What is a helicopter ?

A helicopter is a type of rotor-craft or rotary winged flying machine in which lift and thrust are supplied by one or more engine driven rotors with aerofoil shaped rotor blades. In contrast with fixed-wing aircraft, this allows the helicopter to take off and land vertically, to hover, and to fly forwards, backwards, and laterally. These attributes allow helicopters to be used in congested or isolated areas where fixed-wing aircraft would not be able to take off or land. The capability to efficiently hover for extended periods of time allows a helicopter to accomplish tasks that fixed-wing aircraft and other forms of vertical takeoff and landing aircraft cannot perform.