Very Low Noise, High Efficiency Propeller Designs for Small UAVs

"Sagetech Corporation proposes by this document to perform Navy SBIR task N02-098, Very Low Noise, High Efficiency Muffler Designs for Small UAV's (Unmanned Aerial Vehicles).There are several discrete sources of noise in small aircraft: propeller noise, engine crankcase radiation, engine inlet (carburetor) noise, exhaust noise, and vibration induced airframe noise. Other work (N02-096) addresses propeller noise, the presentsolicitation addresses exhaust noise, and the other sources of noise are addressed elsewhere, insignificant, or unaccounted for. Sagetech Corporation is prepared to address engine crankcase noise, vibration induced airframe noise, and engine inlet noiseshould the need arise.The stock OS Max LA 0.4 engine and muffler was analyzed and the task found to be feasible. A design methodology comprising of equal parts computer assisted noise modeling, test bench hardware verification, and actual hardware noise measurement is proposedto rapidly converge on a cost effective exhaust design which balances noise performance with engine performance.An analysis is presented in which the stock muffler is characterized and a preliminary design is evaluated, nearly meeting design goals. From this it is surmised that the task is feasible and within the technical capability of Sagetech Corporation Commercial applications for the proposed work lie primarily in the RC airplane industry as well as small garden tools (weed wackers). Im