In aeronautics, an aircraft propeller, also called an airscrew, is a propulsion device that converts rotary motion from an aircraft 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 drive gasoline engine) being the first-ever manned fixed-wing aircraft to achieve sustained flight. 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 subsonic airspeeds, 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-payload jet aircraft began supplanting them after the end of the Second World War. Nevertheless, propeller engines remain popular among light/ultralight aircraft in recreational and utility general aviation, while gas turbine-powered turboprop engines are used in commercial aviation for regional air travel, freight and aeromedical services, as well as by the military for low-intensity aerial tasks that warrant low-airspeed/altitude loitering 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 support operations.
History
Early designs
The earliest references for vertical flight came from China. Since around 400 BC, Chinese children have played with bamboo flying toys. This bamboo-copter is spun by rolling a stick attached to a rotor between one's hands. The spinning creates lift, and the toy flies when released. The 4th-century AD Daoist book Baopuzi by Ge Hong (抱朴子 "Master who Embraces Simplicity") reportedly describes some of the ideas inherent to rotary wing aircraft. Designs similar to the Chinese helicopter toy appeared in Renaissance paintings and other works. It was not until the early 1480s, when Leonardo da Vinci created a design for a machine that could be described as an "aerial screw", that any recorded advancement was made towards vertical flight. His notes suggested that he built small flying models, but there were no indications for any provision to stop the rotor from making the craft rotate. As scientific knowledge increased and became more accepted, man continued to pursue the idea of vertical flight. Many of these later models and machines would more closely resemble the ancient bamboo flying top with spinning wings, rather than Leonardo's screw. In July 1754, Russian Mikhail Lomonosov had developed a small coaxial modeled after the Chinese top but powered by a wound-up spring device and demonstrated it to the Russian Academy of Sciences. It was powered by a spring, and was suggested as a method to lift meteorological instruments. In 1783, Christian de Launoy, and his mechanic, Bienvenu, used a coaxial version of the Chinese top in a model consisting of contrarotating turkey flight feathers as rotor blades, and in 1784, demonstrated it to the French Academy of Sciences. A dirigible airship was described by Jean Baptiste Marie Meusnier presented in 1783. The drawings depict a 260-foot-long (79 m) streamlined envelope with internal ballonets that could be used for regulating lift. The airship was designed to be driven by three propellers. In 1784 Jean-Pierre Blanchard fitted a hand-powered propeller to a balloon, the first recorded means of propulsion carried aloft. Sir George Cayley, influenced by a childhood fascination with the Chinese flying top, developed a model of feathers, similar to that of Launoy and Bienvenu, but powered by rubber bands. By the end of the century, he had progressed to using sheets of tin for rotor blades and springs for power. His writings on his experiments and models would become influential on future aviation pioneers. William Bland sent designs for his "Atmotic Airship" to the Great Exhibition held in London in 1851, where a model was displayed. This was an elongated balloon with a steam engine driving twin propellers suspended underneath. Alphonse Pénaud developed coaxial rotor model helicopter toys in 1870, also powered by rubber bands. In 1872 Dupuy de Lome launched a large navigable balloon, which was driven by a large propeller turned by eight men. Hiram Maxim built a craft that weighed 3.5 long tons (3.6 t), with a 110 ft (34 m) wingspan that was powered by two 360 hp (270 kW) steam engines driving two propellers. In 1894, his machine was tested with overhead rails to prevent it from rising. The test showed that it had enough lift to take off. One of Pénaud's toys, given as a gift by their father, inspired the Wright brothers to pursue the dream of flight.
First modern propellers
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