The Hornet has an impressive array of air-to-air and air-to-ground ordinance, and can rapidly switch back and forth between intercept mode and ground strike mode.
The primary air-to-air weapons are the AIM-7 Sparrow and the AIM-9 Sidewinder missiles. The missile can operate with a maximum of six Sidewinders (one on each wingtip, and two on each of the outboard underwing stations). Alternatively, it can carry as many as four Sparrows (one on each side of the fuselage and one on each outer underwing pylon). When operating in ground attack mode, it can carry an array of ordnance on four underwing pylons and on the centerline station.
When operating in the air-to-air mode, the Hornet typically carries an AIM-7 Sparrow semi-active radar homing missile on each fuselage corner slot. It can also carry a Sparrow on each of the outer underwing pylons, for a total of four. The Navy initially viewed the AIM-7 Sparrow as the Hornet's primary air-to-air weapon, since it can be used for beyond visible range (BVR) encounters. However, it is now been largely superseded by the AMRAAM "fire-and-forget" missile.
The Sparrow uses semi-active radar homing and is compatible with either constant-wave or pulse-Doppler radar illumination. The AIM-7 is said to be effective out to distances of 25 miles, although the true effective range varies greatly with the conditions of the encounter. The AIM-7M version is 12 feet long and has a launch weight of about 500 pounds. The missile has two sets of delta-shaped fins--a set of fixed fins at the rear of the missile and a set of movable fins at the middle of the missile for steering. The 88-pound explosive warhead is contained in a stainless steel drum, which shatters upon detonation into 2600 fragments, greatly increasing the prospect of a kill. The Sparrow can be detonated by impact or proximity fuses.
The current Sparrow versions are the AIM-7M and AIM-7P. The first versions to see large-scale service were the AIM-7E, AIM-7E2, and AIM-7F, but combat results with these missiles over Vietnam were rather disappointing. The AIM-7F version of the Sparrow introduced solid-state electronics as substitutes for some of the miniature vacuum tubes of the earlier versions. This miniaturization enabled the warhead to be moved forward of the wings, with the aft part of the missile being devoted almost entirely to the rocket motor. The extra space that was made available by the introduction of solid-state miniaturization made it possible to introduce a dual-thrust booster/sustainer rocket motor that enabled the effective range of the Sparrow to be essentially doubled (up to 28-30 miles) in a head-on engagement. The AIM-7L had fewer tubes and more solid state features. The AIM-7M introduced in 1982 featured a new autopilot, a new fuse, and an inverse-processed digital monopulse seeker which was more effective in bad weather, more difficult to detect and jam, and provided better look-down, shoot-down capability. The AIM-7P was fitted with improved guidance electronics including an on-board computer based on VLSIC technology. It is intended to have better capability against small targets such as cruise missiles and sea-skimming antiship missiles.
The Sparrow missile is now a rather old design (the basic concept dating from the 1950s), and had been largely replaced by the AIM-120 AMRAAM in Hornet service. Although the Sparrow of today is a much more capable weapon than the Sparrow used in Vietnam, it still requires that the target be continually illuminated by the aircraft's on radar transmitter in order for it to home in on reflected radar energy. This means that the Hornet can only fire on one target at a time with this weapon, which makes the fighter extremely vulnerable to attack by other enemy fighters during this phase.
The ultimate BVR weapon for the F/A-18 is the Hughes AIM-120 AMRAAM (Advanced Medium Range Air-to-Air Missile). The AMRAAM is intended to combine the BVR performance of the Sparrow in an airframe that is not much larger than that of the AIM-9 Sidewinder.
On December 8, 1987, an F-18 Hornet AMRAAM firing at Point Mugu, California, evaluated the missile's ability to track and home in on two dissimilar targets. Two days later, another F-18 shot was a look-down, shoot-down attack on a low-altitude target. However, the AMRAAM was the subject of numerous technical problems and protracted delays which caused it to slip at least five years behind its original schedule. The AMRAAM was not cleared for service with the Hornet until after Desert Storm, but the weapon has by now almost entirely superseded the Sparrow as the primary BVR weapon of the Hornet.
The AMRAAM is a "fire and forget" weapon. The AMRAAM is guided to the vicinity of its target by an inertial guidance system which can be updated if necessary by a datalink from the launching aircraft. For the final run to the target, the missile switches over to its own high-PRF radar seeker and homes in on the target. Since this seeker uses its own active radar, it does not require that the launch aircraft illuminate or track the target during the terminal approach. If the target attempts to protect itself with jamming, the AMRAAM seeker can be set to switch over to a medium-PRF home-on-jam mode. Although the AIM-120 handles its own terminal homing onto the target, it usually still requires radar illumination from the fighter for a portion of its initial run-in to the target.
The AMRAAM is 11.97 feet long, has a wingspan of 20.7 inches, and a diameter of 7 inches. The AMRAAM is considerably lighter than the Sparrow that it replaces, weighing about 350 pounds at launch. It carries a 48-pound high-explosive directed-fragmentation warhead. Maximum speed is about Mach 4, and the maximum range is 35-45 miles.
The Hornet normally carries an AIM-9 Sidewinder infrared-homing air-to-air missile at each wingtip, although additional Sidewinders can be carried on underwing pylons if needed. The wingtip launch rails are inclined slightly downwards, reflecting the Hornet's nose-high cruising attitude.
The AIM-9 Sidewinder is 9.4 feet long, has a wingspan of 25 inches and a diameter of 5 inches. The missile has four tail fins on the rear, with a "rolleron" at the tip of each fin. These "rollerons" are spun at high speed by the slipstream in order to provide roll stability. The missile is steered by four canard fins mounted in the forward part of the missile just behind the infrared seeker head. The Sidewinder missile has a launch weight of about 180 pounds, and a maximum effective range of about 10 miles. The blast-fragmentation warhead weighs 22 pounds, and is detonated by either impact or proximity fusing.
While the missile is still on its launch rail, the Sidewinder's seeker head homes in on the infrared emissions coming from the target aircraft. As the target's heat source becomes more prominent, the Hornet pilot starts to hear a noise in his earphones. When the Sidewinder infrared seeker locks onto the target, a squeeze of the trigger by the pilot will launch the missile.
The Sidewinder infrared homing missile dates back to 1956, but the missile has been continuously upgraded over the years. Early F/A-18As carried the AIM-9J, which was the first major post-Vietnam improvement of the Sidewinder missile. The J model had an expanded target-engagement cone which enabled it to be launched at any spot in the rear hemisphere of a target aircraft rather than merely at its exhaust. Compared with the Vietnam-era AIM-9G, it had a more powerful motor and an improved warhead. The AIM-9J introduced the Sidewinder Expanded Acquisition Mode (SEAM), which slaved the seeker head of the missile to the aircraft's radar when in "dogfight" mode, which enabled the AIM-9J seeker head to be uncaged, slewed toward a specific target by the aircraft radar, and made to track only that particular target before being launched. The AIM-9H version introduced some minor improvements. The AIM-9L introduced in 1979 was an "all-aspect" missile, which meant that it was no longer limited to engaging an enemy aircraft from the rear. The seeker head was more sensitive and was able to pick up heat from the friction off the leading edges of an aircraft's wing and was able to distinguish between aircraft and decoy flares. The AIM-9L also uses a higher-impulse rocket motor, a more powerful warhead, and a proximity fuse rigged to blow outward toward the target in order to ensure better probability of a kill. The AIM-9M introduced in 1982 had better capability to distinguish between aircraft infrared emissions and decoy flares, and had a low-smoke rocket motor which made it far less likely to be seen by its prey. The number of vacuum tubes was reduced to two.
Despite the advanced age of the basic design, the all-aspect AIM-9L Sidewinder remains a potent threat, exceeded in effectiveness perhaps only by the Russian-built Molniya/Vympel R-73 (known in the West as the AA-11 *Archer*) which combines aerodynamic and thrust-vectoring control systems.
The AIM-122A Sidearm anti-radiation missile can be carried in place of the Sidewinder at the wingtips, since it is basically an AIM-9C with the infrared seeker head replaced by a broadband passive radar homing device.
Fighting in Vietnam demonstrated that a fighter or strike aircraft needs a gun for air combat during the closest range encounters. The F-18 Hornet is provided with an internal M61A1 20-mm cannon in the upper nose. 578 rounds are carried in an ammunition drum located just aft of the APG-65 radar set. The gun barrel is elevated approximately two degrees to improve target tracking. Although the gun port is located directly above the nose radar, it is claimed that the Hornet pilot can fire the gun without damaging the delicate radar. It is also claimed that although the gun is directly in front of the cockpit windshield, the pilot can fire the gun at night without being blinded by the muzzle flash.
The pilot can select a firing rate of 4000 or 6000 rounds per minute. The ingestion of gun gases into the engines is prevented by a fixed deflector which splits the muzzle blast and diverts gun gases to each side of the aircraft above the leading edge extension. There are three holes in the upper cockpit in front of the gun--one central hole for the cannon shells to pass through, and one on each side for gun gas ejection. Vents on the underside of the nose prevent the buildup of potentially dangerous gases in the gun bay.
The Hornet is capable of carrying an impressive load of air-to-ground ordnance, and can carry and launch virtually every air-to-ground weapon in the Navy arsenal. There are two hardpoints under each wing, plus a hardpoint on the centerline. A maximum of 17,000 pounds of ordnance can be carried, which even in strictly air-to-ground missions typically includes a pair of wingtip-mounted Sidewinders for self-defense.
The aircraft can carry Mark 82, 83, and 84 low-drag iron bombs which weigh respectively 500, 1000, and 2000 pounds each. They are carried on twin-store vertical ejection racks (VER-2s) that are mounted underneath the four underwing weapons pylons. These bombs can be provided with Snakeye fins which can retard the fall of these bombs so that the Hornet can clear the area before the blast during a low-level bombing run. Laser-guided Paveway versions of these bombs can also be carried. The Hornet can carry AGM-62 Walleye I and Walleye I ER/DL electro-optical guided bombs on the outboard wing stations. The aircraft can also carry and launch the Hughes AGM-65 Maverick television-guided air-to-surface missile, and later versions of the Hornet can carry the infrared-homing Maverick as well. All but the innermost stations can accommodate 468-lb Rockeye II anti-tank cluster bomb units or 610 lb BL-755 cluster bombs. Four conventional unguided rocket launchers, Mark 76 and Mark 106 practice bombs and the SUU-20 practice bomb and rocket dispenser can also be carried. The F/A-18 can also carry two B57 or B61 tactical nuclear weapons, although nuclear strike is not a mission that is typically envisaged for the Hornet.
The F-18 can carry the AGM-88A HARM anti-radiation missile for the SAM suppression role. It can also be configured to carry two AGM-84 Harpoon anti-shipping missiles, which uses active radar homing during the terminal stages of the flight to the target.
When not used to carry bombs, the two inboard underwing stations and the fuselage centerline station can carry 330 US gallon external fuel tanks. This is the typical situation, with only the outermost underwing pylons carrying offensive weapons. For ferry flights, 480 US gallon tanks can be substituted on any or all three stations.