Airspeed invalidated shortly after VTOL forward transition when entering orbit

PX4 Autopilot
1

Hi,

I’m experiencing airspeed invalidation on a VTOL quadplane shortly after forward transition when the mission immediately enters an orbit.

Setup:

  • PX4 VTOL quadplane

  • ASPD_DO_CHECKS = 7 (data missing + stuck + innovation)

  • ASPD_FS_INNOV = 7.0, ASPD_FS_INTEG = 15.0, ASPD_FS_T_STOP = 1.0

  • ASPD_FS_T_START = -1

What happens: After forward transition (vtol_state = 4), the mission immediately enters an orbit. Wind estimate (airspeed_wind/windspeed_north/east) oscillates heavily, causing tas_innov to spike up to ~15 m/s. The innovation integrator accumulates and eventually triggers invalidation (~20s after transition).

Analysis from logs (PlotJuggler):

  • Load factor check: passing (~0.8 ratio)

  • Innovation integrator: reaches threshold due to wind estimate oscillation

  • Wind estimate variance remains high (~5.0) throughout, ground_minus_wind never becomes valid

  • tas_innov calculated as |TAS - (groundvel - wind).norm()| spikes due to unstable wind estimate post-transition

Question: Is it expected that the wind estimator needs time to stabilize after forward transition before entering orbit? Is there a recommended straight flight duration post-transition before maneuvers? Or is tuning ASPD_FS_INNOV higher the correct approach here?

Currently testing ASPD_FS_INNOV = 10 which appears to prevent false invalidation in log replay.

Thanks

2

please anyone has opinion ?

3

Usually it’s due to a high airspeed scale error. See Airspeed Scale Handling | PX4 Guide (main) how you can handle that.
And to check if you are affected just compare the airspeed_validated.true_airspeed_m_s to the groundspeed.
If it’s not that then share a log file and we’ll have a look.

4

Thanks for your answer. Since my plane crashed and needs repairs before it can fly again, in the meantime, I’d like to ask if it’s normal for the airspeed sensor to show a negative spike at certain times when I test the airspeed sensor with the fan at home ?

red: ias

blue: differential pressure

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image695×688 10.4 KB

5

Not uncommon to have negative differential pressure spikes yes. Especially around 0. These sensors are very sensitive around 0, once you build up airspeed the data generally looks much smoother.