Effect of Crack Presence on In-Flight Airframe Noises in a Wing Attachment Component
The relation of the occurrence of airframe acoustic emissions to aircraft manoeuvre are reported for Avro CF-100 upper forward wing trunnions. Periods of excessive noise are found when the airframe load is changing during entry to and exit from sustained-G manoeuvres. During constant-G periods, the airframe noise level is reduced by a factor of more than one hundred. These quiet periods provide a suitable signal-to-noise level for the in-flight detection and monitoring of slow, stable crack growth in common airframe materials, even in a noisy load transfer component such as the wing trunnion studied here. Simultaneous in-flight acoustic emission measurements in symmetrically-located airframe components are also reported. The ratio of the number of recorded event counts in a cracked component to that in an uncracked component during the same flight is found to increase linearly with the crack face area for through crack lengths in the range 0–5 mm.