HELICOPTER FLIGHT THEORY

The helicopter is type of aircraft in which lift is obtained by means of one or more power-driven horizontal propellers called rotors. When the rotor of a helicopter turns it produces reaction torque which tends to make the craft spin also. On most helicopters a small rotor near the tail compensates for this torque. On twin-rotor craft the rotors spin in opposite directions, so their reactions cancel each other. The helicopter is propelled in a given direction by inclining the axis of the main rotor in that direction. The helicopter's speed is limited by the fact that if the blades rotate too fast they will produce compressibility effects on the blade moving forward and stall effects on the rearward moving blade, at the same time.

Topics

Historical background

Airfoil theory and propeller action

Configuration of helicopters

Main rotor and design considerations

Dissymmetry of lift

Gyroscopic precession

Vibration

Torque

Cyclic control

Momentum theory

Strength and design considerations

Conclusion