Propeller (aircraft)

An aircraft propeller (noun /prəˈpel·ər/) or airscrew converts rotary motion from an engine or other mechanical power source, to provide propulsive force. It comprises a rotating power-driven hub, to which are attached several radial airfoil-section blades such that the whole assembly rotates about a longitudinal axis. The blade pitch may be fixed, manually variable to a few set positions, or of the automatically-variable "constant-speed" type.

The propeller attaches to the power source's driveshaft either directly or, especially on larger designs, through reduction gearing.

Most early aircraft propellers were carved by hand from solid or laminated wood, while metal construction later became popular. More recently, composite materials are becoming increasingly used.

Propellers are only suitable for use at subsonic airspeeds up to around 480 mph (770 km/h), as above this speed the blade tip speed begins to go supersonic, with the consequent shockwaves causing high drag and other mechanical difficulties.

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 ones 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, men 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.

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Wikipedia