"APM:Copter V3.3 RC5" - Failure and recovery: one motor rotated by 90° during flight

During the first flight of this big hexa one of the six motors rotated about by 90° for a faulty clamp, really bad situation for the attitude, here's how the code and the pilot handle this emergency, with a perfect landing.
Although the drone had been higher i'm sure that the flight attitude would remain good, under control.
This result shows that the efforts of the development team were awarded the reliability.
Special thanks to the whole "APM:Copter Dev Team" for this reliable code, and to Lorenzo Franco (the cam operator).

Marco Robustini

("APM:Copter" Lead Tester)

Views: 1847

Comment by Rob_Lefebvre on June 19, 2015 at 7:16am

Nice one.  I think you got a bit lucky on which direction that prop rotated.  If it had rotated the other way, the yaw controller would have given it more throttle trying to stop the yaw, but just made it worse.

Comment by Johnatan on June 19, 2015 at 7:23am


I wish video recording was with higher frame per second(fps) so we had even more details of the incident!

Comment by Rob on June 19, 2015 at 11:10am

I wonder if we could, in code, somehow detect motor failure (ie figure out which motor it not providing the expected result) and disable it, then attempt to compensate/crash land nicely (for ex slowed down descent while spinning as slowly as possible, since yaw  rotation will be hard to keep)

and of course that would work on quad, hex, etc in a generic manner (i guess it wouldnt work on tris ;)

Comment by Antonie Kruger on June 19, 2015 at 1:27pm

Very impressive guys. I finished a big hex build about a week ago. KDE3510-475 motors and KDE35A ESC's. I mounted 15x5.5 carbon props with quick release bolts. I use 16A 6S batteries. I did a very small maiden just checking the stability. Next day I took her to an open field for the autotune run. On the first twitch of the autotune the one prop flew off. The motor decelerated so fast that the momentum of the prop screwed itself off the the quick release mount. The copter - being in alt hold mode - accelerated upwards in an attempt to stabilize the copter. I had the stick full to the right to maintain some control. I wrestled her down. At times I could see the prop opposite the lost prop motor almost standing still. I suppose this makes sense. I had no damage and all was fine - the decent was not as gracious as the video above. I was pleasantly surprised at the level of stability that the airframe had with this handycap. 

Comment by Darrell Burkey on June 19, 2015 at 6:40pm

That is impressive. Any chance the code will get to the point of being able to fly a hexa on 5 props like this?

Comment by Joe Renteria on June 19, 2015 at 10:37pm
Flying on 5 props is easy enough, this example was more about the reaction to one of the motors going 90 degrees off after a mounting failure...

Comment by Marco Robustini on June 20, 2015 at 12:00am

Flying without a motor is one thing, staying in flight with a propeller rotated 90° is quite another.
In short we will do additional testing to demonstrate that APM:Copter can handle the same failure as DJI.
The important thing is to have a well-sized setup, the hexa in my video remains in pure hovering with throttle at 35%.
During that event i'm in "Stabilize" and i landed the aircraft manually.

Comment by Marco Robustini on June 20, 2015 at 12:10am

@Rob_Lefebvre: i agree Rob, i was also lucky.
@thomas Butler: hexa in the video was assembled from a friend, i only installed all the flight electronics and test it
, so i don't know very well the characteristics of that frame (similar to Cinestar), but a plastic clamp was faulty and i know that he has already replaced.
I don't like this solution, i use only aluminum clamp, anchor itself better on carbon tubes.

Comment by Darrell Burkey on June 20, 2015 at 12:24am

@ Joe - Really? I find that hard to believe and would really like to see a video of it happening. I assumed if it can take off and fly with 5 props then it could handle losing one in flight as well. I've heard a lot of people stating that hexacopters have redundancy but that certainly hasn't been my experience and until I saw that video I had never seen any evidence of DJIs claims. CASA in Australia seems to favor octocopters for commercial activities due to the redundancy advantage and I'd really like to have some proof of how well a hexa does this with the Pixhawk. I actually have a spare hexa without a FC in it right now so I might set it up with a Pixhawk and give it a test. Stay tuned...

Comment by Marco Robustini on June 21, 2015 at 12:27am

The clamp is this one, CineStar Motor Mount, and one i found that it was defective:


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