On Sept. 10, 1956, test pilot Bob Baker took off from Edwards Air Force Base, Calif., to complete the maiden flight of the knife-like YF-107A. Baker reached Mach 1.03. The flight met all its goals and officials from planemaker North American whooped it up. They were certain their new fighter would soon roll out of factory doors in great numbers for the U.S. Air Force. As if to signal a bright future, officials soon dropped the “Y” prefix, which meant “service test.”
But the F-107 became a “might-have-been,” a solid performer that didn’t quite make the grade – described by one observer as “the best Air Force fighter never to go into production.” On the web site Suite 101, author Ivan Castro wrote that the Air Force’s “rejection of the F-107 … is considered one of the greatest military blunders of all time.”
The F-107 was conceived as a nuclear-capable, fighter-bomber version of the F-100 Super Sabre, with a recessed weapons bay under the fuselage. One requirement was to carry the 1,680-pound Mark 7 tactical nuclear gravity bomb as well as smaller nuclear bombs that were expected in the near future. When the centerline recess was not used for ordnance, an additional fuel tank could be carried.
The Air Force gave the go-ahead for 33 aircraft, at the time called F-100B models, on June 11, 1954. The designation was changed to F-107A on July 8, 1954, mostly to reflect changes from the Super Sabre design, including a longer fuselage, an all-moving vertical fin, an automated flight control system, and a system (a variable area inlet duct) that automatically controlled the amount of air fed to its 24,504-pound thrust Pratt & Whitney YJ75-P-9 turbojet engine.
The second and third F-107s made their initial flights on Nov. 28 and Dec. 10, 1956. The third plane introduced the fully automatic variable area inlet duct, the one feature of the F-107 that retained “bugs” throughout tests. Pilots reported an annoying “buzz” in the variable-geometry duct at high altitude.
In flight trials, the F-107 performed well. It achieved Mach 2.0 on Nov. 3, 1956. Pilots praised the aircraft and, contrary to its appearance, were not worried about being swallowed up by its engine: Because of the unusual location of the air intake, it was necessary for the canopy to open straight up rather than in clamshell fashion. But the F-107 was not “ejection unfriendly.” In an emergency, the pilot could eject right through the canopy without having to jettison it first.
Rather than ailerons, the aircraft used spoilers, which enabled it to roll with ease at supersonic speeds.
The F-107 was armed with four, single-barrel Pontiac M39E 20 mm. cannons (not installed on the No. 1 aircraft) and had six under-wing ordnance points in addition to its fuselage center station. This recessed weapons point was semi-conformal, meaning it was partly external, and it became what the Air Force considered the most important difference between the F-107 and its competitor, the Republic F-105 Thunderchief, which had a fully internal weapons bay.
In aviation literature today, the F-107 is often called the Ultra Sabre. Observers who recall the aircraft during the 1950s don’t remember this name ever being coined or used. North American flirted with the idea of calling the F-107 the Super Super Sabre, but this did not catch on.
While the sleek F-107 turned heads and thrilled aviation enthusiasts, the less glamorous and more trouble-prone F-105 Thunderchief was being developed by Republic. The planemaker needed the business. Its F-84 series of fighters was at the end of its production run. Many observers believed the Air Force would purchase the F-107 but would arrange for hungry Republic, rather than busy North American, to manufacture the latter company’s aircraft. Besides, North American was expected to win a handsome contract with a separate project, its XF-108 Rapier long-range interceptor.
Henry Crescibene, a Republic test pilot who performed early work on the F-105, remembers being told to prepare for the F-107.
“Our perception was that the Air Force liked North American and liked North American’s design better than ours,” Crescibene said in a telephone interview.
In March 1957, in an announcement that astonished many, the Air Force chose the F-105 in preference to the F-107. Although prototypes had been flying since Oct. 22, 1955, the first two F-105 variants had lacked the intended J75 engine and both made crash landings in March 1956, with their pilots unhurt but the aircraft mortally damaged. Although a J75-equipped version flew on May 26, 1956, the Thunderchief had a wide range of teething troubles. A direct fly-off competition with the F-107 had to be cancelled because the F-105 was not ready.
Once it became clear the F-107 would not be produced, the first and third airframes were transferred on Dec. 1, 1957, to the National Advisory Committee for Aeronautics (NACA). With the Soviet Union’s first satellite already placed into orbit, the space age was arriving and NACA became NASA seven months layer.
Test pilot Scott Crossfield severely damaged the No. 3 F-107 in a crash landing and it was later scrapped.
The Air Force order for 33 planes was reduced to three. The No. 1 aircraft in the series is now an artifact at the Pima Air and Space Museum in Tucson, Ariz. The No. 2 F-107 is on display at the National Museum of the United States Air Force in Dayton, Ohio. As for the F-105, the “Thud” achieved fame in missions over North Vietnam, where its all-important internal weapons bay never carried anything more lethal than a 365-gallon fuel tank.