A helicopter is a heavier-than-air aircraft that is supported in flight primarily by the reactions of the air on one or more power-driven rotors on substantially vertical axes. Helicopters are classified as rotorcraft, or rotary-wing aircraft, in order to differentiate them from fixed-wing aircraft. While aircraft achieve lift from their wings, helicopters achieve lift with rotor blades that rotate around a mast.
The primary advantage of a helicopter is that the rotor provides lift without the aircraft's need to move forward to generate lift. This allows the helicopter to both take off and land vertically without the need for a runway. It is for this reason that helicopters are often used in congested or isolated areas where fixed-wing aircraft cannot take off or land. The lift from the rotor also allows the helicopter to hover in one place, something fixed-wing aircraft are not capable of. In addition, helicopters can hover more efficiently than other forms of vertical takeoff and landing (VTOL) aircraft, which allows them to perform maneuvers that fixed-wing aircraft cannot.
Helicopters were first developed and built as early as the first half-century of flight. Despite this, it was not until 1942 that helicopters reached full scale production, with 131 of Igor Sikorsky’s first helicopters being produced. His design was the first design to utilize a configuration of both a single main rotor and an anti-torque tail rotor, and it was this design that became known as the first successful helicopter.