Northrop YF-23: Difference between revisions - Wikipedia

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{{short description|Prototype fighterdemonstrator aircraft for the USU.S. Air Force Advanced Tactical Fighter program}}

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{{redirect|YF-23|the Chinese rocket engine|YF-23 (rocket engine)}}

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{{Use dmy dates|date=May 2022}}

{|{{Infobox aircraft begin

| name = YF-23

| image = Ray Wagner Collection Image YF-23.jpg

| caption = YF-23 flying over [[Edwards Air Force Base]].

| alt = The first YF-23 prototype PAV-1, nicknamed "Black Widow", conducts test flights over Edwards Air Force Base

}}{{Infobox aircraft type

| type = [[Fighter aircraft|Stealth fighter]] technology demonstrator

| national originnational_origin = United States

| manufacturer = [[Northrop Corporation|Northrop]]/[[McDonnell Douglas]]

| designer =

| first flightfirst_flight = 27 August 1990

| introducedintroduction =

| status = Canceled

| primary userprimary_user = [[United States Air Force]]

| more usersmore_users =

| produced = 1989–1990

| number builtnumber_built = 2

| program cost =

| unit cost =

| developed fromdeveloped_from =

| variants with their own articles =

}}

|}

The '''Northrop/McDonnell Douglas YF-23''' is an American single-seat, [[twinjet|twin-engine]], supersonic [[Stealth aircraft|stealth]] [[fighter aircraft|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 [[Lockheed YF-22|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 [[McDonnell Douglas F-15 Eagle|F-15]] fighter aircraft to more effectively counter the [[Soviet Union]]'s advanced [[Sukhoi Su-27]] and [[Mikoyan MiG-29]]. Several companies submitted design proposals; the USAF selected proposals from [[Northrop Corporation|Northrop]] and [[Lockheed Corporation|Lockheed]]. 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 [[Lockheed Martin F-22 Raptor|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 to the [[Grumman F-14 Tomcat|F-14]], but these plans were later canceled due to costs.

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{{main|Advanced Tactical Fighter}}

===Concept definition===

American reconnaissance satellites first spotted the advanced Soviet [[Sukhoi Su-27|Su-27]] and [[Mikoyan MiG-29|MiG-29]] fighter prototypes in 1978, 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 [[McDonnell Douglas F-15 Eagle|F-15 Eagle]] and [[General Dynamics F-16 Fighting Falcon|F-16 Fighting Falcon]].<ref>{{Cite web |last=Rich |first=Michael |last2=Stanley |first2=William |date=April 1984 |title=Improving U.S. Air Force Readiness and Sustainability |url=https://www.rand.org/pubs/reports/2006/R3113.1.pdf |archive-url=https://web.archive.org/web/20230702172045/https://www.rand.org/content/dam/rand/pubs/reports/2006/R3113.1.pdf |archive-date=2 July 2023 |website=RAND Corporation |page=7}}</ref> Additionally, U.S. tactical airpower would be further threatened by new Soviet systems such as the [[Beriev A-50|A-50]] [[airborne early warning and control|airborne warning and control system]] (AWACS) and more advanced [[surface-to-air missile]] systems.{{Sfn|Aronstein|Hirschberg|Piccirillo|1998|pp=37-39}} In 1981, the USAF began developing requirements and discussing with the aerospace industry on concepts for an [[Advanced Tactical Fighter]] (ATF) towith replaceboth theair-to-air Fand air-15to-ground missions in consideration. The ATF was to take advantage of emerging technologies, including [[composite material]]s, lightweight [[alloy]]s, advanced flight-control systems, more powerful propulsion systems, and [[stealth technology]].{{Sfn|Miller|2005|p=11}}

[[File:F-22 RFI.jpg|thumb|upright=1.25|Diagram of several designs submitted for ATF RFI. Note the comparatively small sizes of Northrop's designs.|alt=19 designs for the concept jets with annotations of features and specifications]]

The USAF released the ATF [[request for information]] (RFI) was released 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.{{Sfn|Metz|2017|pp=10-12}} 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 superiority fighter|air-to-air combat]] with outstanding kinematic performance the primary role for the ATF, which would replace the F-15.{{Sfn|Sweetman|1991b|pp=10-13}} Northrop's response was a Mach 2+ fighter design designated N-360 with [[delta wing]]s, a single vertical tail, and twin engines with [[thrust vectoring]] nozzles and [[Thrust reversal|thrust reversers]].{{Sfn|Chong|2016|pp=226-227}}{{Sfn|Metz|2017|pp=228-229}} 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 project|black world]]" innovations such as the [[Lockheed Have Blue|''Have Blue'']]/[[Lockheed F-117 Nighthawk|F-117]] ("''Senior Trend''"), [[Northrop Tacit Blue|''Tacit Blue'']], and the Advanced Technology Bomber (ATB) program (which would result in the [[Northrop Grumman B-2 Spirit|B-2]], or "''Senior Ice''").{{Sfn|Aronstein|Hirschberg|Piccirillo|1998|pp=45-58}}

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.{{Sfn|Metz|2017|p=23-24}} 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 [[wing configuration|planform]] shape, and High Stealth Fighter (HSF) that balanced stealth and maneuverability with [[Diamond wing|diamond wings]], all-moving V-tail "[[ruddervators]]" (or butterfly tails), engine exhaust troughs, and aligned edges.{{Sfn|Metz|2017|pp=28-29}}{{Sfn|Chong|2016|pp=233-234}} 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 surface|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.{{Sfn|Metz|2017|p=23-24}}{{Sfn|Winchester|2005|pp=198-199}}

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===Demonstration and validation===

[[File:Northrop AMF USF HSF 300x245.jpg|thumb|From left to right, flat-plate models of Northrop's AMF, USF, and HSF design concepts. HSF was the preferred concept by 1985.|alt=Three metal models of the concept fighter jets]]

By November 1984, concept exploration had allowed the SPO to narrow its requirements and release the Statement of Operational Need, which called for a {{convert|50000|lb|kg|-2|abbr=on}} takeoff weight fighter with stealth and excellent kinematics, including prolonged supersonic flight without the use of [[afterburner]]s, 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.{{Sfn|Aronstein|Hirschberg|Piccirillo|1998|pp=70-78}} The RFP would see some changes after its initial release; following the SPO's discussions with Lockheed and Northrop regarding their experiences with the F-117 and ATB/B-2, all-aspect stealth requirements were drastically increased in Decemberlate 1985.{{Sfn|Aronstein|Hirschberg|Piccirillo|1999|pp=82-85}} 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]]. At this time, the USAF envisioned procuring 750 ATFs at a unit flyaway cost of $35 million in fiscal year (FY) 1985 dollars (~${{Format price|{{Inflation|index=US-GDP|value=35000000|start_year=1985}}}} in {{Inflation/year|end_year=2023|r=0|fmt=eqUS-GDP}}). 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 [[Grumman F-14 Tomcat|F-14 Tomcat]] and called for the procurement of 546 aircraft.{{Sfn|Williams|2002|p=5}}{{Sfn|Aronstein|Hirschberg|Piccirillo|1998|pp=87-88}}

[[File:Northrop ATF DP110 300x258.jpg|thumb|Northrop's DP110 submission for Dem/Val RFP. Note the great similarity to the eventual YF-23.|alt=Model of an early version of the YF-23 design on top of a wood holder]]

Northrop's 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.{{Sfn|Metz|2017|p=25}} 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 [[Lockheed Senior Peg|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.<ref name=":1">{{cite magazine |last=Hehs |first=Eric |date=1998 |title=Design Evolution of the F-22, Part 1 |url=https://www.codeonemagazine.com/f22_article.html?item_id=179 |archive-url=https://web.archive.org/web/20240518062846/https://www.codeonemagazine.com/f22_article.html?item_id=179 |archive-date=18 May 2024 |magazine=Code One |publisher=Lockheed Martin}}</ref>{{Sfn|Metz|2017|p=22}} Northrop's HSF design would be refined into DP110, which was its submission for the Dem/Val RFP.{{Sfn|Metz|2017|pp=28-29}}

In July 1986, proposals for Dem/Val were submitted by [[Lockheed Corporation|Lockheed]], [[Boeing]], [[General Dynamics]], McDonnell Douglas, Northrop, [[Grumman Corporation|Grumman]] and [[Rockwell International|Rockwell]]; the latter two dropped out of the competition shortly thereafter.{{Sfn|Miller|2005|pp=13-14, 19}} As contractors were expected to make significant investments for technology development, companies forming teams was encouraged by the SPO. Following proposal submissions, Lockheed, Boeing,Northrop and GeneralMcDonnell DynamicsDouglas formed a team to develop whichever of their proposed designs was selected, if any. NorthropLockheed, Boeing, and McDonnellGeneral DouglasDynamics formed a team with a similar agreement.{{Sfn|Goodall|1992|p=94}}

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.<ref name=":1" />{{Sfn|Metz|2017|p=22}} Both teams were awarded $691 million in FY 1985 dollars (~${{Format price|{{Inflation|index=US-GDP|value=691000000|start_year=1985}}}} in {{Inflation/year|end_year=2023|r=0|fmt=eqUS-GDP}}) and given 50 months to build and flight-test their prototypes. Concurrently, [[Pratt & Whitney]] and [[General Electric]] were contracted to develop the engines, designated YF119 and YF120 respectively, for the ATF engine competition.{{Sfn|Jenkins|Landis|2008|pp=233-234}} 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.{{refn|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.|group=N}}{{Sfn|Aronstein|Hirschberg|Piccirillo|1998|pp=88-89}}

===Design refinement===

[[File:YF-23 top view.jpg|thumb|Top view of the YF-23 (DP117K), showing the trapezoidaldiamond wings and separation between the forward fuselage and engine nacelles|alt=Top view of black jet aircraft, showing trapezoidaldiamond wings, engine nozzlenozzles with exhaust trenches, and two-piece tail. The separation between the forward fuselage and engine nacelles is apparent.]]

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 [[McDonnell Douglas F/A-18 Hornet|F/A-18 Hornet]].{{Sfn|Metz|2017|p=31}} In addition to the government contract awards, the team would eventually invest $650 million (~${{Format price|{{Inflation|index=US-GDP|value=600000000650000000|start_year=1988}}}} in {{Inflation/year|r=0|fmt=eqUS-GDP}}) combined into their ATF effort; General Electric and Pratt & Whitney, the two engine companies, also invested $100 million (~${{Format price|{{Inflation|index=US-GDP|value=100000000|start_year=1988}}}} in {{Inflation/year|r=0|fmt=eqUS-GDP}}) each.{{Sfn|Aronstein|Hirschberg|Piccirillo|1998|p=164}} 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.{{Sfn|Metz|2017|p=20}} 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.{{Sfn|Metz|2017|pp=26-27}}{{Sfn|Chong|2016|pp=237-238}} 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 [[Convair C-131 Samaritan|C-131]] named the Total In Flight Simulator (TIFS).{{Sfn|Metz|2017|pp=40-41}}

Throughout Dem/Val, the SPO conducted System Requirements Reviews (SRR) where it reviewed results of performance and cost [[trade study|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 {{convert|2000|ft|m}}, which meant the use of [[thrust reversal|thrust reversers]] on their engines. In 1987, the USAF changed the runway length requirement to {{convert|3000|ft|m}} and by 1988 the requirement for thrust reversers was no longer needed. This allowed Northrop to have smaller engine [[nacelle]] housings 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.{{Sfn|Miller|2005|p=23}}{{Sfn|Sweetman|1991a|pp=23, 43}} The number of internal missiles (with the [[AIM-120 AMRAAM|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 {{convert|60000|lb|kg|-2|abbr=on}} while engine thrust was increased from {{convert|30000|lbf|kN|0|abbr=on}} to {{convert|35000|lbf|kN|0|abbr=on|adj=on}} class.{{Sfn|Aronstein|Hirschberg|Piccirillo|1998|pp=106-108}}

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[[File:YF-23 hourglass.png|thumb|The red hourglass painted on the YF-23 PAV-1 for its maiden flight.|alt=Fighter jet with red hourglass identifier painted at center top]]

Formally designated as the YF-23A, the first aircraft ([[United States military aircraft serials|serial number]] ''87-0800''), Prototype Air Vehicle 1 (PAV-1), was rolled out on 22 June 1990;<ref>{{Cite web |date= |title=YF-23 roll out marks ATF debut |url=http://www.flightglobal.com/pdfarchive/view/1990/1990%20-%201803.html |url-status=dead |archive-url=https://web.archive.org/web/20120724011217/http://www.flightglobal.com/pdfarchive/view/1990/1990%20-%201803.html |archive-date=2012-07-24 |access-date=2024-06-13 |website=[[Flight International]] |series=27 June - 3 July 1990 |page=5}}</ref> PAV-1 took its 50-minute [[maiden flight]] on 27 August with Alfred "Paul" Metz at the controls.{{Sfn|Goodall|1992|p=99}} The second YF-23 (serial number ''87-0801'', PAV-2) made its first flight on 26 October, piloted by Jim Sandberg.{{Sfn|Jenkins|Landis|2008|p=237}} 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".<ref name=":0">{{Cite AV media |url=https://www.youtube.com/watch?v=iU8gWgz9n4U |title=YF-23 Walk Around and Design Features by Test Pilot Paul Metz |date=2015-09-06 |last= |publisher=Peninsula Seniors Productions |place=Western Museum of Flight |time=7:20 |access-date=2024-06-15 |archive-url=https://web.archive.org/web/20231121153354/https://www.youtube.com/watch?v=iU8gWgz9n4U |archive-date=21 November 2023 |via=YouTube}}</ref> 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"<ref name=":0" /> 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.{{Sfn|Goodall|1992|p=120}}

===Naval variant===

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[[File:YF-23 front.jpg|thumb|A front view of ''87–0800'' showing the curving exterior of the design.|alt=Front view of jet aircraft showing curving exterior. The ruddervator tail is V-shaped.]]

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 (military)|survivability]], supercruise, stealth, and ease of maintenance.<ref>{{Cite web |date=15 November 1986 |title=ATF procurement launches new era |url=http://www.flightglobal.com/pdfarchive/view/1986/1986%20-%203004.html |url-status=dead |archive-url=https://web.archive.org/web/20120724101828/http://www.flightglobal.com/pdfarchive/view/1986/1986%20-%203004.html |archive-date=24 July 2012 |website=[[Flight International]] |page=10}}</ref> 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, a profile with substantial [[area rule|area-ruling]] to reduce [[aerodynamic drag]] at [[transonic]] and [[supersonic]] speeds, and [[Stabilator|all-moving]] [[V-tail]]s, or "ruddervators".{{Sfn|Metz|2017|p=84}} 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 gear|tricycle landing gear]] configuration with a nose [[landing gear]] leg and two main landing gear legs. A single large weapons bay was placed on the underside of the fuselage between the nose and main landing gear.{{Sfn|Goodall|1992|pp=108-115, 124}} The cockpit had a center stick and side throttle.{{Sfn|Metz|2017|pp=92-93}}

[[File:YF-23 exhaust.jpg|thumb|A rear view of a YF-23, showing its tile-lined exhaust channels|alt=Rear view of the YF 23, the two tile lined exhaust channels can be seen at the center, between the V tails]]

It was powered by two [[turbofan]] engines, with each in a separate engine nacelle with [[S-duct]]s, to shield engine [[axial compressor]]s from [[radar]] waves, on either side of the aircraft's spine.{{Sfn|Sweetman|1991a|pp=42-44, 55}} 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 F119|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]].{{Sfn|Miller|2005|p=23}} As on the B-2, the exhaust from the YF-23's engines flowed through troughs lined with tiles that are “transpiration cooled” to dissipate heat and shield the engines from [[infrared homing]] (IR) missile detection from below.{{Sfn|Winchester|2005|pp=198-199}} The YF-23's propulsion and aerodynamics enabled it to supercruisecruise at over Mach 1.65 without afterburners.<ref name=":2">{{cite web |title=Northrop-McDonnell Douglas YF-23A Black Widow II |url=https://www.nationalmuseum.af.mil/Visit/Museum-Exhibits/Fact-Sheets/Display/Article/195766/northrop-mcdonnell-douglas-yf-23a-black-widow-ii/ |archive-url=https://web.archive.org/web/20230530132209/https://www.nationalmuseum.af.mil/Visit/Museum-Exhibits/Fact-Sheets/Display/Article/195766/northrop-mcdonnell-douglas-yf-23a-black-widow-ii/ |archive-date=30 May 2023 |work=National Museum of the U.S. Air Force}}</ref>

[[File:Northrop McDonnell Douglas YF-23A PAV-1 87-0800 Black Widow II LEngineIntake R&D NMUSAF 25Sep09 (14414042127).jpg|thumb|YF-23 [[S-duct]] engine air intake with the porous suction panel in front|alt=A close up shot of the YF-23's S-duct engine air intake located below the right wing]]

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 [[Flap (aircraft)|wing flaps]] and [[aileron]]s on one side and lowering them on the other provided [[Flight dynamics (aircraft)|roll]]. The V-tail fins were angled 50 degrees from the vertical. [[Flight dynamics (aircraft)|Pitch]] was mainly provided by rotating these V-tail fins in opposite directions so their front edges moved together or apart. [[Yaw (aviation)|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 [[angle of attack]] (AoA) performance compared to legacy aircraft, with trimmed AoA of up to 60°.<ref>{{Cite journal |date=1991-01-14 |title=YF-23 would undergo subtle changes if it wins competition. |url=https://go.gale.com/ps/i.do?p=AONE&sw=w&issn=08890404&v=2.1&it=r&id=GALE%7CA9371744&sid=googleScholar&linkaccess=abs |journal=Defense Daily |language=English |volume=170 |issue=8 |pages=62–63 |via=Gale}}</ref><ref>{{Cite AV media |url=https://www.youtube.com/watch?v=OdFL6r-OszM |title=YF-23 Advanced Tactical Fighter (ATF) - Paul Metz (Part 1) |date=2022-01-04 |last=10 Percent True - Tales from the Cockpit |access-date=2024-06-15 |archive-url=https://web.archive.org/web/20231111214116/https://www.youtube.com/watch?v=OdFL6r-OszM |archive-date=11 November 2023 |via=YouTube}}</ref> Deflecting the wing flaps down and ailerons up on both sides simultaneously provided for [[Air brake (aircraft)|aerodynamic braking]].{{Sfn|Sweetman|1991a|pp=34-35, 43-45}} To keep prototyping costs low despite the novel design, a number of "[[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 [[McDonnell Douglas F-15E Strike Eagle|F-15E Strike Eagle]].{{Sfn|Winchester|2005|pp=198-199}}{{Sfn|Jenkins|Landis|2008|p=237}}

===Production F-23===

[[File:EMD F-23 cutaway 304x196.jpg|thumb|Cutaway drawing of the EMD F-23 design|alt=Cross section drawing of the F-23 intended for production]]

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 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 AMRAAM|AIM-120]] missiles and bombs. An [[M61 Vulcan|M61]] rotary cannon would be installed on the left side of the forward fuselage. The F-23's overall length was slightly increased to {{convert|70|ft|5|in|m|abbr=on|2}} while wingspan remained about the same. Fuselage volume was expanded, the nose wasand radome were enlarged to accept sensors and mission systems, including the AESA [[radar]], and the forebody [[Chine (aeronautics)|chines]] were 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 space 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. 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.{{Sfn|Metz|2017|p=54}}

===NATF-23===

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===Proposed revival===

[[File:FB-23 Rapid Theater Attack.png|thumb|Northrop Grumman concept art of the FB-23 "Rapid Theater Attack" regional bomber|alt=The manufacturer's concept art of the F-23 design repurposed as a supersonic bomber with regional range]]

In 2004, [[Northrop Grumman]]<ref name="NG" group=N>Northrop acquired Grumman in 1994 to become Northrop Grumman.</ref> proposed an F-23-based bomber called the FB-23{{refn|The "F/B-23" designation was also used.|group=N}} "Rapid Theater Attack" (RTA) to meet a USAF solicitation for an [[2037 bomber controversy|interim regional bomber]], for which the [[Lockheed Martin FB-22|FB-22]] and [[Rockwell B-1 Lancer#Variants|Boeing B-1R]] were also competing.<ref>{{Cite web |last=Herbert |first=Adam J. |date=November 2004 |title=Long-Range Strike in a Hurry |url=http://www.airforce-magazine.com/MagazineArchive/Pages/2004/November%202004/1104strike.aspx |url-status=dead |archive-url=https://web.archive.org/web/20090825145639/http://www.airforce-magazine.com/MagazineArchive/Pages/2004/November%202004/1104strike.aspx |archive-date=25 August 2009 |website=Airforce Magazine}}</ref><ref>{{Cite web |date=13 July 2004 |title=YF-23 re-emerges for surprise bid |url=http://www.flightglobal.com/pdfarchive/view/2004/2004-09%20-%201169.html |url-status=dead |archive-url=https://web.archive.org/web/20120723232009/http://www.flightglobal.com/pdfarchive/view/2004/2004-09%20-%201169.html |archive-date=23 July 2012 |website=[[Flight International]]}}</ref> 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 {{convert|1600|nmi|mi km|sigfig=3}}. Northrop Grumman modified the YF-23 PAV-2 to serve as a display model for its proposed interim bomber.{{Sfn|Miller|2005|pp=38-39}} 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.<ref>{{Cite web |date=6 February 2006 |title=Quadrennial Defense Review Report |url=http://www.defenselink.mil/qdr/report/Report20060203.pdf |url-status=dead |archive-url=https://web.archive.org/web/20070215031830/http://www.defenselink.mil/qdr/report/Report20060203.pdf |archive-date=15 February 2007 |access-date=2024-06-13 |website=U.S. Department of Defense |language=en-US}}</ref><ref>{{Cite web |last=Herbert |first=Adam J. |date=October 2006 |title=The 2018 Bomber and Its Friends |url=http://www.airforce-magazine.com/MagazineArchive/Pages/2006/October%202006/10062018.aspx |url-status=dead |archive-url=https://web.archive.org/web/20090923015849/http://www.airforce-magazine.com/MagazineArchive/Pages/2006/October%202006/10062018.aspx |archive-date=23 September 2009 |website=Airforce Magazine}}</ref> The USAF has since moved on to the [[Next-Generation Bomber]] and [[Long Range Strike Bomber]] program.<ref>{{Cite web |last=Majumdar |first=Dave |date=23 January 2011 |title=U.S. Air Force May Buy 175 Bombers |url=http://www.defensenews.com/article/20110123/DEFFEAT04/101230303/U-S-Air-Force-May-Buy-175-Bombers |url-status=dead |archive-url=https://archive.today/20120904021628/http://www.defensenews.com/story.php?i=5520432 |archive-date=4 September 2012 |access-date=2024-06-13 |website=Defense News}}</ref>

The [[Japan Air Self-Defense Force]] (JASDF) launched a program to develop a domestic [[Fifth-generation jet fighter|5th]]/[[Sixth-generation jet fighter|6th generation]] (F-3) fighter after the USU.S. Congress refused in 1998 to export the [[Lockheed Martin F-22 Raptor|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 bring on-board 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.<ref>{{Cite web |last=Mizokami |first=Kyle |date=2018-07-09 |title=Now Northrop Grumman Wants to Build Japan's New Fighter Jet |url=https://www.popularmechanics.com/military/aviation/a22093705/northrop-grumman-japans-fighter-jet/ |url-status=live |archive-url=https://web.archive.org/web/20240523033655/https://www.popularmechanics.com/military/aviation/a22093705/northrop-grumman-japans-fighter-jet/ |archive-date=23 May 2024 |access-date=2024-06-13 |website=[[Popular Mechanics]] |language=en-US}}</ref><ref>{{cite news |date=4 October 2018 |title=Defense Ministry to develop own fighter jet to succeed F-2, may seek int'l project |url=https://mainichi.jp/english/articles/20181004/p2a/00m/0na/001000c |url-status=live |archive-url=https://web.archive.org/web/20190425170901/https://mainichi.jp/english/articles/20181004/p2a/00m/0na/001000c |archive-date=25 April 2019 |access-date=28 April 2019 |newspaper=[[Mainichi Shimbun]]}}</ref>

==Operational history==

Line 98 ⟶ 96:

===Evaluation===

The first YF-23, with Pratt & Whitney engines, supercruised at Mach&nbsp;1.43 on 18 September 1990, while the second, with General Electric engines, reached Mach&nbsp;1.72 on 29 November 1990.{{refn|SpeculationThe fromYF-23 aviationwith pressthe reportsGeneral suggestsElectric thatengines thewas topofficially stated to have been able to supercruise speedat ofover theMach YF-231.6, withand theestimates from General Electric enginesengineers suggest that the top supercruise speed was as high as Mach 1.8.{{sfn|Sweetman|1991a|p=55}}{{sfn|Chong|2016|pp=237-238}}|group=N|name="supercruise_speed"}} By comparison, the YF-22 achieved Mach 1.58 in supercruise.{{Sfn|Goodall|1992|pp=102-103}} The YF-23 was tested to a top speed of Mach 1.8 with afterburners and achieved a maximum angle-of-attack of 25°.<ref>{{Cite journal |date=1991-01-14 |title=YF-23 would undergo subtle changes if it wins competition. |url=https://go.gale.com/ps/i.do?p=AONE&sw=w&issn=08890404&v=2.1&it=r&id=GALE%7CA9371744&sid=googleScholar&linkaccess=abs |journal=Defense Daily |language=English |volume=170 |issue=8 |pages=62–63 |via=Gale}}</ref> The maximum speed is classified, though sources state a speed greater than Mach 2 at altitude in full afterburner.<ref name="test_pilot_interview">{{cite AV media |url=https://www.youtube.com/watch?v=Vpkv1ErWIf8 |title=YF-23 DEM/VAL Presentation by Test Pilots Paul Metz and Jim Sandberg |date=27 August 2015 |publisher=Peninsula Seniors Production |location=Western Museum of Flight |access-date=30 June 2020 |archive-url=https://web.archive.org/web/20231014142723/https://www.youtube.com/watch?v=Vpkv1ErWIf8 |archive-date=14 October 2023 |people=Paul Metz, Jim Sandberg}}</ref>{{Sfn|Aronstein|Hirschberg|Piccirillo|1998|p=136}} 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.{{Sfn|Miller|2005|pp=36, 39}} The two YF-23s flew 50 times for a total of 65.2 hours.<ref>{{Cite web |last=Norris |first=Guy |title=NASA could rescue redundant YF-23s |url=http://www.flightglobal.com/pdfarchive/view/1991/1991%20-%201440.html |url-status=dead |archive-url=https://web.archive.org/web/20110521184547/http://www.flightglobal.com/pdfarchive/view/1991/1991%20-%201440.html |archive-date=21 May 2011 |website=[[Flight International]] |series=5 - 11 June 1991 |page=16}}</ref> The tests demonstrated Northrop's predicted performance values for the YF-23.{{Sfn|Miller|2005|pp=38-39}} Both designs met or exceeded all performance requirements; the YF-23 was stealthier and faster, but the YF-22 was more agile.{{Sfn|Goodall|1992|p=110}}{{Sfn|Sweetman|1991a|p=55}}

[[File:YF-22 and YF-23.jpg|thumb|A YF-22 in the foreground with a YF-23 in the background|alt=Lockheed Martin's YF-22 is at the center of the picture, while the YF-23 "Spider" is at its left]]

The two contractor teams submitted evaluation results and their PSC proposals for full-scale development in December 1990,{{Sfn|Miller|2005|pp=38-39}} and on 23 April 1991, [[Donald Rice]], the [[United States Secretary of the Air Force|Secretary of the Air Force]] announced that the YF-22 team was the winner.{{Sfn|Jenkins|Landis|2008|p=234}} 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.<ref>{{cite report |url=https://www.afmc.af.mil/News/Article-Display/Article/2919261/flashback-northrop-yf-23-black-widow-ii/ |title=Flashback: Northrop YF-23 Black Widow II |author=Landis |first=Tony |date=1 February 2022 |publisher=Air Force Materiel Command History Office |archive-url=https://web.archive.org/web/20240523165544/https://www.afmc.af.mil/News/Article-Display/Article/2919261/flashback-northrop-yf-23-black-widow-ii/ |archive-date=23 May 2024 |url-status=live}}</ref>{{Sfn|Jenkins|Landis|2008|p=234}}{{Sfn|Miller|2005|pp=38-39}} 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.{{Sfn|Williams|2002|p=6}}{{Sfn|Miller|2005|p=76}}

Following the competition, both YF-23s were transferred to NASA's [[Dryden Flight Research Center]] at [[Edwards Air Force Base|Edwards AFB]], California, without their engines.<ref name=NASA_DFRC/>{{Sfn|Winchester|2005|pp=198-199}} 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.<ref name="NASA_DFRC">{{Cite web |date=1996-01-20 |title=YF-23 Photo Gallery |url=http://www.dfrc.nasa.gov/gallery/photo/YF-23/index.html |url-status=dead |archive-url=https://web.archive.org/web/19970605022423/http://www.dfrc.nasa.gov/gallery/photo/YF-23/index.html |archive-date=5 June 1997 |access-date=2024-06-13 |website=NASA Dryden Flight Research Center}}</ref> 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.<ref name=NASA_DFRC/><ref>{{cite web |last=Landis |first=Tony |date=1 February 2022 |title=Flashback: Northrop YF-23 Black Widow II |url=https://www.afsc.af.mil/News/Article-Display/Article/2919531/flashback-northrop-yf-23-black-widow-ii/ |url-status=live |archive-url=https://web.archive.org/web/20240708223346/https://www.afsc.af.mil/News/Article-Display/Article/2919531/flashback-northrop-yf-23-black-widow-ii/ |archive-date=8 July 2024 |work=U.S. Air Force Sustainment Center}}</ref>

==Aircraft on display==

[[File:YF-23 in the restoration area of the usaf museum.jpg|thumb|Restoration work at the [[National Museum of the United States Air Force|USAF Museum]]|alt=A YF-23 undergoing restoration at the USU.S. Air Force Museum, one other plane can be seen at top left, another at top right; jeeps, machines, benches, cables and a plaque can be seen]]

* 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]].<ref name=":2" />

[[File:PAV-1 Display.jpg|thumb|YF-23 "Gray Ghost" on display at the USAF Museum at Wright-Patterson Air Force Base, 2023|alt=The YF-23 painted in charcoal gray, the "Gray Ghost" is seen front and center, with a man walking in front of it at the bottom right of the image. Multiple other aircraft held at the museum can be seen behind it]]

[[File:YF-23 PAV-2 "Spider" Static.jpg|thumb|YF-23 "Spider" on display at the Western Museum of Flight, 2017|alt=The YF-23 painted light gray, the "Spider", can be seen at the center with its labels. An unmarked fighter jet is at its left, while a Navy aircraft is to the right, marked VF-2, probably the squadron it belonged to.]]

* YF-23A PAV-2, AF ser. no. ''87-0801'', "Spider", registration number N232YF, was on exhibit at the [[Western Museum of Flight]] until 2004,<ref name=NASA_DFRC/> when it was reclaimed by Northrop Grumman and used as a display model for an F-23-based regional bomber.{{Sfn|Miller|2005|p=39}} PAV-2 was returned to the Western Museum of Flight and was on display as of 2010 at the museum's new location at [[Zamperini Field]] in [[Torrance, California]].<ref name=YF-23_display>[http://www.wmof.com/display.htm "Static Displays"] {{Webarchive|url=https://web.archive.org/web/20190715211258/http://www.wmof.com/display.htm |date=15 July 2019 }}; [http://www.wmof.com/yf23a.htm "Northrop YF-23A 'Black Widow II'"] {{Webarchive|url=https://web.archive.org/web/20190715212432/http://www.wmof.com/yf23a.htm |date=15 July 2019 }}. ''[[Western Museum of Flight]]''. Retrieved 31 August 2011.</ref>

==Specifications (YF-23A)==

Line 160 ⟶ 158:

|max speed mach=2.2 (1,450&nbsp;mph, 2,335&nbsp;km/h) at high altitude

|cruise speed kts=

|cruise speed note=*'''Supercruise''': Mach 1.72 (1,135&nbsp;mph, 1,827&nbsp;km/h) at altitude<ref group=N name="supercruise_speed"/>

|stall speed kts=

|stall speed note=