Characterization of Propeller Performance and Engine Mission Matching for Small Remotely Piloted Aircraft

Abstract

§** An experimental study is conducted to investigate matching USAF Group I/II RPA propeller performance to an engine map and RPA mission to maximize efficiency and range. Performance characterization of the Fuji Imvac BF-34EI engine is presented. Propeller performance is characterized for 28 commercial-off-the-shelf (COTS) propellers in a vertical wind tunnel using a pneumatic motor to drive the propeller. Propeller thrust, torque, and rotational speed are measured at different forward velocities to characterize propeller efficiency. An uncertainty analysis at a characteristic point is conducted for the measured values and is found to be 3.9%. RPA mission profile requirements are presented. A method to compare different propellers is presented. Propellers are first sorted and downselected by required rate of climb (ROC) for RPA take-off/climb-out conditions. The remaining propellers are then further downselected based on minimizing fuel consumption for RPA cruise conditions. It is discovered that performance differences can occur even between propellers of the same nominal size but from different manufacturers. Of the limited number of propellers characterized in this study, the APC C2 17x10, Top Flight PP 18x12, and APC C3 22x10 are determined to be the best matched COTS propellers in their respective diameter classes to the Fuji Imvac BF-34EI. The data used in the selection process and more detailed data for the three aforementioned propellers is presented. Propeller data for each of the three propellers is overlaid on a typical USAF Group I/II RPA engine map. Even among propellers of the same diameter, mission duration can be extended as much as 100 miles (20%) by selecting the optimal propeller for a given engine.