Parachute launch causes crash :-(

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:

Here is the log:

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.

Many thanks.

While I’m no expert in Copter log analysis, I’ll take a stab at it.

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.

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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…

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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.