Originally Posted by
The Sultan
I understand the roll rate peaked at 100 deg per second. This is moderate for an air vehicle billed as highly maneuverable. Sikorsky billed the ABC rotors as being so stiff you could narrow the gap between rotors with no chance of them colliding in the extreme maneuvers that the concept was promised to be able to do.
We don't know if the collision of the blades was purely down to roll rate/onset. Could be that the erroneous control system caused more havoc, e.g. by controlling both rotors at different rates or overall throws.
I would not immediately conclude from this mishap that the concept as such is flawed. What seems clear is that the control logic needs some tweaking.
That said the prospect of this happening in flight is not so nice. So Sikorsky needs to make sure that even clumsy control input doesn't lead to such dynamic reduction of rotor diameter in flight...