The Spanwise Adaptive Wing project, or SAW, is focused on the use of a new lightweight material that allows aircraft to fold the outer portions of their wings to reach optimal levels of aerodynamic form during flight. This capability allows for leveraging wind gusts that could otherwise hamper airspeeds.
In past research, the ability to fold wings in flight has been dependent on heavy and bulky conventional motors and hydraulic systems, which can be cumbersome and less efficient. The SAW project makes use of a shape memory alloy that is built into an actuator on the aircraft. It’s designed to move the outer portion of an aircraft's wings without the strain of a heavy hydraulic system. The weight savings is estimated to be as high as 80 percent over traditional systems.
A recent series of flight tests demonstrated the material's ability to fold the wings between zero and 70 degrees up and down during flight. Looking long-term, using this material on commercial airliners could help improve maneuverability by relying less on heavy mechanical components such as the tail rudder. This advancement could also improve fuel efficiency. For fighter jets, this technology could allow pilots to fold wing tips downward and use wind gusts to increase speed and handling while reducing drag.
The shape memory alloy is triggered by temperature and works by using thermal memory in a tube to move and function. Upon being heated, the alloy would activate a twisting motion in the tubes, which ultimately moves the wing's outer portion up or down.
SAW is an effort within NASA's Convergent Aeronautic Solutions project under the agency's Aeronautics Research Mission Directorate. Also playing a key role in the tests were Langley Research, Boeing Research and Technology, and Area-I, Inc.