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Technology update
Scimitar cuts noise
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A noise reduction program by Britten-Norman (BN), maker of the Islander, Trislander, and Defender range of aircraft, has shown improvements of between 5 and 7 dB(A), according to the company. BN has worked with Hartzell Propeller Inc. to install experimental three-bladed propellers on a BN2B piston-engined Islander. The propellers have a marked swept scimitar profile. Improved airfoil efficiency results in the same power transfer at reduced engine rpm with the consequential lower tip speed and scimitar planform reducing noise. The trials form part of a program supported by the UK Department of Trade and Industry, to reduce the noise of piston-engined light aircraft in general aviation.
Among the Islander's many applications, it is used by law enforcement agencies. Operations typically involve low-level flights over urban areas, often at night, when noise reduction is a goal.
The next phase of the program focuses on reduction of exhaust noise. BN will be working with muffler specialists in the U.S. and Europe. When trials are completed this year, the new propeller and exhaust silencing system will become standard production on all new piston-engined Islanders, with retrofit kits available for Islanders in operation.
Stuart Birch
Aerospace Engineering May 2000
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