X-29 Advanced Technology Demonstrator Aircraft 

Two X-29 aircraft, featuring one of the more unusual 

designs in aviation history, were flown at NASA 

Ames-Dryden Flight Research Facility (now Armstrong Flight Research Center) at Edwards Air Force 

Base, California. The demonstrators investigated 

advanced concepts and technologies during a multiphased program conducted from 1984 to 1992. The 

program provided an engineering database that is 

available for the design and development of future 

aircraft.

The aircraft's forward-swept wings were mounted 

well back on the fuselage, while its canards (horizontal stabilizers to control pitch) 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 (direction of 

the fuselage relative to the air flow).

The fighter-size X-29 also explored the use of advanced composites in aircraft construction; variable 

camber wing surfaces; the unique forward-swept 

wing and its thin supercritical airfoil; strake flaps; 

close-coupled canards; and a computerized fly-bywire flight control system to maintain control of the 

otherwise unstable aircraft.

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. 

Background

Before World War II, some gliders with forwardswept wings existed, and the NACA (the National 

Advisory Committee for Aeronautics) Langley 

Memorial Aeronautical Laboratory (now Langley 

Research Center) in Hampton, Virginia, performed 

wind-tunnel studies on the concept in 1931. Germany developed a jet-powered aircraft with forwardswept wings, the Junkers Ju 287, during the war. The 

The X-29 advanced technology demonstrator aircraft banks over the Mojave Desert, California. (NASA 

Photo)
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concept, however, was not successful because the technology and 

materials did not exist to construct the wing rigid enough to overcome bending and twisting forces without making the aircraft too 

heavy. Hamburger Flugzuebau designed and built the Hansa Jet 

HFB-320 in the early 1960s; the aircraft first flew in 1964. The 

company built 45 HFB-320s, the only certified civilian business 

jet to use a forward-swept-wing.

The introduction of composite materials in the 1970s opened a 

new field of aircraft construction, making it possible to design 

rugged airframes and structures stronger than those made of 

conventional materials, yet lightweight and able to withstand 

tremendous aerodynamic forces.

The X-29's thin supercritical wing was of composite construction. 

State-of-the-art composites permit aeroelastic tailoring, which 

allows the wing some bending but limits twisting and eliminates 

structural divergence within the flight envelope (deformation of 

the wing or breaking off in flight).

In 1977, the Defense Advanced Research Projects Agency 

(DARPA) and the U.S. Air Force Flight Dynamics Laboratory 

(now the Air Force Research Laboratory or AFRL) at WrightPatterson Air Force Base, Ohio, issued proposals for a research 

aircraft designed to explore the forward-swept wing concept. 

The aircraft was also intended to validate studies that predicted 

better control and lift qualities in extreme maneuvers and possibly reduce aerodynamic drag, as well as fly more efficiently at 

cruise speeds.

The Grumman Corporation was chosen in December 1981 to 

receive an $87 million contract to build two X-29 aircraft. They 

were to become the first new X-series aircraft in more than a decade. First flight of the No. 1 X-29 was Dec. 14, 1984, while the 

No. 2 aircraft first flew on May 23, 1989. Both first flights were 

from NASA Ames-Dryden Flight Research Facility.

Flight Control System

The flight control surfaces on the X-29 were the forward-mounted canards, which shared the lifting load with the wings and 

provided primary pitch control. The wing flaperons (combination 

flaps and ailerons) were used to change wing camber and function 

as ailerons for roll control when used asymmetrically. In addition, 

the strake flaps on each side of the rudder augmented the canards 

with pitch control. The control surfaces were linked electronically 

to a triple-redundant digital fly-by-wire flight control system that 

provided an artificial stability.

The particular forward-swept wing, close-coupled canard design 

used on the X-29 was highly unstable. The X-29 flight control 

system compensated for this instability by sensing flight conditions such as attitude and speed and through computer processing, 

continually adjusted the control surfaces with up to 40 commands 

each second. Conventionally configured aircraft achieved stability by balancing lift loads on the wing with opposing downward 

loads on the tail at the cost of drag. The X-29 avoided this drag 

penalty through its relaxed static stability.

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. If one of the analog computers failed, the two remaining analog computers took over. The 

risk of total systems failure in the X-29 was equivalent to the risk 

of mechanical failure in a conventional system.

Phase 1 Flights

The No. 1 aircraft's research flights demonstrated that, because 

the air moving over the forward-swept wing flowed inward rather 

than outward, the wing tips remained unstalled at the moderate angles of attack. Phase 1 flights also demonstrated that the 

aeroelastic-tailored wing did, in fact, prevent structural divergence of the wing within the flight envelope, and that the control 

laws and control surface effectiveness were adequate to provide 

artificial stability for this otherwise extremely unstable aircraft 

and provided good handling qualities for the pilots.

The aircraft's supercritical airfoil also enhanced maneuvering 

and cruise capabilities in the transonic regime. Developed by 

NASA and originally tested on an F-8 in the 1970s, supercritical airfoils - flatter on the upper wing surface than conventional 

airfoils - delayed and softened the onset of shock waves on the 

upper wing surface, reducing drag. The Phase 1 flights also 

demonstrated that the aircraft could fly safely and reliably, even 

in tight turns.

Phase 2 Flights

The No. 2 X-29 investigated the aircraft's high angle-of-attack 

characteristics and the military utility of its canard and forwardswept wing configuration. In Phase 2, flying at up to 67 degrees 

angle of attack (also called high alpha), the aircraft demonstrated 

much better control and maneuvering qualities than computational methods and simulation models predicted. The No. 1 X-29 was 

limited to 21 degrees angle-of-attack maneuvering.

During Phase 2 flights, NASA, Air Force and Grumman project 

pilots reported the X-29 aircraft had excellent control response 

to 45 degrees angle of attack and still had limited controllability 

at 67 degrees angle of attack. This controllability at high angles 

of attack can be attributed to the aircraft's unique forward-swept 

wing and canard design. The NASA/Air Force-designed highgain flight control laws also contributed to good flying qualities. 

Flight control law concepts used in the program were developed 

from radio-controlled flight tests of a 22-percent X-29 drop model 

at NASA Langley.

NASA and Air Force Flight Test Center (now Air Force Test 

Center) engineers at Edwards Air Force Base performed the detail 

design work. The X-29 achieved its high-alpha controllability 

without leading edge flaps on the wings for additional lift and 

without moveable vanes on the engine's exhaust nozzle to change 
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Armstrong Flight Research Center

P.O. Box 273

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or "vector" the direction of thrust. Researchers documented the 

X-29's aerodynamic characteristics at high angles of attack using 

a combination of pressure measurements and flow visualization. Flight test data satisfied the primary objective of the X-29 

program - to evaluate the ability of X-29 technologies to improve 

future fighter aircraft mission performance.

Vortex Flow Control

In 1992 the Air Force initiated a program to study the use of vortex flow control as a means of providing increased aircraft control 

at high angles of attack when the normal flight control systems 

are ineffective.

The No. 2 X-29 was modified with the installation of two highpressure nitrogen tanks and control valves with two small nozzle 

jets located on the forward upper portion of the nose. The purpose 

of the modifications was to inject air into the vortices that flow off 

the nose of the aircraft at high angles of attack.

Wind tunnel tests at the Air Force's Wright Laboratory (now 

AFRL) and at the Grumman Corporation showed that injection of 

air into the vortices would change the direction of vortex flow and 

create corresponding forces on the nose of the aircraft to change 

or control the nose heading.

From May to August 1992, 60 flights successfully demonstrated 

vortex flow control (VFC). VFC was more effective than expected in generating yaw (left-to-right) forces, especially at higher 

angles of attack where the rudder loses effectiveness. VFC was 

less successful in providing control when sideslip (relative wind 

pushing on the side of the aircraft) was present, and it did little to 

decrease rocking oscillation of the aircraft.

Summary

Overall, VFC, like the forward-swept wings, showed promise 

for the future of aircraft design. The X-29 did not demonstrate 

the overall reduction in aerodynamic drag that earlier studies 

had suggested. The X-29 program did demonstrate several new 

technologies as well as new uses of proven technologies including aeroelastic tailoring to control structural divergence and use of 

a relatively large, close-coupled canard for longitudinal control. 

In addition, the program validated control of an aircraft with 

extreme instability while still providing good handling qualities; 

use of three-surface longitudinal control; use of a double-hinged 

trailing-edge flaperon at supersonic speeds; control effectiveness 

at high angles of attack; vortex control; and military utility of the 

overall design.

Specifications

The X-29 is a single-engine aircraft 48.1 feet long. Its forwardswept wing has a span of 27.2 feet. A General Electric F404-

GE-400 engine producing 16,000 pounds of thrust powered each 

X-29. Empty weight of the aircraft was 13,600 pounds, while 

takeoff weight was 17,600 pounds.

The aircraft had a maximum operating altitude of 50,000 feet, 

a maximum speed of Mach 1.6 and a flight endurance time of 

approximately one hour. The only significant difference between 

the two aircraft was an emergency spin chute deployment system 

mounted at the base of the rudder on aircraft No. 2. External wing 

structure is primarily composite materials incorporated into precise patterns to develop strength and avoid structural divergence. 

The wing substructure and the basic airframe itself are aluminum 

and titanium. Wing trailing edge actuators controlling camber are 

mounted externally in streamlined fairings because of the thinness 

of the supercritical airfoil.

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.

Strake flap

27 ft 2.44 in.

48 ft 1 in. 

14 ft 9.5 in.

F-5A nose

section

Rudder

Canard

Wing flap

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