Editing General Dynamics F-111 Aardvark (section)

==Development==

===Early requirements===
The May [[1960 U-2 incident]], in which an American [[CIA]] [[Lockheed U-2|U-2]] reconnaissance plane was shot down over the USSR, stunned the United States government. Besides greatly damaging US–Soviet relations, the incident showed that the Soviet Union had developed a [[SA-2|surface-to-air missile]] that could reach aircraft above 60,000 feet (18,000 meters). Consequently, the [[United States Air Force]] [[Strategic Air Command]] (SAC) and the [[RAF Bomber Command]]'s plans to send subsonic, high-altitude [[Boeing B-47 Stratojet]] and [[V bomber]] formations into the USSR were realized to be much less viable.<ref name="lax2010">Lax 2010, p. 15.</ref>

By 1960, SAC had begun moving to [[Terrain mask|low-level penetration]], which greatly reduced [[radar]] detection distances. At the time, SAMs were ineffective against low-flying aircraft while [[interceptor aircraft]] had less of a speed advantage at low altitudes.<ref name=Spick_B-1B>Spick 1986, pp. 4–7.</ref> The USAF's [[Tactical Air Command]] (TAC) was largely concerned with the [[fighter-bomber]] and deep strike/[[interdiction]] roles. TAC was in the process of receiving its latest design, the [[Republic F-105 Thunderchief|Republic {{nowrap|F-105}} Thunderchief]], which was designed to deliver nuclear weapons fast and far, but required long runways.<ref name=Gunston_p12-3>Gunston 1978, pp. 12–13.</ref> A simpler [[Variable-sweep wing|variable geometry wing]] configuration with the pivot points farther out from the aircraft's centerline was reported by [[NASA]] in 1958, which made swing-wings viable.<ref name=Thomason_p5-6>Thomason 1998, pp. 5–6.</ref><ref name="Davies2013 p6-7">Davies 2013, pp. 6-7.</ref> This led USAF leaders to encourage its use.<ref name=Miller_p10-1>Miller 1982, pp. 10–11.</ref>

In June 1960, the USAF issued specification ''SOR 183'' for a long-range interdiction/strike aircraft able to penetrate [[Soviet Union|Soviet]] air defenses at very low altitudes and high speeds.{{Sfn|Gunston|1978|pp= 12–13, 16}} Specifically, it was to be capable of at least {{cvt|800|mi|km}} of low-level flight, {{cvt|400|mi|km}} of which was to be at a speed of no less than Mach 1.2.<ref name='knaack 223'>Knaack 1978, p. 223.</ref> Furthermore, the specification also called for the aircraft to possess [[short takeoff and landing]] (STOL) capabilities to permit operations from short, unprepared airstrips that had a length of no more than {{convert|3000|ft|m|sigfig=1}}.<ref name=Miller_p10-1/> An internal payload of {{convert|1000|lb|kg}} was to be carried in the primary mission role. A variant suitable for [[aerial reconnaissance]] flights was also included in the specification.<ref name='knaack 223-224'>Knaack 1978, pp. 223-224.</ref>

In the 1950s, the [[United States Navy]] sought a long-range, high-endurance interceptor aircraft to protect its carrier battle groups against long-range [[anti-ship missile]]s launched from Soviet jet bombers and submarines. The Navy needed a [[fleet air defense]] (FAD) fighter with a more powerful radar, and longer range missiles than the [[McDonnell Douglas F-4 Phantom II|F-4 Phantom II]] to intercept both enemy bombers and missiles.<ref name=Thomason_p3-5>Thomason 1998, pp. 3–5.</ref><ref name="Davies2013 p7">Davies 2013, p. 7.</ref> Seeking a FAD fighter, the Navy started with the [[subsonic aircraft|subsonic]], straight-winged aircraft, the [[Douglas F6D Missileer]] in the late 1950s. The Missileer was designed to carry six long-range missiles and loiter for five hours, but would be defenseless after firing its missiles.<ref name=Thomason_p3-5/>{{Sfn|Gunston|1978|p= 13}} The program was formally canceled in 1961.<ref name=Thomason_p3-5/> The Navy had tried variable geometry wings with the [[XF10F Jaguar]], but abandoned it in the early 1950s.<ref name="Davies2013 p6">Davies 2013, p. 6.</ref> It was NASA's simplification which made the variable geometry wings practical.<ref name=Thomason_p5-6/><ref name='knaack 223'/> By 1960, increases in aircraft weights required improved [[high-lift device]]s, such as variable geometry wings.{{Sfn|Gunston|1978|pp= 11–12}}<ref name=Miller_p11>Miller 1982, p. 11.</ref> Variable geometry offered high speeds, and maneuverability with heavier [[payload]]s, long range, and the ability to take off and land in shorter distances.{{Sfn|Gunston|1978|pp=11–12}}

===Tactical Fighter Experimental (TFX)===
The USAF and Navy were both seeking new aircraft when [[Robert McNamara]] was appointed [[United States Secretary of Defense|secretary of defense]] in January 1961.<ref name=Miller_p13>Miller 1982, p. 13.</ref> Both sought high-supersonic, twin-engine, two-seat aircraft that could carry heavy armament and fuel loads and probably use variable geometry wings.{{Sfn|Gunston|1978|p= 16}}<ref name="Davies2013 p4">Davies 2013, p. 4.</ref> On 14 February 1961, McNamara formally directed the services to study the development of a single aircraft that would satisfy both requirements. Early studies indicated that the best option was to base the design on the USAF requirement, and use a modified version for the Navy.{{Sfn|Gunston|1978|pp=8–17}} In June 1961, Secretary McNamara ordered the go-ahead of [[TFX Program|Tactical Fighter Experimental]] (TFX), despite USAF and Navy efforts to keep their programs separate.{{Sfn|Eden|2004|pp=196–7}}<ref name=erg66colls>{{cite news |url= https://news.google.com/newspapers?id=o-VVAAAAIBAJ&sjid=EuEDAAAAIBAJ&pg=6856%2C3575947<!--https://news.google.com/newspapers?id=b5ghAAAAIBAJ&sjid=MpoFAAAAIBAJ&pg=3595%2C773184-->|work= Eugene Register-Guard |location= Oregon, US |agency= Associated Press |last= Price |first= Bem |title= Capital still buzzing whether TFX a colossal blunder |date= 18 September 1966 |page= 5A}}</ref> According to aviation author Peter E. Davis, military officials were disconcerted by McNamara's focus on compromised requirements for financial reasons.<ref name="Davies2013 p4-5">Davies 2013, pp. 4-5.</ref>

[[File:General Dynamics F-111A cockpit 061003-F-1234S-015.jpg|thumb|The side-by-side seating adopted in the F-111]]
The two services could agree only on swing-wing, two-seat, twin-engine design features. The USAF wanted a [[tandem]]-seat aircraft for low-level penetration ground-attack, while the Navy wanted a shorter, high altitude interceptor with [[side-by-side seating]] to allow the pilot and [[Naval Flight Officer|radar operator]] to share the radar display.{{Sfn|Gunston|1978|pp=8–17}}<ref name='knaack 224'>Knaack 1978, p. 224.</ref> Also, the USAF wanted the aircraft designed for 7.33&nbsp;g with Mach&nbsp;2.5 speed at altitude and Mach&nbsp;1.2 speed at low level with an approximate length of {{convert|70|ft|m|sigfig=3|abbr=on}}. The Navy had less strenuous requirements: 6&nbsp;g with Mach&nbsp;2 speed at altitude and high subsonic speed (about Mach&nbsp;0.9) at low level with a length of {{convert|56|ft|m|sigfig=3|abbr=on}}. The Navy also wanted the aircraft with a nose large enough for a {{convert|48|in|m|sigfig=2|abbr=on|adj=on}} diameter radar dish.{{Sfn|Gunston|1978|pp=8–17}}<ref name=Miller_p11-5>Miller 1982, pp. 11–15.</ref>

McNamara developed a basic set of requirements for TFX based largely on the USAF's requirements and, on 1 September 1961, ordered the USAF to develop it.{{Sfn|Gunston|1978|pp= 8–17}}<ref name=Miller_p11-5/> Nevertheless, a request for proposals (RFP) for the TFX was provided to industry in October 1961.<ref name='knaack 224-225'>Knaack 1978, pp. 224-225.</ref> In December, proposals were received from [[Boeing]], [[General Dynamics]], [[Lockheed Corporation|Lockheed]], [[McDonnell Aircraft|McDonnell]], [[North American Aviation|North American]] and [[Republic Aviation|Republic]]. The evaluation group found all the proposals lacking, but Boeing and General Dynamics were selected to submit enhanced designs.<ref name='knaack 225'>Knaack 1978, p. 225.</ref> Boeing's [[Boeing 818|proposal]] was recommended by the selection board in January 1962, with the exception of the engine, which was not considered acceptable. The board also directed alterations to radar and missile storage and a switch from [[ejection seat]]s to a crew escape capsule. Both companies provided updated proposals in April 1962. USAF reviewers favored Boeing's offering, while the Navy found both submissions unacceptable for its operations.<ref name='knaack 225' /> Two more rounds of updates to the proposals were conducted, and the board eventually recommended the Boeing design.<ref name=erg66colls/>{{Sfn|Gunston|1978|pp=18–20}}

But in November 1962, McNamara selected General Dynamics' proposal due to its greater commonality between USAF and Navy versions.<ref name='knaack 225' /> The Boeing aircraft shared less than half of the major structural components. On 21 December 1962, General Dynamics signed the TFX contract.<ref name='knaack 225-226'>Knaack 1978, pp. 225-226.</ref> A congressional investigation into the procurement processed was conducted, but did not change the selection.<ref name=erg66colls />{{Sfn|Gunston|1978|pp=18–20}}<ref name=retplg>{{cite news |url= https://news.google.com/newspapers?id=StoxAAAAIBAJ&pg=2650%2C6893340 |work= Reading Eagle |location= Pennsylvania, US |agency= Associated Press |title= F-111 problems return to plague President |date= 13 January 1970 |page= 8}}</ref> On 1 May 1964, the definitized contract was issued for the program, including flight testing, spares, ground equipment, training devices, static and fatigue test data, and the production of an initial 23 F-111 aircraft; it was structured as a [[Fixed-price_contract#Contract_types|fixed price incentive fee]] (FPIF) contract with a ceiling price of $529 million along with provisions for deficiency correction amongst other operational clauses and performance criteria.<ref name='knaack 226'>Knaack 1978, p. 226.</ref>

===Design phase===
General Dynamics' design team was led by [[Robert H. Widmer]].<ref>{{cite news |last= Martin |first= Douglas |url= https://www.nytimes.com/2011/07/03/business/03widmer.html?_r=1&ref=deathsobituaries |title= Obituary: Robert H. Widmer, Designer of Military Aircraft, Dies at 95 |newspaper= [[The New York Times]] |date= 2 July 2011}}</ref> Recognizing its lack of experience with carrier-based fighters, General Dynamics teamed with [[Grumman]] in November 1963 for the assembly and testing of the F-111B. In addition, Grumman would also build the aft fuselage and the landing gear of the F-111A.<ref name=Miller_p17_9/><ref name='knaack 236'>Knaack 1978, p. 236.</ref> The General Dynamics and Grumman team faced ambitious requirements for range, weapons load, and aircraft weight.<ref>Thomason 1998, pp. 9–10.</ref> Thus, the F-111 was designed to incorporate numerous features that were new to production military aircraft, such as variable-geometry wings and afterburning turbofan engines.<ref name=Miller_p17_9>Miller 1982, pp. 17, 19.</ref> This use of unfamiliar features has been attributed as a major cause of the aircraft's protracted development and weight increases.<ref name="Davies2013 p5">Davies 2013, p. 5.</ref>

The F-111A and F-111B shared the same airframe structural components and [[Pratt & Whitney TF30|Pratt & Whitney TF30-P-1]] turbofan engines. They featured side-by-side crew seating in an escape capsule as required by the Navy. The [[General Dynamics/Grumman F-111B|F-111B]]'s nose was {{convert|8.5|ft|m|sigfig=3|sp=us}} shorter as the aircraft could fit on existing carrier elevator decks, and had {{convert|3.5|ft|m|sigfig=3|adj=mid|-longer}} wingtips to improve on-station endurance time; it also carried an [[AN/AWG-9]] [[Pulse-Doppler radar]] to guide its [[AIM-54 Phoenix]] missiles. The USAF's F-111A would be equipped with the AN/APQ-113 attack radar and the [[AN/APQ-110]] [[terrain-following radar]] and air-to-ground armament.<ref name=Baug_F-111A>Baugher, Joe. [http://www.joebaugher.com/usaf_fighters/f111_1.html "General Dynamics F-111A."] ''USAAC/USAAF/USAF Fighters'', 23 December 1999. Retrieved: 5 October 2009.</ref>

During September 1963, the F-111A mockup was inspected.<ref name='knaack 226' /> On 15 October 1964, the first test F-111A was rolled out of [[Air Force Plant 4|Plant 4]] of General Dynamics' facility in Fort Worth, Texas; it was powered by YTF30-P-1 turbofans and used a set of ejector seats as the escape capsule was not yet available.<ref name=Baug_F-111A/><ref name='knaack 226' /> On 21 December 1964, the F-111A made its first flight from [[Carswell Air Force Base]], Texas.{{Sfn|Eden|2004|p=197}} Lasting for 22 minutes, less than planned due to a flap malfunction, this initial flight was considered to be satisfactory overall; category I testing commenced immediately thereafter.<ref name='knaack 226-227'>Knaack 1978, pp. 226-227.</ref><ref name=ctfiss>{{cite news |url= https://news.google.com/newspapers?id=qzhWAAAAIBAJ&sjid=wOgDAAAAIBAJ&pg=2676%2C1891540 |work= Spokesman-Review |location= Spokane, Washington, US |agency= Associated Press |title= Controversial TFX test flight is success |date= 22 December 1964 |page= 1}}</ref> Early flights of the F-111, which included supersonic flights, demonstrated favorably simplistic maintenance requirements, amongst other qualities.<ref name='knaack 227'>Knaack 1978, p. 227.</ref>

Various changes to the program were enacted throughout 1965; this was chiefly in response to a steep climb in unit costs from $4.5 million to $6 million.<ref name='knaack 227' /> The cause of the cost rises has been attributed, at least partially, to a directive issued to General Dynamics to incorporate improved avionics as well as to work on [[strategic bomber]] and aerial reconnaissance variants of the aircraft, the latter of which was eventually cancelled. During April 1965, General Dynamics was authorized to produce 431 F-111s, less than half the number of aircraft which had originally been forecast.<ref name='knaack 227, 233'>Knaack 1978, pp. 227, 233.</ref> On 10 May 1967, a new multi-year FPIP contract replaced the prior procurement process, increasing the total aircraft on order to 493 F-111s of multiple models, including 23 F-111Bs intended for the US Navy, 24 F-111Cs for the [[Royal Australian Air Force]], and 50 F-111Ks intended for the [[Royal Air Force]].<ref name='knaack 228'>Knaack 1978, p. 228.</ref>

Early flights of the F-111 were troubled by compressor surges and stalls across certain portions of the flight regime.<ref name='knaack 227-228'>Knaack 1978, pp. 227-228.</ref> General Dynamics had elected to use an uncommon spike-shaped variable intake for the engine for the performance.<ref name="Davies2013 p5"/> Studies performed by NASA, the USAF, and General Dynamics led to the engine inlet being redesigned; modifications were implemented between 1965 and 1966, culminating with the "Triple Plow I" and "Triple Plow II" designs.<ref name=Gunston_p25-7>Gunston 1978, pp. 25–27.</ref><ref name=FASweb>{{cite web |title= F-111 |url= https://fas.org/man/dod-101/sys/ac/f-111.htm |website= FAS.org |publisher= Federation of American Scientists |date= 24 December 1998 |access-date= 15 August 2014}}</ref><ref name='knaack 228-229'>Knaack 1978, pp. 228-229.</ref> During February 1965, the F-111A achieved a speed of Mach 1.3 while flying with an interim intake design.<ref name=Gunston_p25-7/> On 18 May 1965, the <!--first-->F-111B made its first flight; it was also equipped with ejector seats initially.<ref name=Baugher_F-111B>Baugher, Joe. [http://www.joebaugher.com/usaf_fighters/f111_4.html "General Dynamics/Grumman F-111B."] ''USAAC/USAAF/USAF Fighters'', 7 November 2004. Retrieved: 5 October 2009.</ref><ref>Thomason 1998, pp. 16, 20.</ref>

Separately, cracks in the F-111's [[wingbox|wing attach points]] were first discovered in 1968 during ground fatigue testing; during the following year, the crash of an F-111 was attributed to a cracked wingbox.<ref name='knaack 234'>Knaack 1978, p. 234.</ref><ref name=retplg/> On 22 December 1969, the USAF opted to ground the fleet due to this issue, save for those involved in flight testing.<ref name='knaack 230-231'>Knaack 1978, pp. 230-231.</ref> The resolution involved the redesigning of the attach structure and necessitated testing to ensure adequate design and workmanship.<ref name=Miller_p31_47>Miller 1982, pp. 31, 47.</ref> On 31 July 1970, the grounding was lifted.<ref name='knaack 231'>Knaack 1978, p. 231.</ref> Category I flight testing of the F-111A, which had started in 1964, continued through to 31 March 1972.<ref name=Logan_p32>Logan 1998, p. 32.</ref><ref name='knaack 227' /> Category II tests started in January 1966, while Category III testing was repeatedly postponed before being cancelled, having been deemed to be unnecessary.<ref name='knaack 227' />

During 1968, the F-111B was canceled by the Navy on account of weight and performance issues together with revised tactical requirements.{{Sfn|Boyne|2002|p=252}}<ref>Thomason 1998, pp. 52–53.</ref> Australia would procure its own model, the F-111C. Subsequently, the improved F-111E, F-111D, and F-111F models were developed for the USAF. The strategic bomber FB-111A and the EF-111 electronic warfare versions were later developed for the USAF.{{Sfn|Frawley|2002|p= 89}} Production of the F-111 ended in 1976,<ref name=Miller_p65>Miller 1982, p. 65.</ref> following the completion of 563 aircraft.<ref name=Logan_p9 />