Is the variable sweep wing dead?

[Colonial-Marine]

I'm just curious as to what others thing is the future (or lack thereof) of this technology? Were the drawbacks and weight penalties greater than the benefits from the start? Does the focus on stealth make it impractical? Or could UAVs bring about a resurgence? Do unconventional configuration as seen on NASA's old oblique wing demonstrator hold promise? Or has this been disregarded as something of a novelty as what seems to have occured with FSW aircraft?

The last (American) military concepts I've seen with such a configuration were Lockheed's NATF, A-X, and A/F-X concepts. While impressive, I can't help but think such a combination of stealth and variable sweep would be horribly difficult and costly to maintain. I can't think of any recent civil aviation proposals with variable sweep wings.

 

[Kryptid]

My thought is that conventional sweeping wings like those on the F-14 are a thing of the past.

However...

I can definitely see a future for wings that smoothly change planform by morphing in-flight. I've seen concepts for these, but I'm not sure how far along we are in achieving a technology demonstrator for it. I'm also not sure how they work. Electroactive polymers, perhaps? I believe that it will happen one day; the ability to smoothly change not only wingsweep but also aspect ratio, dihedral, wing incidence, etc. would provide enormous aerodynamic benefits.

 

[blackstar]

To answer the original question, I think the answer is pretty clearly yes. When was the last variable sweep wing aircraft designed?

But morphing wings, or at least control surfaces, do seem to hold promise. I'm forgetting the details, but there have been proposals for doing this with various wing control surfaces such as flaps. They could significantly improve performance if the technology can be made to work.

 

[Stargazer]

When was the last variable sweep wing aircraft designed?

Check this: http://en.wikipedia.org/wiki/Northrop_Switchblade
(though one may argue it's more like fold-out wings than real sweep-wing).

 

[Sundog]

It really depends on the mission/technology mix. I would say the 'swing wing' may not be applicable, but there are other forms of VG that are still being seriously studied.

 

[blackstar]

(though one may argue it's more like fold-out wings than real sweep-wing).

I'd argue that a patent application doesn't mean much.

 

[Stargazer]

(though one may argue it's more like fold-out wings than real sweep-wing).

I'd argue that a patent application doesn't mean much.

Except the question was: "When was the last variable sweep wing aircraft designed?" so there's no question here of wondering whether it's feasible, practical, useful or whatever. Just that it was designed...

 

[Zeppelin]

Does, the lack of newer variable geometry wings, have more to do with saving the excessive servicing costs.
I understand that the wing pivots were high maintenance on those long standing RAAF F111. involving many additional inspections.
http://www.dsto.defence.gov.au/publications/2221/DSTO-TN-0271.pdf
Do the same wing issues occur with the RAF & European Tornado or the much bigger variable wings on the USAF B1's ?
I wonder if those more modern carbon fibre composite wings, developed as one complete port and starboard piece will be any cheaper to maintain
and or replace. Or would the maintenance savings just make for a more finite/disposable airframe.
The RAAF did replace original F-111 wings with newer and better build wings. I guess 1 advantage of such modular/movable wings. Extending their use-by date.
http://espace.library.uq.edu.au/eserv/UQ:10121/Burchill_sif04.pdf
Regards

 

[taildragger]

Ed Heinemann, of Douglas, was on record as saying that he was unaware of any VG aircraft design that wouldn't have been improved by switching to a fixed wing. I can't recall ever seeing a Douglas VG design.

 

[Stargazer]

I can't recall ever seeing a Douglas VG design.

Good point. Indeed, I can't think of any myself.

 

[AeroFranz]

VG only comes into its own when you are forced to combine widely different flight regimes.

F-14: high speed vs efficient loiter and carrier landing
Tornado: High speed at low altitude, gust tolerance, short field performance
MiG-23: short field performance, high speed
Tu-160, B-1: efficient cruise, low altitude penetration

IIRC Raymer suggests adding 5% to the empty weight of an aircraft (so maybe 8-10% of takeoff gross weight?). If being able to reconfigure the planform saves you a similar amount of mass, then it might be worth it (there are still maintenance, cost issues). Sometimes you simply cannot fly the mission unless you have VG. I wouldn't want to be in, say, an F-18 trying to fly the high-speed/low-altitude mission profile of a Tornado or F-111.

Regarding morphing structures, there are hosts of problems that come with it. For example, wings traditionally hold fuel. What happens to the fuel tanks as you change the shape of the wing? Now we need morphing fuel tanks.

 

[Kryptid]

Regarding morphing structures, there are hosts of problems that come with it. For example, wings traditionally hold fuel. What happens to the fuel tanks as you change the shape of the wing? Now we need morphing fuel tanks.

A legitimate concern. Admittedly, I lack knowledge of fuel tank design, but I could see two potential solutions. One is like you say; morphing fuel tanks. Not that they have to be made of the same electroactive polymers as the wings, but perhaps some other, passively flexible material. Although, that would then make me be concerned about how safe they would be. A soft fuel tank is an easily-penetrated fuel tank. The other would be to divide the existing fuel tanks into a series of smaller tanks that can slide past each other as the wing is morphed. The downside is that it would add weight and complexity to the fuel system...

 

[Grey Havoc]

An AFRL-SBIR/NASA project from 2015 that may be of interest:

View: https://www.youtube.com/watch?v=TfHUZ2C3HyA

Air Force SBIR/STTR
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In the spring of 2015, the Air Force Research Lab and NASA successfully completed tests to realize a decades long quest in aviation to seamlessly change the shape of aircraft wings in flight. This breakthrough technology will usher in a new era in aviation design. The Air Force is now applying the technology, developed by FlexSys, to a KC-135 under an agreement between FlexSys and Boeing. When further commercialized, the FlexSys Technology will lead to billions of dollars in annual fuel savings, reduced manufacturing costs, and quieter, lighter aircraft, a breakthrough in aviation made possible by the Air Force Small Business Innovation Research/Small Business Technology Transfer Program.