VTOL Failing to Transition to Fixed Wing

PX4 Autopilot
1

Hello! I am having an issue with a custom VTOL airframe, it is failing to transition to fixed wing due to not meeting the transition minimum airspeed. I have swapped our airspeed sensor and re-calibrated multiple times. I will attach a ulg of our recent failed flight as well as the current parameter configuration. Any suggestions/advice would be appreciated!

Failed Transition Flight Log

2

Hi Derek,

Welcome to the PX4 community!

I had an initial look at your Flight Review summary.

Your aircraft is running PX4 1.16 on an ARK FMU V6X, using the Standard VTOL configuration.

One interesting observation is that the flight summary reports a maximum horizontal groundspeed of approximately 27.3 m/s.

However, this does not necessarily mean the aircraft reached the required transition airspeed. We need to check when that speed occurred and compare the measured airspeed with the transition threshold.

Since you have already replaced and recalibrated the airspeed sensor, I would investigate the transition sequence before assuming another sensor failure.

I suggest checking:

  1. Airspeed versus transition threshold

    Compare the measured airspeed against VT_ARSP_TRANS throughout the front transition.

  2. Forward motor thrust

    Check whether the pusher motor reaches the commanded transition throttle (VT_F_TRANS_THR) and whether the aircraft accelerates as expected.

  3. Transition timing

    Examine VT_F_TR_OL_TM, VT_TRANS_TIMEOUT, and the exact event that terminates the transition.

  4. Pitch attitude

    Check whether excessive nose-up attitude or insufficient forward acceleration prevents the aircraft from reaching the required airspeed.

  5. Airspeed measurement

    Compare airspeed, groundspeed, and estimated wind during the transition. Also verify pitot orientation, tubing, and possible propeller-wash interference.

Could you confirm:

  • Your configured VT_ARSP_TRANS value?

  • Your VT_F_TRANS_THR setting?

  • Whether the forward motor reaches its expected output?

  • Whether the vehicle aborts the transition automatically or simply remains in transition mode?

  • The aircraft’s approximate stall speed and VTOL configuration?

I would be particularly interested in identifying the first point where expected and actual transition behavior diverge.

I would avoid reducing the transition airspeed threshold without first confirming that the aircraft has sufficient margin above its stall speed.

With the transition-specific airspeed, attitude, thrust, and mode data, we should be able to narrow this down considerably.

Best regards,
Yiğitcan Öztürk
PAMILANGA LIMITED