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 . 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 . 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 .