f18

Design

A Hornet performing a high-g pull-up during an air show. The high angle of attack causes powerful vortices to form at the leading edge extensions.The F/A-18 is a twin engine, mid-wing, multi-mission tactical aircraft. It is superbly 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. This is because the LEX produce powerful vortices over the wings, creating turbulent airflow over the wings and thus delaying or eliminating the aerodynamic separation responsible for stall, allowing the Hornet's wings to generate lift several times the aircraft's weight, despite high angles of attack. The Hornet is therefore capable of extremely tight turns over a large range of speeds.

Canted vertical stabilizers are another distinguishing design element, and among the other design characteristics that enable the Hornet's excellent high angle-of-attack capability include oversized horizontal stabilators, oversized trailing edge flaps that operate as flaperons, large full-length leading-edge flaps, 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.[12] F/A-18 stabilators were also used as canards on NASA's F-15S/MTD.


F/A-18 Hornet in transonic flight (Note Prandtl-Glauert condensation).The Hornet was among the first aircraft to heavily utilize multi-function displays, which at the switch of a button allow the pilot to perform either fighter or attack roles or both. This "force multiplier" capability gives the operational commander more flexibility in employing tactical aircraft in a rapidly changing battle scenario. It was the first Navy aircraft to incorporate a digital multiplex avionics bus, enabling easy upgrades.[2]

The Hornet is also notable for having been designed with maintenance in mind, 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.[2] For example, whereas replacing the engine on the A-4 Skyhawk required removing the aircraft's tail, the engine on the Hornet is attached at only three points and can be directly removed without excessive disassembly. An experienced maintenance crew can remove and replace an F/A-18 engine in only a couple of hours.


Exhaust nozzles of an RAAF F/A-18 at the Whenuapai Air Show in New Zealand in March 2009.The General Electric F404-GE-400 or F404-GE-402 engines powering the Hornet were also innovative in that they were designed with operability, reliability, and maintainability first. The result is an engine that, while unexceptional on paper in terms of rated performance, demonstrates exceptional robustness under a variety of conditions and is resistant to stall and flameout. By contrast, the Pratt & Whitney TF30 engines that originally powered the F-14A were notoriously prone to compressor stall and flameout under certain flight conditions.