Smart sensors have a very significant role in aerospace, particularly when they can quickly detect potentially serious damage to a structure. Their increasing sophistication and reliability is expected to contribute to huge savings in maintenance, servicing, and support costs, all of which are central to the successful operation of aircraft that may have service lives that span decades.
BAE Systems leads research and development work on the Advanced Structural Health Monitoring System (AHMOS), part of a European R&D-funded initiative, which has now seen smart sensors flight tested on a BAE Hawk aircraft. The trial demonstrated, for what some say is the first time, the operation of a fully integrated automated damage-detection system within a flight environment. BAE regards it as an important step toward the eventual goal of self-inspecting aircraft.
Structural inspection is a significant factor in the cost of supporting fleets of both military and commercial aircraft. In-service lives of 40 years or more are now expected. However, as aircraft age, the servicing needed to maintain stringent airworthiness standards invariably becomes more costly.
“The new system aims to avoid lengthy and expensive structural inspections that require the repeated dismantling of large sections of an aircraft,” said Jim McFeat, AHMOS Technical Manager, BAE. “Very often, such inspections are precautionary and no faults that need repairing are found.”
The flight test Hawk carried an acoustic emissions detection kit that was able to record the existence of cracks in specifically designed dummy structures and download a diagnosis when the aircraft landed.
“Using a combination of strain gauge sensors and fiber-optic cables connected to a computer, and contained within an aerodynamic pod under the fuselage of the Hawk, we demonstrated that the technology works,” said McFeat. “We have been able to compare all of the aircraft’s maneuvers in flight with the pilot’s notes and our own computer.” He added the first two flights by the AHMOS-equipped Hawk had “good results.”
Further flights were to be made with a formal report expected shortly. “Ultimately, we are trying to automate the non-destructive testing process in the same way that car manufacturers have done for engine management systems,” said McFeat. “The customer will plug a computer into a data-box on the aircraft and download in-flight information gathered from gauges and sensors at strategic points.”
If sensors fitted deep inside the aircraft structure can reliably detect the onset of damage, the need to dismantle sections of the airframe would be greatly reduced and new detection process could be performed remotely; at the press of a button or automatically online.
“Engineers are just beginning to realize the potential value of this type of structural monitoring,” added McFeat. “Aircraft are expensive assets, and their owners are pushing to get the maximum possible use from them. Any technology that can help deliver more cost-effective operations or increased availability is bound to be welcome.”