During the Korean War, a number of USAF pilots expressed a need for an aircraft with a simple design, as well as great speed and altitude performance, in essence, an air superiority fighter. During this blog, we'll follow the development of this unique aircraft, the Lockheed F-104 Starfighter.
After interviewing the USAF pilots in 1951, the legendary Lockheed aircraft designer, Kelly Johnson, began design work on the F-104. Johnson adopted the philosophy from F-86 pilots in Korea, whose combat experience reflected a belief that the Soviet built Mig-15 was superior to the larger and more complex Sabre. When Johnson first assembled his design team in March 1952, they considered over one-hundred aircraft configurations, the designs ranging in weight from 8.000 lbs. to 50,000 lbs. To meet performance requirements, Lockheed chose a small and simple aircraft, weighing in at 12,000 lbs., utilizing a high performance engine. Lockheed was competing with three other aircraft companies to secure the high performance jet contract. Republic Aircraft presented the AP-55, an improved version of the XF-91 Thunderceptor, the North American NA-212, which would evolve into the later F-107 and the Northrop N-102 Fang, powered by the General Electric J79 engine. While these were unique aircraft in their own right, Lockheed had gained the upper hand due to their X-7 program, a ramjet/rocket program from which Lockheed gained invaluable experience in aerodynamic research and testing engine thrust. Valuable data gained from the Douglas X-3 Stiletto program was utilized in the design of the XF-104. Since Lockheed's goal was to build a sleek, high performance aircraft, a minimalist design would achieve that goal by wrapping the lightest, most aerodynamic airframe around a single powerful engine. This arrangement would drastically reduce mass and drag. The Starfighter's airframe was constructed of duralumin, with some stainless steel and titanium. The fuselage was about two and a half times the length of the wingspan, with the wings located farther aft than many jet designs of the era. The wing design of the F-104 featured thin wings (.016 in.), so thin that they were a hazard to ground crews with Lockheed installing protective guards on the leading wing edges. While most jet fighters of the era used a swept-wing or delta-wing concept, balancing lift, aerodynamic performance, as well as internal space for fuel and equipment, Lockheed designers determined a small and thin, mid-mounted trapezoidal wing to be the most efficient for high speed supersonic flight. However, the wing design also caused the aircraft to have a relatively high landing speed. As a result of this, Lockheed engineers developed a boundary layer control system, or BLCS of high pressure bleed air, which was blown over the trailing-edge flaps lowering landing speeds by about 35 mph. Flaps in the land position were required for the BLCS to operate. The tail stabilizer was mounted on top of the fin to reduce the tendency to yaw or roll at high speeds.
The Starfighter was powered by the General Electric J79 turbojet engine, fed by side-intakes with fixed inlet cones, set for peak performance at Mach 1.7, later increased to Mach 2.0 for F-104s equipped with the more advanced J79 engines. Though the F-104 did not have variable-geometry inlets, as with many jet fighters, excess air was bypassed around the engine at high speeds. This bypass assisted in cooling the engine with the Starfighter having an excellent thrust-to-drag ratio, which permitted a maximum speed well above Mach 2. The F-104 was armed with the 20 mm M61Vulcan autocannon. Since it was the first aircraft to carry the cannon, testing of the Starfighter revealed problems with the initial version of the M61. For example, the cannon's gatling had problems with its linked ammunition being prone to misfeed, creating a foreign object damage (FOD) issue as ejected links were occasionally sucked into the engine. This was overcome with the development of a linkless ammunition feed system, which is now in use by a wide variety of U.S. combat aircraft. Two AIM-9 Sidewinder air-to-air missiles could be mounted on the wingtip stations, which could also be used mount fuel tanks. The F-104C and later models carried a centerline and two underwing pylons for fuel tanks, rocket pods or bombs. A nuclear weapon could be mounted underneath the centerline pylon. A later modification of the F-104 was a catamaran launcher mounted under the forward fuselage, from which to place two additional Sidewinders. However, the design offered minimal ground clearance, subjecting the missile heads to possible contact with ground debris. The first flight of the XF-104 took place on March 4, 1954 at Edwards AFB. The flight was successful, lasting just over 20 minutes. The total time from awarding of the production contract to the first flight was just one year-a record for the industry.
While the Starfighter was subjected to a number of tests and modifications over the next four years, it finally entered service with the USAF in February 1958. The F-104 had an undistinguished career in USAF service, with the Air Force buying less than half the number of projected examples. During its first three years of operation, the Starfighter had a relatively high accident rate, with a loss of 49 pilots at the end of 1961. Part of the problem was due to the high performance of the aircraft, which could be demanding of the pilots flying it, if they lacked familiarity with the plane. The frequency of J79 engine failures made flying the aircraft hazardous, at best. The downward-firing ejection seat was a very unpopular feature, since it meant that surviving a failure at low altitude was very unlikely. Initially, the downward firing seat was used to keep the pilot from crashing into rear tail stabilizer. However, later pilot seats ejected upward with rocket thrusters, which were able to clear the aircraft's tail. The F104's combat utility was limited, lacking the avionics of a dedicated interceptor, as well as inadequate armament for the role. While both pilots and wing commanders complained about the limited range of the plane, supporters of the aircraft insisted it was comparable to other fast combat jets of the era, which also had limited range if the afterburner were engaged for long periods. The introduction of the F-104C model in 1959 largely remedied this problem. A dozen F-104s were airlifted to Taiwan in 1958 during the Quemoy-Matsu crisis, but saw no action. However, the Starfighter did see combat with the USAF in Viet Nam. When the air war began to increase in 1965, the US found the North Vietnamese air defenses to be more formidable than previously thought, with North Vietnamese Migs posing a threat to American aircraft. The first mission for the Starfighters was to escort early warning radar planes, such as the Lockheed EC-121 (Constellation), which left a distinct radar signature for the North Vietnamese to follow. Even so, the North Vietnamese showed no inclination to engage the F-104s, with the Starfighters seeing no action in this role. They were also utilized in the ground attack role later that year, with some success, due to its speed and small frontal area making it a difficult target for anti-aircraft gunners. The F-104s were gradually replaced in this role with the arrival of McDonnell F-4 Phantoms in December 1965. Both the EC-121 escort missions, as well as the ground attack tasks continued until the final phase out of the Starfighter from Viet Nam in July 1967.
Though the F-104 wasn't without its share of problems, it had a number of credits. It was the first USAF plane to achieve a Mach 2 speed. The Starfighter was also the first aircraft to climb to an altitude of 100,000 ft.-under its own power. It also was the first USAF aircraft to incorporate the M61 autocannon system, used on a number of later aircraft. The F-104 eventually flew with fifteen air forces. It was accepted by six allied nations, West Germany, Canada, Italy, Belgium, Japan and the Netherlands, with West Germany accepting the plane about six months after it began USAF service. Though retired from active USAF service in 1969, the F-104S weather variant was in service with the Italian Air Force until 2004. Largely due to its performance, the Starfighter served as a test aircraft for NASA with three NF-104A aircraft delivered in late 1963. These planes were modified specifically as astronaut qualification craft, one of which set an altitude record of 120,800 ft.-a record which stands to this day.