ASME-Landmark:Hydromatic Propeller

Rapid development of aircraft design in the 1930s required many related innovations, including propeller design. The hydromatic propeller by Hamilton Standard marked a significant advance over the counterweight-type, controllable pitch propeller. The first test flight of the prototype took place in 1938, with a public demonstration by a United Air Lines DC-3 over New York City on April 6, 1938. It played a distinguished role in allied combat aircraft in World War II, and its continuing development has incorporated many features used on later aircraft, including turboprop planes.

The hydromatic propeller was designed for larger blades, faster rate of pitch change, and wider range of pitch control than earlier controllable-pitch propellers. Improvements from a two-position controllable to the constant- speed type propeller were not equal to the demand of high-output engines or rapid airplane maneuvers. The variable-pitch aircraft propeller allowed the adjustment in flight of blade pitch, making optimal use of the engine's power under varying flight conditions. On multi-engined aircraft it also permits feathering (stopping the rotation of) the propeller of a nonfunctioning engine to reduce drag and vibration, among other advances.

The ASME landmark is a Model 23E50 Hamilton Standard quick-feathering hydromatic propeller, typical of many thousands produced from 1938 to 1945. It was set aside as an example from an early production run and donated by Hamilton Standard to the New England Air Museum. See ASME website for more information