Why no more swing-wing and (U.S.) delta-wing warplanes?

Back in the 1960s and 1970s, there was a big run of swing-wing aircraft all over the world. America made the F-111, the F-14 Tomcat, and the B-1 bomber. The Europeans came up with the Tornado, and the Russians made the MiG-23 and MiG-27 Floggers, Su-24 Fencer, and Tu-26 Backfire. All designs since then seem to have abandoned the idea. Why have the swing-wingers disappeared?

The other question, I guess, is more a U.S. vs. European design question. Some of the early American fighters were delta-wingers, like the F-106 Delta Dart and F-102 Delta Dagger, but it seems from the 1960s onward that they have abndoned the concept in favor of the swing-wingers mentioned above or the F-15, F-16 and F-18 style wings. The Europeans, however, have kept on producing delta-wing aircraft, from the Mirage III back in the '50s through to the Mirage 2000 and Saab Viggen of today. The Eurofighter design is a tail-less delta that could almost pass for a Kfir, if you didn’t notice the underbelly intakes and the double engines. What do the Europeans see in the delta design that the Americans don’t?

Actually, we made a delta wing variant of the F-16 too. From what I understand, it had longer range, but was less manuverable. maybe that has something to do with it. I know NASA had one of these at one time.

I’m hazarding a guess here: It may be difficult to make a swing-wing or delta-wing design that can achieve a low radar cross-section. Low-observables technology IIRC is one of the most highly guarded secrets of the U.S. defense industry, so the Europeans may lack it. Therefore, perhaps the Europeans don’t bother including low observability in their list of design criteria.

A possible criticism of the above statement is that the B-2 bomber has roughly a delta-wing configuration, so maybe it isn’t so hard to make a low-observable delta wing after all.

Speculation here:

  1. Swing-wings are heavy, limiting payload and range, and have the reliablity and maintenance problems inherent in any moving part. There are other aerodynamic methods now available to make low-speed controllability less of a problem without those side effects.

  2. Air-to-air missiles and radar are much better, reducing the need for high speed in the aircraft itself. The enemy can much more easily be seen and shot down at long range without having to mix it up. The need for self-defense in a combat aircraft now has more to do with not being detectable by the enemy’s radar than with being able to outrun him.

  3. The need for fast aircraft to catch up with the fleets of Soviet bombers coming over the Pole is gone.

  4. The more-recent European aircraft you’ve listed aren’t true delta wings either - they all have canards to provide low-speed control. The debate over whether forward-mounted elevators or rear-mounted ones make for a better aircraft hasn’t been settled, maybe because it doesn’t matter that much anyway.

  5. Product maturity and simple institutional inertia - the pace of innovation in airframe design is now, shall we say, evolutionary. There are few incentives to try something different because there are few approaches left to try that haven’t already been shown to be no better. Military airframe manufacturers (the few that are left) know how to do what they do - the Yanks are comfortable with rear tails, and the Europeans with canards, and that’s mainly a stylistic choice rather than a technological one.

City Gent likely has a good point as well as the weight of a swing wing structure. The box beam and wing pivots on an F-14 are massive structures. The proposed Boeing SST was designed with a swing wing but engineers found the weight was so much they could have the swing wing or carry passengers but not both. Newer materials and better aerodynamic design have taken away from the advantage swing wings once had.

In fact, the Eurofighter is remarkably similar to the Lavi, a fact I’ve always found somewhat suspicious.

(For those of you with less knowledge of aviation history, the Lavi was an advanced fighter-bomber-interceptor developed independently by the Israeli Army in the late 80’s, in order to replace the American fighters in the IAF’s service. A working prototype was built, but the project was eventually cancelled after the U.S. government offered Israel a really good deal for some F-16s - as well as some veiled threats about reducing military aid).

Elvis’ speculation pretty much got it. Speed used to be the cure all. These days, it’s Low Observability and high maneuverability that wins. Have you seen what vectored thrust can do? It’s amazing what it can make an airplane do. But to make up for the lost energy in a move like the “cobra”, you have to have as light a plane as you can get to make the most of your engines. The swing wing was for low drag at high-speed and high lift and control at low speed. Technology now can provide both while reducing labor, weight, parts, cost, etc.

Geez, what can I add? I’ll lament the passing of the F-14. That aircraft looks good from any angle. But as a 1960s design, it’s a bit long in the tooth. LO technology is the latest “thing”, as are “flying” fuselages. (That is, the fuselage contributes more lift than older designs. The F-14, F-15 and F-16 were some of the first with flat fuselages – barring less successful earlier designs.)

IIRC, the F-16XL (delta wing) was built from an F-16 that bellied in at Edwards AFB. It was flying when I was working at EAFB, as was the AFTI F-16 (Advanced Fighter Technology Integrated) which had canards. LANTIRN was a new thing then as well.

From what I remember, the F16XL was General Dynamics contender for a lightweight strike bomber. The F15E won the competition. Personally, from what I understand the XL would have been a better choice though…

Off topic, I just bought a 1/72 scale model of one. I expect to recieve it any day now.

NASA still has one flying.

The swing-wings were created as a way to cover a wide envelope of flight conditions, with the wing technologies of the late 1960s/early 1970s.

The delta was good for very high speeds, but had diminished aerodynamic efficiency at slow speeds. A long, narrow, slightly swept wing gave good lift for T/O and landing and slow-speed maneouvers, but generated shockwaves and vortices too soon and too hard as you speeded up. A shorty, stubby conventional wing (e.g. F5, F104) or delta-with-tail (A-4, MiG 21) was a common compromise.

In the 50s and early 60s, the USA and USSR could afford to have a variety of flavors of frontline plane for particular situations but many other forces needed something that could adequately perform many different roles. Dassault’s answer for what was good enough in enough different roles was the delta. Later, the US and USSR also began thinking of planes that could handle multiple flight envelopes – but they were not about to “give up” anything so their answer was the swing-wing.

An F-14 or MiG-23 on T/O and landing had an almost straight-out narrow wing (optimized for lift), but when going full-tilt boogie became a de-facto delta wing (optimized for speed) – and the MiG goes more steeply swept in that mode than the fixed delta wings of a Mirage or an F-106.
As pointed out earlier, evolution in materials and design technologies have made it possible to design wings and lifting fuselages that are efficient around a wide envelope. Engine-thrust-vectoring technology also aids tight-space maneuverability. And computer-controlled fly-by-wire systems allow the design of planes that are not inherently stable – which was another limiting factor pre-70s : the motion characteristics of the plane had to be such that a human’s sensory-motor coordination could handle it unaided. Sukhoi is even talking of putting the forward-swept-wing on a regular production fighter.

If you look at the more modern fighters, they generally have broad-cord trapezoidal wings that “merge” into a fuselage which is itself a “lifting body” – and this in itself “stealthens up” the aircraft, since a big part of radar reflectivity is joints and such.

Makers of traditional D-wing aircraft in Europe had the fortunate situation that it is not such a giant leap to refit their platforms with the new wing technology, and you get to keep the distinctive product image.

Regarding the swing wing found on the F-14…

Does the wing angle automatically adjust itself to the aircraft’s speed, or does the pilot change that angle manually, based on his judgement?

The wings and glove vanes on an F-14 are computer-controlled for optimum efficiency, but I think the pilot can override the computer and select the positions manually.

The wings of the F15, F16 and F18 are considered to be delta wings, just not ones that run the full length of the fuselage. Much better maneuverability is achieved with a tail assembly seperate from the lifting wing. For an aircraft that is a pure interceptor, whose mission is to fly quickly to where enemy aircraft are approaching from, launch their payload of missiles and then fly quickly back to base for a refit, tight turns aren’t as critical. When the U.S. began shying away from fighter aircraft that were so mission-specific, the pure delta wing design was abandoned for fighters.

Swing-wing aircraft are on the outs because of improved designs, materials, etc. The mechanisms that change wing position are bulky and heavy, two things that you DON’T want on a fighter. The switch from Tomcat to Hornet was long overdue, IMHO.

On Bombers, weight and bulk are less of a concern. The B1 was a Cold War nuke platform, with a relatively small payload, so the wing assemblies were less of a concern. Of course, they were also fraught with mechanical difficulties, and were not especially LO-capable, so they’ve never really had a trial by fire.

(to add fuel to the fire… but seeing as we’re on the subject anyway)

…Those nifty (did I just say “nifty”?) reverse-wing designs? (Like the X-29)

Did flight testing find them to be more expensive? Not as efficient? Not as maneuverable? Not as sexy?

What do you mean "no more swing-wing?..?? The F-111 flies every day, and while the B-1 is a hangar queen, it is in active service.
I’ve seen prototypes for the new Advanced Tactical Fighter design with swing-wings. I cannot say any more because I’d have to kill you.

The X-29 was built as a technology demonstrator. That is, the manufacturer wanted to prove the theory that an aircraft with forward swept wings would be more maneuverable than a conventional aircraft. I don’t think there was ever an intent to put it into production. One of the X-29s is in front of the NASA Dryden facility at EAFB, and has “Alf” in the cockpit.

Along with some other points here:

Delta wings are very unstable at high angles of attack. There has been consideral emphasis recently in making extremely maneuverable fighters, which means using high angles of attack frequently for these violent maneuvers. Delta wings just aren’t very good at it.

Delta wings make lift at lower speeds by the virtue of the vortices rolling off the leading edge of the wing. At high angles of attack, these vortices break down, alternately rolling off one wing, then the other, leading to critical instability problems. Remember the Concorde crash?

Because vortices play a smaller role in lift, conventional wing designs are not quite as unstable, and the control problems are mitigated during slow speed, high angle of attack maneuvers by a wider variety control surfaces available on the wings and tail.

Russia’s Sukhoi is doing work currently on FSW technology, using their current Su-27(iirc) as basis. But since they already are producing planes as advanced as their air force needs or can afford, it’s iffy if they’ll go into regular production.

A few quick points:

NASA’s Dryden Flight Test Center has both F-16XL prototypes and flies both of them on a regular basis.

For a fleet of “hangar queens”, the B-1B Lancer spends a lot of time in the air, participating in exercises, and deploying overseas. In recent years, B-1B’s have been involved in airstrikes in Iraq and the area that used to be Yugoslavia.

The Boeing X-32A Joint Strike Fighter prototype is a delta-wing design. This is one of the two newest fighter designs out there - the other being Lockheed-Martin’s competing JSF design.

Germany was working on a Foward Swept Wing design in the closing stages of the war. The prototype was never completed, and I believe destroyed during a bombing raid. It is questionable if it could have ever flown anyhow since it would have been such an unstable aircraft.