The recent flight series, which took place at NASA’s Armstrong Flight Research Center in California, was part of the Spanwise Adaptive Wing project, or SAW. This project aims to validate the use of a cutting-edge, lightweight material to be able to fold the outer portions of aircraft wings and their control surfaces to optimal angles in flight.
Above – The subscale testbed PTERA flies over NASA Armstrong Flight Research Center in California with the outer portions of its wings folded 70 degrees upwards. The aircraft took off with its wings zero degrees deflection, keeping them level during takeoff. The wings were folded during the flight using a thermally-triggered shape memory alloy, developed at Glenn Research Center and integrated into an actuator at Boeing Research & Technology. This technology would alloy pilots to fold their aircraft’s wings to different angles to adapt to multiple flight conditions for aerodynamic benefit.
Credits: Area-I Inc.
This material will enable a wide spectrum of aerodynamic benefits in flight by folding wings through the use of an innovative, lightweight material called shape memory alloy. This material is built into to an actuator on the aircraft, which plays a vital role for moving parts on the airplane, where it has the ability to fold the outer portion of an aircraft’s wings in flight without the strain of a heavy hydraulic system. Systems with this new technology may weigh up to 80 percent less than traditional systems.
The recent series of flight tests at Armstrong successfully demonstrated the material’s application and use, by folding the wings between zero and 70 degrees up and down in flight.
On subsonic aircraft, such as commercial airliners, the potential aerodynamic benefit of folding the wings includes increased controllability, which may result in a reduced dependency on heavier parts of the aircraft, including the tail rudder. This may result in a more fuel-efficient aircraft, as well as the ability for future long-winged aircraft to taxi in airports. Additionally, pilots may take advantage of a number of different flight conditions, such as wind gusts, by folding their wings to adapt to any particular condition experienced in flight.
One of the most significant potential benefits of folding wings in flight, however, is with supersonic flight, or flying faster than the speed of sound.
“There’s a lot of benefit in folding the wing tips downward to sort of ‘ride the wave’ in supersonic flight, including reduced drag. This may result in more efficient supersonic flight,” SAW Principal Investigator Matt Moholt said. “Through this effort, we may be able to enable this element to the next generation of supersonic flight, to not only reduce drag but also increase performance, as you transition from subsonic to supersonic speeds. This is made possible using shape memory alloy.”
The shape memory alloy is triggered by temperature, and works by using thermal memory in a tube to move and function as an actuator. Upon being heated, the alloy would activate a twisting motion in the tubes, which ultimately moves the wing’s outer portion up or down.