Characteristics of Braked, Locked and Free-Wheeling Two- and Three-Bladed Propellers

Authors: Malina, Frank Joseph; Jenney, William W.

Year: 1936

Degree: Master's thesis

Advisor: Unknown, Unknown

Committee Member: Unknown, Unknown

Option: Aeronautics

DOI: 10.7907/HYXB-6T51

Abstract

The use of multi-engined aircraft has introduced the problem of aircraft performance when one or more power units have either become unusable or voluntarily shut down during cruising flight. If the use of the engine is to be discontinued because of mechanical failure, the desirable procedure is obviously to stop it altogether, so as to prevent possible destruction to the engine. This can be accomplished by locking the propeller, by a free-wheeling arrangement, or by feathering a variable pitch propeller. If the use of the engine is to be discontinued merely to reduce fuel consumption, the propeller may be allowed to turn the engine, in which case the propeller is braked by a torque equal to the friction of the engine.

Another recent development connected with braked propellers is the fact that the variable pitch propeller now offers the possibility of using the large increment in drag at low blade angles of braked and free-wheeling propellers for reduction in landing speed or landing run of clean, highly powered, multi-engined aircraft.

It was the purpose of the present investigation to provide information not already made available by researches listed under the references at the end of this paper. Therefore the following thesis will be concerned chiefly with the three-bladed propeller and its effect on airplane characteristics, the two-bladed propeller being used principally for comparison purposes with other available data. The tests were performed at model scale, but their acceptance as applicable to full scale is supported by the favorable comparisons made in Reference 5.

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