The F-111 originated in studies for a replacement for Tactical Air Command's F-100 Super Sabres and F-105 Thunderchiefs in the tactical strike role. Tactical Air Command wanted an aircraft which could operate from shorter runways. They also required a longer ferry range as overseas deployments by F-100s were often limited by refuelling problems. The aircraft would also be optimized for very low-level penetration, including a final 370 km dash at Mach 1.2. It would be a multi-role aircraft, capable of Mach 2.5 at high level in the interceptor role. This made it inevitable that the successful design would have a variable geometry, swing wing.
Glueing on the fighter role and the demand for Mach 2.5 capability immediately made the F-111 designers jobs more difficult. Their task, however, would soon be immeasurably complicated by the incoming Secretary of Defense, Robert McNamara. He directed that the USAF (whose primary requirement was still for a low-level strike aircraft) and the US Navy (who need a long-range carrierborne interceptor) should acquire a common aircraft. This became known by the acronym TFX.
Both services initially welcomed the joint common fighter, until it became clear that no single airframe could meet all the different requirements. By then, however, the bit was between McNamara's teeth, and he drove the program forward. Boeing and General Dynamics competed for the lucrative TFX contract, which was awarded to the latter company (the military favored the Boeing submission) in November 1962. The General Dynamics design was more of a compromise, and the US Navy and USAF versions were variants of a common airframe. The Boeing aircraft, however, was tailored more closely to the USAF requirement, while the Boeing Navy version had relatively little commonality with the USAF variant. McNamara was later accused of having bought the second best airplane at the higher price.
Technical difficulties, barely controlled weight growth and massive cost escalation characterized the remainder of the TFX's development. During wind-tunnel testing severe drag problems were encountered. Weight reduction programs on the naval version reduced commonality to a mere 28 per cent or so, before the F-111B altogether, and replaced by the F-14 Tomcat.
The first F-111A made its maiden flight on December 21, 1964, and soon ran into further problems, not least of which was the TF30 engine. This would later severely compromise the F-14 programme as well!
Once the aircraft entered service with the USAF's evaluation unit, the General Dynamics F-111 began to win friends. The aircrews were blown away by the aircraft's performance and its automatic terrain following capability. Engineers were impressed by its reliability and maintainability.
Even before CAT 1 testing was complete, in March 1968, six aircraft were deployed to Vietnam for the Combat Lancer evaluation. These soon demonstrated their combat effectiveness. But things soon went wrong after three aircraft failed to return from routine missions. They had all crashed due to structural fatigue failures. This eventually led to a fleet-wide grounding and a cripplingly expensive series of modifications and fixes.
The engine intakes were redesigned, and avionics were improved, resulting in a succession of sub-variants. The definitive F-111D finally entered service in October 1971. The further improved F-111F (with more powerful engines, improved avionics and Pave Tack pods for laser designating) followed in early 1972. Strategic Air command even acquired two Wings of FB-111s. These were dedicated strategic nuclear strike aircraft, each carrying a pair of SRAMs. These aircraft were eventually converted to F-111G standards and were returned to the tactical role.
The Australians must have rued their selection of the General Dynamics F-111 over the BAC TSR2 during the long years of delay and disappointment. The 24 aircraft, which should have a cost A$112 million, were supposed to have been delivered from 1973, and cost almost twice as much! The RAF did not have the opportunity to regret its involvement in the F-111 program, since none were ever delivered. Britain had cancelled its 50-aircraft order mainly because the United States could not give a fixed price!
During the final years of its USAF career, the Aardvark finally lived down its unfortunate early history. It was, however, never capable of the kind of austere-strip STOL operations once envisaged for it. The F-111 was tied to long concrete runways as its predecessors had been. Time and again, the F-111 proved invaluable in precision attacks against vital targets. After attacking targets in Libya in 1986, the F-111F played a vital role in the Gulf War. Some claimed that the elderly Aardvark was actually the USAF's most effective and accurate precision guided munitions and laser guided bombs delivery platform. Unfortunately, though, Operation Desert Storm proved to be something of a final swansong for the General Dynamics F-111.
With pressure for post-Cold War defense economies becoming increasingly difficult to resist, the USAF finally withdrew its last F-111 bombers in July 1996. The EF-111A electronic warfare and defense suppression aircraft followed during 1998. This allowed the USAF to stop supporting an entire aircraft type, with corresponding savings in logistics support costs.
The F-111 remains in service with the RAAF, who use the aircraft in the attack and reconnaissance roles. The RAAF's aircraft have been comprehensively upgraded and modernized with digital avionics, and are able to use the latest precision-guided munitions. Australia's original batch of 24 F-111Cs (four of them locally converted to RF-111C standards). These aircraft were then augmented by four F-111A attrition replacements delivered in 1982, and by 15 ex-USAF F-111Gs delivered in 1993. These will allow the Australian F-111 fleet to the maintained in service until 2020.