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North American’s F-107 Was the “Ultra Sabre” and Perhaps the “Ultra Might-Have-Been”

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.”


Atomic Bomber

F-107A color on runway

The number two F-107 fighter at the National Museum of the U.S. Air Force in Dayton, Ohio. Note the semi-recessed carriage of the fuel tank beneath the fuselage, which was designed to carry a nuclear free-fall bomb. U. S. Air Force photo

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.

One of NASA’s two F-107As on the dry lake bed at Edwards AFB. This photo shows the spoilers atop the wing and absence of ailerons, the strong family resemblance to the F-100 Super Sabre in wing and tail surfaces, and the all-moving slab elevators and vertical stabilizer. NASA photo

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.


Turning Heads

F-107A delivered to NACA

The arrival of the first F-107A at NACA (later NASA) in November 1957. Note the unusual configuration of the open canopy. NASA received the first and third F-107As for flight testing. Among other things, an F-107A tested a sidestick controller, forerunner of those used in the F-16, F-22 and F-35 today. NASA photo

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.


Robert F. Dorr is an author, U.S. Air Force veteran, and retired American diplomat who...

    li class="comment even thread-even depth-1" id="comment-22823">
    John Fredrickson

    I had the pleasure of processing the photos from that program – NA212. There were several record storage boxes full of negatives – but no prints. Based on the photo record, there was a “non-fatal” accident on the first flight – which was on 9/10/1956. Some F-107 photos were classified for a year; however, these photos were classified until 1964 – which was eight (8) years after the incident. The photos show the airplane stopped off the runway, in a nose down attitude, the radar dome is gone, and the forward bulkhead was pushing a few inches of soil. The nose wheels / tires are broken off and lying some distance from the hulk. The nose gear is collapsed, and the canopy is open. There are lengthy skid marks on the runway and the main gear tires are heavily scuffed. Photos indicate the drag chute still in place in its compartment and NOT deployed. Cockpit photos show the drag chute lever in the out (e.g. deployed) position. Additional photos show the spring loaded pilot chute (to the drag chute) laying on the runway. The lanyard between drag chute and main chute was broken and this, to me, appeared to be the root cause for the accident. The damaged F-107 was lifted by crane and trucked away before the sun went down. Re – ejection seat tests: There were not only static tests of the ejection seat but also a rocket powered sled was built to run on heavy rails. Ten (10) test runs of the rocket sled were documented. I suspect this amount of testing was dictated because of the air inlet immediately aft of the canopy. Yes, one of the tests included ejection through the canopy. The crash dummy for the final test was clad in a pressure suit.

    li class="comment byuser comment-author-chuck-oldham odd alt thread-odd thread-alt depth-1" id="comment-22914">

    Thanks for commenting. It’s always great to hear from someone who was actually there. I wonder where all those photos are now? There were stories, when Fairchild-Republic closed up shop, that all their historical photos were literally thrown into a dumpster. Boeing seems to have more appreciation for history.

    li class="comment even thread-even depth-1" id="comment-202797">

    PS. It was Scott Crossfield who ranoff the runway and damaged the 107.