The Force in Action
As a pedant I would like to point out that the counter rotation of the helicopter is "evidence" that the equal and opposite force exists. It is not the force its self.
This force is not related to the plane of rotation of the engine - think S58 and Hughes 500 where the engine is mounted at an angle to the horizontal.
Tech teachers use the reaction of a fire hose as a demonstration of the force.
Cheers
Blackhand