Italian airframe manufacturer Alenia Aerospace has conducted two flight tests using aC-27J Spartan airlifter as part of its structural health monitoring research efforts within the EU-funded SMIST project.
The first flight was in December 2007 and the second in February 2008, and Alenia is now preparing for another two although these will not extend beyond one hour.
"We placed 12 fibre-optic sensors a few 100 microns thick on the aircraft, four of which were applied on to the external side of the aircraft, the others remaining on the internal surface. No commercial aircraft is flying today with fibre-optic sensor technology which we believe can provide more sensitivity than other types of sensor," says Francesco Camerlingo, head of Alenia's structural health monitoring research.
Structure
"We are not only targeting a reduction of maintenance costs, but one other major advantage is the ability to monitor structural characteristics of composite material. Another area is to test whether the fibre-optic has any effect on the mechanical characteristics of the aircraft structure."
Camerlingo says data is recorded onboard but could be transmitted using telemetry to a ground station via the aircraft's communications systems
Achille Carbone, Alenia Aeronautica's head of special projects says: "These sensors we know would need to be improved in two areas: firstly, the application of the sensor to the structure and, secondly, the sensor itself. What we are now planning is to find out what is the best way of applying the sensors to the structure to obtain the level of information we require with the minimum number of sensors possible.
"There are different sensors you can use. For example, on a wing you would typically need 50 fibre-optic Bragg-grating sensors in order to build a theoretical model to know the behaviour of the wing. Other sorts would require much smaller numbers but we chose these because they give us an advantage in terms of not only maintenance costs but also because they give a better analysis."
Alenia Aeronautica, which is taking the lead in the EU-funded Green Regional Aircraft project within the €1.6 billion ($2.27 billion) Clean Sky Joint Technology Initiative, will be feeding the results of these flight tests into the innovative technology demonstrator that aims to make structural health monitoring a reality by 2014.
"By then, the cost benefit analysis of sensor technology will be known. And while we have to make it competitive to be used on an aircraft, the quality of the data gathered so far has been very encouraging," says Carbone.
Maturity
Camerlingo says sensor technology is expected to have reached a level of maturity by 2010. Within another five years, he says, it is not unrealistic to expect that aircraft with structural health monitoring will be flying in revenue service, on its own aircraft and those of its clients, both Airbus and Boeing.
"Alenia wants to be at the cutting edge of this technology essentially to remain competitive. We are autonomous in deciding to develop whatever technology we choose. We also manufacture our own aircraft and would be contenders to develop the next generation future regional aircraft in our own right," says Carbone.
Source: Flight International
