"Advances in aerodynamics have made the swing-wing obsolete"

[Elysium]

I have constantly encountered this statement, and it always felt iffy to me. Is this actually true? Can anyone actually point to what advancements have reduced the need for swing-wings? I feel like, when we look at famous swing-wing aircraft (F-14, Su-25 Tu-160) we see the same patterns: T/W way less than 1, incredibly broad flight envelope from loitering, to supersonic flight and huge range.

I feel like there's no recently designed aircraft with this set of requirements, modern aircraft tended to mostly designed for either low-to medium speeds (F-35) to medium-to-high ones (F-22).

If you came up to a designer and asked him to design an aircraft today that can do all the same things an F-14 or a Tu-160 can, I doubt they could make one without swing wings. True, modern engines have better T/W than ones in the 70s, but I doubt that alone would compensate.

 

[Manuducati]

Modern flight control systems, materials, and relaxed stability somehow reduce the need for VG wings.
But those who say VG is a 60's thing only tend to forget/ignore that, for example, a good portion of 90's Navy NATF and A/F-X proposals had VG as well.

 

[siegecrossbow]

Modern flight control systems, materials, and relaxed stability somehow reduce the need for VG wings.
But those who say VG is a 60's thing only tend to forget/ignore that, for example, a good portion of 90's Navy NATF and A/F-X proposals had VG as well.

Not to mention addition or LERX and other vortex generation measures for improving lift at low airspeed/high AOA. Why bother adding deadweight for swing wing mechanism when a piece of static airfoil can do the job just as well?

 

[flateric]

a good portion of 90's Navy NATF and A/F-X proposals had VG as well.

A good portion of LRS studies in 00s as well.
LMSW Persistor, SSUCAS etc

 

[DrRansom]

It seems like there are two uses for swing-wing:
1. STOL capability --> SU-24 and Tornado
2. Long range + High Speed Dash (also SU-24 and Tornado haha)

Those two operational capabilities fell out of favor in 1990s - 2010s, but the threat environment pressures that created them are coming back.

 

[Hanz2k]

It seems like there are two uses for swing-wing:
1. STOL capability --> SU-24 and Tornado
2. Long range + High Speed Dash (also SU-24 and Tornado haha)

Those two operational capabilities fell out of favor in 1990s - 2010s, but the threat environment pressures that created them are coming back.

Add F14 and Mig-23/Mig-27. Threat environment yes, but technology is far ahead.

 

[DrRansom]

Add F14 and Mig-23/Mig-27. Threat environment yes, but technology is far ahead.

But what technology is far ahead? A 3-stream engine has improved performance compared to an older turbojet, but a 3-stream engine with a swing-wing would have even better performance.

 

[Archibald]

Modern flight control systems, materials, and relaxed stability somehow reduce the need for VG wings.
But those who say VG is a 60's thing only tend to forget/ignore that, for example, a good portion of 90's Navy NATF and A/F-X proposals had VG as well.

Wasn't it just a matter of a) F-14 legacy and b) that neither F-22 nor F-23 could be navalized straight ahead without VG ? As they were just too heavy ?

Always felt NATF would have been a bloated monster.
As if supersonic stealth fighter wasn't hard and expensive enough: let's add navalization - wait, crap, needs VG to land on carrier. Moar weight cost and complication.
...
[Personal opinion: often think the right stealth fighter for the 1995 USN would have been something akin to... KF-21 Boramae. A miniature F-22 look alike with Superbug twin turbofans. Not a NATF not a F-35C and not a Super Hornet]

 

[Hanz2k]

But what technology is far ahead? A 3-stream engine has improved performance compared to an older turbojet, but a 3-stream engine with a swing-wing would have even better performance.

Is stealth far ahead enough for you? Swing wings on airplanes are dead. Add complication and weight to achieve performance that you can now achieve via proper airframe computational modeling. Different story on PGM or cruise missiles.

 

[Colonial-Marine]

Wasn't it just a matter of a) F-14 legacy and b) that neither F-22 nor F-23 could be navalized straight ahead without VG ? As they were just too heavy ?

Always felt NATF would have been a bloated monster.
As if supersonic stealth fighter wasn't hard and expensive enough: let's add navalization - wait, crap, needs VG to land on carrier. Moar weight cost and complication.
...
[Personal opinion: often think the right stealth fighter for the 1995 USN would have been something akin to... KF-21 Boramae. A miniature F-22 look alike with Superbug twin turbofans. Not a NATF not a F-35C and not a Super Hornet]

Personally I'm not sure what to think about the odds of NATF. From what I've been told here the Navy wasn't too keen on it and was willing to give it up because they felt confident that the modernization of the F-14 fleet would be enough for the foreseeable future. But then the axe came for the Super Tomcat and some additional air-to-air capabilities were tacked onto A-X becoming A/F-X.

With so much upheaval in NAVAIR modernization over the past decade+ and notable recent disasters like the A-12 I think many in the DoD were perfectly fine shoehorning the Navy into the new JSF plan even though it didn't entirely fit what the Navy needed.

As for the NATF from a design standpoint it is quite clear now that it would have been very much different from either ATF proposal. Looking at the F-22 that was built it has a landing approach speed that is too high for the USN to be comfortable with and this is before all of the many changes and additions that would have to take place to meet Navy requirements. The VG wing probably appealed to Lockheed as the solution since it neatly solves the approach speed issue and gives a lot of growth potential for the design so they can fit everything. People rightfully point out that it isn't all that stealth-friendly and yes it would likely not be as stealthy as the F-22 is. But I do wonder if the wings could be locked in a position suitable for high subsonic and supersonic manuever that would also minimize radar signature. If they had to be unswept because the NATF somehow got into a dogfight then any notion of stealth is already out of the window.
I know a lot less about the flight qualities of the F-23 design but I would have expected it to have a lower approach speed and be a bit more suitable for carrier adaptation. Yet Northrop also felt the need for a major redesign for NATF.
One challenge that would exist regardless of the winner would be fitting the eventual AIM-152 long range AAAM internally. The GD design could probably have been made to fit easily enough but that was the more risky option than the larger Hughes ramjet design.

The design you envision sort of reminds me of the fictional F/A-181 which was in the video game ArmA 3. If such a concept were feasible it sounds great though if the USN had their preference (which they clearly did not historically) I think they'd prefer something larger with more fuel. Even in 1995 they knew they wanted the carrier air wing to have more range. The Super Hornet was an improvement over the classic Hornet to be sure but still fell well short of giving them the combat range they desired.

 

[Scott Kenny]

One of the pieces of the puzzle is the supercritical wing. Even without shape-changing shenanigans like leading edge slats, you have a nice thick and rounded leading edge which provides good low-speed performance. Need a hard edge for stealth chine? Put that at the bottom of the leading edge, and hollow out the spot behind the leading edge; see the shape of the B-21 lower wing skin for example.

So you can have a ~40deg wing sweep or more and still have nice low-speed lift and performance. Apparently the F-8 SCW demonstrator was an absolute beast, test pilots had to be told to stop mugging F-14s etc.

 

[Basil]

A good portion of LRS studies in 00s as well.
LMSW Persistor, SSUCAS etc

Sorry for my lack of knowledge ... what are these projects?

 

[flateric]

Use forum search ...

 

[publiusr]

Swing-wings could allow munitions to be dropped in the ocean at slower speeds to keep them from breaking.

Scream out to s trouble spot, slow down--deploy--and speed away.

 

[TomcatViP]

Wouldn't that be a better job for a ballute or a parachute?

 

[Scott Kenny]

Swing-wings could allow munitions to be dropped in the ocean at slower speeds to keep them from breaking.

Scream out to s trouble spot, slow down--deploy--and speed away.

They make parachutes for that. Still supersonic when you drop? Ribbon chute to slow subsonic, then a regular chute to slow down to a reasonable speed.

 

[DrRansom]

One of the pieces of the puzzle is the supercritical wing.

That is very interesting - but not entirely convincing. Because the takeoff run of modern fighter aircraft remains as long as ever.

Close-coupled canards do reduce some need for Swing-Wing (see Gripen's STOL capabilities) but I don't see Gripen doing 800m takeoff run with a land attack payload.

The use case for Swing-Wing in the Pacific, which I don't think the other technologies can fix, is a strike aircraft with something like 2x JASSM payload and 750-1000nm range operating off a <2000m regional airport runway. I don't think you get to that basing flexibility without Swing-Wing designs.

 

[VTOLicious]

One of the pieces of the puzzle is the supercritical wing. Even without shape-changing shenanigans like leading edge slats, you have a nice thick and rounded leading edge which provides good low-speed performance. Need a hard edge for stealth chine? Put that at the bottom of the leading edge, and hollow out the spot behind the leading edge; see the shape of the B-21 lower wing skin for example.

So you can have a ~40deg wing sweep or more and still have nice low-speed lift and performance. Apparently the F-8 SCW demonstrator was an absolute beast, test pilots had to be told to stop mugging F-14s etc.

And none of the combat aircraft manufacturer is aware of that?

 

[Scott Kenny]

And none of the combat aircraft manufacturer is aware of that?

They are, but there have been exactly 4 combat aircraft in the US designed since the Supersonic Supercritical Wing flew in the late 1970s: F-22, F-35, B-2, and B-21.

And all of those have been driven more by Stealth design requirements than by aerodynamics. "We have a 4-channel digital FBW, we can make the compute make the plane fly."

The B-21 is the only plane I'm pretty sure has a supercritical wing shape

 

[aim9xray]

C-17.

 

[Scott Kenny]

C-17.

Ah, fair point. I was only thinking combat aircraft.

 

[VTOLicious]

They are, but there have been exactly 4 combat aircraft in the US designed since the Supersonic Supercritical Wing flew in the late 1970s: F-22, F-35, B-2, and B-21.

And all of those have been driven more by Stealth design requirements than by aerodynamics. "We have a 4-channel digital FBW, we can make the compute make the plane fly."

The B-21 is the only plane I'm pretty sure has a supercritical wing shape

I was just wondering if the wing you described in post #11 is existing already, or why not? Of course with the application supersonic + stealth in mind.

 

[quellish]

We don’t call them swing wings or variable geometry anymore. They’re now morphing aircraft and they are still very much a thing.

 

[Elysium]

One of the pieces of the puzzle is the supercritical wing. Even without shape-changing shenanigans like leading edge slats, you have a nice thick and rounded leading edge which provides good low-speed performance. Need a hard edge for stealth chine? Put that at the bottom of the leading edge, and hollow out the spot behind the leading edge; see the shape of the B-21 lower wing skin for example.

So you can have a ~40deg wing sweep or more and still have nice low-speed lift and performance. Apparently the F-8 SCW demonstrator was an absolute beast, test pilots had to be told to stop mugging F-14s etc.

Didn't the original Su-27 prototype have a supercritical wing shape? Afaik it needed to be redesigned because it didn't end up working out.

 

[Nicknick]

According to my understanding, a supercritical wing only works efficient at high subsonic Mach numbers, what is the point of using it instead of a swing wing?

 

[kqcke for you]

What is a supercritical Wing? Something like a laminar flow wing?

 

[Arjen]

@kqcke for you

Supercritical airfoil - Wikipedia

en.wikipedia.org

 

[kqcke for you]

Thanks Mate

 

[Scott Kenny]

According to my understanding, a supercritical wing only works efficient at high subsonic Mach numbers, what is the point of using it instead of a swing wing?

That was due more to the Gothic arch shape than the airfoil section.

 

[Scott Kenny]

I was just wondering if the wing you described in post #11 is existing already, or why not? Of course with the application supersonic + stealth in mind.

Supersonic+stealth LE+supercritical airfoil section?

I believe the X32 used such a wing shape. B-21 is subsonic, but is supercritical+stealth.

Otherwise, I'm not aware of anyone admitting such.

And again, it's due to the low number of combat aircraft designed since the Supersonic Supercritical Wing was first flown.

 

[VTOLicious]

Supersonic+stealth LE+supercritical airfoil section?

I believe the X32 used such a wing shape. B-21 is subsonic, but is supercritical+stealth.

Otherwise, I'm not aware of anyone admitting such.

And again, it's due to the low number of combat aircraft designed since the Supersonic Supercritical Wing was first flown.

Right, the X-32s wing was a quite innovative one piece carbon fiber composite design. Not sure if it used supercritical airfoils.

 

[Scott Kenny]

Right, the X-32s wing was a quite innovative one piece carbon fiber composite design. Not sure if it used supercritical airfoils.

Judging by how thick it was at the root and the pretty rounded leading edge, I'd say it was.

 

[Nicknick]

So, as I understand it, the supercritical wing is quite efficient at low speeds because it is thick and very efficient at high subsonic speeds because of the reduced and further aft position of the shock wave. The shock wave might even help to increase the laminar length and also to keep the flow attached downstream. Despite that, the supercritical airfoil doesnt appear to me as very well suited for supersonic speed because of its thick round front end. All the swing wing planes were built for supersonic speed, something the supercritical wing is not really designed for, is it???

 

[aim9xray]

You'd have to go back to the NASA F-111A TACT program results. The first T is Transonic.

 

[Scott Kenny]

So, as I understand it, the supercritical wing is quite efficient at low speeds because it is thick and very efficient at high subsonic speeds because of the reduced and further aft position of the shock wave. The shock wave might even help to increase the laminar length and also to keep the flow attached downstream. Despite that, the supercritical airfoil doesnt appear to me as very well suited for supersonic speed because of its thick round front end. All the swing wing planes were built for supersonic speed, something the supercritical wing is not really designed for, is it???

NASA put a supersonic supercritical wing on an F-8A. Pilots loved it.

I haven't seen what that particular wing shape looks like, however.

 

[TomcatViP]

Probably where to start from for readers new to the concept :

 

[BlackBat242]

NASA put a supersonic supercritical wing on an F-8A. Pilots loved it.

I haven't seen what that particular wing shape looks like, however.

Here are a few pics:

 

[paralay]

The "flexible wing" will replace the variable sweep wing

 

[VTOLicious]

Here are a few pics:

View attachment 718088

View attachment 718089

View attachment 718090

View attachment 718091

Thx, great pics!

One should not forget the wing was not the only modification. Careful area ruling was applied to the fuselage (See the bulges in front and aft of the wing). Therefore, the increased transonic performance is not solely due to the supercritical airfoil.

 

[Scott Kenny]

Here are a few pics:

View attachment 718088

View attachment 718089

View attachment 718090

View attachment 718091

Thank you! I don't think I'd seen the B&W or the 3view before.

But what I meant was that I'd never seen the wing chord sections published.

One should not forget the wing was not the only modification. Careful area ruling was applied to the fuselage (See the bulges in front and aft of the wing). Therefore, the increased transonic performance is not solely due to the supercritical airfoil.

The wing was a different shape than the original F-8, so it required extra bumps to adjust the area ruling.