Northrop YF-17 Cobra

The Northrop YF -17 Cobra was a prototype daytime lightweight prototype program designed for technology assessment Light Weight Fighter (LWF) of the United States Air Force. The project LWF was created because the F-15 Eagle was too big and expensive for many combat roles. The YF-17 lost the competition to the F-16 Fighting Falcon, but it was modified and enlarged to operate on Aircraft Carriers, it became the F/A-18 Hornet.

Design and Development[]

U1832299A — YF-17 Cobra during evaluation

The design of the main elements of the aircraft began to early 1965, from the internal Northrop N-300 program. The N-300 was based on the F-5E, with an extended fuselage, small extensions on the leading edges (LEX) and GE15 - J1A1 turbojets each with 40 kN thrust. The wings were moved higher on the fuselage to increase the flexibility of the load. The N-300 evolved into the P530 Cobra, which used GE15-J1A5 engines with 57.8 kN of thrust and a low by-pass ratio . The bypass flow allows cold air in the rear of the engine, giving the nickname "leaky turbojet", which allowed build engines with lighter materials and lower cost.

The wing shape and the nose of the P530 were similar to the F-5 with a form of trapezoid formed by an angle of 20 degrees and a free edge angle, but doubling the wing area . The wings were originally mounted at the top of the fuselage, but were later moved to a middle position . Its most distinctive feature was the LEX, narrowing towards the fuselage under the cockpit which allow maneuvering angles of attack above 50 ° and provide 50% more lift. The extensions were also used to smooth the airflow entering the engines in high angles of attack . Its head looks like a cobra, giving the plane its nickname, later adopted for the YF-17. Studies showed that a single vertical stabilizer was insufficient for high angles of attack and it was replaced by twin stabilizers tilted 45 degrees. The result was an aircraft with improved longitudinal stability and maneuverability. However, Northrop did not trust fly-by-wire controls and retained mechanical control systems . The plane, which was presented on February 28, of 1971, was announced as a model with maximum weight of 18,000 kg and maximum speed of Mach 2, but there was not much interest among foreign buyers.

Features[]

The YF-17 was made mainly of aluminum, in a conventional monohull, although more than 400 kg of its structure was of graphite and epoxy. The nose contains a single radar range. The wings had no fuel and areas such as the leading edge and output consisted of a nucleus hive-shaped Nomex. The back of the plane was full of aluminum stabilizers and vertical stabilizers were of conventional construction. Aerobraking was located above and between the engines.

The plane was powered by a pair of General Electric YJ101-GE -110 turbofans of 67 kN of thrust each mounted next to each other to reduce the asymmetry in case of loss of an engine. Each engine uses an independent hydraulic system . Unlike the P530, the YF-17 had a partial outline of control fly-by-wire, known as increased electronic control system (ECS).

Testing and evaluation[]

710px-YF-16 and YF-17 in flight — An air-to-air right side view of a YF-16 aircraft and a YF-17 aircraft, side-by-side, armed with AIM-9 Sidewinder missiles

When the program Light Weight Fighter was announced in 1971, Northrop modified the P530 design. The P600 was later designated as YF-17A. While the P530 was trying to be a versatile aircraft, the P600 was prepared only for airshows and therefore, the barrel of the bottom of the fuselage was moved to the top. The design of the YF -17 and YJ101 prototype engine (GE15 engine development) consumed more than one million hours and 5,000 hours in wind tunnel testing.

The first prototype (number 72-1569) was submitted at Hawthorne April 4 of 1974 and made its first flight at Edwards base on 9 June. The second (72-1570) first flew on 21 August of that year. During 1974, the YF -17 competed against the YF-16 Fighting Falcon of General Dynamics. The two prototypes performed 288 test flights with a total of 345.5 hours. The YF-17 attained a top speed of Mach 1.95, a load factor of 9.4 g and a maximum altitude of more than 15 240 m. It could maintain an angle of attack of 34ºin level flight and 63º on the rise.

The United States Navy had a small stake in the LWF program. In August 1974, Congress ordered the Navy to make maximum use of LWF technology and hardware in a new light bomber, the VFAX. As the contractor had no experience with naval fighters, it sought business partners to provide expertise and joined General Dynamics LTV Aerospace and Northrop with McDonnell Douglas. Each team sent its revised designs to the needs of the Navy of a radar long-range, multi-purpose capacity.

Origins of the F/A-18[]

Although Northrop hoped to be the winner because of its years of experience in light fighter design and P530 history, the U.S Air Force selected the YF-16 in January 1975. The YF-16 was slightly faster and used a common engine with the F-15 Eagle. The Navy did not think the YF-16 single engine and narrow landing gear was appropriate or easy to adapt to operations aircraft carrier and refused to adopt the design. In May 1975 the Navy received approval to develop its own aircraft based on the YF-17. After becoming a naval project, the Navy designated McDonnell Douglas as prime contractor. As the requirements of the Navy were different from the USAF, the aircraft was extensively modified: the resulting F/A-18 shared neither the size nor structure of the YF-17.

Specifications[]

General Characteristics[]

Crew: 1

Size and physical comparison between YF-17 and F/A-18A
Length: 56 ft 0 in (17.0 m)
Wingspan: 35 ft 0 in (10.5 m)
Height: 16 ft 6 in (5.0 m)
Wing area: 350 ft² (32 m²)
Empty weight: 17,180 lb (7,800 kg)
Loaded weight: 23,000 lb (10,430 kg)
Max takeoff weight: 34,280 lb (15,580 kg)
Powerplant: 2× General Electric YJ101-100 afterburning turbofans, 14,400 lb_f (67 kN) each

Performance[]

Maximum speed: Mach 1.95
Range: 2,990 mi (4,810 km)
Service ceiling: 50,000 ft (15,000 m)
Rate of climb: 50,000 ft/min (250 m/s)
Wing loading: 66 lb/ft² (320 kg/m²)
Thrust/weight: 1.25

Armament[]

Guns: 1× 20 mm (0.79 in) M61 Vulcan gatling gun
Missiles: 2× AIM-9 Sidewinder