An AIM-120 AMRAAM mounted on the wingtip launcher of an F-16 Fighting Falcon
|Type||Medium-range, active radar homing air-to-air missile|
|Place of origin||United States|
|In service||September 1991–present|
|Used by||See operators|
• Hughes: 1991–97
• $300,000–$400,000 for 120C variants
|Variants||AIM-120A, AIM-120B, AIM-120C, AIM-120C-4/5/6/7, AIM-120D|
|Weight||335 pounds (152 kg)|
|Length||12 feet (3.7 m)|
|Diameter||7 inches (180 mm)|
Active RADAR Target Detection Device (TDD)
|Engine||Solid-fuel rocket motor|
|Wingspan||20.7 inches (530 mm) (AIM-120A/B)|
|>180 km (>97 nmi)|
|Speed||Mach 4 (4,900 km/h; 3,045 mph; 1.3612 km/s)|
|inertial guidance, terminal active radar homing|
The AIM-120 Advanced Medium-Range Air-to-Air Missile, or AMRAAM (pronounced "am-ram"), is a modern beyond-visual-range air-to-air missile (BVRAAM) capable of all-weather day-and-night operations. Designed with the same form-and-fit factors as the previous generation of semi-active guided Sparrow missiles, it is a fire-and-forget missile with active guidance. When an AMRAAM missile is being launched, NATO pilots use the brevity code – Fox Three.
- 1 Origins
- 2 Development
- 3 Operational features summary
- 4 Guidance system overview
- 5 Kill probability and tactics
- 6 Variants and upgrades
- 7 Operational history
- 8 Foreign sales
- 9 Cold weather malfunctions
- 10 Operators
- 11 See also
- 12 References
- 13 External links
AIM-7 Sparrow MRM
The AIM-7 Sparrow medium range missile (MRM) was purchased by the US Navy from original developer Howard Hughes in the 1950s as its first operational air-to-air missile with "beyond visual range" (BVR) capability. With an effective range of about 12 miles (19 km), it was introduced as a radar beam riding missile and then it was improved to a semiactive radar guided missile which would home in on reflections from a target illuminated by the radar of the launching aircraft. It was effective at visual to beyond visual range. The early beam riding versions of the Sparrow missiles were integrated onto the F3H Demon and F7U Cutlass, but the definitive AIM-7 Sparrow was the primary weapon for the all-weather F-4 Phantom II fighter/interceptor, which lacked an internal gun in its U.S. Navy, U.S. Marine Corps, and early U.S. Air Force versions. The F-4 carried up to four AIM-7s in built-in recesses under its belly.
Although designed for use against non-maneuvering targets such as bombers, due to poor performance against fighters over North Vietnam, these missiles were progressively improved until they proved highly effective in dogfights. Together with the short range infrared guided AIM-9 Sidewinder, they replaced the AIM-4 Falcon IR and radar guided series for use in air combat by the USAF as well. A disadvantage to semi-active homing was that only one target could be illuminated by the launching fighter plane at a time. Also, the launching aircraft had to remain pointed in the direction of the target (within the azimuth and elevation of its own radar set) which could be difficult or dangerous in air-to-air combat.
AIM-54 Phoenix LRM
The US Navy later developed the AIM-54 Phoenix long range missile (LRM) for the fleet air defense mission. It was a large 1,000 lb (500 kg) Mach 4 missile designed to counter cruise missiles and the bombers that launched them. Originally intended for the straight-wing Douglas F6D Missileer and then the navalized version of the F-111B, it finally saw service with the Grumman F-14 Tomcat, the only fighter capable of carrying such a heavy missile. Phoenix was the first US fire-and-forget multiple launch radar-guided missile: one which used its own active guidance system to guide itself without help from the launch aircraft when it closed on its target. This in theory gave a Tomcat with a six-Phoenix load the unprecedented capability of tracking and destroying up to six targets beyond visual range, as far as 100 miles (160 km) away – the only US fighter with such capability.
A full load of six Phoenix missiles and its 2,000 pounds (910 kg) dedicated launcher exceeded a typical Vietnam-era bomb load. Its service in the US Navy was primarily as a deterrent, as its use was hampered by restrictive Rules of engagement in conflicts such as Operations Desert Storm, Southern Watch and Iraqi Freedom. The US Navy retired the Phoenix in 2004 in light of availability of the AIM-120 AMRAAM on the F/A-18 Hornet and the pending retirement of the F-14 Tomcat from active service in late 2006.
The Department of Defense conducted an extensive evaluation of air combat tactics and missile technology from 1974–78 at Nellis AFB using the F-14 Tomcat and F-15 Eagle equipped with Sparrow and Sidewinder missiles as blue force and Aggressor F-5E aircraft equipped with AIM-9L all-aspect Sidewinders as the Red force. This Joint Test and Evaluation (JT&E) was designated Air Combat Evaluation/Air Intercept Missile Evaluation (ACEVAL/AIMVAL). A principal finding was the necessity to produce illumination for the Sparrow until impact resulted in the Red Force being able to launch their all-aspect Sidewinders before impact thereby resulting in mutual kills. What was needed was Phoenix type multiple launch and terminal active capability in a Sparrow size airframe. This led to a Memorandum of Agreement (MOA) with European allies (principally the UK and Germany for development) for the US to develop an Advanced Medium Range Air-to-Air Missile (AMRAAM) with the USAF as lead service. The MOA also assigned responsibility for development of an Advanced Short Range Air-to-Air Missile to the European team – this would become the British ASRAAM.
By the 1990s, the reliability of the Sparrow had improved so much from the dismal days of Vietnam that it accounted for the largest number of aerial targets destroyed in Desert Storm. But while the USAF had passed on the Phoenix and their own similar AIM-47/YF-12 to optimize dogfight performance, they still needed a multiple-launch fire-and-forget capability for the F-15 and F-16. AMRAAM would need to be fitted on fighters as small as the F-16, and fit in the same spaces that were designed to fit the Sparrow on the F-4 Phantom. The European partners needed AMRAAM to be integrated on aircraft as small as the Sea Harrier. The US Navy needed AMRAAM to be carried on the F/A-18 Hornet and wanted capability for two to be carried on a launcher that normally carried one Sparrow to allow for more air-to-ground weapons.
The AMRAAM became one of the primary air-to-air weapons of the new F-22 Raptor fighter, which needed to place all of its weapons into internal weapons bays in order to help achieve an extremely low radar cross-section.
AMRAAM was developed as the result of an agreement (the Family of Weapons MOA, no longer in effect by 1990), among the United States and several other NATO nations to develop air-to-air missiles and to share production technology. Under this agreement the U.S. was to develop the next generation medium range missile (AMRAAM) and Europe would develop the next generation short range missile (ASRAAM). Although Europe initially adopted the AMRAAM, an effort to develop the MBDA Meteor, a competitor to AMRAAM, was begun in Great Britain. Eventually the ASRAAM was developed solely by the British, but using another source for its infrared seeker. After protracted development, the deployment of AMRAAM (AIM-120A) began in September 1991 in US Air Force F-15 Eagle fighter squadrons. The US Navy soon followed (in 1993) in its F/A-18 Hornet squadrons.
The eastern counterpart of AMRAAM is the somewhat similar Russian Air Force AA-12 "Adder", sometimes referred to in the West as the "AMRAAMski." Likewise, France began its own air-to-air missile development with the MICA concept that used a common airframe for separate radar-guided and infrared-guided versions.
Operational features summary
AMRAAM has an all-weather, beyond-visual-range (BVR) capability. It improves the aerial combat capabilities of US and allied aircraft to meet the threat of enemy air-to-air weapons as they existed in 1991. AMRAAM serves as a follow-on to the AIM-7 Sparrow missile series. The new missile is faster, smaller, and lighter, and has improved capabilities against low-altitude targets. It also incorporates a datalink to guide the missile to a point where its active radar turns on and makes terminal intercept of the target. An inertial reference unit and micro-computer system makes the missile less dependent upon the fire-control system of the aircraft.
Once the missile closes in on the target, its active radar guides it to intercept. This feature, known as "fire-and-forget", frees the aircrew from the need to further provide guidance, enabling the aircrew to aim and fire several missiles simultaneously at multiple targets and perform evasive maneuvers while the missiles guide themselves to the targets.
The missile also features the ability to "Home on Jamming," giving it the ability to switch over from active radar homing to passive homing – homing on jamming signals from the target aircraft. Software on board the missile allows it to detect if it is being jammed, and guide on its target using the proper guidance system.
Guidance system overview
Interception course stage
AMRAAM uses two-stage guidance when fired at long range. The aircraft passes data to the missile just before launch, giving it information about the location of the target aircraft from the launch point and its direction and speed. The missile uses this information to fly on an interception course to the target using its built in inertial navigation system (INS). This information is generally obtained using the launching aircraft's radar, although it could come from an Infra-red search and track system, from a data link from another fighter aircraft, or from an AWACS aircraft.
After launch, if the firing aircraft or surrogate continues to track the target, periodic updates—such as changes in the target's direction and speed—are sent from the launch aircraft to the missile, allowing the missile to adjust its course so that it is able to close to a self-homing distance where it will be close enough to "catch" the target aircraft in the basket (the missile's radar field of view in which it will be able to lock onto the target aircraft, unassisted by the launch aircraft).
Not all armed services using the AMRAAM have elected to purchase the mid-course update option, which limits AMRAAM's effectiveness in some scenarios. The RAF initially opted not to use mid-course update for its Tornado F3 force, only to discover that without it, testing proved the AMRAAM was less effective in BVR engagements than the older semi-active radar homing BAE Skyflash weapon—the AIM-120's own radar is necessarily of limited range and power compared to that of the launch aircraft.
Terminal stage and impact
Once the missile closes to self-homing distance, it turns on its active radar seeker and searches for the target aircraft. If the target is in or near the expected location, the missile will find it and guide itself to the target from this point. If the missile is fired at short range (typically visual range), it can use its active seeker just after launch, making the missile truly "fire and forget". However, this tactic is considerably risky – the now-active AMRAAM will acquire and home in on the first target it sees, regardless of friend or foe.
Apart from the slave mode, there is a free guidance mode, called boresight. This mode is radar guidance-free, the missile just fires and locks the first thing it sees. This mode can be used for defensive shot, i.e. when the enemy has numerical superiority.
Kill probability and tactics
|This section does not cite any references or sources. (October 2010)|
The kill probability (Pk) is determined by several factors, including aspect (head-on interception, side-on or tail-chase), altitude, the speed of the missile and the target, and how hard the target can turn. Typically, if the missile has sufficient energy during the terminal phase, which comes from being launched at close range to the target from an aircraft with an altitude and speed advantage, it will have a good chance of success. This chance drops as the missile is fired at longer ranges as it runs out of overtake speed at long ranges, and if the target can force the missile to turn it might bleed off enough speed that it can no longer chase the target. Operationally, the missile, which was designed for beyond visual range combat, has a Pk of 46% when fired at targets beyond visual range (13 missiles for 6 kills). In addition, the targets lacked missile warning systems, were not maneuvering, and were not attempting to engage the fighter that fired the AMRAAM. One of the targets was a US Army Blackhawk helicopter.
Variants and upgrades
Air-to-air missile versions
There are currently four main variants of AMRAAM, all in service with the United States Air Force, United States Navy, and the United States Marine Corps. The AIM-120A is no longer in production and shares the enlarged wings and fins with the successor AIM-120B. The AIM-120C has smaller "clipped" aerosurfaces to enable internal carriage on the USAF F-22 Raptor. AIM-120B deliveries began in 1994.
The AIM-120C deliveries began in 1996. The C-variant has been steadily upgraded since it was introduced. The AIM-120C-6 contained an improved fuse (Target Detection Device) compared to its predecessor. The AIM-120C-7 development began in 1998 and included improvements in homing and greater range (actual amount of improvement unspecified). It was successfully tested in 2003 and is currently being produced for both domestic and foreign customers. It helped the U.S. Navy replace the F-14 Tomcats with F/A-18E/F Super Hornets – the loss of the F-14's long-range AIM-54 Phoenix missiles (already retired) is offset with a longer-range AMRAAM-D. The lighter weight of the advanced AMRAAM enables an F/A-18E/F pilot greater bring-back weight upon carrier landings.
The AIM-120D is an upgraded version of the AMRAAM with improvements in almost all areas, including 50% greater range (than the already-extended range AIM-120C-7) and better guidance over its entire flight envelope yielding an improved kill probability (Pk). Raytheon began testing the D model on August 5, 2008, the company reported that an AIM-120D launched from an F/A-18F Super Hornet passed within lethal distance of a QF-4 target drone at the White Sands Missile Range.
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. The USN will field it from 2014, and AIM-120D will be carried by all Pacific carrier groups by 2020, although the 2013 sequestration cuts could push back this later date to 2022.
There are also plans for Raytheon to develop a ramjet-powered derivative of the AMRAAM, the Future Medium Range Air-Air Missile (FMRAAM). It is not known whether the FMRAAM will be produced since the target market, the British Ministry of Defence, has chosen the Meteor missile over the FMRAAM for a BVR missile for the Eurofighter Typhoon aircraft.
Raytheon is also working with the Missile Defense Agency to develop the Network Centric Airborne Defense Element (NCADE), an anti-ballistic missile derived from the AIM-120. This weapon will be equipped with a Ramjet engine and an infrared homing seeker derived from the Sidewinder missile. In place of a proximity-fused warhead, the NCADE will use a kinetic energy hit-to-kill vehicle based on the one used in the Navy's RIM-161 Standard Missile 3.
The −120A and −120B models are currently nearing the end of their service life while the −120D variant has just entered full production. AMRAAM was due to be replaced by the USAF, the U.S. Navy, and the U.S. Marine Corps after 2020 by the Joint Dual Role Air Dominance Missile (Next Generation Missile). This was unexpectedly terminated in the 2013 budget plan, and so the future replacement is uncertain.
Raytheon successfully tested launching AMRAAM missiles from a five-missile carrier on a M1097 Humvee. This system will be known as the SLAMRAAM (Surface Launched (SL) and AMRAAM). They receive their initial guidance information from a radar not mounted on the vehicle. Since the missile is launched without the benefit of an aircraft's speed or high altitude, its range is considerably shorter. Raytheon is currently marketing an SL-AMRAAM EX, purported to be an extended range AMRAAM and bearing a resemblance to the RIM-162 ESSM.
The Norwegian Advanced Surface-to-Air Missile System (NASAMS), developed by Kongsberg Defence & Aerospace, consists of a number of vehicle-pulled launch batteries (containing six AMRAAMs each) along with separate radar trucks and control station vehicles.
While still under evaluation for replacement of current US Army assets, the SL-AMRAAM has been deployed in several nations' military forces. The United Arab Emirates (UAE) has requested the purchasing of SL-AMRAAM as part of a larger 7 billion dollar foreign military sales package. The sale would include 288 AMRAAM C-7 missiles.
The National Guard Association of the United States has sent a letter asking for the United States Senate to stop the Army's plan to drop the SLAMRAAM program because without it there would be no path to modernize the Guard's AN/TWQ-1 Avenger Battalions.
On February 22, 2015 Raytheon announced an Extended Range upgrade to NASAMS-launched AMRAAM, calling it AMRAAM-ER.
The AMRAAM was used for the first time on December 27, 1992, when a USAF F-16D shot down an Iraqi MiG-25 that violated the southern no-fly-zone. Interestingly enough, this missile was returned from the flight line as defective a day earlier. AMRAAM gained a second victory in January 1993 when an Iraqi MiG-23 was shot down by a USAF F-16C.
The third combat use of the AMRAAM was in 1994, when a Republika Srpska Air Force J-21 Jastreb aircraft was shot down by a USAF F-16C that was patrolling the UN-imposed no-fly-zone over Bosnia. In that engagement at least 3 other Serbian aircraft were shot down by USAF F-16C fighters using AIM-9 missiles (see Banja Luka incident for more details). At that point three launches in combat resulted in three kills, resulting in the AMRAAM being informally named "slammer" in the second half of the 1990s.
In 1998 and 1999 AMRAAMs were again fired by USAF F-15 fighters at Iraqi aircraft violating the No-Fly-Zone, but this time they failed to hit their targets. During the spring of 1999, AMRAAMs saw their main combat action during Operation Allied Force, the Kosovo bombing campaign. Six Serbian MiG-29 were shot down by NATO (4 USAF F-15C, 1 USAF F-16C, 1 Dutch F-16A MLU), all of them using AIM-120 missiles (the kill by the F-16C may have happened due to friendly fire, from SA-7 MANPAD fired by Serbian infantry).
As of mid 2008, the AIM-120 AMRAAM has shot down nine aircraft (six MiG-29s, one MiG-25, one MiG-23, and one Soko J-21 Jastreb). An AMRAAM was also involved in a friendly-fire incident in 1994 when F-15 fighters patrolling the Northern No-Fly Zone inadvertently shot down a pair of U.S. Army Black Hawk helicopters.
Since 2007 Raytheon has continued to slip on AMRAAM deliveries, leading the USAF to withhold $621 million in 2012 on account of 193 missiles not delivered.
Canadair, now Bombardier, had largely helped with the development of the AIM-7 Sparrow and Sparrow II, and assisted to a less extent in the AIM-120 development. Canada had placed an order for 256 AIM-120's, but cancelled half of them after engine ignition problems due to cold weather conditions. The AIM-9X & AIM-7 were ordered as replacements.
In early 2006, the Pakistan Air Force (PAF) ordered 500 AIM-120C-5 AMRAAM missiles as part of a $650 million F-16 ammunition deal to equip its F-16C/D Block 50/52+ and F-16A/B Block 15 MLU fighters. The PAF got the first three F-16C/D Block 50/52+ aircraft on July 3, 2010 and first batch of AMRAAMs on July 26, 2010.
In 2007, the United States government agreed to sell 218 AIM-120C-7 missiles to Taiwan as part of a large arms sales package that also included 235 AGM-65G-2 Maverick missiles. Total value of the package, including launchers, maintenance, spare parts, support and training rounds, was estimated at around US$421 million. This supplemented an earlier Taiwanese purchase of 120 AIM-120C-5 missiles a few years ago.
2008 has brought announcements of new or additional sales to Singapore, Finland, Morocco and South Korea; in December 2010 the Swiss government requested 150 AIM-120C-7 missiles. Sales to Finland have stalled, because the manufacturer has not been able to fix a mysterious bug that causes the rocket motors of the missile to fail in cold tests.
Cold weather malfunctions
Finnish Defence Forces reported on September 3, 2012 that the United States had not delivered any of the AMRAAM anti-aircraft missiles they had ordered due to a mysterious engine malfunction in cold weather. The manufacturer, Raytheon, has not been able to determine the cause of the problem. Colonel Kari Renko, an engineer at the Finnish Air Force, was quoted by Helsingin Sanomat as saying, "The problem involves the rocket engines which have been in use for decades" and that Finland first was told of the problems by the Americans about two years ago. The reason for the malfunction has been determined to be a change in the chemical formula of the rocket propellant to comply with new environmental regulations. The change caused the supplier of AMRAAM rocket motors, Alliant Techsystems, to produce motors that were unreliable, especially in cold conditions where aircraft carrying them would fly. ATK has been unable to find a solution, and no new AMRAAM missiles had been delivered to the USAF since 2010 as a result. In late 2012, Raytheon solved the problem by selecting Norwegian ammunition manufacturer Nammo Raufoss to be their new supplier of AMRAAM rocket motors.
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