Plane SITL unexpected behavior in DCM after AHRS_GPS_USE 0

ArduPlane Plane Simulation
1

Hi guys, I’m experiencing an interesting behavior in SITL during testing the no-GPS flights.when I set the AHRS_GPS_USE 1 the plane keeps forward flight for 1 minute, then it starts to fly backward with correct heading.

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Has anybody experienced smth similar?

Steps to reproduce:

  1. Launch plane SITL
    python Tools/autotest/sim_vehicle.py -v ArduPlane --console --map

  2. Switch to AHRS_TYPE to DCM

  3. Create the mission with 3 waypoints with total distance of 5 km

  4. Launch the mission in Auto mode, let the plane reach the height.

  5. After 30 seconds
    param set AHRS_GPS_USE 0

  6. Wait for 30-40s, the plane will slow down and will fly backwards with the same heading,

  7. Do param set AHRS_GPS_USE 1, the plane will appear at correct position