Feb_March_AMP_Digital

A D V A N C E D M A T E R I A L S & P R O C E S S E S | F E B R U A R Y / M A R C H 2 0 1 8 1 7 The Spanwise Adaptive Wing (SAW) concept seeks to enhance aircraft perfor- mance by allowing the outboard portions of wings to fold according to different flight conditions. NASA engineers believe this could create lateral-directional stabil- ity and reduce drag. Courtesy of NASA. to 80% less than traditional systems. The recent flight tests at Armstrong successfully demonstrated the materi- al’s application and use, by folding the wings between 0° and 70° up and down in flight. “We wanted to see—can we move wings in flight, can we control them to any position we want to get aerody- namic benefits out of them, and could we do it with this new technology,” ex- plains SAW co-principal investigator Othmane Benafan, who also serves as vice president of ASM’s affiliate soci- ety, the International Organization on Shape Memory and Superelastic Tech- nologies (SMST). “Folding wings has been done in the past, but we wanted to prove the feasibility of doing this us- ing shape memory alloy technology, which is compact, lightweight, and can be positioned in convenient places on the aircraft.” On subsonic aircraft such as com- mercial airliners, the potential aerody- namic benefit of folding wings includes increased controllability, which may re- sult in reduced dependency on heavier parts of the aircraft, including the tail rudder. This may result in a more fu- el-efficient aircraft as well as the abil- ity for future long-winged aircraft to taxi in airports. In addition, pilots may take advantage of a number of differ- ent flight conditions such as wind gusts by folding the wings to adapt while in flight. SUPERSONIC FLIGHT BENEFITS One of the most significant poten- tial benefits of folding wings in flight be- comes more apparent with supersonic flight. “There’s a lot of benefit in fold- ing the wing tips downward to sort of ‘ride the wave’ in supersonic flight, in- cluding reduced drag. This may result in more efficient supersonic flight,” explains SAW principal investigator Matt Moholt. “Through this effort, we may be capable of enabling this ele- ment for the next generation of super- sonic flight, to not only reduce drag but also increase performance as you transition from subsonic to superson- ic speeds. This is made possible using a shape memory alloy.” The shape memory alloy is trig- gered by temperature and works by us- ing thermal memory in a tube to move and function as an actuator. Upon heat- ing, the alloy activates a twisting mo- tion in the tubes, which ultimately moves the wing’s outer portion up or down. NASA Glenn developed the initial alloy material and worked closely with Boeing to be able to use the alloy with an actuator during flight. “The performance of this new al- loy that we developed between NASA N ASAhas successfully applied a new technology in flight that allows air- craft to fold their wings to different angles while in the air. The recent flight series, which took place at NASA’s Arm- strong Flight Research Center in Califor- nia, was part of the Spanwise Adaptive Wing (SAW) project. SAW aims to validate the use of a cutting-edge, lightweightma- terial to be able to fold the outer portions of aircraft wings and their control surfac- es to optimal angles in flight. The project, a joint effort between Armstrong, NASA Glenn Research Cen- ter in Cleveland, Langley Research Center in Virginia, Boeing Research & Technology in St. Louis and Seattle, and Area-I Inc. in Kennesaw, Georgia, may produce multiple in-flight benefits for future aircraft, both subsonic and supersonic. Folding wings in flight is an innovation that has been studied on past aircraft, including the North Ameri- can XB-70 Valkyrie in the 1960s. Howev- er, the ability to fold wings during flight has always been dependent on heavy and bulky conventional motors and hy- draulic systems. SHAPE MEMORY ALLOY SAVES WEIGHT The SAW project intends to obtain a wide spectrum of aerodynamic ben- efits in flight by folding wings through the use of an innovative and light- weight shape memory alloy. This ma- terial is built into an aircraft actuator, which plays a vital role in moving parts on the airplane, where it has the abili- ty to fold the outer portion of an air- craft’s wings in flight without the strain of a heavy hydraulic system. Systems with this new technology may weigh up