In our May 2014 issue, Sridhar Kota, a professor of engineering at the University of Michigan and founder and president of the company FlexSys, published an article about his long-running campaign to take complex, multipart machines and redesign them as flexible, one-piece devices (subscription required). Kota has been working on morphing airplane wings since the 1990s. He and his colleagues have now reached a milestone in that quest: a successful test flight of a flexible aircraft control surface, a shape-shifting one-piece mechanism that could replace the conventional flaps on airplane wings. Kota and his collaborators at NASA and the U.S. Air Force say the test is an aviation first.
Kota tells the whole story of his monoform airplane-wing hunt in the May issue, but the short version goes like this. In the mid 1990s, Kota began wondering whether anyone had ever tried to build a morphing one-piece airplane wing. They had indeed, he found. The Wright Brothers had tried it. So had engineers at nearby Wright-Patterson Air Force Base, who were intrigued when Kota, then still at the University of Michigan, came calling.
Twenty years later, with backing from the United States Air Force Research Laboratory, Kota and his collaborators put the first flexible wing in the air. In flight tests at Edwards Air Force Base in California, FlexSys engineers replaced the primary trailing edge wing flaps on a Gulfstream III jet with an 18-foot span of FlexFoil aircraft control surface, which you can see at work in this video. The plane had no backup flaps whatsoever, Kota tells me.
Here’s how Kota summarized the tests in an email to me this week:
"The first test flight was on Nov 6. Since then, NASA is conducting flight tests every week and they will continue for another 3 months. The flight tests already conducted to-date included speeds at 0.75 Mach at 20,000 and 40,000 ft altitude and various banking maneuvers up to 1.7G (continuous load) and high dynamic pressures subjecting the FlexFoil control surface to various load conditions. All the tests so far were completely successful - no issues what so ever. Most importantly, yesterday’s flight test subjected the wing to one of the most severe dynamic pressures (384 psf) and no issues at all!"
The idea behind the flexible flap is to create a wing that can be fine-tuned throughout flight with a precision unavailable to conventional flaps. The result should be simpler, quieter, more reliable, and more fuel-efficient. In 2006, FlexSys attached a prototype of the flexible wing to the underside of Scaled Composite’s White Knight aircraft and flew test runs over the Mojave Desert. Results from that test led Kota to estimate that eventually, in new aircraft built to take full advantage of the flexible wings, the technology could cut fuel consumption by 12 percent. As Kota wrote in our pages earlier this year, in an industry that burns 16 billion gallons of jet fuel a year, that could be significant.
To read more about Kota’s flexible machines, see his piece in our May issue (subscription required).