Fixed-Wing AUTO Takeoff — No Rotation on Flying Wing

ArduPlane Plane 4.6
1

We’re debugging AUTO takeoff behavior on a fixed-wing flying-wing platform in ArduPilot and are seeing an issue where the aircraft never commands a rotation.

In AUTO mode with a standard TAKEOFF mission item:

  • The aircraft reaches the takeoff point correctly

  • Throttle ramps as expected

  • Elevons remain neutral

  • No pitch-up / rotation command is issued

Manual and assisted fixed-wing modes work normally, so control surfaces, mixing, and authority appear correct.

We’ve been trying to debug this using ground and roll testing (including reduced takeoff speeds to observe behavior safely), but so far we haven’t seen any pitch command generated during AUTO takeoff. Adjusting takeoff-related settings hasn’t changed the behavior.

Relevant details:

  • Flying wing (elevons only, no dedicated elevator)

  • No airspeed sensor installed

What we’re unclear on:

  • What conditions ArduPilot requires before issuing a rotation command during AUTO takeoff

  • Whether the lack of an airspeed sensor can suppress pitch-up behavior

  • Whether flying wings are treated differently from conventional fixed-wing aircraft during AUTO takeoff

  • Whether rotation commands should be observable during roll/bench testing, or if ArduPilot suppresses pitch commands until specific speed or attitude conditions are met

The documentation is vague on the exact gating logic for AUTO takeoff rotation, particularly for flying wings, so any insight into expected behavior or required prerequisites would be very helpful.

2

Wings aren’t treated differently than traditional configuration. You don’t need an airspeed sensor, assuming you have proper GPS lock to give the plane some sort of speed input.

Generally, plane should hold TKOFF_GRN_PITCH until it reaches TKOFF_ROTATE_SPD. After that the plane should attempt to climb out at TECS_PITCH_MAX.

This all assumes the plane is trimmed, within proper C of G, the PIDS are tuned, and the TECS is tuned. (people often forget or miss that last one)

Share a .bin log of a flight or take off attempt if you would like somebody here to look at your situation in more depth.

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