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Air-to-Air Missiles: AIM-120 AMRAAM
The AIM-120 Advanced Medium-Range Air-to-Air Missile (AMRAAM) is a "fire-and-forget" weapon that can operate in any weather and strike targets almost 40 miles away. Developed by a joint Air Force and Navy program in the 1970s, the AIM-120 became operational in 1991. It is capable of reaching a speed of Mach 4 and can operate at beyond visual range (BVR). When fired at long range, the missile uses inertial guidance and receives updates on its target from the launch aircraft. At close range, the AIM-120 guides itself using its onboard radar so that the launch aircraft can engage other targets. The Air Force and Navy have successfully used the AIM-120 in Operation Desert Storm and Operation Allied Force. The U.S. Army tested a ground-based version of the AIM-120 known as the SL-AMRAAM but decided to terminate the program for budgetary reasons. The AIM-120 is currently used on all aircraft operated by the Air Force, Navy, and the Marine Corps, as well as other militaries around the world.
AIM-120 AMRAAM Air-to-Air Missile Development
The AIM-120 began with a 1975 study that recommended future aerial threats be engaged at a range of up to 40 miles. This range exceeded the capability of the AIM-7 Sparrow, though was less than the long-range AIM-54 Phoenix. The poor performance of the AIM-7 Sparrow, in particular during the Vietnam War, underscored the need for a new weapon.
Hughes and Raytheon were chosen in February 1979 as finalists in the development of a prototype known as the YAIM-120A AMRAAM. Hughes received a contract in December 1981 for full-scale development of the new missile, after defeating Raytheon in a "fly-off" competition. The first production-level AIM-120A was launched from a F-16 fighter in February 1984, and the first supersonic launch was completed in September 1987.
Technical and budgetary problems plagued the AIM-120. Its unexpectedly long development time also resulted in cost overruns. In October 1988, the first low-rate initial production (LRIP) AIM-120A was delivered. Finally, initial operational capability (IOC) was reached in September 1991.
The AIM-120 is smaller, faster, and lighter than the AIM-7 Sparrow it was intended to replace. It not only has better capabilities against low-altitude targets, but also includes a datalink to guide the missile before its onboard active radar turns on and makes terminal intercept of its target. The AIM-120 also has an inertial reference unit and micro-computer system to reduce its dependence on the launch aircraft's fire control system.
The AIM-120 missile is launched from the LAU-127/A, LAU-128/A, or LAU-129/A common rail launchers (CRLs) found on all current U.S. fighter aircraft. These launchers also support the AIM-9 Sidewinder.
The AIM-120 has a two-stage guidance system when fired at long range. The launch aircraft sends data to the missile just prior to launch, including the location, speed, and direction of the target aircraft. The AIM-120 uses this data to fly an intercept course using its onboard inertial navigation system (INS). The launch aircraft typically provides this data from its radar, but an infrared search and tracking system (IRST) or data link from another aircraft can also provide it.
The AIM-120 receives periodic updates about the speed and direction of the target from the launch aircraft so that it can adjust its course to reach a self-homing distance, controlling its flight with four movable tail fins. Once at self-homing distance, the AIM-120 can lock onto the target, turn on its active radar seeker, and use its autonomous self-guidance to reach the target. Upon intercept, an active-radar proximity fuse detonates the 40-pound high-explosive warhead to destroy the target.
At close range, the AIM-120 is fired within its self-homing distance. The missile guides itself all the way using its onboard radar. This allows the launch aircraft the freedom to engage other targets, making the AIM-120 a "fire-and-forget" weapon.
The first production variant of the AIM-120 is the AIM-120A, but it was quickly replaced by the AIM-120B, which had a new guidance section, updated software in reprogrammable EPROM modules and other improvements to its electronics. Soon after the AIM-120C was introduced, with smaller aerosurfaces so that it could be fitted into a weapons bay, as found on aircraft such as the F-22 Raptor.
The AIM-120C has undergone steady improvement. The AIM-120C-6 included an improved fuse. The AIM-120C-7 saw improvements in homing and increased range. Development of the AIM-120C-7 began in 1998 and was successfully tested in September 2003. It replaced the AIM-54 Phoenix on F-14 Tomcats, and became the missile of choice for the F/A-18E/F Super Hornet.
The AIM-120D is a general upgrade to the missile. Range was increased by 50 pct, and guidance was improved. This variant also has more precise navigational capabilities and improve high-angle off-boresight (HOBS) firing. This resulted in an improved kill probability for the missile. Raytheon started testing the AIM-120D on 5 August 2008. The AIM-120D is in full production as of 2011, and the AIM-120A and AIM-120B variants are being phased out.
AIM-120 AMRAAM Operational History
During Operation Desert Storm, F-15 fighters carried a small number of AIM-120s. However, none was fired. The AIM-120A was first used operationally on 27 December 1992, when an Air Force F-16D shot down a MiG-25 Foxbat that violated the southern no-fly zone in Iraq. A second kill was achieved in January 1993, when an Air Force F-16C shot down an Iraqi MiG-23.
In 1994, an Air Force F-16C shot down a Republika Srpska Air Force J-21 Jastreb in the U.N. no-fly zone in Bosnia. The AIM-120 earned the nickname "slammer" for its perfect kill ratio at that time.
The AIM-120 was again used against Iraqi aircraft violating the no-fly zone in 1998 and 1999, but the targets were not hit.
During Operation Allied Force, the AIM-120 was used to shoot down six Serbian MiG-29s, though one of these kills may have been the result of a SA-MANPAD fired by the Serbian infantry.
The AIM-120 was also involved in a friendly fire incident in 1994, when F-15 fighters patrolling the Iraqi southern no-fly zone unintentionally shot down two U.S. Army Black Hawk helicopters.
Characteristics of the AIM-120 AMRAAM
Recommended Book about Air-to-Air Weapons