Wow, Sorry for your loss. I used carbon fiber props one time 3 years ago, and when I had a brush with the edge of a tree, I must say I would prefer my dji standard plastic prop to break and save damaging my motors with that super hard carbon fiber...peace
Sudden "crazy", then crash
- Thread starter kevinlieb
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Correct.....That's why he mentioned the original .dat and that is where the graph in Post#20 came from as more of confirmation of the assessment.
Agreed, but based on the DAT data I'm not sure that the cause was a broken prop. If you look at motor speed and motor current data:
The left back motor is clearly behaving strangely, but not how one would expect for a lost or partially lost prop, which would reduce lift and moment of inertia. Looking at those combined for the left back motor:
It's clear that the motor current spikes while the motor speed drops. That implies a motor obstruction or other issue, since a lost or partially lost prop would result in an increase in motor speed, not a decrease, especially since the current increases significantly.
The observation being in the absence of the .dat the initial attitude and yaw changes observed at the suspected issue presentation seem to be proving very reliable in identifying the cause.
I'd say that they are pretty reliable but, on a few occasions, and for no reason that I could ever determine, they led me to identify the wrong motor. The responsible physics escapes me. So now I'm a little more circumspect in my attribution before seeing the DAT data.
That is why I looked at the PWM control. It was intermittently maximum, leading to the thought of the left rear motor. Agreed with the motor speeds. One would think your assessment is correct in relation to that, as I thought as well. The PWM data to me indicates the controller was attempting to speed the motor, but could not due to the lack of drag that the prop would indicate to the FC to compensate. I could be very wrong, and have no problem being so, but that is what I see for what it is worth.
The high PWM values are just the FC attempting to get the motor speed back up - hence the associated high motor current. Something was slowing down that motor, and it was not external drag - hence the imbalanced angular momentum and the CCW spinning flight.
Agreed, that is what I mentioned.
By "drag" I meant the calculations on power applied to the motor. The slow down, could have been ( And I am really stretching this ) A large insect struck by the rotor, hence slowing down the motor speed, increasing the current, and the PWM failing to control the effects. Yes, I know its a stretch by a long ways, but possible....Not probable....
Agreed, that is what I mentioned.
By "drag" I meant the calculations on power applied to the motor. The slow down, could have been ( And I am really stretching this ) A large insect struck by the rotor, hence slowing down the motor speed, increasing the current, and the PWM failing to control the effects. Yes, I know its a stretch by a long ways, but possible....Not probable....
The unusual noise that the OP reported may be related - I'd be curious to know what caused that. It would also be interesting to know whether that motor/ESC still works.
Yes if something seems strange while flying land Land LAND!
I don't mean this to sound harsh but since you continued flying after "but i heard a strange vibration / noise as it left the ground " this one goes down under the heading of operator error. When in doubt check it out.
Good luck and hopefully the repairs will be minimal
That is great advice BigA107, that is exactly what a pilot flying a manned aircraft would do.
Would you have continued if you were piloting a small plane? I never would. If your aircraft is sending you a message stop and figure out what it means.
Exactly. As silly as this may sound to many, I fly our sUAS in very much the same manner as when I climb into the cockpit of manned aircraft. It's probably way overkill and too cautious but it's allowed us to have an impeccable safety record even considering the high # of flight hours we build each month. Better safe than sorry.
Also flying on the state level for Emergency Services we are required to operate at a level of safety and risk abatement that can be mind boggling.
I’m sure it doesn’t sound silly to all those who’s carbon unit crashed their drone. And for the rest, I hope they are wise enough to adhere to your advice.
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Harsh, but lesson learnt I hope. ANY strange or un usual noise/vibration when the rotors get up to speed at takeoff tells me DON't FLY! Check everything out, especially the props where even a small chip can lead to failure. In my humble opinion all props should also be regularly balanced as at the speed they rotate even dust in the air can cause (uneven) erosion at the leading edges leading to unbalance and vibration.
Not sure if this capacitor popped off before, during or after flight but it is definitely a "bad thing". I took the case off gently (it was so cracked it came off easily) so it was not done during disassembly.
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