Page 16 - The Future of Aerospace is X - X-Planes 2021

X-29 Advanced Technology Demonstrator Aircraft

The Grumman X-29 was an Ameri- airfoil; strake flaps; close-coupled ca- Research Projects Agency and the
can experimental aircraft that tested nards; and a computerized fly-by-wire U.S. Air Force issued proposals for a
a forward-swept wing, canard control flight control system to maintain con- research aircraft designed to explore
surfaces, and other novel aircraft tech- trol of the otherwise unstable aircraft. the forward-swept wing concept. The
nologies. The X-29 was developed Research results showed that the aircraft was also intended to validate
by Grumman, and the two built were configuration of forward-swept wings, studies that predicted better control and
flown by NASA and the U.S. Air Force. coupled with movable canards, gave lift qualities in extreme maneuvers and
The aerodynamic instability of pilots excellent control response at up possibly reduce aerodynamic drag, as
the X-29s airframe required the use to 45 degrees angle of attack, higher well as fly more efficiently at cruise
of computerized fly-by-wire con- than comparable fighter aircraft. Dur- speeds.
trol. Composite materials were used to ing its flight history, X-29s were flown Grumman was chosen in December
control the aeroelastic divergent twist- on 422 research missions. Aircraft No. 1981 to receive an $87 million contract
ing experienced by forward-swept 1 flew 242 in the Phase 1 portion of to build two X-29 aircraft. They were to
wings, and to reduce weight. The air- the program; 120 flights were flown by become the first new X-series aircraft
craft first flew in 1984, and two X-29s aircraft No. 2 in Phase 2; and 60 flights in more than a decade. First flight of the
were flight tested through 1991. were completed in a follow-on “vortex No. 1 X-29 was Dec. 14, 1984, while
The aircraft’s forward-swept wings control” phase. the No. 2 aircraft first flew on May 23,
were mounted well back on the fuse- 1989.
lage, while its canards (horizontal sta- Before World War II, some gliders
bilizers to control pitch) were in front with forward-swept wings existed, and Flight control system
of the wings instead of on the tail. The the the National Advisory Commit- The flight control surfaces on the
complex geometries of the wings and tee for Aeronautics (NACA) Langley NASA photograph X-29 were the forward-mounted ca-
canards combined to provide excep- Memorial Aeronautical Laboratory in nards, which shared the lifting load
tional maneuverability, supersonic Virginia, performed wind-tunnel stud- This photo shows the X-29 during a 1991 research flight. Smoke generators with the wings and provided primary
in the nose of the aircraft were used to help researchers see the behavior of
performance and a light structure. Air ies on the concept in 1931. the air flowing over the aircraft. The smoke here is demonstrating forebody pitch control. The wing flaperons (com-
moving over the forward-swept wings Germany developed a jet-powered vortex flow. This mission was flown Sept. 10, 1991, by NASA research pilot bination flaps and ailerons) were used
tended to flow inward toward the root aircraft with forward-swept wings, the Rogers Smith. to change wing camber and function
of the wing instead of outward toward Junkers Ju-287, during the war. The as ailerons for roll control when used
the wing tip as occurs on an aft-swept concept, however, was not successful asymmetrically. In addition, the strake
wing. This reverse airflow kept the because the technology and materials ness jet to use a forward-swept-wing. The X-29’s thin supercritical wing flaps on each side of the rudder aug-
wing tips and their ailerons from stall- did not exist to construct the wing rigid The introduction of composite ma- was of composite construction. State- mented the canards with pitch control.
ing at high angles of attack (direction enough to overcome bending and twist- terials in the 1970s opened a new field of-the-art composites permit aeroelastic The control surfaces were linked elec-
of the fuselage relative to the air flow). ing forces without making the aircraft of aircraft construction, making it pos- tailoring, which allows the wing some tronically to a triple-redundant digital
The fighter-size X-29 also explored too heavy. Hamburger Flugzuebau de- sible to design rugged airframes and bending but limits twisting and elimi- fly-by-wire flight control system that
the use of advanced composites in signed and built the Hansa Jet HFB-320 structures stronger than those made of nates structural divergence within the provided an artificial stability.
aircraft construction; variable camber in the early 1960s; the aircraft first flew conventional materials, yet lightweight flight envelope (deformation of the The particular forward-swept wing,
wing surfaces; the unique forward- in 1964. The company built 45 HFB- and able to withstand tremendous aero- wing or breaking off in flight).
swept wing and its thin supercritical 320s, the only certified civilian busi- dynamic forces. In 1977, the Defense Advanced See X-29, Page 19
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