NASA to test in flight folding wing

NASA is set to begin testing a new wing design that would change shape in flight, bending up or down, to increase yaw stability, reduce required rudder size, and decrease drag. The Boeing 777X is set to introduce wingtips that fold on the ground, to allow the aircraft to fit in existing gates with a longer wingspan. NASA is set to begin testing the Spanwise Adaptive Wing, which would add shape-memory alloy actuators to the wingtip area that would bend the tips up or down. The SMA actuators would activate when heated electrically, so there is no need for complex hydraulic lines or actuators.

Beginning in Spring of 2017, NASA will start flying the Area-I PTERA UAV. It has a 176 inch wingspan, with the outer 15 inches moving as far as 75 degrees up or down. PTERA is not set up for SAW, but it appears that it could see a 40% rudder authority. The idea behind SAW is similar to what was done with the XB-70, with the wingtips angled down.

Boeing will introduce folding wings to commercial aviation when the 777X airliner enters service at the end of 2019. But the devices could become commonplace on future aircraft as wingspans increase in an effort to reduce drag and fuel burn.

The 777X has almost 24 ft. more wingspan than today’s 777 to optimize lift distribution and maximize cruise efficiency. Folding the tips on the ground keeps the larger aircraft compatible with existing taxiway and gate size restrictions. But NASA is investigating whether also folding the wing in flight could save still more fuel.

The Spanwise Adaptive Wing (SAW) concept will be tested on the ground and in flight in a rapid feasibility assessment under NASA’s new Convergent Aeronautics Solutions project. The goal is to show that angling the outboard wing sections up or down can increase yaw stability and control, and reduce rudder size and tail drag.

aviationweek.com...

does this work well with thrust vectoring?

a reply to: dashen

Not really. It's most efficient for larger aircraft with a longer span. You aren't going to find thrust vectoring with that type of aircraft. It wouldn't work well with a highly maneuverable aircraft, as it's mostly for cruise efficiency, and fuel burn. If it works, they'll be able to reduce the size of the rudder, which means a smaller vertical fin, which means less drag.

originally posted by: Zaphod58
a reply to: dashen

Not really. It's most efficient for larger aircraft with a longer span. You aren't going to find thrust vectoring with that type of aircraft. It wouldn't work well with a highly maneuverable aircraft, as it's mostly for cruise efficiency, and fuel burn. If it works, they'll be able to reduce the size of the rudder, which means a smaller vertical fin, which means less drag.

This is very cool, Zaphod..! Thanks for sharing!

originally posted by: Zaphod58
a reply to: dashen

Not really. It's most efficient for larger aircraft with a longer span. You aren't going to find thrust vectoring with that type of aircraft. It wouldn't work well with a highly maneuverable aircraft, as it's mostly for cruise efficiency, and fuel burn. If it works, they'll be able to reduce the size of the rudder, which means a smaller vertical fin, which means less drag.

Not always. There are 2 types of drag. The first is parasitic drag, which is what you get when you stick your hand out the car window palm forward. It does relate to the size of the object in the airflow. The other type of drag is called induced drag, and is the drag that is created or induced by creating lift. It increases and decreases in proportion to the amount of lift created and also by a function of the aspect ratio of the lifting surface. Aspect ratio is defined as the ratio of the span of the lifting sorface (wingspan) divided by the mean aerodynamic chord (mean distance from leading edge to trailing edge of the lifting surface.) High aspect ratio (think gliders and U-2) gives a better lift/drag result than low aspect ratio (think brick.)