Aircraft Factfile and Recognition Guide – F-104 Starfighter

Background

"Kelly" Johnson, chief engineer at Lockheed's Skunk Works, visited Korea in December 1951 and talked to fighter pilots about what sort of plane they wanted. At the time the US pilots were meeting the MiG-15 'Fagot' in their F-86 Sabres, and many of the American pilots felt that the MiGs were superior to the larger and more complex American design. The pilots requested a small and simple aircraft with excellent performance.

On his return to the US, Johnson immediately started the design of just such an aircraft. In March his team was assembled, and they studied several aircraft designs, ranging from small designs at 8,000 lb, to fairly large ones at 50,000 lb. In November 1952, a follow-on study started, the lessons learned from the earlier designs being used to eventually result in the Lockheed L-246, of about 12,000 lb. The L-246 remained essentially identical to the L-083 Starfighter as eventually delivered.

The design was presented to the Air Force in November 1952, and they were interested enough to create a new proposal and to invite several companies to participate. Three additional designs were received: the Republic AP-55, an improved version of its prototype XF-91 Thunderceptor, the North American NA-212 which would eventually evolve into the F-107, and the Northrop N-102 Fang, a new General Electric J79-powered design. Although all were interesting, Lockheed had an insurmountable lead, and was granted a development contract in March 1953.

Work progressed quickly, with a mock-up ready for inspection at the end of April, and work starting on two prototypes late in May. At the time, the J-79 engine was not ready; so, both prototypes were designed to use the Wright J-65 engine instead, a licensed version of the Armstrong Siddeley Sapphire. The first prototype was completed by early 1954, and started flying in March. The total time from design to first flight was about two years, a very short time even then, and unheard of today, when ten to fifteen years is more typical.

The F-104 had a radical wing design. Most jet fighters of the period (and to this day) used a swept-wing or delta-wing platform. This allowed a reasonable balance between aerodynamic performance, lift, and internal space for fuel and equipment. Lockheed's tests, however, determined that the most efficient shape for high-speed, supersonic flight was a very small, straight, mid-mounted, trapezoidal wing. The wing was extremely thin, with a thickness-to-chord ratio of only 3.36%. Its aspect ratio was 2.45. The wing's leading edges were so thin (0.016 in / 0.41 mm) and so sharp that they presented a hazard to ground crews, and protective guards had to be installed during ground operations. The thinness of the wings meant that fuel tanks and landing gear had to be contained in the fuselage. The motors driving the control surfaces had to be only one inch (25 mm) thick to fit.

The stabilator (horizontal tail surface) was mounted atop the fin to reduce inertia coupling. Because the vertical tailfin was only slightly shorter than the length of each wing and nearly as aerodynamically effective, it could act as a wing on rudder application (a phenomenon known as Dutch roll). To offset this effect, the wings were canted downward, given 10° anthedral. The wings had both leading- and trailing-edge flaps. Later Starfighter marks incorporated a system that allowed the flaps to be extended during combat maneuvering, reducing turn radius and generally improving sustained turn rate.

The combination provided extremely low drag except at high angle of attack (alpha), at which point induced drag became very high. As a result the Starfighter had superb acceleration, rate of climb, and potential top speed, but its sustained turn performance was very poor, described by some as more like a milk truck than a fighter. It was sensitive to control input, and extremely unforgiving of pilot error.

The small, highly-loaded wing resulted in an unacceptably high take-off and landing speed, so a boundary layer control system (BLCS) of blown flaps was incorporated, bleeding engine air over the trailing edge flaps to improve their lift. The system was a boon to safe landings, although it proved to be a maintenance problem in service, and landing without the BLCS could be harrowing.

NACA wind tunnel tested a model of the F-104, to evaluate its stability, and found it became increasingly unstable at higher angles of attack, to the point that it was recommended to limit the servo-control power to generate those higher angles and shake the stick to warn the pilot. In the same report, NACA stated that the wingtip tanks, possibly because of their stabilizing fins, reduced somewhat the model's instability problems at high angles of attack.

A research version called Lancer, fitted with a bigger, higher aspect ratio wing and a rocket engine, was employed to develop rocket controls for yaw, pitch and roll, to be used at extremely high altitudes, where conventional aerodynamic control surfaces lost much of their effectiveness. The few pilots to have flown the Lancer used to say that, due to its bigger wing, it was extremely nimble and a better dogfighter than any other plane. Later, those same rocket controls were installed on the X-15 rocket plane for use in its record-breaking high-altitude flights.

The Starfighter's fuselage had a high fineness ratio, i.e., tapering sharply towards the nose, and small frontal area. The fuselage was tightly packed, containing the radar, cockpit, cannon, all fuel, landing gear, and engine.

Several two-seat training versions of the Starfighter were produced. They were generally similar to the comparable single-seater, but the additional cockpit required removing the cannon and some internal fuel. Two-seaters were combat-capable, and, despite a slightly larger vertical fin and increased weight, have similar performance to the single-seater.

The F-104 was built around the General Electric J79 turbojet engine, fed by side-mounted intakes with fixed inlet scoops and a conical ramp optimized for supersonic speeds. (Unlike some supersonic aircraft, the F-104 does not have variable-geometry inlets.) Its thrust-to-drag ratio was superb, allowing a maximum speed well in excess of Mach 2: the top speed of the Starfighter is limited more by the aluminum structure and the temperature limits of the engine than by thrust or drag (which gives an aerodynamic maximum speed of Mach 2.2). Later models used updated marks of the J79, improving thrust by almost 30%.

Recognizing the F-104 Starfighter

The F-104 is an unmistakable aircraft to identify on the ground or in the air.  Here's tips on how to identify one:

Wings: Mid-mounted, equally tapered, with a negative slant. Missiles or fuel tanks at the square tips.
Engine: One turbojet in midsection of the body. Semicircular air intakes forward of the wings’ leading edges.
Fuselage: Long and slender, thickens at the air intakes. Sharp-pointed nose. Bubble canopy.
Tail: Unequally tapered tail fin. About 1/3 of the fin overhangs the exhaust. Tail flats are equally tapered with square tips mounted high on the tail fin forming a T.

Specifications - F-104 Starfighter

Primary Function: Fighter
Contractor: Lockheed Aircraft Corporation
Crew: One
Powerplant:  One General Electric J79-GE-3B at 9,600 lb (4,354 kg) each
Length: 54 feet 8 inches (16.6 m)
Wingspan: 21 feet 9 inches (6.6 m)
Height: 13 feet 5 inches (4.0 m)
Empty:  13,384 lb (6,071 kg)
Maximum Takeoff: 25,840 lb (11,271 kg)
Speed:  1,450 mph (Mach 2.2) at 35,000 ft.
Ceiling: 64,795 ft (19,750 m)
Range:  730 miles (1,175 km)
Armament:  M-61 Vulcan 20mm cannon; 4,000 lbs of bombs under the wings two AAM-N-7 Sidewinder missiles on tips

Sources: Wikipedia F-104 Starfighter

© 2007 Steven Holzinger