The General Dynamics F-111 Aardvark is a retired, supersonic, medium-range fighter-bomber. Production models of the F-111 had roles that included attack (e.g., interdiction), strategic bombing (including nuclear weapons capabilities), reconnaissance, and electronic warfare. Its name "Aardvark" comes from the long-nosed, insect-eating African animal.
Developed in the 1960s by General Dynamics under Robert McNamara's TFX Program, the F-111 pioneered variable-sweep wings, afterburning turbofan engines, and automated terrain-following radar for low-level, high-speed flight. Its design influenced later variable-sweep wing aircraft, and some of its advanced features have become commonplace. The F-111 suffered problems during initial development, largely related to the engines. A multirole carrier-based fighter/long-range interception variant intended for the United States Navy, the F-111B, was canceled before production. Several specialized models, such as the FB-111 strategic bomber and the EF-111 electronic warfare aircraft, were also developed.
The F-111 entered service in 1967 with the United States Air Force (USAF). In the meantime, the Australian government had ordered the F-111C, to replace the English Electric Canberra then used by the Royal Australian Air Force (RAAF). The F-111C entered service with the RAAF in 1973.
As early as March 1968, the USAF was deploying F-111s into active combat situations; the type saw heavy use during the latter half of the Vietnam War to conduct low-level, ground-attack missions, flying in excess of 4,000 combat missions while incurring only six combat losses in the theater. The F-111s also participated in the Gulf War (Operation Desert Storm) in 1991; the F-111Fs completed 3.2 successful strike missions for every unsuccessful one, better than any other US strike aircraft used in the operation. RAAF F-111s never saw offensive action, but were deployed periodically as a deterrent, such as for the Australian-led International Force East Timor.
Being relatively expensive to maintain amid post-Cold War budget cuts, the USAF elected to retire its F-111 fleet during the 1990s; the last F-111Fs were withdrawn in 1996, while the remaining EF-111s also departed in 1998. The F-111 was replaced in USAF service by the Strike Eagle for medium-range, precision strike missions, while the supersonic bomber role has been assumed by the B-1B Lancer. The RAAF continued to operate the type until December 2010, when the last F-111C was retired; its role was transitioned to the Boeing F/A-18E/F Super Hornet as an interim measure until the Lockheed Martin F-35 Lightning II became available.
Development
Early requirements The May 1960 U-2 incident, in which an American CIA 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 surface-to-air missile that could reach aircraft above 60,000 ft (18,000 m). Consequently, the USAF 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.Lax 2010, p. 15.
By 1960, SAC had begun moving to 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.Spick 1986, pp. 4–7. 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 Thunderchief, which was designed to deliver nuclear weapons fast and far, but required long runways.Gunston 1978, pp. 12–13. A simpler 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.Thomason 1998, pp. 5–6.Davies 2013, pp. 6-7. This led USAF leaders to encourage its use.Miller 1982, pp. 10–11.
In June 1960, the USAF issued specification SOR 183 for a long-range, interdiction/strike aircraft able to penetrate Soviet air defenses at very low altitudes and high speeds. Specifically, it was to be capable of at least of low-level flight, half of which was to be at a speed of no less than Mach 1.2.Knaack 1978, p. 223. 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 . An internal payload of was to be carried in the primary mission role. A variant suitable for aerial reconnaissance flights was also included in the specification.Knaack 1978, pp. 223-224.
Around this time, the United States Navy had been seeking a long-range, high-endurance, fleet air defense fighter to protect its carrier battle groups against long-range antiship missiles launched from Soviet jet bombers and submarines. It would need a more powerful radar and longer-range missiles than the F-4 Phantom II it would replace.Thomason 1998, pp. 3–5.Davies 2013, p. 7. The Navy had proposed a subsonic, straight-winged aircraft, the Douglas F6D Missileer in the late 1950s. The Missileer could carry six long-range missiles and loiter for five hours, but would be defenseless after firing its missiles. The program was formally canceled in 1961. The Navy had tried variable-geometry wings with the XF10F Jaguar, but abandoned it in the early 1950s.Davies 2013, p. 6. NASA's simplification made the variable-geometry wings practical. By 1960, increases in aircraft weights required improved high-lift devices, such as variable-geometry wings.Miller 1982, p. 11. Variable geometry offered high speeds, and maneuverability with heavier payloads, long range, and STOL capability.
Tactical Fighter Experimental The USAF and Navy were both seeking new aircraft when Robert McNamara was appointed secretary of defense in January 1961.Miller 1982, p. 13. Both sought high-supersonic, twin-engined, two-seat aircraft that could carry heavy armament and fuel loads and probably use variable-geometry wings.Davies 2013, p. 4. 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. In June 1961, Secretary McNamara ordered the go-ahead of Tactical Fighter Experimental (TFX), despite USAF and Navy efforts to keep their programs separate. According to aviation author Peter E. Davis, military officials were disconcerted by McNamara's focus on compromised requirements for financial reasons.Davies 2013, pp. 4-5.
The two services could agree only on swing-wing, two-seat, twin-engined 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 radar operator to share the radar display.Knaack 1978, p. 224. Also, the USAF wanted the aircraft designed for 7.33 g with Mach 2.5 speed at altitude and Mach 1.2 speed at low level with an approximate length of . The Navy had less strenuous requirements: 6 g with Mach 2 speed at altitude and high subsonic speed (about Mach 0.9) at low level with a length of . The Navy also wanted the aircraft with a nose large enough for a diameter radar dish.Miller 1982, pp. 11–15.
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. Nevertheless, a request for proposals for the TFX was provided to industry in October 1961.Knaack 1978, pp. 224-225. In December, proposals were received from Boeing, General Dynamics, Lockheed, McDonnell, North American, and Republic. The evaluation group found all the proposals lacking, but Boeing and General Dynamics were selected to submit enhanced designs.Knaack 1978, p. 225. Boeing's 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 seats 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. Two more rounds of updates to the proposals were conducted, and the board eventually recommended the Boeing design.
But in November 1962, McNamara selected General Dynamics' proposal due to its greater commonality between USAF and Navy versions. The Boeing aircraft shared less than half of the major structural components. On 21 December 1962, General Dynamics signed the TFX contract.Knaack 1978, pp. 225-226. A congressional investigation into the procurement process was conducted, but did not change the selection. 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 incentive-fee (FPIF) contract with a ceiling price of $529 million, along with provisions for deficiency correction among other operational clauses and performance criteria.Knaack 1978, p. 226.
Design phase General Dynamics' design team was led by Robert H. Widmer. 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.Knaack 1978, p. 236. The General Dynamics and Grumman team faced ambitious requirements for range, weapons load, and aircraft weight.Thomason 1998, pp. 9–10. 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.Miller 1982, pp. 17, 19. This use of unfamiliar features has been attributed as a major cause of the aircraft's protracted development and weight increases.Davies 2013, p. 5.
The F-111A and F-111B shared the same airframe structural components and Pratt & Whitney TF30-P-1 turbofan engines. They featured side-by-side crew seating in an escape capsule as required by the Navy. The F-111B's nose was shorter as the aircraft could fit on existing carrier elevator decks, and had 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.Baugher, Joe. "General Dynamics F-111A." USAAC/USAAF/USAF Fighters, 23 December 1999. Retrieved: 5 October 2009.
During September 1963, the F-111A mockup was inspected. On 15 October 1964, the first test F-111A was rolled out of 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. On 21 December 1964, the F-111A made its first flight from Carswell Air Force Base, Texas. 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.Knaack 1978, pp. 226-227. Early flights of the F-111, which included supersonic flights, demonstrated favorably simplistic maintenance requirements, among other qualities.Knaack 1978, p. 227.