Aircraft damage detection from acoustic and noise impressed signals found by a cockpit voice recorder

Abstract

Currently, research is being conducted to detect damage through structural acoustics, signal processing, and transducer designs. The present study illustrates that damage detection may be carried out with an existing system acting as a latent signal transducer. One example involved a reliability problem in a commuter liner aircraft engine mount design where undetected crack growth created a critical whirl flutter condition destroying the aircraft. This reliability problem prompted the need for an in-place damage detection system to identify critical engine mount conditions. Signal analysis of data acquired by a cockpit voice recorder prior to and during the catastrophic aircraft whirl flutter event provided insight into critical signals that indicated the failure onset. Although regularly scheduled inspections failed to detect the problem, cockpit voice recorder signals contained a dynamic signature of this damage feature throughout the duration of the tape. It is highly probable that this damage signature existed for a much longer period of time, but due to the endless loop configuration of the cockpit voice recorder the earlier data were erased. The study indicated that even in the case of an unused cockpit voice recorder track, careful signal processing can extract surprising details about detecting potential damage. [See NOISE-CON Proceedings for full paper.]