Quad on 3 motors?

[basophil]

What would be the flight characteristics of a quadcopter if it lost a rotor? Is it predictable in any way, e.g. spiral to ground? Or is it completely chaotic and uncontrollable? Or would it invert, shut off and drop like a rock? Any thoughts appreciated.

 

[Meta4]

What would be the flight characteristics of a quadcopter if it lost a rotor? Is it predictable in any way, e.g. spiral to ground? Or is it completely chaotic and uncontrollable? Or would it invert, shut off and drop like a rock? Any thoughts appreciated.

It's a downward spiral.

 

[Simmo]

 

[Kilrah]

Or is it completely chaotic and uncontrollable?

This, just flips continuously while falling mostly straight.

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Yup it's nice, but no current commercial aircraft implements that.

 

[Simmo]

Agreed Kilrah, but a University finds some thing that works, could save 'something', and it all goes quiet!!!
I mean that vid is years old, and nothing!!!

 

[Kilrah]

Unfortunately what they showed here only works becasue they're in their indoor environment with external position sensors.
Doesn't translate to an outdoor situation in a snap.

Also has requirements on sensors and mechanics that are constraining other areas which likely makes it too restrictive for the limited benefit (basically the only realistic scenario it covers is loss of a prop, potentially a failing ESC).
Aka we probably couldn't have a Mavic with folding arms if it was designed to be able to use that recovery method. Battery would have to be fully encased and less convenient to use, machine would be bigger as a result,...

 

[Simmo]

I didn't know there were external sensors??
I thought the main thing in the algorithum was changing motor direction etc?
I do remember the cage tests with the hoop etc, that was most definately positional sensors and a hell of a lot of computer power.!!
I really thought this was all onboard, and only an add on script to existing firmware??

 

[Kilrah]

If it was they wouldn't have left the 3 positioning balls on the aircraft, or would even have showed it outside of their arena...

It can likely keep itself in the air on its own and keep height in control, but position would probably quickly drift in random directions with substantial speed without the external references.

 

[Congoblue]

I think they were maybe just using external positioning because that was the best tech available at the time. The Mavic's internal sensors could handle this.

It might be theoretically possible to implement this on a mavic, basically you need to be able to reverse the rotor opposite the one that has failed to control the "flip". But I am not sure if the Mavic hardware allows to run a rotor backwards, or if the rotor locking mechanism would take it.

 

[Kazo]

How about just try as experiment to remove one propeller and try to take off? Or am I crazy?

 

[Congoblue]

If you try it make sure you post the video here for us to watch...

 

[old man mavic]

What would be the flight characteristics of a quadcopter if it lost a rotor? Is it predictable in any way, e.g. spiral to ground? Or is it completely chaotic and uncontrollable? Or would it invert, shut off and drop like a rock? Any thoughts appreciated.

unfortunatly the are designed to fly with 4 props counter rotating in pairs a drone with 6 or 8 props can fly with a prop failure enough to get down and land

 

[Flycaster]

Ever see a rock try to fly???

 

[Congoblue]

If you shut down the opposing rotor to the failed one, you basically have a Chinook helicopter, and they fly, so it must be possible...

 

[LivinLarge]

When a quad loses a rotor, It can't use the opposite rotor for lift without flipping over. Now you are down to only two rotors which are both spinning in the same direction so you have half the lift and full yaw in one direction. Best you could hope for is a controlled crash.

 

[LivinLarge]

If you shut down the opposing rotor to the failed one, you basically have a Chinook helicopter, and they fly, so it must be possible...

Not quite. The Chinook props must be turning in opposite directions. On a quad, diagonally opposite props turn in the same direction.
For a quad to become a working bicopter you would have to reverse direction of one rotor and also reverse the prop pitch.

 

[meens]

a controlled crash is better than a crash

 

[dannybgoode]

a controlled crash is better than a crash

Isn’t a controlled crash a landing?

 

[Congoblue]

Not quite. The Chinook props must be turning in opposite directions. On a quad, diagonally opposite props turn in the same direction.
For a quad to become a working bicopter you would have to reverse direction of one rotor and also reverse the prop pitch.

Ahhh, I knew there must be a flaw in the plan somewhere!