I am testing a (possibly oversized, overpowered) parachute deployment device on my drone. For testing, after hovering in place for some seconds, I get the drone to pitch up at 40 degrees to deploy the chute away from the drone (normally it would deploy when the drone tumbles at an off-vertical attitude with props not spinning much). Due to installation error, the parachute device came loose and may have hit a propeller which may have caused a crash (yes, it is ironic).
The pitch is commanded to steadily decrease after parachute deployment to avoid tangling in this spinning-prop test. The roll/desRoll doesn’t look great:
I’m basically hoping someone will be able to say to me if they think that the parachute device may have hit a prop and caused the crash, or if the crash was caused by some other reason. I notice the voltage dipped a bit but I wouldn’t expect that to cause a crash.
I missed observing the actual parachute launch due to a fault with my camera but caught the drone’s descent with my own eyes and a ground camera that showed all 4 props intact, all 4 arms intact, but the drone oscillating back and forth as it rapidly descended to the ground, almost as if it only had 3 props powered.
It looks like motor 4 was the first to experience an issue, saturating at max throttle (presumably because it’s producing little to no thrust), with motor 3 compensating to low throttle. Thereafter, the tumbling makes it difficult to discern anything further. Battery current looks like it follows throttle demands, so I don’t think there’s a power supply issue.
I don’t see anything in the log to indicate precisely when the parachute was activated, but it seems safe to assume that it was commensurate with the motors beginning to misbehave.
Thanks for the reply. I am a bit curious as I previously thought that the battery current monitoring was broken on the PDB I am using. :-S
The parachute was launched in the 300ms after 09:43:56.750
Motor 4 is the rear right motor which makes sense position-wise as the parachute device went in roughly that direction. The motor 4 prop is cracked at the root which I haven’t seen before when crashing; usually the damage is just to the tips of the props.
Could it be that the prop nut became loose as a result of the blade impact with the parachute device? Or maybe the damaged floppy prop didn’t produce thrust because one of the 2 blades was flopping about in an unaerodynamic manner?
Usually you see a mechanical failure like a prop or similar coming in the flightlog in the form of increased vibration before the incident… in this case the flightlog is not showing that sort of build-up and things happen very abruptly…
Indeed, but here the launching of the parachute coincided with the detachment of the parachute container which I am thinking might have hit the prop causing an instant failure.
