Principles of Rotary Flight - Lift

Lift
Rotor blades are the helicopter's equivalent to the wings of an aeroplane. Like any wing the shape is very important; it is designed so that the air passing over the upper surface moves faster, causing a difference in pressure between the upper and lower surfaces, creating an upward force known as LIFT.

Principles of Rotary Flight - Tail Rotor

Tail Rotor
Most helicopters have a single main rotor on top and a smaller tail rotor at the back, controlling the direction the helicopter flies.

The tail rotor is very important. If you spin a rotor using an engine, the rotor will rotate, but the engine and the helicopter will try to rotate in the opposite direction. This is called TORQUE REACTION.

The tail rotor is used like a small propeller, to pull against torque reaction and hold the helicopter straight. By applying more or less pitch (angle) to the tail rotor blades it can be used to make the helicopter turn left or right, becoming a rudder.

The tail rotor is connected to the main rotor through a gearbox.