Aircraft

NASA wants to fold airplane wings ... while they're flying

NASA wants to fold airplane wi...
“We are revisiting folding-wing aircraft,” says NASA’s Matt Moholt, “because new technologies that did not exist in the 1960s allow actuation to be put in tighter wings, in smaller volumes.”
“We are revisiting folding-wing aircraft,” says NASA’s Matt Moholt, “because new technologies that did not exist in the 1960s allow actuation to be put in tighter wings, in smaller volumes.”
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NASA plans to test these ideas on the scale model PTERA (Prototype-Technology Evaluation and Research Aircraft) in the spring of 2017
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NASA plans to test these ideas on the scale model PTERA (Prototype-Technology Evaluation and Research Aircraft) in the spring of 2017
“We are revisiting folding-wing aircraft,” says NASA’s Matt Moholt, “because new technologies that did not exist in the 1960s allow actuation to be put in tighter wings, in smaller volumes.”
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“We are revisiting folding-wing aircraft,” says NASA’s Matt Moholt, “because new technologies that did not exist in the 1960s allow actuation to be put in tighter wings, in smaller volumes.”

When a hawk folds its wings, it plummets to the earth in a controlled high-speed dive. Not exactly the kind of scenario we'd imagine being ideal for modern aircraft. But in flight wing folding can have advantages and NASA wants to make it happen.

The idea here isn't to create controlled dives, of course, but to increase the efficiency and capabilities of aircraft. The space agency calls this the Spanwise Adaptive Wing (SAW). So far, articulating wings on airplanes have largely been for parking purposes, to allow planes to take up less space on an aircraft carrier's decks or fit into smaller hangars. A few very large aircraft have articulating wings to allow them to taxi between infrastructure at an airport. What NASA is working on is very different from all of this.

Of course, the National Aeronautics and Space Administration isn't new to aircraft design experimentation. They've been working on a lot of similar things for years. The Environmentally Responsible Aviation project, for example, has been working on bendable wings. Another project under the SAW umbrella is using these wings to reduce or eliminate the vertical tail fin on a plane. This would have obvious environmental benefits by greatly reducing drag and aircraft weight, thus reducing fuel use.

Supersonic aircraft and very heavy aircraft both require vertical stabilizers for yaw control during flight. NASA says that smaller, more precise wing articulation and control is now possible thanks to advancements in the actuators required to move the wings. Most wing articulation is currently accomplished with heavy, bulky actuators that are usually hydraulic rather than electric. This has been because hydraulic actuators are the most time-tested physical movement option on aircraft today. There hasn't been much change in how they work since the 1960s.

NASA plans to test these ideas on the scale model PTERA (Prototype-Technology Evaluation and Research Aircraft) in the spring of 2017
NASA plans to test these ideas on the scale model PTERA (Prototype-Technology Evaluation and Research Aircraft) in the spring of 2017

"We are revisiting folding-wing aircraft," says NASA's Matt Moholt, "because new technologies that did not exist in the 1960s allow actuation to be put in tighter wings, in smaller volumes." This allows a much thinner wing and a thinner portion of the wing to become articulable. Namely the tips of wings, which are normally rigidly fixed.

One example of the use of this technology would be for supersonic aircraft. When flying at very high speeds, aircraft create a lot of lift, but have less yaw control as a result. Folding the ends of the aircraft's wings up or down would add stability by creating more vertical surface to augment the rear tailfin. Yet the plane would not lose critical lift during the difficult takeoff and landing stages because the wings could then be straightened to add the lift surface to flight.

Moreover, NASA says, the adjustable wing ends would be able to change position dynamically, creating mixtures of lift and yaw control as needed during different flight conditions.

NASA plans to test these ideas on the scale model PTERA (Prototype-Technology Evaluation and Research Aircraft) in the spring of 2017. That will coincide with ground-based tests of full-sized actuators capable of scale wing articulation. The objectives of this testing will be the validation of tools and the vetting of the system's theoretical vehicle control law evaluation. Analysis of airworthiness and potential fuel savings will also be undertaken.

Source: NASA

8 comments
MD
Telescoping wings for low speed to high speed flight is also another interesting option. (fowler flaps are already a form of chordwise telescoping wing, but the retracted wing still has the same aerodynamic longitudinal axial section, (unlike a lateral axis telescoping section) which increases drag at high speed, all that huge wing area is only needed for takeoff and landing on relatively short runways.. Folding the wing as shown in the pictures, while increasing directional stability, doesn't reduce drag much, as it has the same approximate longitudinal cross section and skin surface area. A bird folds its wing in a very different way (as all aerodynamicists know). In many cases the hydraulic actuators are smaller, lighter and more compact than electric actuators, however they need a pump and connecting pipes (and messy fluid).. As most distributed systems now use many small electric pumps (triple redundancy is necessary) at point of actuation (to increase efficiency-pumping/transmission losses) this makes it seem that the hydraulics are the heavy component, when it ractually may be that multitude of electric motors and pumps. (it is also a whole lot easier to route an electric grid than a hydraulic one ).. The philosophy in this story is to merely avoid the electric-hydraulic-mechanical energy transfer with electric straight to mechanical... But there are many applications where hydraulic power provides a more elegant solution (maybe not the lowest cost, and that is likely the real driver here, cost of installation, electric actuators are often much cheaper, lower precision, more easily created in a sweatshop..
Rusty Harris
No big deal...the XB-70 did something similar back in the 60's to achieve Mach 3 speed.
highlandboy
Increased lift is usually an issue during takeoff and landing. Greater yaw control is (except for fighter jets) also required at takeoff and landing. Because moveable wing tips increase yaw at the expense of lift and vice versa, in the time of greatest need, foldable wing tips are compromised as a solution.
JerryCook
They need to go back further than the 60's. There are recorded instances of the Chance - Vought F4U corsair actually taking off with its wings folded during the 40's and 50's.
Nik
I thought the 'swing wing' had already accomplished all of these intended improvements.
BundyGil
Swing wing design worked fine in the F111 fighter/bomber recognisance aircraft of the '60s to 2010 era. It's capabilities have yet to be surpassed.
fb36
Why not take out all moving parts from wings (flaps and ailerons etc) and instead just make the joints between wings and fuselage rotatable, so that angle of attack of each wing can be adjusted independently (within a certain angular range). I think the adjustments could be done by a computer using lift/stall sensors. (The pilot would just set the speed.)
jerryd
A low aspect ratio wing does all these without having to change length. Make it mostly wing with trailing edge flaps, etc and steering engine thrust removing the need, drag , radar of a tail.