W.D. Bryce

In order to understand better the sideline noise characteristics of aircraft with rear-fuselage engine installations, a series of noise measurements made in 1976 using a BAC 1-11 aircraft have been analysed. In these tests, aimed at measuring the effects of wing vortices on the engine noise radiation, the aircraft was flown in a large flat circular arc at 0.25M and at a bank angle of 20°, crossing a radial microphone array at a height of 500 feet. The noise measurements were made with the aircraft close to the vertical plane containing the array and have been processed to produce thirdoctave spectra corrected for atmospheric absorption and to a constant distance . The frequency range of the acceptable data falls into three octaves with centre frequencies of 500 Hz, 1 kHz and 2 kHz and the variation of the aircraft octave sound pressure levels as a function of the azimuth angle are presented. There are marked dips in the noise levels, peaking at 61h dB, at angles near the wing plane and there is little dependence on frequency over the range studied. Noise reductions are evident up to about 20° below the wing plane. The observed radiation patterns are believed to arise primarily from wing vortex refraction effects although jet-by-jet shielding effects will contribute.

DGLR/AIAA 14th Aeroacoustics Conference, 1992

Conference Paper

englisch

21,0 x 29,7 cm, 4 Seiten

DGLR-Bericht, 1992, 1992-03, DGLR/AIAA 14th Aeroacoustics Conference - Proceedings; S.936-939; 1992; Deutsche Gesellschaft für Luft- und Raumfahrt - Lilienthal-Oberth e.V., Bonn

NA

aeroacoustics, engine airframe integration, bac 1-11 aircraft

Bibliothek

1992