The F-111's versatility did not exist in one airframe. The navalized F-111B had a single mission of fleet air defense (FADF). Its outstretched wings would allow a long time on station, then swept back, it would dash to meet oncoming targets and clear the sky with its 6 heavy AIM-54 Phoenix missiles. It was never meant for combat air patrol or escort. Whoever had written up the requirements never fitted it with armament as basic as a gun or even the simple AIM-9 Sidewinder fielded by the F-8 Crusader. Neither would it be equipped to deliver bombs, even though the nearly identical F-111A had a prodigious range, payload and low level navigation capabilities far exceeding either the A-6 Intruder or A-5 Vigilante. Similarly, the F-111A was not equipped to fire missiles like the Phantom's AIM-7 Sparrow. The winning contractor General Dynamics chose Grumman to apply their carrier aircraft expertise to the F-111B. However adapting what was really a medium low-level bomber meant compromises such as a smaller radar than the Navy required, it was drastically overweight at nearly 80,000 lb at takeoff. It was judged underpowered, as agile as a Greyhound bus, and its visibility was judged ill-suited to carrier operations.
When the Navy ordered Grumman to study the effectiveness of the F-111B in such a scenario, they concluded it was much less maneuverable than the F-4, and would not survive in a dogfight. The silver lining was that the F-111B's performance was so abysmal, and the penny wise approach to fighter design was so discredited, that both the Navy and USAF embarked on studies on what would become a generation of 4 new air superiority fighters. The Navy's counterpart to FX was VFAX (Navy Fighter Attack Experimental). It called for a lightweight fighter that would complement the F-111B. It would be a more agile fighter than the F-4 and a more effective bomber than the A-7.
The F-14 has often been called "underpowered", but using the Pratt & Whitney TF30 engines from the cancelled F-111B reduced weight and gave it a better thrust to weight ratio than any previous US fighter. Increased thrust to weight ratio improves sustained turn rates. While the F-14 was designed to accommodate future engines to provide a thrust to weight ratio of greater than 1.0, the versions which would rival the F-15 Eagle in power would not appear until late in its career. Rather than the F-111B's single Phoenix load out, the F-14 would be able to carry and deliver everything larger than a 20mm shell to almost anything smaller than the B-52's massive AGM-28 Hound Dog strategic missile. The 20mm M61 Vulcan Gatling gun, previously fitted to the USAF F-4E variant of the F-4 Phantom II was incorporated to destroy maneuvering targets at very close range.
According to Bill Gunston, the F-14 would employ essentially swinging versions of the same wings used by Grumman's A-6 Intruder subsonic bomber. It had not only a large wing area, but a wide, flat pancake body to increase lift and lower drag. Flaps and slats could be deployed at full forward sweep for full maneuverability even at combat speeds, while special maneuvering flaps were designed, though later disabled after tests showing reduced stability. This gives an edge to the F-14 at very slow and supersonic speeds compared to fixed wings optimized for low supersonic speeds. Engineering manager Bob Kress says that the wings gave very good turning performance. Maneuverability was predicted to be twice that of the F-4, especially at high speed and altitude, later verified in tests against F-4Js.
The F-14 with wings at full forward sweep resembles a huge bat. Since the adoption of the F-14, the fighter slang term "bat turn" has been used to describe a maximum G 180 degree turn in full afterburner, a signature tactic of Tomcat crews. Aviation writer Bill Gunston, however notes that opposing pilots have learned to read the F-14's wings to judge its energy status and speed.
When the Navy saw Grumman's design that combined the capabilities of the F-111B and the VFAX in a single airframe, plans would be dropped to adopt a mixed fleet of F-111B interceptors and small agile VFAX planes. The Navy hastily rewrote the VFX (Navy Fighter Experimental) specification in July 1968 evidently around Grumman's innovative proposal for an agile VFAX air superiority and strike fighter that could also carry the AWG-9/Phoenix for a fleet air defense in a single type in a form of commonality quite different from that promoted by the TFX. Though later offered to the Air Force, their FX would become a single seat, fixed wing fighter unburdened by heavy Phoenix missiles, the F-15 Eagle which would be delayed until the development of new technology engines, though planners designed in interchangeability between core engine design parameters.
On January 14, 1969, the Navy announced the award of the contract for the VFX fighter, now designated F-14, to Grumman. It would be introduced in a brief captioned photo of an aircraft with canards in Flight Magazine International as the "VFX air superiority fighter". The F-14 would inherit not only the F-111B's radar / missile system and TF30 engines, but also adapt the subsonic wings, landing gear, and inlets of the A-6 Intruder, which lowered costs. Upon being granted the contract for the F-14, Grumman greatly expanded its Calverton, Long Island, New York facility to test and evaluate the new swing-wing interceptor. Much of the testing was in the air of the Long Island Sound as well as the first few in-flight accidents, including the first of many compressor stalls and ejections.
The Navy planned a series of upgrades, with F-14A assigned to the first airframe equipped with updated TF30 engines and the AN/AWG-9 weapons system from the F-111B. Its first flight took place on December 21, 1970. The original plan was to only build a few F-14As, as the TF30 was known to be a troublesome engine. In addition, the engine was not designed for rapid thrust changes or a wide flight envelope and only supplied 74% of the intended thrust for the F-14. An F-14B would follow in November 1987 using the engine from the advanced technology engine competition. The F-14C was intended to denote a variant implementing a replacement for the AN/AWG-9. However, it was delayed, and this variant was never produced. When it finally arrived as the AN/APG-71, the designation assigned to the new aircraft was F-14D, which first flew November 24, 1987. Though the Marine Corps initially sent pilots to VF-124 to train as instructors, the Corps pulled out of the program in 1976, after deciding the F-14 was too expensive for their needs.