Author: W. H Lewis (Jr)

Publisher:

Published: 1976

Total Pages: 91

ISBN-13:

This joint program between the Lockheed-Georgia Company and the Air Force Materials Laboratory was concerned with measuring the structure-borne noise background in a large aircraft during four test flights to determine the feasibility from a signal-to-noise standpoint of using acoustic emission techniques to monitor structure during flight. Measurements were made in the frequency range from 0.1 MHz to 2.0 MHz using off-the-shelf acoustic emission transducer and 40-db preamplifiers in conjunction with a Lockheed-designed spectrum analyzer and a pulse code modulation data system. Calibration and flight data were recorded on the flight instrumentation magnetic tape recorder. Transducer and preamplifiers were installed at nine locations on the aircraft including the wing, pylong, main landing gear well and the empennage. A commercial flaw locator system was also installed to monitor the center wing lower surface during the four flights. The results showed that structure-borne noise can vary considerably over the aircraft structure and that a suitable acoustic emission signal-to-noise ratio can be achieved at most locations within the frequency range 0.5 MHz to 0.75 MHz, although the noisiest areas may require operation up to 1.0 MHz. (Author).