January 16, 2014
By Dan Namowitz
No aerodynamic design, no matter how broad its historical acceptance, is exempt from scrutiny for one more improvement. Whether an aircraft needs a weight reduction, a power increase, or a way to reduce drag, the search for enhancements is always on a drawing board, somewhere.
Sometimes gains come at the expense of earlier innovation long held to be the practical solution to a much-pondered engineering challenge: Hinged flight control surfaces came along shortly after the wing-warping technology developed by the Wright Brothers, and remain the usual method of construction for flight control surfaces.
Now, wing “morphing” may be emerging as an alternative approach that would replace jointed control surfaces on aircraft with seamless, deformable surfaces. The concept will undergo flight testing later this year, and was on display at a recent science and technology exposition in National Harbor, Md., outside Washington, D.C.
The developer, Ann Arbor, Mich.-based Flexsys believes it has achieved “the long sought, elusive goal of practical seamless control surface technologies” with its Flexfoil control surfaces. The company, founded in 2000 by Sridhar Kota, a University of Michigan professor of mechanical engineering, exhibited in January at SciTech 2014, organized by the American Institute of Aeronautics and Astronautics (credo: “In search of the next impossible thing.”).
Flexsys announced that flight tests will be conducted by NASA at the Dryden Research Center in July, using a Gulfstream bizjet modified with the seamless control surfaces in place of trailing-edge flaps.
“In retrofit applications, the technology can cut fuel consumption by 4 – 8 percent, and that number can grow to 12 percent or more in clean-sheet builds,” said Flexsys in its news release. Other projected benefits include “significant noise reduction”—up to 40 percent on landing—and lower maintenance costs for the longer-lived control surfaces.
Setting its sights on cutting what Flexsys called the U.S. aviation community’s $54 billion fuel bill, the company offered an explanation for why it believes it has overcome past impediments to superseding the accepted solution of hinged control surfaces.
Earlier efforts “suffered from complexities with the actuators,” and were saddled by dependence on heavy components. By contrast, “the FlexFoil control surface technology employed a new approach, called distributed compliance, to achieve practical variable geometry wings—lightweight, reliable and cost effective,” it said.
Benefits of variable-geometry wings could accrue to “a variety of aircraft” without a high level of structural or control complexity, according to Peter Flick, a program manager working with Flexsys at the Air Force Research Laboratory at Wright-Patterson Air Force Base in Ohio.
The design could also be applied to other control surfaces, including helicopter rotor design, Flexsys said, adding that prototypes have been produced.
Flexsys predicted that success of practical “wing morphing” in tests would gain the attention of both “designers and accountants.”
Dan Namowitz is an aviation writer and flight instructor.
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