INVESTIGATION OF HYDRAULIC POWER TRANSMISSION SYSTEMS FOR V/STOL AIRCRAFT
WESTERN CO OF NORTH AMERICA RICHARDSON TX RESEARCH DIV
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A comparison is presented between the efficiency and weight of the UH-1 helicopter gear transmission and speed reducer systems to a hydraulic power transmitting system for the UH-1. The hydraulic transmission system is composed of a turbine speed hydraulic pump and a hydraulic motor. The hydraulic transmission system utilizes recently developed non-Newtonian, viscoelastic fluids which greatly reduce fluid friction losses, increase hydraulic component volumetric efficiency, and allows a substantial reduction in connecting fluid line sizes without the usual high fluid friction losses which normally result from use of small lines. The results of the comparison show the hydraulic transmission system efficiency closely matches the gear system efficiency, and the hydraulic transmission system is lighter than the gear system. A limited aircraft effectiveness study shows that the flexibility of design which is possible with a hydraulic transmission can result in an increase in useful engine horsepower, reduced infrared signature, improved foreign object damage protection and a reduction in engineairframe vibration. The hydraulic transmission system is based upon hydraulic components which were chosen from an industry and government agency wide search for the best hydraulic components. Design data and calculated and test performance are shown for the hydraulic components. Test data is shown for the fluid flow friction reducing hydraulic fluid. Vulnerability, maintenance, logistics and operational considerations for a hydraulic transmission are presented.