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“Until the days of supersonic speed and jet propulsion of rocket ships, the propeller is a relatively efficient method of moving our airplanes through the air up to speeds of 5 to 6 hundred miles per hour. In general, the size of a propeller is dependent upon the power of the engine…”
US Army Air Corps Pilot Training Film TF1-246
Originally a public domain film from the US Army Air Corps, slightly cropped to remove uneven edges, with the aspect ratio corrected, and one-pass brightness-contrast-color correction & mild video noise reduction applied.
The soundtrack was also processed with volume normalization, noise reduction, clipping reduction, and/or equalization (the resulting sound, though not perfect, is far less noisy than the original).
Wikipedia license:
An aircraft propeller, 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…
Theory and design of aircraft propellers
A well-designed propeller typically has an efficiency of around 80% when operating in the best regime. The efficiency of the propeller is influenced by the angle of attack (α). This is defined as α = Φ – θ, where θ is the helix angle (the angle between the resultant relative velocity and the blade rotation direction) and Φ is the blade pitch angle. Very small pitch and helix angles give a good performance against resistance but provide little thrust, while larger angles have the opposite effect. The best helix angle is when the blade is acting as a wing producing much more lift than drag. Angle of attack is similar to advance ratio, for propellers…
