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The AIM-120 AMRAAM (Advanced Medium-Range Air-to-Air Missile) is a fire-and-forget air-to-air missile, and has replaced the AIM-7 Sparrow as the U.S. military's standard BVR (Beyond Visual Range) intercept missile.
In the late 1970s, the U.S. military services decided that they needed a medium-range air-to-air missile with a true fire-and-forget capability. The SARH (Semi-Active Radar Homing) guidance of the AIM-7 Sparrow required the launching aircraft's radar to illuminate the target until impact, which made the aircraft a target itself and also limited its ability to engage several targets simultaneously. In February 1979, Hughes and Raytheon were selected as finalists for the YAIM-120A AMRAAM (Advanced Medium-Range Air-to-Air Missile) competition, and in December 1981 Hughes was declared winner. A year before, a joint U.S./European agreement for development of a new family of air-to-air weapons had been signed. This agreement put the responsibility for the BVR AMRAAM to the United States, while the complementary ASRAAM (Advanced Short-Range Air-to-Air Missile) (later AIM-132) would be developed in Europe. In February 1984 the first production-representative AIM-120A missile was launched from an F-16 aircraft, but it was not before September 1987 that the first supersonic launch succeeded. The AMRAAM program was troubled by all sorts of technical and political problems, not the least of which was severe cost overrun because of the protracted development period. The first LRIP (Low-Rate Initial Production) AIM-120A was delivered in October 1988, but it took until September 1991 that IOC (Initial Operational Capability) was finally achieved.
The AIM-120A is powered by a solid-propellant rocket motor in a WPU-6/B propulsion section. Before launch, the launching aircraft's fire control system programs the missile's inertial autopilot in the WGU-16/B guidance unit to bring it into a homing basket in the vicinity of the target. The autopilot can receive mid-course updates from the aircraft via a data link. The AMRAAM's WCU-11/B control section controls the missile in flight with the four movable tail fins. As soon as the target is within range, the AMRAAM activates its active radar seeker for autonomous terminal homing. The 23 kg (50 lb) WDU-33/B fragmentation warhead is detonated by an FZU-49/B fuzing system consisting of a "smart" (anti-clutter) proximity fuze and an impact fuze. The effective range of the AIM-120A of course highly depends on the firing parameters, and official performance data are classified. Typical quoted figures for maximum range vary between 50 km (30 miles) and 70 km (45 miles). For the lower portions of the AMRAAM's range envelope (minimum range is said to be 2 km (2200 yds)), where the mid-course guidance updates are not needed, the AIM-120 is a true fire-and-forget weapon.
Non-tactical variants of the AIM-120A are the CATM-120A captive-carry training missile, the DATM-120A for ground-handling training, and the JAIM-120A with telemetry electronics for test and evaluation purposes.
Although a few AIM-120As were deployed to the Gulf during Operation Desert Storm in early 1991, no AMRAAMs were fired in that conflict (officially, at least). The first combat use of an AIM-120A occurred in December 1992, when an F-16C shot down an Iraqi MiG-25 during Operation Southern Watch.
The AIM-120B, which was first delivered in late 1994, had a new WGU-41/B guidance section. It had software in reprogrammable EPROM modules, a new digital processor and other electronics updates. Non-tactical versions are the CATM-120B captive-carry and JAIM-120B test and evaluation missiles.
|AIM-120A/B (exact model unknown)|
The AMRAAM P3I (Pre-Planned Product Improvement) program led to the AIM-120C, first delivered in 1996. The major new feature of the basic AIM-120C (P3I Phase 1) are the clipped wings and fins. Although this feature was introduced to allow carriage in the internal weapons bays of the F/A-22 Raptor, the -120C can also be used from other AMRAAM-capable aircraft. The guidance unit of the AIM-120C is upgraded to WGU-44/B standard. The first P3I Phase 2 missile is the AIM-120C-4 (first delivered in 1999), which has an improved WDU-41/B warhead. The AIM-120C-5 is a C-4 with a slightly larger motor in the new WPU-16/B propulsion section and a new shorter WCU-28/B control section with compressed electronics and ECCM upgrades. Deliveries of the AIM-120C-5 began in July 2000. It was followed on the production line by the AIM-120C-6, which features an updated TDD (Target Detection Device). The AIM-120C-7 (P3I Phase 3), development of which has begun in 1998, incorporates improved ECCM with jamming detection, an upgraded seeker, and longer range. The latter feature was specifically requested by the U.S. Navy to get a (somewhat) suitable replacement for the AIM-54 Phoenix very-long range missile, which was then planned to be retired together with the F-14D Tomcat around 2007 (actual official retirement was already in September 2004). The AIM-120C-7 was successfully tested against combat-realistic targets in August and September 2003, and IOC was then planned for 2004. This has slipped somewhat, but as of early 2006, the AIM-120C-7 is beginning to be fielded. Equivalent to the -120A/B, there are also CATM-120C and JAIM-120C non-tactical variants of the AIM-120C.
The AIM-120D (P3I Phase 4, formerly known as AIM-120C-8) is a development of the AIM-120C with a two-way data link, more accurate navigation using a GPS-enhanced IMU, an expanded no-escape envelope, improved HOBS (High-Angle Off-Boresight) capability, and a 50% increase in range. The AIM-120D is a joint USAF/USN project, and is currently in the testing phase. First production deliveries are expected for December 2007. The CATM-120D is the inert captive-carry training version of the AIM-120D.
More than 12000 AIM-120 missiles of all versions have been built so far, including a significant amount for non-U.S. customers. The AMRAAM can be carried by all current U.S. fighter aircraft (F-14D, F-15, F-16, F/A-18, F/A-22), and is launched from LAU-127/A, -128/A or -129/A CRLs (Common Rail Launchers), which can also be used for the AIM-9 Sidewinder.
NCADE (Network Centric Airborne Defense Element) is a program to develop an air-launched anti-missile interceptor missile using AMRAAM components. The NCADE missile replaces the AIM-120's radar seeker with the IIR (Imaging Infrared) seeker of the AIM-9X Sidewinder, and changes the propulsion system to a two-stage rocket. The latter consists of an AIM-120 first stage and a new Aerojet second stage, which can provide a thrust of 0.55 kN (125 lb) for more than 25 seconds. NCADE's airframe, flight control system and aircraft interface are essentially the same as on the AIM-120, making the missile immediately compatible with many existing launch platforms.
The NCADE missile is intended to intercept short- to medium-range ballistic missiles in the boost, ascent, or terminal phase. To achieve this, the missile is fired upwards by the first-stage motor in a very steep angle. At high altitude, the IIR seeker can acquire a target, and then the missile will use its long burning second-stage motor for the intercept.
At the time of this writing, the NCADE program is undergoing component tests (propulsion and seeker). No planned timeframe for a test of an all-up NCADE round has been announced so far.
The AIM-120 missile is also used in some ground-launched applications. Norway uses the NASAMS (Norwegian Advanced Surface-to-Air Missile System), which employs the AMRAAM missile from a six-round box launcher. NASAMS became operational in 1995. Although the designation MIM-120A is sometimes quoted for the missiles, this is not an official DOD designation.
|AIM-120A (on Hawk launcher)|
Beginning in 1995, the U.S. Army evaluated the use of AMRAAM from modified Hawk launchers and from HMMWV (High-Mobility Multipurpose Wheeled Vehicle) in a system known as HUMRAAM ("Hummer-AMRAAM"). The U.S. Marine Corps version of HUMRAAM was known as CLAWS (Complimentary Low-Altitude Weapon System), and in April 2001 Raytheon received a development and pre-production contract for CLAWS. The system was intended to replace the USMC's retired MIM-23 Hawk system from 2006/2007, but CLAWS was cancelled in 2006.
|AIM-120A (on HUMRAAM (CLAWS/SLAMRAAM) launcher)|
U.S. Army plans for a ground-based AMRAAM system are called SLAMRAAM (Surface-Launched AMRAAM). The SLAMRAAM system is also based on HMMWV vehicles, and is planned to become operational in 2008. It will replace some of the Army's Avenger air-defense systems, which use the smaller and less capable FIM-92 Stinger missile.
Note: Data given by several sources show slight variations. Figures given below may therefore be inaccurate! Especially the range figures are rough estimates only.
Data for AIM-120A/B/C:
|Length||3.66 m (12 ft)|
|Wingspan||53.3 cm (21 in)||44.7 cm (17.6 in)|
|Finspan||63.5 cm (25 in)||44.7 cm (17.6 in)|
|Diameter||17.8 cm (7 in)|
|Weight||157 kg (345 lb)|
|Range||50-70 km (30-45 miles)||> 105 km (65 miles)|
|Propulsion||Hercules/Aerojet solid-fueled rocket|
|Warhead||23 kg (50 lb) WDU-33/B blast-fragmentation||18 kg (40 lb) WDU-41/B blast-fragmentation|
 Norman Friedman: "US Naval Weapons", Conway Maritime Press, 1983
 Norman Friedman: "World Naval Weapons Systems, 1997/98", Naval Institute Press, 1997
 Christopher Chant: "World Encyclopaedia of Modern Air Weapons", Patrick Stephens Ltd., 1988
 Hajime Ozu: "Missile 2000 - Reference Guide to World Missile Systems", Shinkigensha, 2000
 Bernard Blake (ed.): "Jane's Weapon Systems 1987-88", Jane's, 1988
 AMI International Website
 Raytheon Co. Website
 Defense Industry Daily Website
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