A helicopter, also known as a chopper, is a kind of rotor craft wherein lift and thrust are sent by one or more engine driven rotors. In contrast with fixed-wing aircraft, this allows the helicopter to take off and land vertically, to hover, and to fly forth, back and laterally. These attributes permit helicopters to be used in crowded areas where fixed-wing airplane would not be able to take off or land.

The capability to efficiently hover for extended periods of time allows a helicopter to complete tasks that fixed-wing aircraft and other forms of vertical takeoff and landing aircraft cannot perform.

Rotor:

The rotor system is the revolving component of a helicopter which produces lift. The rotor system can be moved horizontally as key rotors are lifting vertically as a tail rotor to elevate horizontally like thrust to work against torque effect. The rotor is comprised of rotor blades, hub and mast. The mast is a cylindrical metallic barb which lifts upwards as well as is moved by the transmission. There is a hub (attachment point) at the top of the mast for the rotor blades. The blades are attached to the attachment point by many different methods.

Anti torque:

The majority of helicopters have one main rotor, but torque is produced as the engine turns the rotor against its air drag and this causes the chopper to revolve in the opposite direction to the rotor. A few helicopters use alternate anti torque controls in lieu of the tail rotor, like the ducted fan, and NOTAR. The NOTAR provides anti torque the same way a wing develops lift, with the use of a Coandă effect on the tail boom.

Primarily, there are 3 common configurations that use the opposite rotating effect to help the rotorcraft. The Tandem rotors are 2 rotors with 1 mounted behind the other. The Coaxial rotors are 2 rotors that are lifted one above the other with the same axis. The Intermeshing rotors are 2 rotors that are lifted close to each other at an adequate angle to allow the rotors to intermesh over the top of the aircraft. Transverse rotors are other structures found on tilt rotors, where the couple of rotors are mounted at each end of the wings.

Engine:

The type, number and size of engine are used in a helicopter to determine the capability of that helicopter with respect to design size and function. The first helicopter engines were simple mechanical devices, like spindles or rubber bands.

Initial helicopter designs used custom-built or rotary engines designed for aircrafts, although these were soon changed by more powerful automobile engines as well as radial engines.

Turbine engine brought revolution in the aviation industry as well as the turbo barb engine finally provided helicopters an engine with much of power along with a less weight penalty. The turbine engine was capable to be measured to the size of the chopper being designed.

Particular jet engines improved to move the rotor from its end are mentioned to as tip jets. The jets supported by an isolated compressor are mentioned as cold tip jets, whereas the jets supported by burning exhaust are mentioned as hot tip jets.