From around the mid 1960s, a new type of aircraft led the way in introducing new multi role fighters and bombers both in the United States and in the Soviet Union and then Europe. This hybrid style of aircraft looked to combine the low-speed flexibility and efficient cruise of straight-wing aircraft and the high-speed capabilities of swept-wing supersonic aircraft in one platform.
The first of these to reach full production would be the F-111 Aardvark and although it had a problematic birth it would go on to be one of the USAF’s most dependable aircraft for 30 years.
From the ’60s up until 1981, aircraft with swing wing designs were made by the US, soviet and European manufacturers and were used on some of the most cutting-edge designs of the era like the F-14 Tomcat, the B1-B bomber, Panavia Tornado, Mig-23, Sukhoi Su-24, Tupolev Tu-160 and others.
But then there was a sudden change and from 1981 onwards, no new swing-wing aircraft have been built anywhere in the world. So why did swing-wing aircraft become so important in the 60s and 70s and then fall out of Favor from the ’80s onwards and why have only military aircraft used this technology and not commercial ones?
To understand why variable geometry or swing wing aircraft became important to the military you have to go back to the mid 1935 when the German aeronautical research scientist Adolf Busemann was working on transonic and supersonic air flows and how they affected things like wings and propeller blades.
All production wings at the time were straight and perpendicular to the fuselage with lift and stability as their main goals, aircraft speeds were still low by today’s standards and super Sonic performance was just a distant goal. But in the mid-1930s with the advent of a jet engine, that goal began to move much closer to a practical reality though few people knew that the existing straight wing technology would not be suitable for transonic and supersonic flight.
Adolf Busemann discovered that if a wing was swept back, it would delay the onset of wave drag, a form of aerodynamic drag that increases dramatically as a wing travels at the speed of sound and led to the concept of a sound barrier. This would be reinforced by early tests where aircraft would lose control because of the severe vibrations the wave drag created on both the wing, fuselage, and control surfaces.
In 1935, Busemann presented a paper at the Fifth Volta Conference in Rome about supersonic lift, and although several important future aerodynamicists were at the conference, his work was thought more to be an academic curiosity because at the time because aircraft speeds of over 300 mph were a rarity.
At the time, all propeller-driven fighter aircraft had straight wings primarily designed to give lift and stability and even in high speed dives didn’t go fast enough to be affected by wave drag.
But one Spitfire Mark 11 did reach Mach 0.89, 620 mph or 1,000km/h, in high-speed trials in 1943 during a 45° dive before the propeller was ripped off due to a reduction gear failure. The pilot survived and managed to glide the Spitfire back to base but this was very much a fluke occurrence.
As jet engine technology was independently developed in both Britain and Germany in the late 30s and early 40s, the aerodynamics of both the fuselage and the wings became increasingly important which brought Busemanns work, which by 1936 was classified by the Luftwaffe to the fore.
Up until 1942, Busemann conducted a large amount of wind tunnel testing on the shape of wings and how they responded at supersonic speeds which would be put to use by the Luftwaffe with experimental aircraft like the jet-powered Messerschmitt Me P.1101, the rocket-powered Messerschmitt Me-163 Komet and jet powered Me-262.
After the war Britain was also experimenting with potentially supersonic aircraft like the 1946 the De Havilland DH108 and the Miles M.52.
In 1947, Chuck Yeager in the rocket-powered Bell X1 which was very similar to the Miles M.52, broke the sound barrier, though ironically that used straight wings, it was the fact that they were very thin, almost like fins rather than wings and combined with an all-moving tailplane that they got it to work.
In 1945 just, as the war concluded, Operation Lusty which was short for “Luftwaffe Secret Technology” was set up by the United States Air Force to try capture and evaluate German aeronautical technology during and after World War II. This was split into two teams.
It was here that the second team came across Busemann and his work at the Braunschweig labs on the 7th May 1945 and the huge amount of data he had created. Some of the team had been at the conference in Rome where he had presented his paper in 1935 although they couldn’t remember what the main points of it was about.
On realizing the importance of the data, one of the team, George Schairer, immediately wrote to Boeing and told them to investigate the concept which led to the remodeling of the B-47 Stratofortress with swept-back wings.
In 1947, Adolf Busemann moved to the United States and started work at the NACAs Langley research center where he worked alongside Robert T. Jones another pioneering aerodynamicist to develop both swept wings, oblique wings, and delta wings.
Also as part of Operation Lusty the, a jet-powered Messerschmitt Me P.1101 was discovered at Messerschmitt’s Bavarian Oberammergau complex. Along with the jet engine, the Me P.1101 also featured a variable-sweep wing although this could only be changed on the ground and not during flight.
It was brought back to America and studied in detail by Bell aircraft which recreated their version of it and this became the basis for the 1951 Bell X5, the first aircraft to be able to change the sweep of its wings during flight with three preset settings of 20°, 40° and 60° of sweep.
Even though the idea worked the X5 had a flawed aerodynamic layout in particular the poorly positioned tail and vertical stabilizer which in some wing positions could lead to an irrecoverable spin. This led to plans by the USAF to modify the design into a low cost tactical fighter for NATO to be canceled.
But it wasn’t just the Germans that had been interested in supersonic flight. The jet engine had been patented in England by Frank Whittle in 1930 at first flown in Germany in 1934, bringing supersonic flight to the mind of one Britain’s greatest wartime inventors, Barnes Wallace who had created the bouncing bomb and the massive earthquake bombs Tall Boy and Grand Slam, the largest non-nuclear bombs dropped in World War 2.
After the war, he started research into Creating a new type of aircraft with a fully operational swing wing at its heart. In the late 1940s he designed the Vickers wild goose, an unmanned aerial vehicle that he created to research a tailless variable sweep aircraft which would be controlled by moving the wings in flight and avoiding the need for conventional control surfaces or tail
This led to the development of the Vickers type 010 Swallow, a Mach 2.5 swing wing controlled aerodyne with no tail or control services which was proposed as a replacement for the Vickers Valiant V force bomber.
It’s four jet engines would be mounted at the end of the swing wings and could rotate and tilt to control the aircraft and maintain the line of thrust. In 1956, a series of tests with scale flying models showed that most of the technical problems had been overcome.
However, in the now infamous 1957 Defence White Paper, most of the new aircraft projects were cut and the Swallow in particular was deemed as being too advanced by the ministry.
The project was shown to the Americans and although there was a great deal of interest from engineers at NASA, the US Department of Defence was opposed to financing the project and it pretty much ended there.
Barnes Wallace’s team would later go on to create the swing-wing technology used by aircraft like the Panavia Tornado and during the 1960s and into his retirement, he developed ideas for an “all-speed” aircraft, capable of efficient flight at all speed ranges from subsonic to hypersonic.
Wallace’s swing wing technology which was shown to NASA in the Swallow designs, would later go on to influence along with the work from the Bell X5, the 1964 F-111 Aardvark, the world’s first swing-wing aircraft to be put into production. It was also an attempt by secretary of defence Robert McNamara to create one aircraft that would be suitable for both the USAF and the US Navy and hopefully cut costs however things didn’t quite work out that way for the Navy.
Seeing how well the F-111 combined the qualities of both low-speed flight, economy of cruising and supersonic capabilities, the Soviets soon set about creating their own versions and they ended up making far more than the US, producing 10,922 swing-wing aircraft to America’s 1,379.
The Soviets took a slightly different approach in creating two different systems which varied in the distance as a percentage of total wingspan between the wing pivots. This also could be adapted to fit existing airframes without a complete redesign such as the Sukhoi SU-17 In 1966. This would be supplemented by a more advanced design in the MiG-23 of 1967, the Tupolev Tu-22M bomber of 1969 and Sukhoi Su-24 of 1970.
In the US, after the failure of the Navy to get the F-111B to work for them, Grumman produced the F-14 Tomcat in 1970 which went on to be one of the finest fighter aircraft of not only the 70s but the 80s and up into the 90s.
But it wasn’t just fighter aircraft that benefited from the variable geometry designs, large bomber aircraft such as the 1974 B-1B Lancer, the prospective replacement for the B52 and in 1981 Tupolev created their even larger Soviet version of the B-1 with the TU-160.
However, the Tupolev TU-160 would prove to be the last aircraft to use swing-wing technology.
By the 1970s in the US, advances in wing design, new more powerful and fuel-efficient engine’s and computer-controlled or fly-by-wire flight regimes for aircraft with relaxed stability started with the 1974 General Dynamics F-16. This new type of aircraft was basically aerodynamically unstable and could not fly without the aid of a computer but this made them far more agile and that eroded away what advantages swing wing designs had back in the 60s.
In the 1960s, the goal was to cut costs and create one aircraft that could do multiple different roles but now aircraft were becoming more specialized, and instead of trying to be a Jack of all trades, the new designs would be honed to do primarily just one job.
Advancements in materials, computer-aided design, computer control of slats, flaps and spoilers meant that new wing designs could do much of what the swing wing designs would do but without the disadvantages.
Swing wings were a product of their time but they were also heavier, more complex, cost more in maintenance and lost valuable space to the swing-wing mechanisms, issues which the new designs had little to none of and soon the emphasis would be on the ability to fly into a theatre of war without being seen by radar.
This was exemplified by the new stealth technology of aircraft like the F -117 and the B2 spirit bomber. No matter how well swing wing designs might have been tweaked, the one thing they were poor at was being stealthy.
Stealth designs rely upon extremely complex fuselage and wing shapes to reflect as little radar energy as possible. A swing-wing design on the other hand, because of the constant changing of the wing profile could never be made truly stealthy although the B-1 Lancer did a good job considering its size with a radar cross-section of 10m2, it was nothing compared to its successor the B2 with a radar cross-section of 0.0001m2, about the same size as a bumblebee.
So, the simple answer to why swing wings stopped being made was that we found better ways of doing the same job without the mechanical complexity and the requirement to be stealthy excluded a moving wing design.
Although commercial aircraft have never used a variable geometry design, right back at the beginning of the race to create an American supersonic transport aircraft to rival Concorde the original 1960s design of the Boeing SST did feature a swing wing.
However, the titanium mechanism became too big and heavy at 2,100kg reducing the range and reduced space in the cabin so it no longer made economic sense as a commercial aircraft and they switched to a delta wing design like the Concorde.
But that was before it nearly sunk Boeing financially and was eventually cancelled, leaving the subsonic Boeing 747 to rebuild the company’s fortunes.
Swing wings were never used in commercial aircraft because unlike military fighters and bombers they only ever had one job to do from the beginning and variable geometry design was just not needed.
Swing wing manufacture may well have stopped in the 1980s but many are still in service today with two of the most prominent being the B1-B Lancer and the Tupolev TU-160, and in a strange twist, in 2022 a new TU-160M, a highly modernized version took to the air and production restarted with two planned for delivery in 2022 and 10 more on order. So I hope you enjoyed the video and if you did then please thumbs up, share and subscribe, and a big thanks goes to all of our patrons for their ongoing support.
