F18

The engine air inlets of the Hornet, like that of the F-16, are "fixed", while those of the F-4, F-14, and F-15 have variable geometry or variable ramp engine air inlets. The variable geometry enables high-speed aircraft to keep the velocity of the air reaching the engine below supersonic. This is one 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. The less sophisticated design is also more robust.

Because it was designed as a light multirole aircraft to complement the specialized F-14 and A-6 airframes, it had a relatively low internal fuel fraction. That is, its internal fuel capacity is small relative to its takeoff weight, at around 23%, a fuel fraction of .23. Most aircraft of its class have a fuel fraction between .30 to .35. This situation was exacerbated by the addition of new avionics over its lifespan, further reducing the fuel fraction. This led to 330-gallon external tanks being a common sight on F/A-18s, with the centerline and inner wings stations (numbered 3, 5 and 7) being plumbed to transfer fuel.


[edit] Design evolution
In the 1990s, the US Navy faced the need to replace its aging A-6 Intruders, EA-6 Prowlers, A-7 Corsair IIs and F-14 Tomcats without proper replacements 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 utilizing the design concepts of the Hornet. Hornets and Super Hornets will serve complementary roles in the US Navy carrier arsenal, until the deployment of the F-35C Lightning II, which will primarily replace F/A-18A-D Hornets.