Auto landing Bug & crash with 3D video and logs ArduPilot 3.6.0

Flying Bixler 3 with Pixhawk in auto mission.

On Do_ Start_Land the plane shut down itself and crashed.

Log files

I’m on travel right now but I’ll make sure to look at this log when I get back to my desk. Next Monday. I’ve never heard of a problem like this on do land start so I’m interested to see what happened. We are going to release 3.7 soon and I want to make sure this is not an outstanding issue.

the crash was not actually related to DO_LAND_START. It crashed as it flared in a landing at high altitude. It flared as is thought the plane was not flying due to this code:
that starts a flare if in a landing sequence if the sink rate is low and the is_flying() algorithm thinks the plane is not flying.
The flare causes the plane to shut down the throttle, which caused it to lose airspeed and crash.
I’ve pushed in this fix:
that change means the crash detection in landing is only enabled if CRASH_DETECT is enabled (set to 1).
I also think this flight log shows a weakness in is_flying(). The is_flying() code was fooled by a headwind in a plane that doesn’t have an airspeed sensor. The ground speed was very low which implies a strong headwind and is_flying() decided the aircraft was not flying when it was.
I don’t think we should be using is_flying() for any critical decisions unless the aircraft has an airspeed sensor, and even then I think it should depend on parameters like CRASH_DETECT.

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