Airplane wings are more flexible than many might think, but important details of how a wing behaves in flight have long been a mystery, and safety has dictated a conservative approach to such unknowns. New research has reduced the guesswork.
An aircraft with a lighter, more flexible wing structure would fly more efficiently, but there’s a trade-off: Too much flexing spells failure that no one can live with. Understanding how wings behave under loads has for years been a goal of researchers seeking more fuel-efficient aircraft that are just as safe as the airplanes of today.
NASA, Lockheed Martin Skunk Works, and the Air Force Research Laboratory worked on this problem in 2012 using unmanned aircraft; much more recently, it was Brazilian airplane maker Embraer teaming up with the German Aerospace Center (Deutsches Zentrum für Luft- und Raumfahrt, or DLR) and the Netherlands Aerospace Center to test a highly elastic, custom-made fiberglass wing in a wind tunnel in Amsterdam. Embraer initiated the project seeking to validate its computer model projections, enlisting help from the German and Dutch government aerospace agencies to design a wing tailored for the wind tunnel, and carry out the tests that aimed to probe the wing’s limits and analyze various loads without actually inducing a fatal flutter.
With instruments arrayed to measure stress and strain, the wind tunnel was cranked up to speeds ranging from Mach 0.7 to Mach 0.9 with the test wing positioned at various angles of attack.
The result was success, DLR reported in a recent news release: the first real-time analysis of wing behavior under stress, as the wing approaches flutter.
"This is a brand new method to analyse aircraft flutter," said Yves Govers of the DLR Institute of Aeroelasticity, in the news release. “It should also allow future aircraft to be tested more efficiently and more quickly.”