Helicopters and Angular Momentum

The main function of the tail blade (rotor?) is to counteract the torque applied to the main rotor. You can also use the tail rotor to control where the helicopter is pointing. If you lose drive to the tail rotor (/fan / nozzle) you are in real trouble.

 

The tail rotor is used to counter act the torque along the main rotor axis (yaw). This results in a net force to one side, so a true hover requires a helicopter to lean a bit towards the thrust side of the tail rotor.

The gyroscopic effect of the main rotor results in a pitch reaction to roll torque and vice versa. The pilot pitch and roll controls end up being advanced by 90° along the rotor axis to compensate for this.

 

For the best description, ever, of all this, read the first couple of chapters in 'Chickenhawk' by an ex Vietnam Chopper pilot. He describes learning to fly a Bell Huey and leaves you, the reader, sweating and with palpitations as if you're actually in the pilot's seat. No fly-by-wire in those days.