Networks of sensors mounted on commercial aircraft might one day check continuously for the formation of structural defects, possibly reducing or eliminating scheduled aircraft inspections. Like nerve endings in a human body, in situ sensors offer levels of vigilance and sensitivity to problems that periodic checkups cannot, says Dennis Roach, who leads a Sandia National Laboratories team evaluating some of the first sensor systems for aircraft. “With sensors continually checking for the first signs of wear and tear, you can restrict your maintenance efforts to when you need human intervention,” he says.
Structural health monitoring, or SHM, techniques are gaining the support of airframe manufacturers, airlines, and regulators. SHM incorporates into the aircraft structure itself nondestructive inspection (NDI) technologies currently used in manual inspections — to scan for small cracks in the airframe, for example. Widespread adoption of SHM could significantly reduce maintenance and repair expenses for commercial aircraft, now estimated at about a quarter of the fleet’s operating costs. Ground crew technicians might plug a laptop or diagnostic station into a central port on the aircraft to download structural health data. Eventually “smart structures” fitted with many sensors could self-diagnose and signal an operator when repairs are needed. The SHM sensors being developed or evaluated at Sandia can find fatigue damage, hidden cracks in hard-to-reach locations, disbonded joints, erosion, impact damage, and corrosion, among other defects commonly encountered in aging aircraft. Ultimately an integrated network of sensors could monitor not only structural elements, but also the health of electronics, hydraulics, avionics, and other systems.