The overall shape of the X-29 is quite similar to that of the F5 Freedom Fighter, which is not uncommon because Grumman built it from the airframes of two existing Northrop F-5A fighters.

Introduce

The forward-swept wing design was once considered a revolution in aircraft manufacturing, but for various reasons this design was not widely used. The first forward-swept wing aircraft in the world was the Nazi-made Junkers Ju 287 bomber in 1944.

The forward-swept wing design was supposed to help the aircraft operate more efficiently at low altitudes. There were two Ju 287 prototypes built, but due to the failure of the Nazis, this project was not completed.

After the Soviet Union entered Berlin, they seized a lot of documents of the Ju 287 to build their OKB-1 140 forward-swept wing jet bomber. Two OKB-1 140 prototypes were completed, but like the Ju 287, it was also canceled in 1950.

As a science and technology power, the United States did not stand out in the arms race. General Dynamic launched the F-16 SFW with forward-swept wing based on the F-16A platform in 1976. However, the fate of the F-16 SFW soon ended when engineers realized the manufacturing of the aircraft is very complicated, time-consuming and costly.

In early 1981, Grumman X-29 light fighter project was selected. According to calculations, they will have a fighter with superior features compared to the F-16 but the size is compact only equivalent to the F-5.

Grumman created two experimental X-29 prototypes. To reduce production costs of the X-29, Grumman also took advantage of the machinery and systems of other aircraft such as F14 or F16. The aircraft first flew in 1984, and two X-29s were flight tested through 1991.

Design

The overall shape of the X-29 is quite similar to that of the F5 Freedom Fighter, which is not uncommon because Grumman built it from the airframes of two existing Northrop F-5A fighters. The X-29 design made use of the forward fuselage and nose landing gear from the F-5As with the control surface actuators and main landing gear from the F-16.

What makes the X-29 different is its wings, the forward-swept wings were mounted well back on the fuselage. The technological advancement that made the X-29 a plausible design was the use of carbon-fiber composites.

The wings of the X-29, made partially of graphite epoxy, were swept forward at more than 33 degrees. It had a single vertical tailfin while no horizontal tailplanes. The X-29’s horizontal stabilizers to control pitch, the canards, were in front of the wings instead of on the tail.

The complex geometries of the wings and canards combined to provide exceptional maneuverability, supersonic performance and a light structure. Air moving over the forward-swept wings tended to flow inward toward the root of the wing instead of outward toward the wing tip as occurs on an aft-swept wing. This reverse airflow kept the wing tips and their ailerons from stalling at high angles of attack.

This X-29 aircraft only has a single seat for test pilot. It has an empty weight of about 6.2 tons, a length of 17.7 meters (58 ft), a wingspan of 8.29 (27.2 ft) meters and a wing area of 17.54 square meters.

Powerplant

A General Electric F404 turbofan engine was used, providing thrust up to 71.2 kiloNewtons. The maximum speed Grumman X-29 reaches was approximately Mach 1.8, equivalent to 1,770 km/h at an altitude of 10,000 meters.

The service ceiling of the Grumman X-29 was about 16,800 meters, but its maximum range was only 560 km.

End of the project

The particular forward-swept wing, close-coupled canard design used on the X-29 was highly unstable. The aerodynamic instability of the X-29’s airframe required the use of computerized fly-by-wire control, continually adjusted the control surfaces with up to 40 commands each second. Each of the three digital flight control computers had an analog backup. If one of the digital computers failed, the remaining two took over. If two of the digital computers failed, the flight control system switched to the analog mode.

Research results showed that the configuration of forward-swept wings, coupled with movable canards, gave pilots excellent control response at up to 45 degrees angle of attack, higher than comparable fighter aircraft. During its flight history, X-29s were flown on 422 research missions. Aircraft No. 1 flew 242 in the Phase 1 portion of the program; 120 flights were flown by aircraft No. 2 in Phase 2; and 60 flights were completed in a follow-on “vortex control” phase.

Overall, the X-29 program ended without any aircraft being born. However, the program did demonstrate several new technologies as well as new uses of proven technologies. The program provided an engineering database that is available for the design and development of future aircraft. Currently, the X-29 No. 1 is on display at the National Museum of the Air Force in Dayton, Ohio. Aircraft No. 2 is on display at the NASA Armstrong Flight Research Center.

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