Bummed. New P3A Crashed. Pls Advise

syotr · Dec 1, 2015

On the earlier Phantoms and NAZA controllers, there is only output from the controller to the ESC. The communication is one way. The FC has no way of knowing if the motor has stopped or thrown a prop. As Phantom tilts, the FC would command the motor to speed up, eventually reaching what would be full speed command if the tilt was not corrected. The ESC does receive pulses back from the motor, but certainly on earlier models, it could not be communicated to the flight controller.
I don't know what happens with the P3.

syotr · Dec 1, 2015

So the motor could actually be stopped?

BudWalker · Dec 1, 2015

syotr said:
So the motor could actually be stopped?

I suppose that's right. I just confirmed that it's a commanded value and not actual.

BudWalker · Dec 2, 2015

@Luap , @TheRealNick , @syotr Could we please move, or continue, the discussion about finding the actual motor speed data to New version of .DAT converter | DJI Phantom Forum I've been looking into some and I might have something to report later today or tomorrow. Thanks

TheRealNick · Dec 4, 2015

Thanks to @BudWalker's conversion tool I made another chart at the time of the incident adding the field BudWalker found that seems to be some indication of engine load. In the below chart the commanded motor speed is on the right axis and the motor load is on the left axis. At the time of the altitude drop the commanded motor speed went to 10,000 for the right front motor and just before that the motor load went negative for some reason. I checked the earlier portions of the flight and nothing like that occurred, so it is not typical. After it went negative it jumps around and seemed to track with the Left Back motor while the Left Front and Right Rear moved together. If the prop came off I would expect the commanded speed to go up to max, but as it tumbled out of the sky I would have expected it to go crazy like it did for the other motors, it seems weird to me that it flat lined at what appears to be the max command value. At the same time based on BudWalker's post I would have expected the motor load to go to 0, or at a min to look much different than the other motors if it had lost the prop. It is not the lowest on the graph for most of the time after the incident. If the motor seized I would expect the load to flat line at a high value which it also doesn't do. To me it looks like something definitely happened to that corner, but I am not positive what happened. Maybe the ESC failed for that corner...

Luap · Dec 5, 2015

I did same in Dashware - I think Bud inverted the load column names. Pretty perfect match when I remap per below - 0 load on RPM right front.
So that prop flew off in flight - Or could it still be an ESC failure?

BudWalker · Dec 5, 2015

I've responded to this in New version of .DAT converter | DJI Phantom Forum
@Luap, @TheRealNick , @syotr

TheRealNick · Dec 5, 2015

Luap said:
I did same in Dashware - I think Bud inverted the load column names. Pretty perfect match when I remap per below - 0 load on RPM right front.
So that prop flew off in flight - Or could it still be an ESC failure?
View attachment 37210

I might be missing something but I don't see any of the motors going to 0 load....even on your charts...

Luap · Dec 5, 2015

Well not 0 but I imagine the motor still has some resistance in it?

TheRealNick · Dec 5, 2015

Luap said:
View attachment 37225
Well not 0 but I imagine the motor still has some resistance in it?

In Buds chart no prop was pretty much zero and flat. I would expect it to be flat. If you look at the graph I made the left rear and right front are around the same values and cross at some point. In my chart the lowest is left rear, so if they were changed it would make right front the lowest, but they both seem to be moving with about the same difference as the other motors.