In recent decades, the concept of swing wings has become widely adopted. However, most of the time, they aren’t forward swing wings, like the Grumman X-29!
Despite Grumman and the USAF spending millions of dollars developing the jet, much of its technology has since been proven to be useless. So what exactly did the US get out of the program? And why did it fail?
As a result of the aircraft’s technology and primary objective, the X-29 has arguably the weirdest aircraft design in history!
Pre-X-29
The concept of forward-swept wings is not a new one. Rough sketches of forward swept aircraft date back to the time of the Wright Brothers! However, these designs proved to be ultimately futile.
During WWII, the idea was picked up again during the development of the jet engine. The Germans believed that a forward-swept wing may help with the jet engine’s performance, however, were ultimately proven wrong.
Through this development, two forward-swept bombers were developed in the form of the experimental Junkers Ju 287 and OKB-1 EF 131. At the end of the war, many of the designs were scrapped and their documentation destroyed.
However, in the 1960’s, the HFB 320 Hansa Jet was designed to be one of the first business jets. This was the first successful use of forward-swept wings. To this day, it remains the only mass-produced forward-swept aircraft.
In the 1980’s, the USAF and NASA wanted to evaluate the concept of forward-swept wing wings once again (having first done so in the 1930’s). This time, they wanted to evaluate its performance at supersonic speeds.
At this time, the Americans and Soviets were attempting to design high altitude, supersonic jets. Both countries wondered if forward-sweeping swing wings would be beneficial, leading to the Soviet’s Su-47 Berkut.
Development
In 1983, the USAF and NASA contacted Grumman and asked them if they were interested in the idea (as they had previously developed the swing wing F-14 Tomcat). Grumman responded that they indeed were.
To do this, Grumman decided to contact Northrop and negotiate a price for their failed F-5A Freedom Fighter (an aircraft that failed against the F-16 and F-18). After several months of negotiating, Grumman acquired the F-5A.
During this time, Grumman also contacted General Dynamics, purchasing several F-16 systems as well. Much of the F-5A fuselage was kept the same, with increased weight, leading to F-16 engines and landing gear to be added.
Grumman also had to completely redesign the F-5A’s wings, with much of the control surfaces’ design being derived from those of the F-16. This also saw Grumman redesign the X-29’s cockpit, in order to accommodate more controls.
In order to make the X-29 more stable at subsonic and supersonic speeds, Grumman also designed canards to be used on the X-29. This would help give the pilot more control and maneuverability.
On top of this, the X-29 was one of the first aircraft to have rear control surfaces, acting as both horizontal stabilizers and as ailerons. By 1984, both X-29s had been completed and had been delivered to NASA and the USAF.
Design Issues
As the three previous forward-swept aircraft had found, due to the nature of the aircraft there were several different issues.
Perhaps the largest one was to do with weight. As the Boeing 2707 had found years earlier, air resistance and swing wings don’t mix. As such, they need to be reinforced in several different ways.
However, due to the wings facing forwards, the issue was twofold. This required Grumman to invent several new types of reinforcements, all of which were incredibly heavy.
As such, much of the fuselage had to be made out of composite materials, and where possible, out of carbon fiber. This gave the Grumman X-29 a higher gross weight than what the F-5A had.
Due to how the wings were designed, when they were fully swept and the aircraft was flying at supersonic speeds, the wing tips began to bend upwards. This saw the wing also being reinforced to prevent it from being broken.
Thanks to all of this, the X-29 is inherently aerodynamically unstable. This caused Grumman wind tunnel tests to take quite a while, as they were constantly developing new control surfaces to compensate for this.
During pre-test flights, pilots concluded that the aircraft would also need a parachute in order to safely land. This has made it the first single engine aircraft to use a parachute to land (every time).
Flight Testing
Upon completion of the two Grumman X-29s in late 1984, they were shipped to Edwards Air Force Base. Here, a combined USAF/Grumman team would perform a series of initial tests with the aircraft.
Following this, on December 14 1984, the X-29 performed its first test flight. Here, they flew basic flights in order to get a feel of how the aircraft handles. They also spent much of the time practicing landing with the parachute.
In April 1985, NASA joined the X-29 project, seeing potential space-bound applications for the X-29’s technology. This would see both X-29s repainted in NASA and USAF colors to reflect that.
Almost exactly a year after its first flight, on December 13 1985, the X-29 became the first forward-sweeping swing wing aircraft to travel faster than the speed of sound. The X-29 is one of only two to date.
By August 1986, the X-29 was flying both USAF test flights and NASA research flights. By this time, both sets of missions could last for several hours, containing multiple flights.
The last X-29 flight took place in late 1991, before being retired. Between 1984 and 1991, the X-29 flew 242 times. For the vast majority of these flights, it was under the USAF banner, however, the majority of the findings were done by NASA.
Findings
Although much of the findings remain classified for obvious reasons, some of it has since been leaked or have been released to the public by either NASA or the USAF.
For the most part, the USAF was happy with the X-29. However, the implementation of stealth technology soon made the extremely unstealthy X-29 irrelevant. Had things gone differently, the X-29 may have entered USAF service.
Even NASA and Grumman understood the military benefits of the X-29. However, the USAF saw the future in stealth technology and decided to abandon the Grumman X-29 it had spent seven years testing.
On the other hand, NASA research flights yielded several new technologies and flying techniques. The latter of which are still in use today, almost forty years on!
On top of this, due to the X-29’s unique layout, several pre-existing technologies were given new uses. Many of these technologies proved to do a better job for their new role than their primary purpose!
Several of the NASA flights saw the X-29 change its angle of attack, demonstrating the sort of design that NASA would need in order to have an extremely aerodynamic aircraft that does beyond the 15 degree stall angle of attack.
Specifications
Despite only ever being an experimental aircraft, with neither the X-29 or an X-29-inspired aircraft entering mass production, it is still important to know how the X-29 operated.
As both X-29’s were built using F-5A Freedom Fighter airframes, their specs do (somewhat) resemble those of the F-5A. However, many modifications were made to the aircraft subsequently…
| Specifications | Grumman X-29 |
|---|---|
| Length | 53 ft 11.25 in (16.44 m) |
| Width | 27 ft 2.5 in (8.3 m) |
| Height | 14 ft 3.5 in (4.36 m) |
| Crew | 1 |
| Max Speed | 1.8 Mach (1,200 kn; 1,381 mph; 2,222 km/h) |
| Max Range | 350 nmi (400 mi, 650 km |
| Service Ceiling | 55,000 ft (17,000 m) |
| Aspect Ratio | 3.9 |
| MTOW | 17,800 lb (8,100 kg) |
What Was it Like to Fly The Grumman X-29?
Unlike most experimental aircraft projects, the Grumman X-29 wasn’t highly classified. Yes, much of the findings and such stay incredibly classified, but a lot of it is still unclassified.
This was even so during the 1980’s when it was being tested! To date, if you have the correct magazines, you can actually find a series of articles on the Grumman X-29, including interviews with spokesmen and pilots.
For the most part, these pilots tended to talk about how difficult the aircraft is to operate. They tended to explain just how unstable the aircraft is, and how, if it was in a dogfight it would struggle, due to pilots overtaxing themselves.
However, when they weren’t focusing on that issue, they were talking about the potential military advantages of the aircraft, especially in its first few years of flight.
Mostly, this was the relative unknown of the X-29. Soviet pilots wouldn’t really know how to combat an X-29, especially if it was alongside a series of F-16s or F-15s (or both!)
It was believed that the Soviets would definitely not attack X-29s. until further study.
For the most part, pilot’s attitudes towards the X-92 were quite positive, believing that new tactics could make it incredibly deadly. However, they did also emphasize its difficulty.
Avgeeks
At the time, the Grumman X-29 took the avgeek world by storm. Many avgeeks genuinely believed that the X-29 was the aircraft of the future, and that one day, most militaries would use a forward sweeping swing wing aircraft.
This resulted in most major aircraft magazines, both military and general writing a series of articles about the X-29. This culminated in quite a few interviews with X-29 pilots.
However, most of these avgeeks did not believe that the X-29 itself would enter service as something like the F-29. Instead, they believed that it would serve as the basis for future forward-sweeping swing wing designs.
Many of my personal friends in the avgeek community have told me stories about their love for the X-29, even thirty years on. Many of them have told me stories about how they have visited museums for the sole purpose of the X-29.
Even today, many of those who remember the X-29 still like the concept behind it, even if it is from a bygone era. One of them pointed this out to me as well:
Whilst it isn’t a good fit for the USAF now, it was during the 1980’s and 1990’s. Perhaps if aircraft like the F-22 and F-35 hadn’t been so attractive, the X-29 or a similar aircraft would’ve entered service.
I doubt it would’ve been a primary aircraft for the USAF, but it would’ve been a great supplement to the F-15 and F-16 that the USAF currently uses!
Legacy
Despite being a failure, the X-29 left a fairly large impact on the aviation industry as a whole!
Grumman
The X-29 project brought both Grumman and Northrop closer together. Grumman negotiated with Northrop for the two F-5A Freedom Fighter airframes, with both companies’ executives gaining a mutual respect for one another.
Despite the US Government covering most of the X-29’s costs, Grumman wanted the X-29 to be perfect, believing that it would pay off very well in the future. To do this, Grumman took out large loans for the development.
However, the X-29 was a failure due to newer technology making it obsolete. This caused the two experimental aircraft to be scrapped, and left Grumman with a lot of debt and not much to show for it.
Over time, and with the reduction in orders for their other aircraft, eventually caused financial instability within Grumman. This eventually led to the 1994 Grumman-Northrop merger, forming Northrop Grumman.
Grumman X-29
The last Grumman X-29 flight was in 1991. Following this, there was no need for the aircraft, giving Grumman a number of options. However, the main three were scrapping them, giving them to museums and/or storing them.
Grumman chose to donate the two X-29s to museums. The first one was given to the National Museum of the United States Air Force at the Wright-Patterson Air Force Base in Dayton, Ohio.
The second X-29 was given to NASA’s Armstrong Flight Research Center in Edwards Air Force Base. Both aircraft are currently on display (as of the time of writing).
In 1989, in order to promote the X-29 program, Grumman commissioned a full-scale replica of the X-29. This was placed on display in the National Air and Space Museum’s National Hall building. It was taken off display in 2011.
Future Aircraft
For much of the foreseeable future, swing wing military aircraft are irrelevant. Instead, the future will be with supersonic stealth aircraft instead.
And if the future does once again see technology improve to allow for stealth swing wing aircraft, they probably won’t be forward swing wings. Instead, they will probably swing wings like the F-111 and F-14.
With that being said, if technology progresses to accommodate both specs, the possibility of forward swing wings is plausible. However, new control surfaces will need to be developed, not to mention new, more durable and lighter materials.