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YF-23
YF-23 flying over Edwards Air Force Base.
General information
Type	Stealth fighter technology demonstrator
National origin	United States
Manufacturer	Northrop/McDonnell Douglas
Status	Canceled
Primary user	United States Air Force
Number built	2
History
Manufactured	1989–1990
First flight	27 August 1990

The Northrop/McDonnell Douglas YF-23 is an American single-seat, twin-engine, stealth fighter technology demonstrator prototype designed for the United States Air Force (USAF). The design team, with Northrop as the prime contractor, was a finalist in the USAF's Advanced Tactical Fighter (ATF) demonstration/validation competition, battling the YF-22 team for full-scale development and production. Two YF-23 prototypes were built.

In the 1980s, the USAF began looking for a replacement for its F-15 fighter aircraft to more effectively counter emerging threats such as the Soviet Union's advanced Sukhoi Su-27 and Mikoyan MiG-29. Several companies submitted design proposals; the USAF selected proposals from Northrop and Lockheed for demonstration/validation. Northrop teamed up with McDonnell Douglas to develop the YF-23, while Lockheed, Boeing, and General Dynamics developed the YF-22. The YF-23 was stealthier and faster, but less agile than its competitor. After a four-year development and evaluation process, the YF-22 team was announced as the winner in 1991 and developed the F-22 Raptor, which first flew in 1997 and entered service in 2005. The U.S. Navy considered using a naval version of the ATF as a replacement for the F-14, but these plans were later canceled due to costs.

After flight testing, both YF-23s were placed in storage while various agencies considered plans to use them for further research, although none proceeded. In 2004, Northrop Grumman used the second YF-23 as a display model for its proposed regional bomber aircraft, but this project was dropped because longer range bombers were required. The two YF-23 prototypes are currently exhibits at the National Museum of the United States Air Force and the Western Museum of Flight respectively.

Development

Concept definition

American reconnaissance satellites first spotted the advanced Soviet Su-27 and MiG-29 fighter prototypes between 1977 and 1979, which caused concern in the U.S. Both Soviet models were expected to reduce the combat and maneuverability advantages of contemporary U.S. fighter aircraft, including the newly introduced F-15 Eagle and F-16 Fighting Falcon. Additionally, U.S. tactical airpower would be further threatened by new Soviet systems such as the A-50 airborne warning and control system (AWACS) revealed in 1978 and more advanced surface-to-air missile systems. In 1981, the USAF began developing requirements and discussing with the aerospace industry on concepts for an Advanced Tactical Fighter (ATF) with both air-to-air and air-to-ground missions in consideration. The ATF was to take advantage of emerging technologies, including composite materials, lightweight alloys, advanced flight-control systems, more powerful propulsion systems, and stealth technology.

The USAF released the ATF request for information (RFI) in May 1981 to several aerospace companies on possible features for the new fighter. Initially code-named "Senior Sky", the ATF at this time was still in the midst of requirements definition, which meant that there was considerable variety in the industry responses. Northrop submitted three designs for the RFI, ranging from ultra low-cost, to highly agile, to low-observable missileer; all were on the small and light end of the response spectrum. In 1983, the ATF System Program Office (SPO) was formed at Wright-Patterson Air Force Base from the initial Concept Development Team. After discussions with aerospace companies and Tactical Air Command (TAC), the CDT/SPO made air-to-air combat with outstanding kinematic performance the primary role for the ATF, which would replace the F-15. Northrop's response was a Mach 2+ fighter design designated N-360 with delta wings, a single vertical tail, and twin engines with thrust vectoring nozzles and thrust reversers. Around this time, however, the SPO would begin to increasingly emphasize stealth for survivability and combat effectiveness due to very low radar cross section (RCS) results from the Air Force's "black world" innovations such as the Have Blue/F-117 ("Senior Trend"), Tacit Blue, and the Advanced Technology Bomber (ATB) program (which would result in the B-2, or "Senior Ice").

Northrop was able to quickly adapt to the ATF's increasing emphasis on stealth. Since October 1981, a small team of engineers under Rob Sandusky within its ATB/B-2 division had been working on stealth fighter designs. Sandusky would later be the Northrop ATF's Chief Engineer, while fellow B-2 stealth engineer Yu Ping Liu was recruited in 1985 as the chief scientist. Three design concepts were studied: the Agile Maneuverable Fighter (AMF) similar to N-360 with two canted vertical tails and the best aerodynamic performance of the three while having minimal stealth, Ultra Stealth Fighter (USF) that emphasized maximum stealth through edge alignment with only four RCS lobes and nicknamed "Christmas Tree" for its planform shape, and High Stealth Fighter (HSF) that balanced stealth and maneuverability with diamond wings, all-moving V-tail "ruddervators" (or butterfly tails), engine exhaust troughs, and aligned edges. HSF would take many design cues from the B-2 to reduce its susceptibility to radar and infrared detection, and Liu's understanding of both radar signatures and aerodynamics would lend itself to key design features, such as the shaping of the nose (nicknamed the "platypus" for the initial shape and pronounced chine edges) and canopy with their Gaussian surfaces. By 1985, HSF had evolved to be recognizably similar to the eventual YF-23 and emerged as the optimal balance of stealth and aerodynamic performance.

Demonstration and validation

By November 1984, concept exploration had allowed the SPO to narrow its requirements and release the Statement of Operational Need, which called for a 50,000 lb (22,700 kg) takeoff weight fighter with stealth and excellent kinematics, including prolonged supersonic flight without the use of afterburners, or supercruise. In September 1985, the USAF issued the request for proposal (RFP) for demonstration and validation (Dem/Val) to several aircraft manufacturers with the top four proposals, later cut down to two to reduce program costs, proceeding to the next phase; in addition to the ATF's demanding technical requirements, the RFP also emphasized systems engineering, technology development plans, and risk mitigation. The RFP would see some changes after initial release; following the SPO's discussions with Lockheed and Northrop regarding their experiences with the F-117 and B-2, all-aspect stealth requirements were drastically increased in late 1985. The requirement to include the evaluation of prototype air vehicles from the two finalists was added in May 1986 due to recommendations from the Packard Commission, a federal commission by President Ronald Reagan to study Department of Defense procurement practices. At this time, the USAF envisioned procuring 750 ATFs at a unit flyaway cost of $35 million in fiscal year (FY) 1985 dollars (~$84.2 million in 2023). Furthermore, the U.S. Navy under the Navy Advanced Tactical Fighter (NATF) program eventually announced that it would use a derivative of the ATF winner to replace its F-14 Tomcat and called for the procurement of 546 aircraft.

Northrop's early work on the HSF would pay off for the Dem/Val RFP. By January 1986, the HSF would evolve into Design Proposal 86E (DP86E) as a refined and well-understood concept through extensive computational fluid dynamics simulations, wind tunnel testing, and RCS pole testing and became Northrop's preference for its ATF submission. Furthermore, Northrop's ability to design and analyze stealthy curved surfaces, stemming back to its work on Tacit Blue and the ATB/B-2, gave their designers an early advantage, especially since Lockheed, the only other company with extensive stealth experience, had previously relied on faceting as on the F-117 and lost the ATB to Northrop as a result. That loss, along with the poor aerodynamic performance of their early faceted ATF concept, forced Lockheed to also develop designs and analysis methods with curved stealthy surfaces. Northrop's HSF design would be refined into DP110, which was its submission for the Dem/Val RFP.

In July 1986, proposals for Dem/Val were submitted by Lockheed, Boeing, General Dynamics, McDonnell Douglas, Northrop, Grumman and North American Rockwell; the latter two dropped out of the competition shortly thereafter. As contractors were expected to make significant investments for technology development, companies forming teams was encouraged by the SPO. Following proposal submissions, Northrop and McDonnell Douglas formed a team to develop whichever of their proposed designs was selected, if any. Lockheed, Boeing, and General Dynamics formed a team with a similar agreement.

Lockheed and Northrop, the two industry leaders in stealth aircraft, were selected as finalists on 31 October 1986 for Dem/Val as first and second place, although the approaches to their proposals were markedly different. Northrop's refined and well-understood design proposal was a significant advantage, especially in contrast to Lockheed's immature design, but the Lockheed proposal's focus on systems engineering rather than a point aircraft design actually pulled it ahead. Both teams were awarded $691 million in FY 1985 dollars (~$1.66 billion in 2023) and given 50 months to build and flight-test their prototypes. Pratt & Whitney and General Electric were contracted to develop the engines, designated YF119 and YF120 respectively, for the ATF engine competition. Because of the late addition of the prototyping requirement due to political pressure, the prototype air vehicles were to be "best-effort" machines not meant to perform a competitive flyoff or represent a production aircraft that meets every requirement, but to demonstrate the viability of its concept and mitigate risk.

Design refinement

As one of the winning companies for the Dem/Val proposals, Northrop was the program lead of the YF-23 team with McDonnell Douglas; the two had previously collaborated on the F/A-18 Hornet. In addition to the government contract awards, the team would eventually invest $650 million (~$1.45 billion in 2023) combined into their ATF effort; General Electric and Pratt & Whitney, the two engine companies, also invested $100 million (~$222 million in 2023) each. Airframe fabrication was divided roughly evenly, with Northrop building the aft fuselage and empennage in Hawthorne, California and performing final assembly at Edwards Air Force Base while McDonnell Douglas built the wings and forward fuselage in St. Louis, Missouri. Manufacturing was greatly assisted by the use of computer-aided design software. However, the YF-23 design would largely be a continual refinement from Northrop's DP110 with little influence from McDonnell Douglas's design, which had swept trapezoidal wings, four empennage surfaces, and chin-mounted split wedge inlets and did not perform well for stealth. The YF-23's design evolved into DP117K when it was frozen as the prototype configuration in January 1988, with changes including a sharper and more voluminous nose from the earlier "platypus" shape for better radar performance and a strengthened aft deck with lower drag shaping. Due to the complex surface curvature, the aircraft was built outside-in, with the large composite skin structures fabricated first before the internal members. To ensure precise and responsive handling, Northrop developed and tested the flight control laws using both a large-scale simulator as well as a modified C-131 named the Total In Flight Simulator (TIFS).

Throughout Dem/Val, the SPO conducted System Requirements Reviews (SRR) where it reviewed results of performance and cost trade studies with both teams and, if necessary, adjusted requirements and deleted ones that added substantial weight or cost while having marginal value. The ATF was initially required to land and stop within 2,000 feet (610 m), which meant the use of thrust reversers on their engines. In 1987, the USAF changed the runway length requirement to 3,000 feet (910 m) and by 1988 the requirement for thrust reversers was no longer needed. This allowed Northrop to have smaller engine nacelle housings with the space between them filled in to preserve area ruling in subsequent design refinements for the F-23 full system design, or Preferred System Concept (PSC). As DP117K had been frozen by then, the nacelles — nicknamed "bread loafs" for their flat upper surface — were not downsized on the prototypes. The number of internal missiles (with the AIM-120A as the reference baseline) was reduced from eight to six. Despite these adjustments, both teams struggled to achieve the 50,000-lb takeoff gross weight goal, and this was subsequently increased to 60,000 lb (27,200 kg) while engine thrust was increased from 30,000 lbf (133 kN) class to 35,000 lbf (156 kN) class.

Aside from advances in air vehicle and engine design, the ATF also required innovations in avionics and sensor systems with the goal of achieving sensor fusion to enhance situational awareness and reduce pilot workload. The YF-23 was meant as a demonstrator for the airframe and propulsion system design and thus did not mount any mission systems avionics of the PSC. Instead, Northrop and McDonnell Douglas tested these systems on ground and airborne laboratories with Northrop using a modified BAC One-Eleven as a flying avionics laboratory and McDonnell Douglas building the Avionics Ground Prototype (AGP) to evaluate software and hardware performance and reliability. Avionics requirements were also the subject of SPO SRRs with contractors and adjusted during Dem/Val. For example, the infrared search and track (IRST) sensor was dropped from a baseline requirement to provision for future addition in 1989.

Formally designated as the YF-23A, the first aircraft (serial number 87-0800), Prototype Air Vehicle 1 (PAV-1), was rolled out on 22 June 1990; PAV-1 took its 50-minute maiden flight on 27 August with chief test pilot Alfred "Paul" Metz at the controls. The second YF-23 (serial number 87-0801, PAV-2) made its first flight on 26 October, piloted by Jim Sandberg. The first YF-23 was painted charcoal gray and was nicknamed "Gray Ghost". The second prototype was painted in two shades of gray and nicknamed "Spider". PAV-1 briefly had a red hourglass painted on its ram air scoop to prevent injury to ground crew. The red hourglass resembled the marking on the underside of the black widow spider further reinforcing the unofficial nickname "Black Widow II" given to the YF-23 because of its 8-lobe radar cross section plot shape that resembled a spider. When Northrop management found out about the marking, they had it removed.

Naval variant

A proposed naval variant of the YF-23, sometimes known as the NATF-23 (the design was never formally designated), was considered as an F-14 Tomcat replacement. The original YF-23 design was first considered but would have had issues with flight deck space, handling, storage, landing, and catapult launching, thus necessitating a different design. By 1989, the design was narrowed down to two possible configurations, DP533 with four tails and DP527 with two tails and canards. DP527 was eventually determined to be the best solution. The NATF-23 design was submitted along with the F-23 proposal for full-scale development, or engineering and manufacturing development (EMD), in December 1990, although by late 1990 the Navy was already beginning to back out of the NATF program and fully abandoned it by FY 1992 due to escalating costs. A wind tunnel test model of DP527, tested for 14,000 hours, was donated (with canards removed) by Boeing St. Louis (formerly McDonnell Douglas) in 2001 to the Bellefontaine Neighbors Klein Park Veterans Memorial in St. Louis, Missouri.

Design

The YF-23A (internally designated DP117K) was a prototype air vehicle intended to demonstrate the viability of Northrop's ATF proposal designed to meet USAF requirements for survivability, supercruise, stealth, and ease of maintenance. Owing to its continual maturation from the HSF concept which it still greatly resembled, the YF-23's shaping was highly refined. It was an unconventional-looking aircraft, with diamond-shaped wings tapered symmetrically at 40° in both the leading edge back sweep and trailing edge forward sweep, a profile with substantial area-ruling to reduce aerodynamic drag at transonic and supersonic speeds, and all-moving V-tails, or "ruddervators". The cockpit was placed high, near the nose of the aircraft, for good visibility for the pilot, and the chiseled shape of the nose generated vortices to improve high angle of attack (AoA) characteristics. The aircraft featured a tricycle landing gear configuration with a nose landing gear leg and two main landing gear legs. The aerial refueling receptacle was centered on the spine of the forward fuselage. A single large weapons bay was placed on the underside of the fuselage between the nose and main landing gear. The cockpit had a center stick and side throttle.

It was powered by two turbofan engines, with each in a separate engine nacelle with S-ducts to shield engine axial compressors from radar waves, on either side of the aircraft's spine. The fixed-geometry inlets were trapezoidal in frontal profile, with special porous suction panels in front to absorb the turbulent boundary layer and vent it over the wings. Of the two aircraft built, the first YF-23 (PAV-1) had Pratt & Whitney YF119 engines, while the second (PAV-2) was powered by General Electric YF120 engines. The aircraft had single-expansion ramp nozzles (SERN) and, unlike the YF-22, did not employ thrust vectoring. As on the B-2, the exhaust from the YF-23's engines flowed through troughs in the aft deck to shield the engines from infrared homing (IR) missile detection from below. The troughs were lined with tiles built by GM Allison that were “transpiration cooled” from engine bleed air to dissipate heat. The YF-23's propulsion and aerodynamics enabled it to cruise at over Mach 1.5 without afterburners.

The YF-23 was statically unstable — having relaxed stability — and flown through fly-by-wire with the flight control surfaces controlled by a central management computer system. Raising the wing flaps and ailerons on one side and lowering them on the other provided roll. The V-tail fins were angled 50 degrees from the vertical. Pitch was mainly provided by rotating these V-tail fins in opposite directions so their front edges moved together or apart. Yaw was primarily supplied by rotating the tail fins in the same direction. Test pilot Paul Metz stated that the YF-23 had superior high AoA performance compared to legacy aircraft, with trimmed AoA of up to 60°. Deflecting the wing flaps down and ailerons up on both sides simultaneously provided for aerodynamic braking. To keep prototyping costs low despite the novel design, some "commercial off-the-shelf" components were used, including an F-15 nose wheel, F/A-18 main landing gear parts, and the forward cockpit components of the F-15E Strike Eagle.

Production F-23

The proposed production F-23 configuration (DP231 for the F119 engine and DP232 for the F120 engine) for full-scale development, or Engineering and Manufacturing Development (EMD), would have differed from the YF-23 prototypes in several ways. Instead of a single weapons bay, the EMD design would instead have had two tandem bays in the lengthened forward fuselage, with the forward bay designed for short range AIM-9 missiles and the aft main bay for AIM-120 missiles and bombs. An M61 rotary cannon would be installed on the left side of the forward fuselage. The F-23's overall length was slightly increased to 70 ft 5 in (21.46 m) while wingspan remained about the same at 43 ft 7 in (13.28 m). Fuselage volume was expanded, the nose and radome were enlarged to accept sensors and mission systems, including the AESA radar, and the forward fuselage cross section was more squared off with the forebody chines less pronounced and raised to the same waterline height as the leading edge of the wing. The deletion of thrust reversers enabled the engine nacelles to have a smaller, more rounded cross-section and the trough between them filled in to preserve area-ruling. The inlet design changed from the trapezoidal profile with suction panels to a serrated semicircular with a compression bump and the boundary layer control vents were simplified. The fuselage and empennage trailing edge pattern would also have fewer serrations and the engine thrust lines were toed in at 1.5° off center. The EMD proposal had both single-seat F-23A and two-seat F-23B variants.

NATF-23

The naval NATF-23 variant (internally designated DP527), the schematics of which surfaced in the 2010s, was different in many ways due to the requirements of aircraft carrier operations as well as a greater emphasis on long range sensors, weapons, and loiter time for fleet air defense. The diamond wings were located as far back as possible, and the aircraft had ruddervators with more serrations to reduce length, folding wing capability for flight deck storage, reinforced landing gear, tailhook and slightly canted canards for increased maneuverability at low speeds to land on aircraft carriers, and thrust vectoring nozzles. The inlet design was also different, being a quarter circle with serrations and a bumped compression surface. The internal weapons bay was split into two compartments by a bulkhead along the centerline in the forward fuselage to strengthen the aircraft's keel and would have accommodated the Navy's planned AIM-152 advanced air-to-air missiles (AAAM) as well as potentially the AGM-88 HARM and AGM-84 Harpoon. The bay doors would carry AIM-9 missiles and an M61 rotary cannon would be installed in a fairing in the right wing. The NATF-23 had an increased 48 ft (14.63 m) wingspan, while length was reduced to 62 ft 8.5 in (19.11 m), the same as the F-14. Folded wingspan would be 23 ft 4 in (7.11 m). Like the Air Force version, the NATF-23 had both single-seat and two-seat variants.

Proposed revival

In 2004, Northrop Grumman proposed an F-23-based bomber called the FB-23 "Rapid Theater Attack" (RTA) to meet a USAF solicitation for an interim regional bomber, for which the Lockheed Martin FB-22 and Boeing B-1R were also competing. The FB-23 would have a two-seat cockpit and a similar planform shape as the F-23, but considerably larger in all dimensions to fulfill the bomber role with a combat radius of over 1,600 nautical miles (1,840 mi; 2,960 km). Northrop Grumman modified the YF-23 PAV-2 to serve as a display model for its proposed interim bomber. The possibility of an FB-23 interim bomber ended with the 2006 Quadrennial Defense Review, which favored a long-range strategic bomber with much greater range. The USAF has since moved on to the Next-Generation Bomber and Long Range Strike Bomber program.

The Japan Air Self-Defense Force (JASDF) launched a program to develop a domestic 5th/6th generation (F-3) fighter after the U.S. Congress refused in 1998 to export the F-22. After a great deal of study and the building of static models, the Mitsubishi X-2 Shinshin testbed aircraft flew as a technology demonstrator from 2016. By July 2018, Japan had gleaned sufficient information and decided it would need to involve international partners to complete this project. Northrop Grumman was one of the companies that responded and there was speculation that it could offer a modernized version of the F-23 to the JASDF, while Lockheed Martin offered an airframe derived from the F-22; Japan ultimately did not select these proposals due to costs and industrial work-share concerns.

Operational history

Evaluation

The first YF-23, with Pratt & Whitney engines, supercruised at Mach 1.43 on 18 September 1990, while the second, with General Electric engines, reached Mach 1.72 on 29 November 1990. By comparison, the YF-22 achieved Mach 1.58 in supercruise. The YF-23 was tested to a top speed of Mach 1.8 with afterburners and achieved a maximum angle-of-attack of 25°. The maximum speed is classified, though sources state a speed greater than Mach 2 at altitude in full afterburner. The aircraft's weapons bay was configured for weapons launch, and used for testing weapons bay acoustics, but no missiles were fired; Lockheed fired AIM-9 Sidewinder and AIM-120 AMRAAM missiles successfully from its YF-22 demonstration aircraft. PAV-1 performed a fast-paced combat demonstration with six flights over a 10-hour period on 30 November 1990. Flight testing continued into December. The two YF-23s flew 50 times for a total of 65.2 hours. The tests demonstrated Northrop's predicted performance values for the YF-23. Both designs met or exceeded all performance requirements; the YF-23 was stealthier and faster, but the YF-22 was more agile.

The two contractor teams submitted evaluation results and their PSC proposals for full-scale development in December 1990, and on 23 April 1991, Donald Rice, the Secretary of the Air Force announced that the YF-22 team was the winner. The Air Force also selected the Pratt & Whitney F119 engine to power the F-22 production version. The Lockheed and Pratt & Whitney designs were rated higher on technical aspects, considered lower risk (the YF-23 flew considerably fewer sorties and hours than its counterpart), and were considered to have more effective program management. It has been speculated in the aviation press that the Lockheed design was also seen as more adaptable as the basis for the Navy's NATF, but by FY 1992 the U.S. Navy had abandoned NATF.

Following the competition, both YF-23s were transferred to NASA's Dryden Flight Research Center at Edwards AFB, California, without their engines. NASA planned to use one of the aircraft to study techniques for the calibration of predicted loads to measured flight results, but this did not happen. Both YF-23 airframes remained in storage until mid-1996 when they were transferred to museums, with PAV-2 briefly serving as a display model for the proposed FB-23 regional bomber in 2004.

Aircraft on display

• YF-23A PAV-1, Air Force serial number 87-0800, "Gray Ghost", registration number N231YF, is on display in the Research and Development hangar of the National Museum of the United States Air Force near Dayton, Ohio.

• YF-23A PAV-2, AF ser. no. 87-0801, "Spider", registration number N232YF, was on exhibit at the Western Museum of Flight until 2004, when it was reclaimed by Northrop Grumman and used as a display model for an F-23-based regional bomber. PAV-2 was returned to the Western Museum of Flight in 2010 and is on display after the museum's relocation at Zamperini Field in Torrance, California.

Specifications (YF-23A)

Data from Pace, Sweetman, Winchester, Metz & Sandberg, Aronstein & Hirschberg (note, some specifications are estimated)

General characteristics

• Crew: 1
• Length: 67 ft 5 in (20.55 m)
• Wingspan: 43 ft 7 in (13.28 m)
• Height: 13 ft 11 in (4.24 m)
• Wing area: 950 sq ft (88 m)
• Empty weight: 29,000 lb (13,154 kg) contractor weight (without engines)
• Gross weight: 64,000 lb (29,030 kg) takeoff, 51,320 lb (23,280 kg) combat weight
• Powerplant: 2 × Pratt & Whitney YF119-PW-100N or General Electric YF120-GE-100N afterburning turbofan engines, 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 high altitude
• Supercruise: Mach 1.72 (1,135 mph, 1,827 km/h) at altitude
• Range: 2,424 nmi (2,789 mi, 4,489 km)
• Combat range: 700–800 nmi (810–920 mi, 1,300–1,500 km)
• Service ceiling: 65,000 ft (19,800 m)
• Wing loading: 67.4 lb/sq ft (329 kg/m) (54 lb/sq ft at combat weight)
• Thrust/weight: 1.09 (1.36 at combat weight)
• Maximum g-load: +7.1 g (highest tested)

Armament
None as tested but provisions made for:

• 1 × 20 mm (0.79 in) M61 Vulcan cannon
• 4 × AIM-120 AMRAAM or AIM-7 Sparrow medium-range air-to-air missiles
• 2 × AIM-9 Sidewinder short-range air-to-air missiles

See also

• Advanced Tactical Fighter

Aircraft of comparable role, configuration, and era

• Lockheed YF-22

Related lists

• List of military aircraft of the United States
• List of fighter aircraft

References

Notes

1. ^ Northrop acquired Grumman in 1994 to become Northrop Grumman.
2. The contractor teams were to give the SPO "sealed envelope" flight performance predictions against which their prototypes would be evaluated against, rather than against each other.
3. Metz would later be the chief test pilot for the EMD/production F-22.
4. 70 ft 5 in was the length of DP231, while DP232 was 5 in (12.7 cm) longer at 70 ft 10 in (21.59 m) due to the slightly larger F120 engines, with a small additional notch in the fuselage and empennage trailing edge pattern; wingspan and height remain the same.
5. The DP527 drawings show the same F119 engines as the Air Force version, but the final powerplant may have been a modified variant with greater bypass ratio for improved fuel efficiency at the expense of supercruise performance.
6. The "F/B-23" designation was also used.
7. ^ The YF-23 with the General Electric engines was officially stated to have been able to supercruise at over Mach 1.6, and estimates from General Electric engineers suggest that the top supercruise speed was as high as Mach 1.8.

Citations

1. Rich, Michael; Stanley, William (April 1984). "Improving U.S. Air Force Readiness and Sustainability" (PDF). RAND Corporation. p. 7. Archived from the original (PDF) on 2 July 2023.
2. Aronstein, Hirschberg & Piccirillo 1998, pp. 37–39.
3. Miller 2005, p. 11.
4. Metz 2017, pp. 10–12.
5. Sweetman 1991b, pp. 10–13.
6. Chong 2016, pp. 226–227.
7. Metz 2017, pp. 228–229.
8. Aronstein, Hirschberg & Piccirillo 1998, pp. 45–58.
9. ^ Metz 2017, p. 23-24.
10. ^ Metz 2017, pp. 28–29.
11. Chong 2016, pp. 233–234.
12. ^ Winchester 2005, pp. 198–199.
13. Aronstein, Hirschberg & Piccirillo 1998, pp. 70–78.
14. Aronstein, Hirschberg & Piccirillo 1999, pp. 82–85. sfn error: no target: CITEREFAronsteinHirschbergPiccirillo1999 (help)
15. Williams 2002, p. 5.
16. Aronstein, Hirschberg & Piccirillo 1998, pp. 87–88.
17. Metz 2017, p. 25.
18. ^ Hehs, Eric (1998). "Design Evolution of the F-22, Part 1". Code One. Lockheed Martin. Archived from the original on 18 May 2024.
19. ^ Metz 2017, p. 22.
20. Miller 2005, pp. 13–14, 19.
21. Goodall 1992, p. 94.
22. Jenkins & Landis 2008, pp. 233–234.
23. Aronstein, Hirschberg & Piccirillo 1998, pp. 88–89.
24. ^ Metz 2017, p. 31.
25. Aronstein, Hirschberg & Piccirillo 1998, p. 164.
26. Metz 2017, p. 20.
27. Metz 2017, pp. 26–27.
28. ^ Chong 2016, pp. 237–238.
29. Metz 2017, pp. 40–41.
30. ^ Miller 2005, p. 23.
31. Sweetman 1991a, pp. 23, 43.
32. ^ Aronstein, Hirschberg & Piccirillo 1998, pp. 106–108.
33. Aronstein, Hirschberg & Piccirillo 1998, pp. 113–114.
34. "YF-23 roll out marks ATF debut". Flight International. 27 June - 3 July 1990. Reed Business Information. p. 5. Archived from the original on 24 July 2012. Retrieved 13 June 2024.
35. Goodall 1992, p. 99.
36. ^ Jenkins & Landis 2008, p. 237.
37. ^ YF-23 Walk Around and Design Features by Test Pilot Paul Metz. Western Museum of Flight, Torrance, California: Peninsula Seniors Productions. 6 September 2015. Event occurs at 7:20. Archived from the original on 21 November 2023. Retrieved 15 June 2024 – via YouTube.
38. Goodall 1992, p. 120.
39. ^ Chong 2016, pp. 238–239.
40. ^ Metz 2017, pp. 74–79.
41. "Memorial Day's service will include unveiling of plane". St. Louis Post-Dispatch (Main ed.). 24 May 2001. p. 100 – via Newspapers.com.
42. "ATF procurement launches new era". Flight International. Reed Business Information. 15 November 1986. p. 10. Archived from the original on 24 July 2012.
43. Metz 2017, p. 84.
44. Goodall 1992, pp. 108–115, 124.
45. Metz 2017, pp. 92–93.
46. ^ Sweetman 1991a, pp. 42–44, 55.
47. ^ "Northrop-McDonnell Douglas YF-23A Black Widow II". National Museum of the U.S. Air Force. Archived from the original on 30 May 2023.
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Bibliography

• Aronstein, David C.; Hirschberg, Michael J; Piccirillo, Albert C. (1998). Advanced Tactical Fighter to F-22 Raptor: Origins of the 21st Century Air Dominance Fighter. Arlington, Virginia: AIAA (American Institute of Aeronautics & Astronautics). ISBN 978-1-56347-282-4.
• Chong, Tony (2016). Flying Wings & Radical Things, Northrop's Secret Aerospace Projects & Concepts 1939-1994. Forest Lake, Minnesota: Specialty Press. ISBN 978-1-58007-229-8.
• Goodall, James C (1992). "The Lockheed YF-22 and Northrop YF-23 Advanced Tactical Fighters". America's Stealth Fighters and Bombers, B-2, F-117, YF-22, and YF-23. St. Paul, Minnesota: Motorbooks International Publishing. ISBN 9780879386092.
• Jenkins, Dennis R.; Landis, Tony R. (2008). Experimental & Prototype U.S. Air Force Jet Fighters. North Branch, Minnesota: Specialty Press. ISBN 978-1-58007-111-6.
• Metz, Alfred "Paul" (2017). Air Force Legends Number 220. Northrop YF-23 ATF. Forest Lake, Minnesota: Specialty Press. ISBN 9780989258371.
• Miller, Jay (2005). Lockheed Martin F/A-22 Raptor, Stealth Fighter. Hinckley, UK: Midland Publishing. ISBN 9781857801583.
• Pace, Steve (1999). F-22 Raptor. New York: McGraw-Hill. ISBN 9780071342711.
• Sweetman, Bill (1991a). YF-22 and YF-23 Advanced Tactical Fighters. St. Paul, Minnesota: Motorbooks International Publishing. ISBN 9780879385057.
• Sweetman, Bill (1991b). "The Fighter They Didn't Want". World Air Power Journal. 7 (Autumn/Winter 1991). London: Aerospace Publishing. ISBN 9781874023135. ISSN 0959-7050.
• Williams, Mel, ed. (2002). "Lockheed Martin F-22A Raptor". Superfighters: The Next Generation of Combat Aircraft. London: AIRtime Publishing. ISBN 9781880588536.
• Winchester, Jim, ed. (2005). "Northrop/McDonnell Douglas YF-23". Concept Aircraft. Rochester, Kent, UK: Grange Books. ISBN 9781840138092.

External links

• YF-23 photos on DFRC/NASA site
• "YF-23 Black Widow II, Declassified: Web of Secrecy" – documentary film (2000)
• Northrop/McDonnell Douglas YF-23 page on Joe Baugher's site
• YF-23 "Black Widow II", Northrop/McDonnell Douglas page on fighter-planes.com Archived 14 April 2008 at the Wayback Machine

• McDonnell Douglas aircraft
• Northrop aircraft
• Stealth aircraft
• 1990s United States fighter aircraft
• V-tail aircraft
• Twinjets
• Mid-wing aircraft
• Aircraft first flown in 1990
• Cancelled military aircraft projects of the United States