F18 hornet

Development

F/A-18 attached to catapult on the flight deck of USS Abraham Lincoln.Northrop had enlisted the aid of McDonnell Douglas as a secondary contractor on the NACF proposal to capitalize on the latter's extensive experience in building carrier aircraft, including the highly successful F-4 Phantom II. On the F-18, the two companies agreed to split the parts manufacture evenly, with McDonnell Douglas completing the final assembly, representing ~20% of the work. McDonnell Douglas built the wings, stabilators, and forward fuselage; Northrop built the center and aft fuselage and vertical stabilizers. McDonnell Douglas was the prime contractor for the naval versions.[6] Northrop would become the prime contractor and take over final assembly for the F-18L land-based version which Northrop hoped to sell on the export market.[5]

The F-18, initially known as McDonnell Douglas Model 267, was drastically modified from the YF-17 while retaining the same basic configuration. For carrier operations, the airframe, undercarriage, and arrestor hook were strengthened, folding wings and catapult attachments were added, and the landing gear widened.[7] To meet Navy range and reserves requirements, McDonnell increased fuel capacity by 4,460 pounds (2,020 kg), with the enlargement of the dorsal spine and the addition of a 96 gallon fuel cell to each wing (the YF-17 had dry wings). Most visibly, a "snag" was added to the leading edge of the wings and stabilators to prevent a flutter discovered in the F-15 stabilator. The wings and stabilators were enlarged, the aft fuselage widened by 4 inches (102 mm), and the engines canted outward at the front. These changes added 10,000 lb (4,540 kg) to the gross weight, bringing it to 37,000 lb (16,800 kg). The computer-assisted control system of the YF-17 was replaced with a wholly digital fly-by-wire system with quadruple-redundancy, the first to be installed in a production fighter.[7]


Heads up display (HUD) in an F/A-18 HornetThe original plan specified acquiring 780 total of three closely related models: the single seat F-18A fighter and A-18A attack aircraft, differing only in avionics, and the dual-seat TF-18A, which retained full mission capability of the F-18,[2] except with a reduced fuel load. With redesign of the stores stations and improvements in avionics and multifunction displays, it became possible to combine the A-18A and F-18A into one aircraft.[5] Starting in 1980, the aircraft began being referred to as the F/A-18A, and the designation was officially announced on 1 April 1984. The TF-18A was redesignated F/A-18B.[5][2]


[edit] Northrop's F-18L
Northrop developed the F-18L as a potential export aircraft. Since it did not have to be strengthened for carrier service, it was expected to be lighter and better performing,[8] and a strong competitor to the F-16 Fighting Falcon then being offered to American allies. The F-18L's maximum gross weight was 7,700 pounds (3,493 kg) (approximately 30%) lighter than the F/A-18A, due to lighter landing gear, removal of the wing folding mechanism, reduced part thickness in areas and lower fuel capacity. Though the aircraft retained a lightened arresting hook, the most obvious external difference was the removal of the "snags" on the leading edge of the wings and stabilators. It still retained 71% commonality with the F/A-18 by parts weight, and 90% of the high-value systems, including the avionics, radar, and ECM suite, though alternatives were offered. Unlike the F/A-18, the F-18L carried no fuel in its wings and lacked weapons stations on the intakes. It had three underwing pylons on each side instead.[9]

The partnership between the McDonnell Douglas and Northrop soured over competition for foreign sales for the two models. Northrop felt that McDonnell Douglas would put the F/A-18 in direct competition with the F-18L. In October 1979, Northrop filed a series of lawsuits charging that McDonnell was using Northrop technology developed for the F-18L for foreign sales in violation of their agreement, and asked for a moratorium on foreign sales of the Hornet via McDonnell Douglas. The case was resolved in 1985 when McDonnell agreed to pay Northrop $50 million for complete rights to the design, without any admission of wrongdoing. By then Northrop had ceased work on the F-18L, and most export orders were captured by the F-16 or the F/A-18.[9]


Into production

A US Navy F/A-18 in flightDuring flight testing, the snag on the leading edge of the stabilators was filled in, and the gap between the Leading edge extensions (LEX) and the fuselage mostly filled in. The gap, called the boundary layer air discharge (BLAD) slots, controlled the vortices generated by the LEX and presented clean air to the vertical stabilizers at high angles of attack. However, they also generated a great deal of parasitic drag, worsening the problem of the F/A-18's inadequate range. McDonnell filled in 80% of the gap, leaving a small slot to bleed air from the engine intake. This may have contributed to early problems with fatigue cracks appearing on the vertical stabilizers due to extreme aerodynamic loads, resulting in a momentary grounding in 1984 until the stabilizers were strengthened. Starting in May 1988, a small vertical fence was added to the top of each LEX to broaden the vortices and direct them away from the vertical stabilizers. This also provided a minor increase in controllability as a side effect.[10]

The first production F/A-18A flew on 12 April 1980. After a production run of 380 F/A-18As[11] (including the nine assigned to flight systems development), manufacture shifted to the F/A-18C in September 1987.[2]