Power speed reduction units for general aviation part 3: Simplified gear design piston-powered, propeller-driven general aviation aircrafts

The power speed reduction unit (PSRU) is the device that is loaded by the piston engine and the thruster. The thruster, a propeller of a fan, acts on the PSRU to extract the required power at the optimum speed for the aerial vehicle. Inertia, thrust and vibrations load the PRSU. PSRU has been "the problem" of the years before WWII. These problems periodically come back from common design errors or from the introduction of new technologies. For historical reasons, FAR and JAR do not allow the use of belt and chain transmissions in PRSUs for aircrafts. However, recent advances in timing belts make it possible to manufacture lubrication free PRSUs. Multi-Groove-V belts have also been used successfully in helicopters and homebuilt aircrafts. Belt PRSU are critical in design and they will be fully analyzed in another paper. This third paper deals with the general problem of designing the PRSU gear drives on a general aviation aircraft [1-2].