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Alternatively, a constant-speed propeller is one where the pilot sets the desired engine speed , and the blade pitch is controlled automatically without the pilot's intervention so that the rotational speed remains constant. The device which controls the propeller pitch and thus speed is called a propeller governor or constant speed unit.
A 6-bladed Hamilton Standard 568F propeller on an ATR 72 short-haul airliner. Lowry [27] quotes a propeller efficiency of about 73.5% at cruise for a Cessna 172.This is derived from his "Bootstrap approach" for analyzing the performance of light general aviation aircraft using fixed pitch or constant speed propellers.
The momentum theory or disk actuator theory – a theory describing a mathematical model of an ideal propeller – was developed by W.J.M. Rankine (1865), Alfred George Greenhill (1888) and Robert Edmund Froude (1889). The propeller is modelled as an infinitely thin disc, inducing a constant velocity along the axis of rotation.
They introduced a twist in their blades to keep the angle of attack constant. Their blades were only 5% less efficient than those used 100 years later. [28] Understanding of low-speed propeller aerodynamics was complete by the 1920s, although increased power and smaller diameters added design constraints. [29]
Same as the B1E but with a front inlet fuel injector, propeller governor on front of the crankcase and a retard magneto. [2] [4] IO-360-M1B 180 hp (134 kW) at 2700 rpm, Minimum fuel grade 91/96 avgas, compression ratio 8.50:1. Same as the M1A but with a rear-mounted propeller governor and impulse magneto. [2] [4]
The constant-speed propeller was popularly known as the "gearshift of the air." [12] [13] [14] Caldwell and Ernest G. McCauley hold three joint patents for propeller innovations. [6] In 1990, the Hydromatic Propeller, on display at the New England Air Museum of Windsor Locks, was pronounced as an International Historic Mechanical Engineering ...
However, the actual propeller speed remains stable only if operational conditions (e.g., airspeed) do not change, otherwise the pilot has to constantly adjust the pitch to maintain the desired propeller speed. Constant-speed propeller control system simplifies this for the pilot by introducing a propeller governor, where the lever controls the ...
Propellers: 2-bladed constant-speed pusher propeller; Performance. Maximum speed: 115 kn (132 mph, 213 km/h) Combat range: 1,100 nmi (1,200 mi, 2,000 km) 12 hours loiter;