In July of 1954, the USAF decided to purchase 17 service test aircraft under the designation YF-104A. This was done under a "fly-before-you-buy" philosophy, under which these aircraft would participate in development tests before any commitment to large-scale production was made. If large-scale production was actually undertaken, these YF-104As could later be brought up to full production standard and delivered to operational units.
Fearing that the General Electric J79 turbojet might not be ready in time, the first service test Starfighters were to be powered by the afterburning J65 turbojet. However, the J79 engine was flight tested by the Navy in a borrowed Navy XF4D in December of 1955, and it was concluded that early versions of the General Electric J79 engine should be available by the time that the YF-104A was ready, and the service test aircraft were built with the General Electric engine in mind.
The seventeen YF-104A service test aircraft (serials 55-2955/2971) were powered by early experimental versions of the General Electric J79 engine instead of the J65 engine which powered the XF-104s. The YF-104A aircraft were initially fitted with the General Electric XJ79-JE-3 turbojet, rated at 9300 lb.s.t. dry and 14,800 lb.s.t. with afterburning. The YF-104A differed from the XF-104 in having a 5 feet 6 inch extension in the length of the fuselage to accommodate the new J79 engine. The vertical fin was slightly taller, raising the overall height from 12.7 feet to 13.49 feet. A forward-retracting nosewheel replaced the rearward-retracting unit of the XF-104, in order to provide improved ejection seat clearance out of the bottom of the aircraft. A narrow dorsal spine was added to the upper fuselage. Two additional fuel cells were installed in the fuselage. The air intakes were modified in shape and were fitted with half-cone center bodies which had been omitted from the two XF-104s. The fixed-geometry central intake shock cone had an internal bleed slot which exhausted some intake air through the fuselage for afterburner cooling and helped to reduce the aircraft's base drag. An AN/ASG-14T1 fire control system was fitted, plus AN/ARN-56 TACAN. There were provisions for four underwing and one under-fuselage stores pylon.
With an empty weight increased only slightly to 12,561 pounds, the YF-104A maximum takeoff weight (clean) rose to 15,700 pounds for the XF-104 to 18,881 pounds. With provision for four underwing and one fuselage stores pylon, the maximum takeoff weight was 24,584 pounds.
The first YF-104A (55-2955) was completed in February of 1956, and was trucked out in high secrecy to Edwards AFB. It made its first flight there on February 17, 1956, with Lockheed test pilot Herman "Fish" Salmon at the controls.
On February 16, 1956, the second YF-104A (55-2956) was used for a media-covered official rollout ceremony at Lockheed's Burbank factory. This was the first display of the Starfighter to the public. Before that, there had been only rumors in the aviation press about the existence of a truly revolutionary new fighter aircraft, plus a few speculative drawings. The engine air intakes were covered with temporary fairings, since the Air Force didn't want people to see the half-cones in the air intakes.
The first Starfighter photographs were released in the spring of 1956. These were limited to air-to-air shots of the prototype and ground photos of YF-104A 55-2956 with the intake fairings still fitted. It was not until mid-1956 that the J79-engined F-104 lateral intakes were finally revealed to the public.
The J79 engine provided a spectacular improvement in performance. 55-2955 reached Mach 2 on February 28, 1956, becoming the first fighter aircraft capable of double-sonic speed in level flight.
An initial order for production F-104As was issued on October 14, 1956.
Together with the first 35 production F-104As, all seventeen YF-104As were used for flight-test and to evaluate early versions of the J79 (the -3, -3A, and -3B) engine, the Vulcan cannon, the AIM-9 (formerly GAR-8) Sidewinder air-to-air missile and the wingtip-mounted fuel tanks. Airframe strengthening and local redesign were progressively introduced. Various forms of flap blowing were tested, and a ventral fin was introduced to improve directional stability at supersonic speed. Some YF-104As were also used to test wingtip racks for either 170 US-gallon drop tanks or Sidewinder infrared-homing air-to-air missiles.
On May 7, 1958, Major Howard C. Johnson reached an altitude of 91,249 feet in a zoom climb at Edwards AFB in California, setting a new altitude record. On May 16, 1958, Captain Walter W. Irwin flying a YF-104A set a new world's air speed record of 1404.19 mph flying over a 15/25 kilometer course at Edwards AFB. For the first time in history, the same aircraft type held both the world speed and altitude records at the same time.
A large percentage of the seventeen YF-104As were lost in crashes during the test program. At the end of this program, the surviving YF-104As were brought up to F-104A production status and were turned over to USAF squadrons for duty. Following the withdrawal of the F-104A from active service in 1960, at least four of the ex-YF-104As (55-2956, 2957, 2969, 2971) were converted into unmanned QF-104A target drones. They were all most likely shot down during tests.
Of the seventeen YF-104As built, only two are known to survive today. The first survivor is the seventh YF-104A (55-2961). This aircraft was transferred to the National Advisory Committee for Aeronautics (NACA) in August of 1956. It was initially numbered 018, which was later changed to a civilian registration of N818NA. In 1958, NACA was reorganized as NASA, and the YF-104A remained with NASA until November of 1975. This aircraft is now hanging in the National Air and Space Museum in Washington. I saw it there in October of 1993. The other survivor is the thirteenth YF-104A (55-2967). It is now on display at the Air Force Academy in Colorado Springs, Colorado. I remember seeing it sitting outside the Chapel when I visited the Air Force Academy in 1971.
55-2955/2971 Lockheed YF-104A Starfighter c/n 183-1001/1017