Efficient Propulsion for Long Loiter Tactical Mini Air Vehicles

We propose to demonstrate self starting, computer controlled, high efficiency, heavy fuel IC engines for small UAVs with extended loiter capability. Internal combustion engines were supplanted by gas turbines for most military aircraft after WWII, butthey are still the obvious choice for small, low subsonic UAVs. We will investigate adapting mass production direct injected 2 stroke engines for UAV use. A loitering UAV needs a lightweight powerplant with good specific fuel consumption across a wideoperating range because the operating point changes dramatically as fuel is burned off. We modify and test a direct injected 50cc engine derived from a low emissions scooter and compare it's performance with a high output fuel injected 4-stroke. Withstratified charging to minimize throttling losses and improved charge trapping, we expect a BSFC below 0.5 lb/hp-hr throughout the flight envelope. We will also design optimized propellers and provide detailed performance estimates for this propulsionsystem in candidate airframes. An efficient, robust, self starting heavy fuel IC engine is sought by all branches of the military and could see widespread use for portable power for commercial use.