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In the late 1950s, the main mission of the U.S. Air Force’s Tactical Air Command was using fighter-bombers for deep strike against Soviet targets using tactical nuclear weapons.
For this mission, TAC needed an aircraft with very long range that could fly at very low altitudes and very high speeds, but at the same time have good range and reasonable short-field performance. In June 1960, the USAF issued a specification for a fighter-bomber with a low-level speed of Mach 1.2, a high-altitude speed of Mach 2.5, a combat radius of about 900 miles, ferry range long enough to reach Europe without refueling and reasonable short-field performance. The first priority was high speed at low level and, to get this, two engines and a variable geometry “swing” wing would be required.
At about the same time, the U.S. Navy was searching for a long-range air-to-air inter-ceptor/fighter to defend its carrier battle groups against Soviet jet bombers armed with long-range anti-ship missiles. The aircraft would have to carry large radar and a number of big, very long-range missiles and also be able to fight at close range. Such an aircraft would be large and heavy, so to land on and take off from a carrier – the first priority for the Navy – the service settled on a variable geometry “swing” wing and two engines, for entirely different reasons than the Air Force had made the choice.
Neither the Air Force nor the Navy paid much attention to the other’s design, but in February 1961, the new Secretary of Defense, Robert McNamara, introduced “commonality” into the defense lexicon. “Commonality” was the idea that the same aircraft with slight modifications could fulfill even different missions for both the Air Force and Navy, with the concomitant savings involved in developing only one aircraft instead of two.
Focusing on “a fighter with variable geometry wings and two engines” idea, Secretary McNamara formally directed that the Air Force and Navy study the development of a single aircraft that would satisfy both requirements. The two services were dismayed because of their different requirements – the USAF wanted tandem seating in a fighter with a capability to pull 7.33 Gs and fly at Mach 1.2 at low level, while the Navy wanted an inter-ceptor with side-by-side seating, capable of pulling 6 Gs and only high subsonic speed, Mach 0.9, at low level. The Navy was even more dismayed when a study showed the best option was to base the new fighter – Tactical Fighter, Experimental – on the Air Force requirement and use a modified version for the Navy.
In June 1961, Secretary McNamara ordered the go-ahead on TFX and in December 1961, Boeing and General Dynamics were selected for the final design. The Air Force favored Boeing’s offering, while the Navy found both submissions unacceptable. Secretary McNamara selected General Dynamics’ proposal in November 1962 because of its greater commonality between Air Force and Navy TFX versions. By this time, the Navy was totally disenchanted with the idea, but agreed if Grumman Aircraft Corporation – a long-time builder of Navy aircraft – was allowed to participate. The USAF’s F-111A and USN’s F-111B used the same airframe structural components, turbofan engines and side-by-side crew seating in escape capsule. The main difference was that the F-111B’s nose was more than eight feet shorter to fit on carrier elevators and it carried six AIM-54 Phoenix missiles and their large associated radar.
The first F-111B made its first flight – without the escape capsule – on May 18, 1965 and had its Naval Preliminary Evaluation in October 1965. But by then it was already in trouble – it was seriously overweight at 78,000 pounds, well over the upper limit of 55,000 pounds, was grossly underpowered and its range was below specifications. General Dynamics cut a great deal of weight to try to bring it down to 55,000 pounds, but the fourth F-111B was fitted with an escape capsule that more than offset the weight savings achieved by the weight reduction program.
General Dynamics installed more powerful engines but, by October 1967, the Navy was publically saying that the F-111B was a lost cause and in mid-1968, the program was canceled. With a sigh of relief, the Navy turned to Grumman for a new, twin-engine fighter with the Phoenix – the F-14 Tomcat – and leading to speculation that Grumman had been less than enthusiastic about supporting General Dynamics and the F-111B.
Questions or comments, contact Dr. Michel at marshall.michel@ramstein.af.mil.
