Lockheed Aircraft

The Lockheed F-104 Starfighter is a single-engine, supersonic interceptor aircraft which later became widely used as an attack aircraft.

Lockheed F-104G Starfighter

Design/Development

The F-104 featured a radical wing design. Most jet fighters of the period used a swept-wing or delta-wing design, which provided a reasonable balance between aerodynamic performance, lift, and internal space for fuel and equipment. The Lockheed tests, however, determined that the most efficient shape for high-speed supersonic flight was a very small, straight, mid-mounted, trapezoidal wing.

Lockheed F-104A

The new wing design was extremely thin, with a thickness-to-chord ratio of only 3.36% and an aspect ratio of 2.45. The wing's leading edges were so thin (.016 in, 0.41 mm) that they presented a cut hazard to ground crews: protective guards had to be installed on the edges during ground operations maintenance The thinness of the wings required fuel tanks and landing gear to be placed in the fuselage, and the hydraulic cylinders driving the ailerons were limited to 1-inch (25 mm) thickness to fit.

The small, highly loaded wing resulted in an unacceptably high landing speed, even with both leading- and trailing-edge flaps installed. As a result, the aircraft designers developed a boundary layer control system (BLCS) of blown-flap bleed air over the trailing-edge flaps to help lower landing speeds, making landings safer. The system proved to be a maintenance problem in service, however, and landing without the BLCS engaged could be a harrowing experience.

The stabilator (horizontal tail surface) was mounted atop the fin to reduce inertia coupling. Because the vertical fin was only slightly shorter than the length of each wing and nearly as aerodynamically effective, it could act as a wing on rudder application, rolling the aircraft in the opposite direction of rudder input. To offset this effect, the wings were canted downward, giving 10° anhedral.

The fuselage had a high fineness ratio, i.e. slender, tapered towards the sharp nose, and a small frontal area. The tightly packed fuselage contained the radar, cockpit, cannon, fuel, landing gear, and engine. The fuselage and wing combination provided low drag except at high angle of attack (alpha), at which point induced drag became very high. The F-104 had good acceleration, rate of climb, and potential top speed, but its sustained turn performance was poor.

Engine

The F-104 was designed to use the General Electric J79 turbojet engine,fed by side-mounted intakes with fixed inlet cones optimized for supersonic speeds. Unlike some supersonic aircraft, the F-104 did not have variable-geometry inlets, instead at high mach numbers excess air is bypassed around the engine. This bypass air also helps cool the engine. The F-104 had an excellent thrust-to-drag ratio, allowing a maximum speed well in excess of Mach 2