I encountered this Osprey aeroplane at the mouth of the Nene where it comes out into the Wash. There is a military range on the far bank. It is a strange aircraft because the propellers that are seen here pointing forwards as normal can be swivelled to be vertical so it can operate like a twin rotor helicopter. It was doing that over the marsh when it was a long way off but I noticed through binoculars that the two rotors were rotating in opposite directions: one went clockwise and the other went anti-clockwise. The reason is this. One rotor would produce an equal an opposite torque that would spin the plane in the opposite direction to the rotor. Rotor would spin one way and the plane would spin the other. If the other rotor is doing the opposite then the two torques on the plane would be equal and opposite and the plane will not rotate.
