. Second crash log

    XUAV TALON LOGS - Google Drive

The aircraft setup is:

  • Airframe: XUAV Talon

  • Motor: SunnySky X3520 520KV

  • ESC: ZTW Beatles G2 80A ESC, 2–6S, 5/6V 8A SBEC

  • Battery: 6S 10000 mAh LiPo

  • Flight mode during the issue: FBWA

The aircraft had previously flown successfully several times with the same servo setup. After one crash, we suspected that the problem might be related to weak servos, so we replaced the aileron/servo setup with stronger servos. However, in the next flight, the aircraft experienced almost the exact same crash behavior again.

The general behavior was as follows:

The aircraft took off normally and initially seemed to fly straight. Shortly after takeoff, the pilot gave right roll input, but instead of rolling right, the aircraft started banking/rolling to the left. The pilot continued giving corrective inputs, but the aircraft did not respond as expected. The left roll increased, and the aircraft eventually rolled over/inverted and crashed.

This happened in a very similar way in both crash flights. The second crash happened in almost calm/no-wind conditions, so we do not think wind was the main cause.

We checked the control surfaces many times. In both Manual and FBWA modes, the aileron directions appear correct. We checked for reversed ailerons, wrong servo direction, and basic control surface movement several times, but everything looked normal on the ground.

Because of this, we are trying to understand whether there could be a problem that only appears under flight load, such as:

  • Servo rail / BEC / ESC power issue under full throttle

  • Control surface losing effectiveness under aerodynamic load

  • Mixer or parameter difference between the successful flight and crash flights

  • Aileron or V-tail mixing issue

  • RC input vs servo output mismatch

  • IMU/EKF or attitude estimation issue

  • Any other log abnormality that could explain why the aircraft rolls left even when right roll correction is commanded

Could someone please help us compare the successful flight log with the two crash logs and check if there is any clear difference in parameters, RC input, servo output, attitude response, power/BEC behavior, or FBWA control behavior?

We especially want to understand whether the autopilot was commanding the correct roll direction, whether the servo outputs were responding correctly, and why the aircraft did not physically respond to the right roll correction.

Any help or suggestions would be greatly appreciated.