Lockheed YF-22

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YF-22
A YF-22 during a test flight
Role Stealth fighter technology demonstrator
National origin United States
Manufacturer Lockheed / Boeing / General Dynamics
First flight 29 September 1990
Status Retired
Primary user United States Air Force
Produced 1989–1990
Number built 2
Developed into Lockheed Martin F-22 Raptor

The Lockheed/Boeing/General Dynamics YF-22 is an American single-seat, twin-engine fighter aircraft technology demonstrator designed for the United States Air Force (USAF). The design was a finalist in the USAF's Advanced Tactical Fighter (ATF) competition, and two prototypes were built for the demonstration/validation phase of the competition. The YF-22 team won the contest against the YF-23 team for full-scale development, and the design was developed into the Lockheed Martin F-22 Raptor. The YF-22 has a similar aerodynamic layout and configuration as the F-22, but with notable differences in the overall shaping such as the position and design of the cockpit, tail fins and wings, and in internal structural layout.

In the 1980s, the USAF began looking for a replacement for its fighter aircraft, especially to counter the advanced Su-27 and MiG-29. A number of companies, divided into two teams, submitted their proposals. Northrop and McDonnell Douglas submitted the YF-23. Lockheed, Boeing and General Dynamics proposed and built the YF-22, which, although marginally slower and having a larger radar cross-section, was more agile than the YF-23. The Lockheed team was picked by the Air Force as the winner of the ATF in April 1991. Following the selection, the first prototype was retired to a museum, while the second continued flying until an accident relegated it to the role of an antenna test vehicle.

Development[edit]

Main article: Advanced Tactical Fighter

Concept definition[edit]

In 1981, the U.S. Air Force developed a requirement for an Advanced Tactical Fighter (ATF) that would eventually become a new air superiority fighter to replace the F-15 Eagle and F-16 Fighting Falcon. This was made more crucial by the emerging worldwide threats, including development and proliferation of Soviet MiG-29 "Fulcrum" and Su-27 "Flanker"-class fighter aircraft, A-50 "Mainstay" airborne warning and control system (AWACS), and more advanced surface-to-air missile systems. It would take advantage of the new technologies in fighter design on the horizon including composite materials, lightweight alloys, advanced flight-control systems, more powerful propulsion systems and stealth technology.[1]

Diagram of several designs submitted for ATF RFI. Note Lockheed's large design with inspiration from the SR-71 family.

The ATF request for information (RFI) was sent out in May 1981 to canvas to the aerospace industry on what the future fighter aircraft could potentially look like.[2] Initially code-named "Senior Sky", the ATF at this time was still in the midst of requirements definition, and consequently there was substantial variety in the responses from the industry. Lockheed's initial concept was a particularly large aircraft called CL-2016, nicknamed "battlecruiser" for its size, that resembled the SR-71/YF-12 and would have had similarly high operating speed and altitude.[3][4]

In 1983, the ATF Concept Development Team, which had become the System Program Office (SPO) at Wright-Patterson Air Force Base, narrowed the requirements to an air superiority fighter with outstanding kinematic performance in speed and maneuverability to replace the F-15, as well as increasingly emphasizing stealth due to the Air Force's experience from "black world" projects such as the Have Blue/F-117 and the Advanced Technology Bomber (ATB) program (which would result in the B-2).[5] With stealth becoming a core requirement, Lockheed design team, under its Skunk Works division, migrated away from its initial SR-71-like "battlecruiser" concept and instead began drafting a design that resembled the F-117. However, the faceted shape, resulting from Lockheed using the same "Echo" computer program that it had used to design the F-117, gave the design very poor aerodynamic performance. Lockheed would perform poorly throughout the concept exploration phase, placing amongst the bottom of the competing contractors.[3]

Demonstration and validation[edit]

By November 1984, the SPO had further narrowed the requirements and released the Statement of Operational Need (SON), with requirements calling for a 50,000 lb (22,700 kg) takeoff weight fighter that places strong emphasis on stealth and supersonic cruise without afterburners, or supercruise.[6] In September 1985, the Air Force sent out technical request for proposals (RFP) to a number of aircraft manufacturing teams for demonstration and validation (Dem/Val). In addition to the ATF's demanding technical requirements, Dem/Val also placed a great deal of importance on systems engineering, technology development plans, and risk mitigation. The top four proposals, later reduced to two, would proceed with Dem/Val. At the time, the Air Force anticipated procuring 750 ATFs at a unit flyaway cost of $35 million in FY 1985 dollars.[3][6][7]

Having performed poorly during ATF concept exploration while also losing to Northrop's curved surface design for the ATB, Lockheed abandoned faceting in 1984 and began incorporating curved shapes and surfaces. Although its analytical tools were initially yet to be able to calculate for such shapes, good empirical results from radar range testing gave Lockheed confidence in designing a stealthy aircraft with smooth, curved surfaces, thus greatly improving its aerodynamic characteristics. As Lockheed was gradually able to analyze curved surfaces, the final design submitted for Dem/Val, designated Configuration 090P, would have an arrowhead-like forward fuselage shape, swept trapezoidal wings, four empennage surfaces with thrust vectoring, s-shaped inlet ducts obscuring the engine face, and an internal rotary missile launcher.[3] In addition to the change in aircraft design, Lockheed also shifted much more engineering talent and manpower to its ATF effort, appointing Sherman Mullin as the program manager, and had its draft proposals aggressively red-teamed by a group led by retired Air Force general Alton D. Slay.[8] The resulting proposal improvements were substantial, particularly the systems engineering volume.[9]

The ATF RFP would see some alterations after its first release; stealth requirements were drastically increased in December 1985 after discussions with Lockheed and Northrop regarding their experiences with the Have Blue/F-117 and ATB/B-2, and the requirement for flying technology demonstrator prototypes was added in May 1986 due to recommendations from the Packard Commission.[10][11] The seven bids were submitted in July 1986. Owing to the immense investments companies were expected to make on their own, teaming was encouraged. Following proposal submissions, Lockheed, Boeing, and General Dynamics formed a team to develop whichever of their proposed designs was selected, if any. Northrop and McDonnell Douglas formed a team with a similar agreement.[12] At the same time, the U.S. Navy, under the Navy Advanced Tactical Fighter (NATF) program, under Congressional pressure announced that it would use a derivative of the ATF winner to replace its F-14 Tomcat. The NATF program called for the procurement of 546 aircraft along with the USAF's planned procurement of 750 aircraft.[13]

On 31 October 1986, Lockheed and Northrop were selected as the top and second ranking respectively; Sherman Mullin would credit Lockheed's proposal's system engineering volume for the top rank. The two teams, Lockheed/Boeing/General Dynamics and Northrop/McDonnell Douglas, would undertake a 50-month demonstration phase, culminating in the flight test of the two teams' prototypes, the YF-22 and the YF-23; Pratt & Whitney and General Electric had earlier been awarded contracts to develop the propulsion systems with the designations YF119 and YF120.[14][15][16] Because the requirement for flying prototypes was a late addition due to political pressure, the prototypes were to be "best-effort" vehicles not meant to perform a competitive flyoff or represent a production aircraft, but to demonstrate the viability of its concept and to mitigate risk.[17]

Design evolution[edit]

The division of work amongst the team would be divided roughly equally. Because Lockheed's submission was selected as one of the winners, the company assumed leadership of the program partners. It would be responsible for the forward cockpit and fuselage, as well as final assembly at Palmdale, California. Meanwhile, the wings and aft fuselage would be built by Boeing, with the center fuselage, weapons bays, tail and landing gear built by General Dynamics.[18] The partners brought their design experience and proposals with them. Boeing's design was large and long with a chin-mounted inlet, trapezoid wings, v-tail empennage surfaces (deemed sufficient due to the high operating speed), and palletized internal weapons. General Dynamics' design was smaller with fuselage and delta wings optimized for maneuver and supercruise, shoulder-mounted inlets, a large single vertical tail as the only empennage surface (which compromised all-aspect stealth), and weapon bays in the center fuselage. However, much of the scrutiny fell on Lockheed's Configuration 090P, which was problematic due to being highly immature as a result of Lockheed's greater focus on systems engineering rather than a point design. Nevertheless, 090P was the initial starting point that the team worked to refine.[19]

Throughout Dem/Val, the SPO held System Requirement Reviews (SRR) with contractor teams and used the results of their performance and cost trade studies to adjust ATF requirements and delete ones that were significant weight and cost drivers while having marginal value.[20] The requirement for eight missiles (represented by the baseline AIM-120A) was reduced to six. The team continually refined the design, making extensive use of analytical and empirical methods such as wind tunnel testing (18,000 hours by the end of Dem/Val), pole testing at radar ranges, and computational fluid dynamics (CFD) and computer-aided design (CAD) software. By early 1987, the design had evolved into Configuration 095, which replaced the rotary launcher with a flatter weapons bay to reduce volume and drag, and the shapes of the forward fuselage and leading-edge root extensions were recontoured to prevent uncontrollable pitch-up moments. Around this time, the design had split into two families, the 500 prefix that represent the design to be carried forward for full-scale development and the 1000 prefix representing the design to be built for the prototypes; Configuration 095 thus became 595 and 1095 respectively.[19]

By mid-1987, detailed weight analysis of Configuration 595/1195 revealed that it was overweight by 9,000 lb (4,100 kg) even if it could still nominally meet maneuver parameters.[19] With weight likely to increase and compromises not forthcoming, the team chose to completely start over with a new design in July 1987, with Lockheed bringing a new director of design engineering, Dick Cantrell.[21] Various different layouts were explored and after an intensive three-month effort, the team chose a new design, Configuration 614/1114, as the starting point with shoulder-mounted inlets and diamond-like delta wings similar to General Dynamics' design, and four empennage surfaces; notably, the diamond-like delta's longer root chord had performance approaching the original swept trapezoidal profile while offering much lower weight. The design evolved through the rest of 1987 and into May 1988, when Configuration 632/1132 was frozen as the YF-22. Changes include the shapes of the empennage surfaces to diamond-like and recontouring of the fore and aft fuselage to reduce wave drag following the deletion of the thrust reverser requirement after another SRR;[22] the prototype thrust vectoring nozzles still retained thrust reversing hardware provisions however, resulting in the prototype aft fuselage being bulkier than needed. Ultimately, the 50,000-lb takeoff weight still proved to be unachievable and was adjusted to 60,000 lb (27,200 kg), resulting in engine thrust increasing from 30,000 lbf (133 kN) to 35,000 lbf (156 kN) class.[23]

In addition to the air vehicle and propulsion design, the ATF required a leap in sensor and avionics capability. Avionics development was marked by extensive testing and prototyping and supported by ground and flying laboratories, with Boeing being responsible for avionics integration. As the YF-22 was a technology demonstrator for the airframe and engines, it would not have any of the mission systems avionics. Boeing would provide a Boeing 757 modified with the mission systems as a flying laboratory for avionics development; this aircraft would be named the Flying Test Bed.[24][25] The SPO would similarly adjust avionics requirements as a result of SRRs with contractors. Side-looking radar and infrared search and track (IRST) were deleted from the baseline requirement and became provisions for potential future addition, and a $9 million cap for avionics per aircraft in FY 1985 dollars was placed by the SPO in 1989 on the baseline proposal for full-scale development.[19]

Naval variant[edit]

Due to Congressional pressure, the U.S. Navy joined the ATF program and announced that it would procure a variant/derivative of the winning design as the NATF to replace the F-14. Because the NATF would have lower landing speed than the ATF while still attaining Mach 2-class speeds, the Lockheed team's NATF design would incorporate variable-sweep wings, although the resulting aircraft would have been heavier, more complex, and more expensive than the ATF counterpart. Lockheed would submit its NATF design along with its ATF full-scale development proposal in December 1990.[26]

Design[edit]

Two jet aircraft with outward-canted vertical stabilizers parked on an angle on ramp.
Both YF-22 aircraft on a taxiway at Edwards AFB

The YF-22 (Configuration 1132) is a prototype air vehicle intended to demonstrate the viability of the ATF air vehicle and propulsion design, which was ultimately meant to meet USAF requirements for survivability, supercruise, stealth, and ease of maintenance.[27] The airframe has large diamond-like delta wings, shoulder-mounted inlets, three internal weapons bays, and four empennage surfaces: canted vertical tails with rudders and all moving horizontal stabilizers. Compared with its Northrop/McDonnell Douglas counterpart, the YF-22 has a more conventional design – its wings have larger control surfaces, such as full-span trailing edge,[28] and, whereas the YF-23 had two tail surfaces, the YF-22 had four, which made it more maneuverable than its counterpart.[29] Two examples of each prototype air vehicle (PAV) were built for the Demonstration-Validation phase: one with General Electric YF120 engines, the other with Pratt & Whitney YF119 engines.[1][30]

Formally designated as the YF-22A, the first aircraft (PAV-1, serial number 87-0700, N22YF), with the GE YF120,[31][32] was rolled out on 29 August 1990[18][33] and first flew on 29 September 1990, taking off from Palmdale piloted by David L. Ferguson.[18][34] During the 18-minute flight, PAV-1 reached a maximum speed of 250 knots (460 km/h; 290 mph) and a height of 12,500 feet (3,800 m), before landing at Edwards AFB.[32] Following the flight, Ferguson said that the remainder of the YF-22 test program would be concentrated on "the manoeuvrability of the aeroplane, both supersonic and subsonic".[32] The second YF-22A (PAV-2, s/n 87-0701, N22YX) with the P&W YF119 made its maiden flight on 30 October at the hands of Tom Morgenfeld.[18]

The YF-22 was given the unofficial name "Lightning II" after Lockheed's World War II-era fighter, the P-38 Lightning, which persisted until the mid-1990s when the USAF officially named the aircraft "Raptor".[35] The F-35 later received the "Lightning II" name in 2006.[36]

Operational history[edit]

Evaluation[edit]

Two different jet aircraft in flight towards right of screen.
The YF-22 (foreground) and YF-23 (background)

During the flight test program, unlike the YF-23, weapon firings and high (60°) angle of attack (AoA, or high-alpha) flights were carried out on the YF-22.[37] Though not a requirement, the aircraft fired AIM-9 Sidewinder and AIM-120 AMRAAM missiles from internal weapon bays.[37][38] Flight testing also demonstrated that the YF-22 with its thrust vectoring nozzles achieved pitch rates more than double that of the F-16 at low-speed maneuvering. The first prototype, PAV-1 with the General Electric engines, achieved Mach 1.58 in supercruise, while PAV-2 with the Pratt & Whitney engines reached a maximum supercruise speed of Mach 1.43; maximum speed was in excess of Mach 2.0.[39][40] Flight testing continued until 28 December 1990, by which time 74 flights were completed and 91.6 airborne hours were accumulated.[16] Following flight testing, the contractor teams submitted proposals for ATF production, with the Lockheed team design evolving to Configuration 638.[41]

On 23 April 1991, the Lockheed team was announced by Secretary of the Air Force Donald Rice as the winner of the ATF competition.[42] While both designs met or exceeded all performance requirements, the YF-23 was stealthier and faster, but the YF-22 was more agile.[43] It was speculated in the aviation press that the YF-22 was also seen as more adaptable to the Navy's Navalized Advanced Tactical Fighter (NATF), but the US Navy abandoned NATF by 1992.[37][44] Instead of being retired, as with the case of PAV-1, PAV-2 subsequently flew sorties following the competition – it amassed another 61.6 flying hours during 39 flights.[37] On 25 April 1992, the aircraft sustained serious damage during a landing attempt as a result of pilot-induced oscillations. It was repaired but never flew again, and instead served as a static test vehicle thereafter.[45][46] In 1991, it was anticipated that 650 production F-22s would be procured.[47]

F-22 production[edit]

Main article: Lockheed Martin F-22 Raptor
F/A-22 Raptor test and training flight operations resumed here March 22 after a brief delay following a nose-gear-retraction incident in 2003.

As the Lockheed team won the ATF competition, it was awarded the full-scale development, or engineering, manufacturing and development (EMD) contract, which would ultimately allow it to proceed with production of operational aircraft. The EMD/production design would evolve into Configuration 645.[19] The EMD initially called for seven single-seat F-22A and two twin-seat F-22Bs, although the latter was eventually canceled to save on development costs and the orders were converted to single-seaters. On 9 April 1997, the first of these, Spirit of America, was rolled out. During the ceremony, the F-22 was officially named "Raptor". Due to limited funding, the first flight, which had previously been scheduled for mid-1996, occurred on 7 September 1997.[45] Flight testing for the F-22 continued until 2005, and on 15 December 2005 the USAF announced that the Raptor had reached its initial operational capability (IOC).[48]

In many respects, the YF-22s were different from EMD/production F-22s. Contrary to the F-117 Nighthawk, which was initially difficult to control because of small vertical stabilizers, Lockheed over-specified the fin area on its YF-22. Therefore, the company reduced the size of those on F-22s by 20–30 percent. Lockheed recontoured the shape of the wing and stabilator trailing edges to improve aerodynamics, strength, and stealth characteristics; the wing and stabilitor sweep was reduced by 6° from 48°. The shapes of the radome and fuselage were changed to improve radar performance and aerodynamics. Finally, to improve pilot visibility, the canopy was moved forward 7 inches (178 mm), and the engine intakes were moved rearward 14 inches (356 mm).[49][50][51]

Accidents[edit]

In April 1992, the second YF-22 crashed while landing at Edwards AFB. The test pilot, Tom Morgenfeld, escaped without injury. The cause of the crash was found to be a flight control software error that failed to prevent a pilot-induced oscillation.[52]

Surviving aircraft[edit]

Starboard view of jet aircraft in museum among suspended aircraft and an American flag.
YF-22 on display at the USAF Museum

Specifications (YF-22A)[edit]

Lockheed YF-22 3-view diagram
Lockheed YF-22 3-view diagram

Data from Baker and Aronstein (note, some specifications are estimated).[55][56]

General characteristics

  • Crew: 1 (pilot)
  • Length: 64 ft 6 in (19.65 m)
  • Wingspan: 43 ft 0 in (13.1 m)
  • Height: 17 ft 9 in (5.39 m)
  • Wing area: 830 sq ft (77.1 m2)
  • Empty weight: 33,000 lb (14,970 kg)
  • Gross weight: 62,000 lb (28,120 kg)
  • Powerplant: 2 × Pratt & Whitney YF119-PW-100 or General Electric YF120-GE-100 afterburning turbofans, 23,500 lbf (105 kN) thrust each (YF120) dry, 30,000 or 35,000 lbf (130 or 160 kN) with afterburner

Performance

  • Maximum speed: Mach 2.2 (1,450 mph, 2,335 km/h) at altitude
  • Supercruise: Mach 1.58 (1,040 mph, 1,680 km/h) at altitude (military power only)
  • Combat range: 800 mi (1,290 km, 696 nmi)
  • Service ceiling: 65,000 ft (19,800 m)
  • Maximum g-load: +7.9 g

See also[edit]

Related development

Aircraft of comparable role, configuration, and era

  • Northrop YF-23 – Prototype fighter aircraft for the US Air Force Advanced Tactical Fighter program

Related lists

References[edit]

Notes[edit]

  1. ^ a b "Fact sheet: Lockheed-Boeing-General Dynamics YF-22". U.S. Air Force. 11 February 2009. Archived from the original on 19 January 2012. Retrieved 18 June 2011.
  2. ^ Aronstein and Hirschberg 1998, p. 30
  3. ^ a b c d Hehs 1998, Part 1
  4. ^ Aronstein and Hirschberg 1998, pp. 39-42
  5. ^ Aronstein and Hirschberg 1998, pp. 45-58
  6. ^ a b Aronstein and Hirschberg 1998, pp. 70-78
  7. ^ Aronstein and Hirschberg 1998, pp.87-88
  8. ^ Mullin 2012, p. 13
  9. ^ Mullin 2012, pp. 18-19
  10. ^ Aronstein and Hirschberg 1998, pp. 82-85
  11. ^ Mullin 2012, pp. 19-21
  12. ^ Goodall 1992, p. 94.
  13. ^ Williams 2002, p. 5.
  14. ^ Miller 2005, pp. 19–20.
  15. ^ Jenkins and Landis 2008, pp. 233–234.
  16. ^ a b Williams 2002, pp. 5–6.
  17. ^ Aronstein and Hirschberg 1998, pp.87-88
  18. ^ a b c d Jenkins and Landis 2008, p. 235.
  19. ^ a b c d e Hehs 1998, Part 2
  20. ^ Mullin 2012, pp. 31-32
  21. ^ Mullin 2012, p. 29
  22. ^ Mullin 2012, p. 30
  23. ^ Aronstein and Hirschberg 1998, p. 119
  24. ^ Aronstein and Hirschberg 1998, pp. 104–121
  25. ^ Kohn, Lt. Col. Allen E. and Lt. Col. Steven M. Rainey. "F-22 Flight Test Program Update." 9 April 1999. Archived from original.
  26. ^ Mullin 2012, pp. 38-39
  27. ^ Flight International 1986, p. 10.
  28. ^ Flight International 1990, p. 4.
  29. ^ Flight International 1990, p. 46.
  30. ^ "YF-23 fact sheet". National Museum of the U.S. Air Force. Archived from the original on 16 July 2011. Retrieved 24 June 2011.
  31. ^ Williams 2002, p. 5.
  32. ^ a b c Flight International 1990, p. 6.
  33. ^ Bailey 1990, p. 34.
  34. ^ Goodall 1992, p. 99.
  35. ^ "Military Aircraft Names". Aerospaceweb.org. Archived from the original on 12 October 2009. Retrieved 26 September 2010.
  36. ^ ""Lockheed Martin Joint Strike Fighter Officially Named 'Lightning II'" (Press release). Official Joint Strike Fighter program office. 7 July 2006. Archived from the original on 15 July 2006. Retrieved 23 June 2011.
  37. ^ a b c d Williams 2002, p. 6.
  38. ^ "YF-23 would undergo subtle changes if it wins competition". Defense Daily, 14 January 1991
  39. ^ Jenkins and Landis 2008, p. 236.
  40. ^ Goodall 1992, pp. 102–103.
  41. ^ Miller 2005, pp. 38–39.
  42. ^ Jenkins and Landis 2008, p. 234.
  43. ^ Goodall 1992, p. 110.
  44. ^ Miller 2005, p. 76.
  45. ^ a b William 2002, pp. 6–7.
  46. ^ Warwick 1992, p. 12.
  47. ^ Pearlstein, Steven; Gellman, Barton (24 April 1991). "Lockheed Wins Huge Jet Contract; Air Force Plans to Buy 650 Stealth Planes At $100 million Each". The Washington Post.
  48. ^ "F-22A Raptor goes operational". U.S. Air Force. 15 December 2005. Archived from the original on 23 July 2012. Retrieved 24 June 2011.
  49. ^ William 2002, p. 5.
  50. ^ Pace 1999, pp. 12–13.
  51. ^ "YF-22/F-22A comparison diagram". GlobalSecurity.org. Archived from the original on 23 June 2011. Retrieved 24 June 2011.
  52. ^ Harris, Jeffery and Black, G.T. "F-22 control law development and flying qualities." AIAA Paper 96-3379 (A96-35101), p. 156.
  53. ^ "YF-22 Raptor/87-700". aerialvisuals.ca. Retrieved 18 June 2021.
  54. ^ "YF-22 Raptor/87-701". aerialvisuals.ca. Retrieved 13 May 2022.
  55. ^ Baker 1995, pp. 28–29, 32.
  56. ^ Aronstein 1998, pp. 131, 154.

Bibliography[edit]

Additional sources[edit]

  • Aronstein, David C.; Hirschberg, Michael J. (1998). Advanced Tactical Fighter to F-22 Raptor: Origins of the 21st Century Air Dominance Fighter. Arlington, Virginia: American Institute of Aeronautics & Astronomy. ISBN 978-1-56347-282-4.
  • Crosby, Francis (2002). Fighter Aircraft. London: Lorenz Books. ISBN 0-7548-0990-0.
  • Miller, Jay (1995). Lockheed Martin's Skunk Works: The Official History... Leicester, UK: Midland Publishing. ISBN 1-85780-037-0.
  • Pace, Steve (1991). X-Fighters: USAF Experimental and Prototype Fighters, XP-59 to YF-23. Osceola, Wisconsin: Motorbooks International. ISBN 0-87938-540-5.
  • Sweetman, Bill (July 2000). "Fighter EW: The Next Generation". Journal of Electronic Defense. 23 (7). ISSN 0192-429X.
  • ------- (1998). F-22 Raptor. St. Paul, Minnesota, USA: Motorbooks International Publishing. ISBN 0-7603-0484-X.
  • Winchester, Jim, ed. (2005). "Northrop/McDonnell Douglas YF-23". Concept Aircraft: Prototypes, X-Planes, And Experimental Aircraft. The Aviation Factfile. Rochester, Kent, UK: Grange Books. ISBN 1-84013-809-2.

External links[edit]

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