Power Plant and Drive Train of the NPS Hummingbird Remotely Piloted Helicopter.

Originally designed as a target drone for the U.S. Army, the NPS Hummingbird has undergone several modifications to convert it into a reliable research platform. The 163 pound remotely piloted helicopter RPH is powered by a Weslake Aeromarine Engines Limited WAEL 342 two stroke, twin cylinder, 25 hp, gasoline engine. An engine failure due to cylinder overheating halted research efforts until investigation as to the cause and subsequent corrections could be made. Costing approximately 3000 per engine, another failure is unacceptable. The tasks undertaken in this thesis were to investigate the cause of the overheat failure and improve the engine cooling system. Cooling system corrections required total redesigns of the engine cooling and engine start systems. Additionally, research of the RPHs history revealed a need for a torsional shock absorber to be incorporated in the drive train to increase component life. The changes made to Hummingbird provide a decrease in empty weight, minimal center of gravity change and, most importantly, an increase in user safety finishing the Department of Aeronautics and Astronautics with a dependable vehicle for rotary wing research.