08 Mar 2007
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C130 aircraft
Structural monitoring has been an important factor for operators of fast jet aircraft fleets for some years.
Airframe fatigue management relies on recording and predicting the usage of the aircraft. Strain gauges distributed on a structure will give the most direct and accurate indication of fatigue consumption. This approach does, however, rely on reliable strain measurements in a sufficient number of locations. Optical fibre sensors, especially the Bragg grating strain sensors, offer significant advantages over electrical, resistive foil strain gauges which are currently the state of the art for structural monitoring purposes.
The Optics and Laser Technology department of the ATC has developed and evaluated strain gauge systems using optical fibres. Initial laboratory validation proceeded to deployment onto large-scale structures. Initially a maritime application in the form of a 35 m composite yacht mast with embedded Bragg grating sensors was demonstrated. This was a convenient platform on which to tackle some of the key installation and system issues. Having gained confidence, the work then progressed to the more demanding aerospace environment, only this time using surface mounted sensor configurations.
Fibre optic sensors were embedded into a carbon fibre, ocean going yacht mast. A complete structural monitoring systems was developed and underwent sea trials aboard a luxury yacht equipped with a 35-metre mast rig. Following the successful maritime demonstration a similar system was fitted to a BAE Systems Jetstream test aircraft and underwent a series of test flights from the Air Systems Warton aerodrome.
