The principles behind the helicopter have been known for many centuries, but the necessary materials and the technology needed to construct one were not available or developed until the 20th century.
The first design for a helicopter-type aircraft, was produced by Leonardo da Vinci, however, a practical helicopter did not fly until 1936. This helicopter was the Focke-Achgelis Fa 61. An American helicopter flew in 1942, and was named the VS-316A (later known as the R-4). This model was designed by Russian engineer Igor Sikorsky.
The helicopter has many advantages over conventional types of aircraft. Firstly, they have the ability to take off and land vertically, rather than horizontally. Also the design of the helicopter allows it to motionlessly hover in the air. For this reason, helicopters can be used in many conditions and places that a conventional aircraft would not be able to cope with. This ability is probably best demonstrated when it acts as a rescue vehicle. The helicopter can hover directly over the site of an incident and then lower the rescuers and necessary equipment by means of a winch. With its superb accuracy the rescuers can be placed exactly where they want to be.
The helicopter is powered via a set of slim blades attached firmly to a shaft. The blades rotate rapidly through the air until the required lift for flight is generated. The helicopter will begin to rise when the overall lift of the rotor surpasses the weight of the aircraft.
The direction of the helicopter is controlled by the pilot who makes use of the pitch control lever. As the rotor is spinning, a circle is traced in the air, this area is known as the rotor disc. By altering the angle of attack (the tilt of the blades) the rotor disc can slant accordingly and the speed or direction is then determined.
