Northrop YF-17

The Northrop YF-17 (unofficially nicknamed "Cobra") was a prototype lightweight fighter aircraft designed for the United States Air Force's Lightweight Fighter (LWF) technology evaluation program. The LWF was created because many in the fighter community believed that aircraft like the F-15 Eagle were too large and expensive for many combat roles. The YF-17 was the culmination of a long line of Northrop designs, beginning with the N-102 Fang in 1956, continuing through the F-5 family. Although it lost the LWF competition to the F-16, the YF-17 was selected for the new VFAX specification. In enlarged form, the F/A-18 Hornet was adopted by the United States Navy and United States Marine Corps to replace the A-7 Corsair II and F-4 Phantom II, complementing the more expensive F-14 Tomcat.[1] This design, conceived as a small and lightweight fighter, would ironically be scaled up to the F/A-18E/F Super Hornet, which is similar in size to the original F-15. The Super Hornet has replaced the F-14 in USN inventory, and performs all jet combat aircraft roles in the Navy from attack to fighter, tanker and electronic warfare.

Development:

The aircraft's main design elements date to early 1965, from the internal Northrop project N-300. The N-300 was itself derived from the F-5E, and features a longer fuselage, small leading-edge root extensions (LERX), and more powerful GE15-J1A1 turbojets, rated at 9,000 lbf (40 kN) each. The wing was moved higher on the fuselage to increase ordnance flexibility. The N-300 further evolved into the P-530 Cobra, utilizing 13,000 lbf (58 kN) GE15-J1A5 engines, with a very small .25 bypass ratio leading to the nickname "leaky turbojet". The bypass effectively was only a cooling stream for the rear of the engine, allowing the engine bay to be constructed of lighter, cheaper materials.[1] The P-530's wing planform and nose section was similar to the F-5, with a trapezoidal shape formed by a sweep of 20° at the quarter-chord line, and an unswept trailing edge, but was over double the area, with 400 sq ft (37 m2) as opposed to the 186 of the F-5E. Initially shoulder mounted, the wings were gradually shifted down to the mid position. Its most distinctive new feature were the LERXs, that tapered into the fuselage under the cockpit. They enabled maneuvering at angles of attack exceeding 50°, by providing about 50% additional lift. The extensions also trapped airflow under them at high angles of attack, ensuring airflow into the engines. The resemblance to the head of a cobra lead to the adoption of the nickname "Cobra", often unofficially used for the YF-17.[2] Studies showed a single vertical stabilizer was insufficient at high angles of attack, and it was changed to twin vertical stabilizers, canted at 45°. The result was an aircraft that had relaxed longitudinal stability, enhancing maneuverability. However, Northrop was not yet confident in fly-by-wire controls and retained mechanically signaled flight controls. The resulting aircraft, unveiled on 28 January 1971, advertised a max weight of 40,000 lb (18,144 kg) and maximum speed of Mach 2, but stirred little interest among foreign buyers.