Aircraft

Experimental X-56A's thin, bendy wings herald a revolution in airliner design

Experimental X-56A's thin, ben...
The X-56A is scheduled for November flights to further investigate how highly-flexible, lightweight wings function
The X-56A is scheduled for November flights to further investigate how highly-flexible, lightweight wings function
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James Smith and Gary Cosentino prepare the X-56A for flight. Researchers are using the aircraft to investigate if highly-flexible, lightweight wings can be controlled.
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James Smith and Gary Cosentino prepare the X-56A for flight. Researchers are using the aircraft to investigate if highly-flexible, lightweight wings can be controlled.
The X-56A is scheduled for November flights to further investigate how highly-flexible, lightweight wings function
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The X-56A is scheduled for November flights to further investigate how highly-flexible, lightweight wings function
Lockheed Martin's X-56A experimental aircraft
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Lockheed Martin's X-56A experimental aircraft

According to NASA, the future of long-range aircraft lies in long, thin, flexible wings, which can develop as much lift as the relatively short, wide wings on today's airliners, but dramatically reduce weight and aerodynamic drag to bring fuel costs way down.

The relatively short, wide wings on today's airliners are actually surprisingly flexible in their own right. Every Boeing 747, for example, is tested in a rig that bends its wings upward to a full 90 degrees. But NASA's plan is to take things to a whole new extreme.

There's one big problem, though. Long, narrow, flexible wings have a tendency to suffer from flutter – a bending, twisting vibration that can easily build up to a point where it tears the airframe apart. This kind of thing is frowned upon in aviation. You can see the destructive effects of flutter in this video:

X-56A: Breaking the Flutter Barrier

Working with Lockheed Martin's famous Skunk Works experimental aircraft department, NASA has been building and testing prototype UAVs that use active flutter control measures to detect when the vibrations are beginning, and intervene to smooth out both flutter vibrations and, potentially, air turbulence, so that passengers can enjoy a smoother ride while their aircraft is also not tearing itself apart and falling to a fiery doom.

The program has been running since 2012, with a number of flight tests already complete in the X-56A test beds. In order to test the active flutter suppression technology in an airframe that would give good representative data for a full-sized aircraft, the X-56A is a decent sized beast, weighing 480 lb (218 kg), with a 28-foot (8.5-m) wingspan and two JetCat P400 turbojets.

Lockheed Martin's X-56A experimental aircraft
Lockheed Martin's X-56A experimental aircraft

The first time the flexible wings were flight tested on these airframes ended in minor disaster, as one of two X-56As flown in this first test crashed soon after takeoff. Nicknamed Fido, the aircraft ran into trouble at low speed and didn't appear to have had time to deploy its ballistic parachute before plunging to Earth. This crash happened in November 2015.

Things have been going much better in more recent tests and, according to X-56A project manager Cheng Moua, "past challenges experienced during takeoffs and landings are now resolved."

James Smith and Gary Cosentino prepare the X-56A for flight. Researchers are using the aircraft to investigate if highly-flexible, lightweight wings can be controlled.
James Smith and Gary Cosentino prepare the X-56A for flight. Researchers are using the aircraft to investigate if highly-flexible, lightweight wings can be controlled.

Without going into too much detail, a press release credits this to improvements to the landing gear and braking system, as well as extensive vibration data analysis and upgrades to the flight controller. "We want to show that this kind of wing can be built," says Moua, "and the control technology exists to control flutter on them."

With these issues sorted out, flight testing will begin to slowly accelerate through November.

Having sat through the odd intercontinental flight and experienced severe turbulence once or twice, we're perfectly comfortable with this kind of research progressing at a painstakingly slow rate. But I think everyone can agree that once the technology is rigorously proven, it has the opportunity to deliver huge dividends in efficiency, transport costs, airline emissions and even potentially passenger comfort.

Source: NASA

7 comments
Reece Agland
The issue fir airlineds will be taxing and oarking planes with such long wings. Airports try and cram as many planes in and this would go against that.
Alien
...And if they succeed in making it fly with guaranteed safety, then someone will have to work out how on earth to manage this type of aircraft when it's on the ground. Taxiing and parking would necessitate a complete rethink of airport layouts ...and probably double their size.
noteugene
It will only be cost efficient if the wings can hinge in half after landing. Having 1 wide strip for take off and landing is ok but not having to enlarge the entire lot x2 just to park. That would wreck whatever savings were generated and also impractical. But I don't see that folding the wings up for parking is much of a challenge, that concept has already been proven.
Douglas Bennett Rogers
The wings won't need to be hinged. They will just roll up.
787cape
Every Boeing 747 is NOT tested in a rig that bends its wing a full 90 degrees. As part of certification, a structural test specimen of the wing is bent until it reaches 150% of predicted maximum service loads. The test wing is then often loaded further until it breaks. I don't think I've ever seen a wing bent 90 degrees; failure generally takes place at much lower deflection angles. And BTW, the airplane in the linked photo is a 787, not a 747. Its composite wing structure is much more flexible than traditional metal wings, so it will bend more than past wings - but nowhere near 90 degrees.
fb36
I think long wings are not practical and neither making them foldable. How about thin but short wings back to back or like a biplane?
Bob
I suspect that a wider cabin with a lifting body design would be more efficient than thinner and longer wings. What is possible and what is practical and economical will be very different designs.