During climb to 55m, transition started however failed due to either esc or motor failure which did not make the transition speed (previous flights were fine). After transition time out was announced ( and spotted by the pilot) an attempt to go and manually transition ( full throttle and FBWA) the vtol motors stopped producing lift BEFORE pilot initiated control and the aircraft pitched down and impacted the ground, destroying it.
The VTOL motors should have kept going as the airspeed hadnt been reached.
An attept to use Chat GPT gave varying solutions but not definitive.
Is it possible that i have the Q_TRANS_FAIL_ACT set to QRTL instead of QLAND and it can shut down the motors?
My time out Q_TRANS_FAIL is 20 s.
We have a few of these and need to iron this problem out.
When hovering, about 70 amps flow (red line). Then, all of a sudden, it was down to about 30 amps or less. I suspect that motor 4 or its power supply failed.
Yes, over the weekend i sifted through all the carbon fiber splinters and in the process found the wooden pusher prop had lost grip with the knurled double sided washer. This washer had a metal to metal contact with motor prop hub and under closer examination, the motor side has 50% of the face UNKNURLED which decreased contact even further. Pre flight checked the nuts were reasonably tight and the previous flight showed no issues with 20 mins of FW flight carried out. As you say, this should have not been the cause of the loss of thrust of the VTOL motors and would have been a inconvenience at the most to have to land and re torque the prop (maybe even ditching this double sided knurled washer) and re attempt the mission. However a hard lesson to learn that there was something else underlying that would have precipitated in the field in operations. I have tested the right side VTOL motors without props on and power connected and using a servo tester (removing the Cube Pilot out of the equation) and they operated and spun ok. Both signal and ground wires continuity checked ok.
Next is to mount the motors on a rig with all the original components secured and test them under load. Ill probably just use a receiver and a y- splitter to keep it simple. Ill simulate the same PWM and duration to see if an over temp occurred or if connectors fail . No arching, evidence of over heating or discoloration was seen on the connectors or wires. I wish I had data recording ESC’s If they turn out to work OK under load, what else could be a reason for the shut down? Was it a shutdown or could a commanded shutdown have occurred?
Having looked at it again, I am certain that the change in motor power was not intentional, but rather the result of a failure at M4. If the flight controller had malfunctioned, the copter would have tilted to the left and not to the right. However, I cannot rule out an external force, possibly a large bird, pulling the copter down by the arm of M4.
When you mean a failure, could we be talking about desyncing, overheating or pwm signal loss (if power to the esc was ok) ? My eyesight is average but the props were spinning from what i could tell.
The cause was a sudden loss of thrust on M4. The log file no longer indicates what caused this.
In my oppinion it is not possible to tell whether thrust is applied.
I would conduct a test run with reverse propellers (downward thrust) to rule out thermal overload after a certain period of time. However, I would probably install ESCs with telemetry.
I am also unfamiliar with the mechanical design. Is it possible that the same fault could occur as with the forward motor?
If they turn out to work OK under load, what else could be a reason for the shut down? Was it a shutdown or could a commanded shutdown have occurred?