The YF-23 was a stealth air-superiority fighter, which lost the competition with the YF-22. The YF-23 was the most unconventional of the two designs; it had a diamond-shape wing platform and a V-tail. Missiles were to be carried in two fuselage bays. The second prototype had the General Electric YF120 engine.
The body of the YF-23A is a blend of stealthy shapes and aerodynamic efficiency, hopefully providing a low radar cross section without compromising performance. The YF-23A was longer and more slender than the Lockheed YF-22A. The main load-bearing fuselage structure, measured from the stablizer to the front of the cockpit, is about 7 feet longer than the YF-22A. From the side, the profile of the YF-23A is reminiscent of that of the Lockheed SR-71. The general impression from other angles is that of a long, high forebody mounted between two widely-separated engine nacelles. The lengthwise variation in cross-sectional area is very smooth, minimizing transonic and supersonic drag. The forward section has a modified double-trapezoid cross section, one above the other in mirror image, with the aft region blending into a circular cross section and disappearing into the rear fuselage. The upper component of the engine box is dominated by two parallel engine nacelles that blend smoothly into the wing, each nacelle being of a modified trapezoidal cross section. The forebody has the cockpit, the nose landing gear, the electronics, and the missile bay. The YF-23 engine nacelles were larger than they would have been on the production F-23, since they had been designed to accommodate the thrust reversers originally planned for the ATF but later deleted.
Trapezoid-shaped air inlets are located underneath each wing, with the leading edge forming the forward lip of a simple fixed-geometry two-shock system. The placement of the intakes underneath the wings has the advantage in removing them from the sides of the fuselage so that a large boundary-layer scoop is not needed. Instead, the thin boundary layer which forms on the wing ahead of the inlet is removed through a porous panel and is vented above the wing. An auxiliary blow-in inlet door is located on each of the upper nacelles just ahead of the engine to provide additional air to the engines for takeoff or for low speeds. The inlet ducts leading to the engines curve in two dimensions, upward and inward, to shield the faces of the compressors from radar emitters coming from the forward direction.
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