The proposed study will evaluate the feasibility of producing a low acoustic emission propulsion unit for fixed wing UAV applications, utilizing optimized propeller designs matched to a low cylinder count small reciprocating engine. Acoustic performance will be enhanced by operating the propeller at reduced speed with high advance while improving the operating point of the coupled engine and further stabilizing combustion behaviors at the critical loiter operating point. The key issues of engine and drive dynamics will be addressed to allow design of a reduced weight, reliable system. The lower acoustic emissions of such propulsion system, coupled with improved performance and reduced consumption, will greatly enhance UAV ISR mission capability and be applicable across a significant range of FW assets. Improved consumption and greatly reduced acoustic emissions will enhance the commercial applications of UAVs. The reduced consumption will allow lower operating costs and extended operational range. Reduced acoustic emissions allow operation in close proximity to populated areas, and reduced disturbance to both wildlife and livestock in scientific and agricultural applications and studies.
