Discussion of Two Specialized Aircraft Propeller Problems

Citation

McCoy, Howard Monroe and Longfelder, Harlowe Julius (1941) Discussion of Two Specialized Aircraft Propeller Problems. Engineer's thesis, California Institute of Technology. doi:10.7907/9YND-4B66. https://resolver.caltech.edu/CaltechETD:etd-11122008-082157

Abstract

Part I: Governing and Synchronization The design and construction of an aircraft propeller governor or synchronizer is a specialized problem concerning Servo-Mechanism Theory. Search developed that adequate theory existed to cover the specific variables involved. The sources used in this report are listed in the extensive bibliography. Short descriptions are presented of the various governing and synchronizing means used to control present day propellers. In this research an airplane engine-propeller system was simulated and a single unit of a synchronizer, suitable for use as a governor for one engine, was invented and constructed. It was demonstrated to meet the United States Army Air Corps tentative specifications for propeller synchronizers. Time and unavailability of material and overworked shop facilities did not permit the construction of a model for full scale multi-motored airplane test. It is contemplated that such a model will later be constructed at the Materiel Division, United States Air Corps, Wright Field, Dayton, Ohio. A detailed description of this invention is presented in Appendix I. A discussion is presented of the general servo-mechanism theory as applied to airplane propeller governors and synchronizers. In addition, a short discussion is presented of how synchronization of propellers influences the tactical employment of military aircraft. The physiological effect on occupants of aircraft is also shortly discussed. Part II: Effect of Variable Engine Reduction Gearing on Aircraft Performance The demand for improved performance in aircraft has led through the years to the development of more efficient propulsive systems, starting with the fixed pitch propeller directly driven from the engine and progressing to the modern geared constant speed variable pitch propeller. This development and the reasons for it are briefly described. The continued increase in performance leads to the two speed reduction gear and finally to the continuously variable reduction gear combined with the constant speed variable pitch propeller. The possible advantages of such an installation and the reasons for these advantages are described. Two examples of modern military airplanes are used to illustrate in detail the gains in performance that may be obtained. The extension to probable developments in airplanes to be built in the near future is considered. Mechanical difficulties and control problems are briefly discussed.

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