Advice on log with crash, specific airframe tuning setup issue

ArduPlane Plane 3.6
1

Hi,

I wonder if anyone had any thoughts looking at this bin log from a failed take off https://drive.google.com/open?id=0B07f-MuLfSBFOHRXcTJ5QVBramM

for the reason of the crash at FBWA during take off

This is a new airframe so any thoughts are welcome

Thanks

2

Can you explain in some more detail about the crash and your setup?

I had a quick look at the log in APM Planner, I do not see the switch to FBWA that you mentioned. Also, the Baro Altitude and the GPS altitude do not seem to follow the same pattern.

3

Hi,

Thanks

Well it should have been on FBWA prior to take off (?) you are right in the log I can’t see any change other than the switch back to manual after the crash.

Happened a bit fast, but I think I reacted to the plane going to an uncontrolled pitch up position by cutting off the throttle, I just can’t remember if the small increase in throttle a few seconds after the plane was chucked away at take off induced an attitude change which then caused me cut off throttle.

Flying wing, tractor setup, two ailerons and two differential spoilers, wing loading on the heavy side of things.

Also it looks like there divergence of roll and des_roll and pitch and des_pitch prior to the stall (?)

4

What type of wing? How was your CoG? Typically always try to keep flying wings nose heavy and depending on motorization you need to watch out for torque roll on launch that can make things unstable/uncontrollable. Maybe try using a bungee for launch as this really helps with keeping the aircraft attitude under control for takeoff ie straight and level until enough airspeed to climb.

5

Thanks Jeff,

That particular flying wing has flown a couple of times, I did fly it with pusher configuration in the past and now changed to tractor. I did change the PID values for roll a bit, and I was wondering if there was something obvious by looking at the log. CG was the same as from previous flights. As there is a deviation of roll and pitch from des-roll and des-pitch in the log, I wonder if that was caused by bad tuning.

Think will take the PID settings back to default as last time I tried the autotune on this frame there were significant vibrations,

best