Propeller (aeronautics)

In aeronautics, an aircraft propeller, also called an airscrew, is an aircraftpropulsion device that converts rotary motion from an engine or other power source into a swirling slipstream that generates thrust. A typical propeller engine comprises the motor driving a rotating shaft (driveshaft), to which several radial airfoil-section blades are attached, so that the whole blade assembly (i.e. the propeller) rotates around an axis of rotation longitudinal to the direction of travel. The propeller blades, which can be made from wood, metal or composite materials, attaches to the driveshaft either directly or through reduction gearing, and the blade pitch may be fixed, manually variable to a few set positions, or of the automatically variable "constant-speed" type.

Propeller-driven fixed-wing aircraft are the earliest type of powered heavier-than-air aircraft (i.e. aerodynes), with the Wright Flyer (which used two push propellers powered by a chain drivegasoline engine) being the first-ever manned fixed-wing aircraft to achieve sustained flight. In addition to conventional shaft engine propeller aircraft, almost all human- and solar-powered aircraft, as well as some lighter-than-air aircraft (i.e. powered airships), also use propellers to sustain and/or to steer flight. Tiltrotor/tiltwing aircraft can use a rotatable nacelle/wing mechanism to turn a rotorwing (which generates lift for vertical takeoff and landing) from a vertical axis to a horizontal one, which converts the rotorwing into a functional propeller — sometimes referred to as a proprotor. Propeller engines are typically only capable of subsonicairspeeds, generally below about 480 mph (770 km/h), although a transonic speed of Mach 1.01 was recorded in a dive by the McDonnell XF-88B experimental propeller-equipped aircraft, with a propeller efficiency of 78%.

Propeller aircraft, since their debut in 1903, played a dominant role in aviation of the first half of the 20th century and in the aerial theaters of both World Wars, until the advent of the much faster and heavier-payloadjet aircraft began supplanting them after the end of the Second World War. Nevertheless, propeller engines remain popular among light/ultralight aircraft in recreational and utilitygeneral aviation, while gas turbine-powered turboprop engines are used in commercial aviation for regionalair travel, freight and aeromedical services, as well as by the military for low-intensity aerial tasks that warrant low-airspeed/altitudeloitering or simply do not require fast airspeeds, such as tactical airlift, early warning and control, maritime patrol/anti-submarine warfare, electronic warfare and even gunship/close air supportoperations.