On the Design and Test of a Low Noise Propeller - CAFE Foundation

Report No. 1761Bolt Beranek and Newman Ino.ON THE mSION AND TEST OF A LOW NOISE PROPELLERAn extensive review of noise and performance of generalaviation propellers was performed at MIT" Research was done inthree areas: A review of the acoustic and aerodynamic theory ofgeneral aviation propellers, wind tunnel tests of three onequarterscale models of general aviation propellers, and flight.test of two low noise propellers.One of the two low noise propellers was designed and testedat MIT and has already been described2. The second propeller wasdesigned at MIT and flight tested at OSU. The design and testingof the second propeller is reviewed herein.This rpport deac ribes the general aerodynamic considerat ionsneeded to design 8 new propeller, reviews the design point.analysis of low noise propellers, and finally, compares thepredicted and measured noise levels.To design a fixed pitch propeller for an existing aircraftthere are two points to consider. First, the propeller must bematched to the engine, Second, the power result lng from theengine propeller combination must be matched to the needs of thealrcraf t, Fig. 1 lllustretes this problem,In Fig. 1, the vertical axis is power and the horizontalaxis is aircraft speed. The solid black line represents thepower needed to overcome aircraft drag at any particularvelocity. This power is given by the expression: