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Grumman X-29

January 06, 2023

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.

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

Design and development

Two X-29As were built by Grumman after the proposal had been chosen over a competing one involving a General Dynamics F-16 Fighting Falcon. The X-29 design made use of the forward fuselage and nose landing gear from two existing F-5A Freedom Fighter airframes (63-8372 became 82-0003 and 65-10573 became 82-0049).[1] The control surface actuators and main landing gear were from the F-16. 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; forward-swept wings were first trialed 40 years earlier on the experimental Junkers Ju 287 and OKB-1 EF 131. The Grumman internal designation for the X-29 was "Grumman Model 712" or "G-712".[2]

 
X-29 cockpit

Three-surface design and inherent instability

The X-29 is described as a three surface aircraft, with canards, forward-swept wings, and aft strake control surfaces,[3] using three-surface longitudinal control.[4] The canards and wings result in reduced trim drag and reduced wave drag, while using the strakes for trim in situations where the center of gravity is off provides less trim drag than relying on the canard to compensate.[3]

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

 
X-29 with aft control surfaces deflected

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 anisotropic elastic coupling between bending and twisting of the carbon fiber composite material to address this aeroelastic effect. Rather than using a very stiff wing, which would carry a weight penalty even with the relatively light-weight composite, the X-29 used a laminate which produced coupling between bending and torsion. As lift increases, bending loads force the wing tips to bend upward. Torsion loads attempt to twist the wing to higher angles of attack, but the coupling resists the loads, twisting the leading edge downward reducing wing angle of attack and lift. With lift reduced, the loads are reduced and divergence is avoided.[6]

Operational history

The first X-29 took its maiden flight on 14 December 1984 from Edwards AFB piloted by Grumman's Chief Test Pilot Chuck Sewell.[1] The X-29 was the third forward-swept wing jet-powered aircraft design to fly; the other two were the German Junkers Ju 287 (1944) and the HFB-320 Hansa Jet (1964).[7] On 13 December 1985, an X-29 became the first forward-swept wing aircraft to fly at supersonic speed in level flight.

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 National Museum of the United States Air Force on Wright-Patterson Air Force Base near Dayton, Ohio.[11] The other craft is on display at the Armstrong Flight Research Center on Edwards Air Force Base. A full-scale model was on display from 1989 to 2011 at the National Air and Space Museum's National Mall building in Washington, DC.[12] The full-scale replica was moved to the Cradle of Aviation Museum in Garden City, New York in 2011.

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 × General Electric F404-GE-400 afterburning turbofan engine, 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

See also

Aircraft of comparable role, configuration, and era

Related lists

References

Notes

  1. ^ a b Gehrs-Pahl, Andreas, ed. (1995). . AIS.org. Archived from the original on 6 May 2001. Retrieved 1 September 2009.
  2. ^ a b c Donald 1997, p. 483.
  3. ^ a b Roskam 1985, pp. 85–87.
  4. ^ a b c "Fact Sheet: X-29 Advanced Technology Demonstrator Aircraft". NASA Armstrong Flight Research Center. 28 February 2014. Retrieved 24 August 2014.
  5. ^ a b Butts & Hoover 1989.
  6. ^ a b Pamadi 2004.
  7. ^ Green 1970, pp. 493–496.
  8. ^ Webster & Purifoy 1991.
  9. ^ Winchester 2005, p. 261.
  10. ^ a b Winchester 2005, p. 262.
  11. ^ "Grumman X-29A". National Museum of the U.S. Air Force. 28 May 2015. Retrieved 29 August 2015.
  12. ^ . National Air and Space Museum. Archived from the original on 16 June 2012. Retrieved 14 October 2011.
  13. ^ Taylor, John W.R., ed. (1988). Jane's All the World's Aircraft 1988-89 (79th ed.). London: Jane's Information Group. pp. 399–400. ISBN 0-7106-0867-5.
  14. ^ Jenkins, Landis & Miller 2003, p. 37.
  15. ^ 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. {{cite journal}}: Cite journal requires |journal= (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. doi:10.2514/4.862274. 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.
  • Roskam, Jan (1985). Airplane Design, Part II: Preliminary Configuration Design and Integration of the Propulsion System. Ottawa, Kansas: Roskam Aviation and Engineering Corporation. 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). . 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 National Aeronautics and Space Administration.

External links

 
Wikimedia Commons has media related to Grumman X-29.

January 06, 2023
grumman, american, experimental, aircraft, that, tested, forward, swept, wing, canard, control, surfaces, other, novel, aircraft, technologies, developed, grumman, built, were, flown, nasa, united, states, force, aerodynamic, instability, airframe, required, c. 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 X 29A Grumman X 29 in flightRole Experimental aircraftNational origin United StatesManufacturer GrummanFirst flight 14 December 1984Status RetiredPrimary users United States Air ForceNASANumber built 2 Contents 1 Design and development 1 1 Three surface design and inherent instability 1 2 Aeroelastic considerations 2 Operational history 3 Aircraft on display 4 Specifications X 29 5 See also 6 References 6 1 Notes 6 2 Bibliography 7 External linksDesign and development EditTwo X 29As were built by Grumman after the proposal had been chosen over a competing one involving a General Dynamics F 16 Fighting Falcon The X 29 design made use of the forward fuselage and nose landing gear from two existing F 5A Freedom Fighter airframes 63 8372 became 82 0003 and 65 10573 became 82 0049 1 The control surface actuators and main landing gear were from the F 16 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 forward swept wings were first trialed 40 years earlier on the experimental Junkers Ju 287 and OKB 1 EF 131 The Grumman internal designation for the X 29 was Grumman Model 712 or G 712 2 X 29 cockpit Three surface design and inherent instability Edit The X 29 is described as a three surface aircraft with canards forward swept wings and aft strake control surfaces 3 using three surface longitudinal control 4 The canards and wings result in reduced trim drag and reduced wave drag while using the strakes for trim in situations where the center of gravity is off provides less trim drag than relying on the canard to compensate 3 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 Edit X 29 with aft control surfaces deflected 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 anisotropic elastic coupling between bending and twisting of the carbon fiber composite material to address this aeroelastic effect Rather than using a very stiff wing which would carry a weight penalty even with the relatively light weight composite the X 29 used a laminate which produced coupling between bending and torsion As lift increases bending loads force the wing tips to bend upward Torsion loads attempt to twist the wing to higher angles of attack but the coupling resists the loads twisting the leading edge downward reducing wing angle of attack and lift With lift reduced the loads are reduced and divergence is avoided 6 Operational history EditThe first X 29 took its maiden flight on 14 December 1984 from Edwards AFB piloted by Grumman s Chief Test Pilot Chuck Sewell 1 The X 29 was the third forward swept wing jet powered aircraft design to fly the other two were the German Junkers Ju 287 1944 and the HFB 320 Hansa Jet 1964 7 On 13 December 1985 an X 29 became the first forward swept wing aircraft to fly at supersonic speed in level flight Grumman X 29A at the National Museum of the United States Air Force 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 EditThe first X 29 82 003 is now on display in the Research and Development Gallery at the National Museum of the United States Air Force on Wright Patterson Air Force Base near Dayton Ohio 11 The other craft is on display at the Armstrong Flight Research Center on Edwards Air Force Base A full scale model was on display from 1989 to 2011 at the National Air and Space Museum s National Mall building in Washington DC 12 The full scale replica was moved to the Cradle of Aviation Museum in Garden City New York in 2011 Specifications X 29 Edit Data from Jane s All the World s Aircraft 1988 89 13 NASA X Planes 14 Donald 2 Winchester 10 General characteristicsCrew 1 Capacity 4 000 lb 1 814 kg payload Length 53 ft 11 25 in 16 4402 m including nose probe48 ft 1 in 15 m fuselage only dd dd dd 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 General Electric F404 GE 400 afterburning turbofan engine 16 000 lbf 71 kN with afterburnerPerformance 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 FCSSee also Edit Aviation portalJunkers Ju 287 Hansa Jet OKB 1 EF 131Aircraft of comparable role configuration and era Sukhoi Su 47 Rockwell MBB X 31Related lists List of experimental aircraftReferences EditNotes Edit 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 amp Hoover 1989 a b Pamadi 2004 Green 1970 pp 493 496 Webster amp 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 Taylor John W R ed 1988 Jane s All the World s Aircraft 1988 89 79th ed London Jane s Information Group pp 399 400 ISBN 0 7106 0867 5 Jenkins Landis amp Miller 2003 p 37 Lednicer David The Incomplete Guide to Airfoil Usage m selig ae illinois edu Retrieved 16 April 2019 Bibliography Edit 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 a href Template Cite journal html title Template Cite journal cite journal a Cite journal requires journal help Donald David ed 1997 Grumman X 29A The Complete Encyclopedia of World Aircraft New York Barnes amp 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 doi 10 2514 4 862274 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 Roskam Jan 1985 Airplane Design Part II Preliminary Configuration Design and Integration of the Propulsion System Ottawa Kansas Roskam Aviation and Engineering Corporation 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 National Aeronautics and Space Administration External links Edit Wikimedia Commons has media related to Grumman X 29 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 Retrieved from https en wikipedia org w index php title Grumman X 29 amp oldid 1120859154, wikipedia, wiki, book, books, library,

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