McDonnell Douglas F/A-18 Hornet

YF-17

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Originally, it was planned to acquire a total of 780 aircraft of three variants: 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 with a reduced fuel load.

Following improvements in avionics and multifunction displays, and a redesign of stores stations, the A-18A and F-18A were able to be combined into one aircraft.

Starting in 1980, the aircraft began to be 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.

Northrop's F-18L

Northrop developed the F-18L as a potential export aircraft. Since it was not strengthened for carrier service, it was expected to be lighter and better performing, 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 (3,490 kg) (approximately 30%) lighter than the F/A-18A, via lighter landing gear, lack of wing folding mechanism, reduced part thickness in areas, and lower fuel-carrying capacity.

Though the aircraft retained a lightened arresting hook, the most obvious external difference was removed "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.

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, with no 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.

Into production

During 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 gaps, 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, but 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 short 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.

F/A-18s of early versions had a problem with insufficient rate of roll, exacerbated by the insufficient wing stiffness, especially with heavy underwing ordnance loads.

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.

Improvements and design changes

In the 1990s, the US Navy faced the need to replace its aging A-6 Intruders, and A-7 Corsair IIs with no replacement in development.

To answer this deficiency, the Navy had the F/A-18E/F Super Hornet developed.

Despite its designation, it is not an upgrade of the F/A-18 Hornet, but rather, a new, larger airframe using the design concepts of the Hornet.

Hornets and Super Hornets will serve complementary roles in the US Navy carrier fleet until the Hornet A-D models are completely replaced by the F-35C Lightning II.

The Marines have chosen to extend the use of certain of their F/A-18s up to 10000 flight hours, due to delays in the F-35B version.

Design

The F/A-18 is a twin engine, mid-wing, multi-mission tactical aircraft. It is highly maneuverable, owing to its good thrust to weight ratio, digital fly-by-wire control system, and leading edge extensions (LEX).

The LEX allow the Hornet to remain controllable at high angles of attack.

The wing is a trapezoidal shape with 20-degree sweepback on the leading edge and a straight trailing edge. The wing has full-span leading edge flaps and the trailing edge has single-slotted flaps and ailerons over the entire span.

Canted vertical stabilizers are another distinguishing design element, one among several other such elements that enable the Hornet's excellent high angle-of-attack ability include oversized horizontal stabilators, oversized trailing edge flaps that operate as flaperons, large full-length leading edge slats, and flight control computer programming that multiplies the movement of each control surface at low speeds and moves the vertical rudders inboard instead of simply left and right.

The Hornet's normally high angle-of-attack performance envelope was put to rigorous testing and enhanced in the NASA F-18 High Alpha Research Vehicle (HARV). NASA used the F-18 HARV to demonstrate flight handling characteristics at high angle-of-attack (alpha) of 65–70 degrees using thrust vectoring vanes.

F/A-18 stabilators were also used as canards on NASA's F-15S/MTD.

The Hornet was among the first aircraft to heavily use multi-function displays, which at the switch of a button allow a pilot to perform either fighter or attack roles or both.

This "force multiplier" ability gives the operational commander more flexibility to employ tactical aircraft in a fast-changing battle scenario.

It was the first Navy aircraft to incorporate a digital multiplex avionics bus, enabling easy upgrades.

The Hornet is also notable for having been designed to reduce maintenance, and as a result has required far less downtime than its heavier counterparts, the F-14 Tomcat and the A-6 Intruder.

Its mean time between failure is three times greater than any other Navy strike aircraft, and requires half the maintenance time.

Its General Electric F404 engines were also innovative in that they were designed with operability, reliability and maintainability first.

The engine, while unexceptional in rated performance, demonstrates exceptional robustness under various conditions and is resistant to stall and flameout.

The F404 engine connects to the airframe at only 10 points and can be replaced without special equipment; a four person team can remove the engine within 20 minutes.