7. Helicopter

A helicopter's lift and propulsion are provided by a rotating wing. The helicopter shown in figure 26 uses a single lift rotor and a tail rotor located at the aft end of the fuselage. The lift rotor blades always rotate at a constant angular velocity; it's the variation in their angle of incidence that generates torque and controls attitude. To pitch up, for example, we modify the angle of incidence of the blades so that their lift is maximal at the front of the aircraft, and minimal at the rear. This variation in incidence is also used for variations in heel. The movement of the lift rotor generates drag, which tends to cause the aircraft to rotate around its axis. The anti-torque rotor seeks to counteract this undesirable effect.