Competitors to the F-111 Aardvark from the LA area

The General Dynamics F-111 Aardvark fighter-bomber is one of the most controversial combat aircraft of the Cold War era to have entered service with the United States Air Force, ridiculed by several American politicians as the "Flying Edsel". Despite having a rocky start to its combat career during the Vietnam War in 1968 and congressional criticism, it eventually overcame several technical problems and became best known for conducting airstrikes on Libya on April  15, 1986 as part of Operation El Dorado Canyon, the US Air Force military operation to hold Libyan dictator Colonel Muammar al-Gaddafi accountable for his backing of international terrorism, including a bomb blast at a discotheque in West Berlin ten day earlier. The F-111 also was adapted for use as an electronic countermeasures (ECM) platform (EF-111 Raven) and an interim strategic bomber (FB-111), and it served with some USAF tactical combat units until the 1990s, when it was retired and replaced by the F-15E Eagle. In the past few years, I saw the F-111 in person for the first time, encountering a derelict  F-111D at the Yanks Air Museum and an FB-111 at the March Field Air Museum. Given that the F-111 was built by the Convair Fort Worth Division of General Dynamics in Forth Worth, Texas, I thought it would be worthwhile to discuss on this post rival designs from the Los Angeles area envisaged for the TFX (Tactical Fighter Experimental) contest that led to the F-111.

Fuselage hulk of a General Dynamics F-111D (serial number 68-0092) in the storage facility of the Yanks Air Museum in Chino, California. The General Dynamics F-111 design outcompeted the Boeing 818, Lockheed CL-590, and other designs in the TFX competition.

In 1958, the US Air Force began shopping for a new Mach 2 all-weather fighter that could also perform vertical takeoff and landing, but the SDR-17 (System Development Requirement) specification issued in February 1960 dropped the need for VTOL capability; the SDR-17 requirement was covered by US Air Force specification WS-324A. The SOR-183 requirement, which superseded SDR-17 in July, called for a two-seat Mach 2.5 fighter-bomber with all-weather capability and STOL performance to replace the Republic F-105 Thunderchief fighter-bomber, capable of carrying 15,000 lb (6,804 kg) of external stores and able to fly at an altitude of 60,000 feet (18,288 meters) with a low-level combat radius of 921 miles (1,482 km). However, plans to issue a Request for Proposals in October was put on hold, and by December the SOR-183 requirement was christened the TFX. After John F. Kennedy entered the White House, his Secretary of Defense, Robert S. McNamara, a staunch critic of manned strategic bombers and feverish advocate of intercontinental ballistic missiles, sought a new fighter-bomber to satisfy the parameters spelled out in the initial SOR-183/TFX requirement and the US Navy's VAX requirement for an A-4 Skyhawk replacement (which led to the Vought A-7 Corsair II), and in June 1961 he gave the go-ahead for the TFX program to proceed, culminating in September a revised SOR-183 requirement for a multi-role TFX. The proposed Air Force version was to have a maximum weight of 60,000 lb (27,216 kg) while the Navy all-weather fighter-bomber would weigh 55,000 lb (24,948 kg) with full avionics suite comprising an airborne missile control system to provide fire control, multiple target detection and tracking, and the multiple launch of long-range air-to-air missiles. Six designs for the TFX competition were submitted in late September by Boeing, General Dynamics plus Grumman, Republic plus Vought, Lockheed, McDonnell plus Douglas, and North American, all of them featuring swing wings.

Top: Drawing of the Lockheed CL-507-27, ancestor of the CL-590 project.
Bottom: Drawing (left) and full-scale mockup (right) of the CL-590 design for the TFX competition. 

In the run-up to the initiation of the TFX contest, in 1960 Lockheed had envisaged several design studies for a heavy STOL fighter-bomber under the designation CL-507. The first CL-507 iteration, the CL-507-1-1, had tapered fixed wings, a pair of jet engines in the rear fuselage, a length of 73 feet 2 in (22.30 meters), a wingspan of 43 feet 2 in (13.16 meters), and a wing area of 620 square feet (57.66 square meters). The next design study, called CL-507-4, had swing wings, two jet engines in individual pods, a length of 80 feet 6 in (24.54 meters), and a wingspan of 51 feet 4 in (15.65 meters), with the total wing area being 500 square feet (46.50 square meters) when the wings were in forward position or 458 square feet (42.59 square meters) when the wings were swept. The CL-507-5 was a delta wing proposal with canards as well as podded jet engines and a pair of 12,200 lb (54.2 kN) thrust lift fans in ahead of and behind the main landing gear, with a length of 94 feet 4 in (28.75 meters), a wingspan of 34 feet 8 in (10.57 meters), and a wing area of 600 square feet (55.80 square meters). The CL-507-27 was similar to the CL-507-4 in being a swing-wing design but differed in having the jet engines housed in the rear fuselage, and it was 77 feet 4 in (23.57 meters) long with a wing area of 500 square feet (46.50 square meters) and a wingspan of 60 feet (18.29 meters) when the wings were in forward position; the wings were swept at 20 degrees for subsonic speed and at 90 degrees in supersonic flight. After the TFX competition was announced by McNamara, in December 1961 Lockheed submitted a design for a multirole fighter-bomber under the designation CL-590, and eight versions were devised. The CL-590-1, the only variant for which company drawings are extant, had wings that spanned 60 feet 6  in (18.44 meters) in forward position and 29 feet 8 in (9.04 meters) when fully swept, and it would have attained Mach 1.2 at sea level and Mach 2+ at altitude. The Air Force and Navy versions of the CL-590-1 slightly differed in length and gross weight, with the Air Force variant being 67 feet 5 in (20.54 meters) long and weighing 59,209 lb (26,857 kg) fully loaded, whereas the Navy variant was 65 feet 8 in (20.02 meters) long with a gross weight of 55,000 lb (24,948 kg). Power was supplied by two General Electric MF295A turbofans mounted alongside the sides of the rear fuselage, and the crew sat in a tandem fashion, and armament provisions were made for different types of air-to-surface missiles and bombs. The pylons for mounting ASMs or bombs would have had to rotate in order to remain parallel with the fuselage of the CL-590-1 as the wings were swept forward or back. 

Artist's rendering of the US Air Force version of the one of North American's designs for the TFX competition 

Very little technical information exists for the TFX design studies from North American Aviation, apart from artist's conceptions by North American, which were recently uncovered in the Boeing archives. However, North American apparently investigated three TFX configurations, all similar to each other in having a long, sleek fuselage, a raised cockpit canopy and forward fuselage, and turbofans mounted side-by-side in the rear fuselage. The primary design (which includes the only available images of the Air Force and Navy versions) featured side-fuselage air intakes below the fixed inner wings and twin vertical stabilizers, and second design was similar to the first but with the air intakes positioned further forward to the fixed inner wing's leading edge. The third proposal had a single vertical stabilizer along with a distinct jet pipe arrangement and forward-swept intakes for the turbofans ahead of the wing roots (Buttler 2021, pp. 229-232). Mention must be made of the fact that the El Segundo Division of Douglas was enlisted as a team member by McDonnell for that company's Model 156 submission, which was investigated in both side-by-side and tandem seating arrangements for the crew. The Air Force and Navy versions of the Model 156 with side-by-side seating were 80 feet 8 in (24.59 meters) and 65 feet 6 in (19.96 meters) in length respectively, while the tandem seating proposals were slightly smaller, with the Air Force design 73 feet (22.25 meters) long and the Navy design measuring 62 feet (18.90 meters) long. Armament provisions for the Air Force version included GAM-83 Bullpup and GAR-8/AIM-9 Sidewinder missiles as well as demolition and fire bombs, while the Navy variant would have been armed with long-range air-to-air missiles or AIM-7C Sparrow III AAMs, Bullpups, and demolition and napalm bombs (Butler 2010, p. 138).   

On November 24, 1962, the Defense Department declared the General Dynamics/Grumman design the winner of the TFX competition, largely because the Air Force and Navy variants of the GD/Grumman submission had greater commonality compared to other contending designs, and on December 21, the aircraft was designated F-111, with an order placed for 18 F-111As (to be built by General Dynamics) and five F-111Bs (to be built by Grumman). The F-111A took to the skies on December 21, 1964, and in spite of engineering problems early in the F-111's service life, over 550 F-111s were built, serving not only in the Vietnam War but also in Operation El Dorado Canyon and Operation Desert Storm in early 1991. 

References:

Buttler, T., 2010. American Secret Projects: Bombers, Attack, and Anti-Submarine Aircraft 1945 to 1974. Hinckley, UK: Midland Publishing.

Buttler, T., 2021. American Secret Projects 4: Bombers, Attack, and Anti-Submarine Aircraft 1945 to 1974. Manchester, UK: Crécy Publishing.