Grumman X-29
X-29 | |
---|---|
A Grumman X-29 in flight | |
Role | Experimental aircraft |
National origin | United States |
Manufacturer | Grumman |
First flight | 14 December 1984 |
Status | Retired |
Primary users | United States Air Force NASA |
Number built | 2 |
The Grumman X-29 was an American experimental aircraft that tested a forward-swept wing, canard control surfaces, and other novel aircraft technologies. The X-29 was developed by Grumman, and the two built were flown by NASA and the United States Air Force. The aerodynamic instability of the X-29's airframe required the use of computerized fly-by-wire control. Composite materials were used to control the aeroelastic divergent twisting experienced by forward-swept wings, and to reduce weight. The aircraft first flew in 1984, and two X-29s were flight tested through 1991.
Design and development
Two X-29As were built by
Three-surface design and inherent instability
The X-29 is described as a
The configuration, combined with a center of gravity well aft of the aerodynamic center, made the craft inherently unstable. Stability was provided by the computerized flight control system making 40 corrections per second. The flight control system was made up of three redundant digital computers backed up by three redundant analog computers; any of the three could fly it on its own, but the redundancy allowed them to check for errors. Each of the three would "vote" on their measurements, so that if any one was malfunctioning it could be detected. It was estimated that a total failure of the system was as unlikely as a mechanical failure in an airplane with a conventional arrangement.[4]
The high pitch instability of the airframe led to wide predictions of extreme maneuverability. This perception has held up in the years following the end of flight tests. Air Force tests did not support this expectation.[5] For the flight control system to keep the whole system stable, the ability to initiate a maneuver easily needed to be moderated. This was programmed into the flight control system to preserve the ability to stop the pitching rotation and keep the aircraft from departing out of control. As a result, the whole system as flown (with the flight control system in the loop as well) could not be characterized as having any special increased agility. It was concluded that the X-29 could have had increased agility if it had faster control surface actuators and/or larger control surfaces.[5]
Aeroelastic considerations
In a forward swept wing configuration, the aerodynamic lift produces a twisting force which rotates the wing leading edge upward. This results in a higher angle of attack, which increases lift, twisting the wing further. This aeroelastic divergence can quickly lead to structural failure. With conventional metallic construction, a torsionally very stiff wing would be required to resist twisting; stiffening the wing adds weight, which may make the design unfeasible.[6]
The X-29 design made use of the
Operational history
The first X-29 took its maiden flight on 14 December 1984 from
The X-29 began a NASA test program four months after its first flight. The X-29 proved reliable, and by August 1986 was flying research missions of over three hours involving multiple flights. The first X-29 was not equipped with a spin recovery parachute, as flight tests were planned to avoid maneuvers that could result in departure from controlled flight, such as a spin. The second X-29 was given such a parachute and was involved in high angle-of-attack testing. X-29 number two was maneuverable up to an angle of attack of about 25 degrees with a maximum angle of 67° reached in a momentary pitch-up maneuver.[8][9]
The two X-29 aircraft flew a total of 242 times from 1984 to 1991.[2][10] The NASA Dryden Flight Research Center reported that the X-29 demonstrated a number of new technologies and techniques, and new uses of existing technologies, including the use of "aeroelastic tailoring to control structural divergence", aircraft control and handling during extreme instability, three-surface longitudinal control, a "double-hinged trailing-edge flaperon at supersonic speeds", effective high angle of attack control, vortex control, and demonstration of military utility.[4]
Aircraft on display
The first X-29, 82-003, is now on display in the Research and Development Gallery at the
Specifications (X-29)
Data from Jane's All the World's Aircraft 1988-89[13] NASA X-Planes,[14] Donald,[2] Winchester[10]
General characteristics
- Crew: 1
- Capacity: 4,000 lb (1,814 kg) payload
- Length: 53 ft 11.25 in (16.4402 m) including nose probe
- 48 ft 1 in (15 m) fuselage only
- Wingspan: 27 ft 2.5 in (8.293 m)
- Height: 14 ft 3.5 in (4.356 m)
- Wing area: 188.84 sq ft (17.544 m2)
- Aspect ratio: 3.9
- Airfoil: root: Grumman K MOD 2 (6.2%); tip: Grumman K MOD 2 (4.9%)[15]
- Empty weight: 13,800 lb (6,260 kg)
- Max takeoff weight: 17,800 lb (8,074 kg)
- Fuel capacity: 3,978 lb (1,804 kg) in two fuselage bladder tanks and two strake integral tanks
- Powerplant: 1 × afterburning turbofanengine, 16,000 lbf (71 kN) with afterburner
Performance
- Maximum speed: 956 kn (1,100 mph, 1,771 km/h) at 33,000 ft (10,058 m)
- Maximum speed: Mach 1.6
- Range: 350 nmi (400 mi, 650 km)
- Service ceiling: 55,000 ft (17,000 m)
Avionics
- Litton LR-80 AHRS
- Magnavox AN/ARC-164 UHF
- Teledyne RT-1063B/APX-101V IFF/SIF
- Honeywell triple redundant fly-by-wire FCS
Notable appearances in media
The 1989 flight simulator game F29 Retaliator was based around the X-29 and imagined a future where it had been developed into a production fighter jet and fitted with various advanced weaponry.[citation needed]
The X-29 appeared on the cover of the Smile album by the Japanese band Boris.[citation needed][importance?]
See also
- Junkers Ju 287
- Hansa Jet
- OKB-1 EF 131
Aircraft of comparable role, configuration, and era
Related lists
References
Notes
- ^ a b Gehrs-Pahl, Andreas, ed. (1995). "The X-Planes: From X-1 to X-34". AIS.org. Archived from the original on 6 May 2001. Retrieved 1 September 2009.
- ^ a b c Donald 1997, p. 483.
- ^ a b Roskam 1985, pp. 85–87.
- ^ a b c "Fact Sheet: X-29 Advanced Technology Demonstrator Aircraft". NASA Armstrong Flight Research Center. 28 February 2014. Retrieved 24 August 2014.
- ^ a b Butts & Hoover 1989.
- ^ a b Pamadi 2004.
- ^ Green 1970, pp. 493–496.
- ^ Webster & Purifoy 1991.
- ^ Winchester 2005, p. 261.
- ^ a b Winchester 2005, p. 262.
- ^ "Grumman X-29A". National Museum of the U.S. Air Force. 28 May 2015. Retrieved 29 August 2015.
- ^ "Beyond the Limits". National Air and Space Museum. Archived from the original on 16 June 2012. Retrieved 14 October 2011.
- ISBN 0-7106-0867-5.
- ^ Jenkins, Landis & Miller 2003, p. 37.
- ^ Lednicer, David. "The Incomplete Guide to Airfoil Usage". m-selig.ae.illinois.edu. Retrieved 16 April 2019.
Bibliography
- Butts, S. L.; Hoover, A. D. (May 1989). "Flying Qualities Evaluation of the X-29A Research Aircraft". U.S. Air Force Flight Test Center. AFFTC-TR-89-08.
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(help) - Donald, David, ed. (1997). "Grumman X-29A". The Complete Encyclopedia of World Aircraft. New York: Barnes & Noble. ISBN 978-0-7607-0592-6.
- Green, William (1970). Warplanes of the Third Reich. New York: Doubleday. ISBN 978-0-385-05782-0.
- Jenkins, Dennis R.; Landis, Tony; Miller, Jay (June 2003). American X-Vehicles: An Inventory—X-1 to X-50 (PDF). Monographs in Aerospace History No. 31. NASA. OCLC 68623213. SP-2003-4531.
- Pamadi, Bandu N. (2004). Performance, Stability, Dynamics, and Control of Airplanes (2nd ed.). American Institute of Aeronautics and Astronautics. ISBN 978-1-56347-583-2.
- Putnam, Terrill W. (January 1984). X-29 Flight-Research Program (PDF). AIAA 2nd Flight Test Conference. Las Vegas, Nevada. 16–18 November 1983. NASA. TM-86025.
- ISBN 978-1-88488-543-3.
- Thruelsen, Richard (1976). The Grumman Story. New York: Praeger Publishers. ISBN 978-0-275-54260-3.
- Treadwell, Terry (1990). Ironworks: Grumman's Fighting Aeroplanes. Shrewsbury, UK: Airlife Publishers. ISBN 978-1-85310-070-3.
- Warwick, Graham (16 June 1984). "Forward-sweep Technology". Flight International: 1563–1568.
- Webster, Frederick R.; Purifoy, Dana (July 1991). X-29 High Angle-of-Attack Flying Qualities. U.S. Air Force Flight Test Center. AFFTC-TR-91-15. Archived from the original on 26 August 2014. Retrieved 24 August 2014.
- Winchester, Jim (2005). "Grumman X-29". X-Planes and Prototypes. London: Amber Books. ISBN 978-1-904687-40-5.
This article incorporates public domain material from websites or documents of the
External links
- X-29 fact sheet at NASA.gov
- X-29 fact sheet by the National Museum of the United States Air Force
- X-29 photos, and X-29 videos at NASA.gov
- "X-29: Aircraft with Forward Swept Wings", part 1, part 2 at Military.com