Sixty years ago this month, the USAF/North American F-107A aircraft flew for the first time. Interestingly, the Mach 2-capable fighter-bomber prototype went supersonic on its maiden flight.
The F-107A was designed, developed and tested by North American Aviation (NAA) in the mid-1950′s. With it, the contractor hoped to satisfy Tactical Air Command’s (TAC) need for a front line fighter-bomber. However, Republic Aircraft also had a candidate for the same role; the F-105 Thunder Chief.
The competition between Republic and North American for the TAC fighter-bomber production contract has a story of its own. Suffice it to say here that the competitive effort was (1) extremely close and (2) tinged with political intrigue. In the end, Republic Aircraft reaped the spoils of victory.
Although the F-107A came out on the short end of the stick in the TAC fighter-bomber competition, such did not imply an inferiority in fulfilling the intended role. Indeed, like the Northtrop YF-23′s loss to the General Dynamics YF-22 in the ATF competition of the early 1990′s, North American’s failure to get the nod with the F-107A is still a subject of passionate debate.
The F-107A measured 60.8 feet in length and had a wing span of 36.6 feet. Gross take-off weight was around 41,000 pounds. The aircraft was powered by a single Pratt and Whitney YJ75-P-11 turbojet that produced 15,500 pounds of thrust in military power and 23,500 pounds of thrust in full afterburner.
F-107A longitudinal control was provided by an all-flying horizontal tail. Similarly, an all-flying vertical tail was employed for directional control. Lateral control was provided by a unique 3-segment spoiler-deflector system mounted on each wing. The aircraft was also configured with inboard flaps and leading edge slats for lift augmentation at low speeds.
A unique and prominent feature of the F-107A was its dorsal-mounted air induction system known as the Variable-Area Inlet Duct (VAID). Internally, this unit incorporated a system of adjustable ramps to efficiently decelerate and compress freestream prior to entering the engine compressor face. Ramp deflection scheduling with Mach number was controlled automatically. Ramp boundary layer bleed air was vented from the top of the VAID.
The F-107A carried weapons externally. In addition to wing pylon-mounted stores, the aircraft was designed to carry a single “special weapon” from a semi-submerged recess located on the aircraft ventral centerline. The term “special weapon” means that it was a tactical nuclear bomb. The Sandia-developed store could also be used in combination with a special saddle fuel tank to extend aircraft range.
A total of three (3) F-107A aircraft were built and flown. USAF-assigned tail numbers include 55-5118, 55-5119 and 55-5120. On Monday, 10 September 1956, the No. 1 ship (55-5118) took-off from Edwards Air Force Base on its first flight. NAA Chief Test Pilot Robert Baker, Jr. was at the controls. The aircraft attained a maximum Mach number of 1.03 in a 43 minute flight test.
The F-107A could really scream. The type had a maximum climb rate of around 40,000 feet per minute in full afterburner. The max demonstrated Mach number attained by the F-107A was Mach 2.18. Program engineers estimated that by increasing the inlet area slightly, the F-107A was capable of reaching roughly Mach 2.4.
The trio of F-107A aircraft flew 272 flight tests totalling 176.5 hours. Included in this testing was successful separation of a special store prototype at Mach 2. Test pilots of note who flew the F-107A included XB-70A pilot Al White and X-15 pilots Scott Crossfield, Bob White, Jack McKay and Forrest Peterson.
Though it never became a production aircraft, the F-107A contributed in significant ways to aviation progress. Indeed, many future aircraft would greatly benefit from F-107A flight control and air induction technology including the A-5 Vigilante, XB-70A, A-12, SR-71, YF-12A and F-15.
The F-107A was the last of NAA’s fighter aircraft which includes such notables as the P-51 Mustang, the F-86 Sabre and the F-100 Super Sabre. While the F-107A has often been referred to in print as the Ultra Sabre, Ultimate Sabre, Super Super Sabre or such, it was never officially assigned a nickname. Alas, there was never an XF-107A or YF-107A designation either. North American Aviation’s TAC fighter-bomber candidate was simply known as the F-107A.
Today, the No. 1 F-107A (55-5118) is displayed at the Pima Air and Space Museum (PASM) in Tucson, Arizona. The No. 2 ship (55-5119) resides at the USAF Museum at Wright-Patterson Air Force Base in Dayton, Ohio. The No. 3 airplane (55-5120) no longer exists as it was relegated to the status of a fire fighting prop and ultimately destroyed in that role sometime in 1961 or 1962.