McDonnell Douglas F/A-18 Hornet - Design

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.

The engine air inlets of the Hornet, like that of the F-16, are of a simpler "fixed" design, while those of the F-4, F-14, and F-15 have variable geometry or variable ramp air inlets. This is a speed limiting factor in the Hornet design. Instead, the Hornet uses bleed air vents on the inboard surface of the engine air intake ducts to slow and reduce the amount of air reaching the engine. While not as effective as variable geometry, the bleed air technique functions well enough to achieve near Mach 2 speeds, which is within the designed mission requirements.

A 1989 USMC study found that single seat fighters were well suited to air to air combat missions while dual seat fighters were favored for complex strike missions against heavy air and ground defenses in adverse weather. The question being not so much as to whether a second pair of eyes would be useful, but as to having the second crewman sit in the same fighter or in a second fighter. Single-seat fighters that lacked wingmen were shown to be especially vulnerable.