@Nihal wrote:
Hi,
I need some help understanding the cause of this crash.Setup - Arduplane 3.5.2, Pixhawk 1, X-UAV Talon, 3dr airspeed sensor and compass/GPS
Description of Crash - Plane was flying well previously on the same day. I disabled ARSPD_ENABLE to see how the aircraft flies without an airspeed sensor. I changed the parameter and launched the aircraft in FBWA. The aircraft flew fine, I climbed to about 100m and switched to loiter mode from my transmitter. The plane rolled right and continued to roll beyond the limits (LIM_ROLL_C = 4500).
As it approached close to 90(all within a few seconds), I switched back to FBWA to try and recover the aircraft. By this time, the aircraft had rolled over and was inverted. It had also pitched down during this process and was heading towards earth fast. All attempts to recovery failed and the plane crashed head first into the ground.
My analysis from the logs:
It seemed that the Pitch tuning in the aircraft was off. I flew a grid and did several low pass manoeuvres. When I looked at the logs, I saw that the ATT.DesPitch was very high and never followed the actual ATT.pitch. It was as high as 45 degrees during the auto grid. The plane flew the grid well, I found no issues during the flight. What could be the possible reasons for this? My CG was properly positioned. The aircraft had been previously tuned. I had flown just a couple of days earlier and the pitch response in the logs was as expected.
When I switched to loiter, The aircraft rolled beyond the limiting roll angle. What could be the cause for this? I also noticed that the pitch was negative.
The throttle output was high during loiter. The plane demanded 100% throttle. Is this normal behaviour?
Synthetic Airspeed as estimated by arduplane seemed natural. How does using the airspeed sensor affect the flight behaviour? It is worth noting that ARSPD_USE was still set to 1, only ARSPD_ENABLE was set to 0 during the last leg of the flight.
I would love to hear your thougts on this crash.
Edit : forgot to attach the dataflash log. Here it is
Best,
Nihal
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