Definitions

homing on

AIM-120 AMRAAM

The AIM-120 Advanced Medium-Range Air-to-Air Missile, or AMRAAM (pronounced am-ram), is a modern Beyond Visual Range (BVR) air-to-air missile (AAM) capable of all weather day and night performance. It is also commonly known as the Slammer in USAF service. When an AMRAAM missile is being launched, NATO pilots use the brevity code Fox Three in radio communication, as with all active-guidance missiles.

Origins

AIM-7 Sparrow MRM

The AIM-7 Sparrow medium range missile (MRM) was developed by the US Navy in the 1950s as its first operational BVR air-to-air weapon. With an effective range of about , it was introduced as a radar beam riding missile and then improved to a semi-active 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, gun-less F-4 Phantom II fighter/interceptor with up to four carried in special recesses under the fuselage.

Although designed for non maneuvering targets such as bombers, due to poor performance against fighters over North Vietnam, these missiles were progressively improved until they proved 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 launch aircraft at a time; also, the launch aircraft had to remain pointed in the direction of the target (within the azimuth of the aircraft radar, up to 60 degrees off the nose on some systems), which could be difficult or dangerous in 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 an impressive Mach 5 missile designed to counter cruise missiles and their (Bomber) launch platforms. It was intended that eight of its first incarnation would be fitted to the straight-wing F6D Missileer, and then the F-111B. Neither aircraft was introduced into service and Grumman won the competition to replace the F-111B with a dogfighter with enough weight and volume for the Phoenix that became the F-14 Tomcat. 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 gave a Tomcat with a six Phoenix load the unprecedented capability of tracking and destroying up to six targets as far as away.

The Phoenix could only be carried by the huge F-14, making the Tomcat the only US fighter with a multiple shot, fire-and-forget radar missile. A full load of six Phoenix weighed , and with the additional of dedicated launcher, it was so heavy it exceeded a typical Vietnam era bomb load; typically only two or four missiles were flown off the carrier as a full load was too heavy to be brought back on board for landing. Although highly lauded in the press, its operational service with the US Navy was primarily as a deterrent as its use was hampered by restrictive Rules of Engagement and the only reported combat successes were with Iranian Tomcats against Iraqi opponents. The US Navy retired its Phoenix capability in 2005 in light of availability of the AIM-120 AMRAAM on the F/A-18 Hornet.

ACEVAL/AIMVAL

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 Evaluaton 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 develop an Advanced Medium Range Air-to-Air Missile 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.

Requirements

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 desired the Navy's 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 since the 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.

AMRAAM would eventually be the primary weapon for the F-22 Raptor which needed to fit all its missiles in internal weapons bays like the old F-106 Delta Darts in order to maintain a stealthy radar cross-section. The US Navy ultimately decided to retire its Tomcats and pass the Fleet Air Defense mission to the F/A-18C and F/A-18E/F Hornets, which needed even more advanced versions of AMRAAM to replace the Phoenix capability.

Development

AMRAAM was developed as the result of an agreement, the Family of Weapons Memorandum of Agreement 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). When the German ASRAAM seeker development ran into problems, the MOA was abrogated and this breakdown led to the U.S. developing AIM-9X Sidewinder and Germany the IRIS-T. Although Europe initially adopted AMRAAM, an effort to develop the MBDA Meteor, a competitor to AMRAAM was begun. Eventually ASRAAM was developed solely by the UK with another source for its seeker. After protracted development, deployment of AMRAAM (AIM-120A) began in September 1991 began with USAF F-15 Eagle squadrons. The US Navy followed suit in 1993 with the F/A-18C.

The eastern counterpart of AMRAAM is the very similar Russian R-77 AA-12 Adder, commonly known in the west as "AMRAAMski." Likewise, France began its own missile development with the MICA concept that used the same airframe for separate radar and IR guidance versions.

Operational features summary

AMRAAM has an all-weather, beyond-visual-range (BVR) capability. It improves the aerial combat capabilities of U.S. and allied aircraft to meet the future threat of enemy air-to-air weapons. 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, mistakenly called "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. This, contrary to the attack sequence on a non-jamming target, truly can be described as "fire and forget", as it does not require any guidance provided to the missile after launch.

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 tracking system (IRST), from a data link from another fighter aircraft, or from an AWACS aircraft.

If the firing aircraft or surrogate continues to track the target, periodic updates are sent to the missile telling it of any changes in the target's direction and speed, allowing it to adjust its course so that it is able to close to self-homing distance while keeping the target aircraft in the basket (the radar seeker's field of view) in which it will be able to find it.

Not all AMRAAM users 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. At the point where an AMRAAM switches to autonomous self-guidance, the NATO brevity code "PITBULL" would be called out on the radio, just as "Fox Three" would be called out upon launch.

Kill probability and tactics

General considerations

Once in its terminal mode, the missile's advanced electronic counter countermeasures (ECCM) support and good maneuverability mean that the chance of it hitting or exploding close to the target is high (on the order of 90%), as long as it has enough remaining energy to maneuver with the target if it is evasive. 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 close enough to the target from an aircraft flying high and fast enough, it will have an excellent 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.

Lower-capability targets

This leads to two main engagement scenarios. If the target is not armed with any medium or long-range fire-and-forget weapons, the attacking aircraft need only to get close enough to the target and launch the AMRAAM. In these scenarios, the AMRAAM has a high chance of hitting, especially against low-maneuverability targets. The launch distance depends upon whether the target is heading towards or away from the firing aircraft. In a head-on engagement, the missile can be launched at longer range, since the range will be closing fast. In this situation, even if the target turns around, it is unlikely it can speed up and fly away fast enough to avoid being overtaken and hit by the missile (as long as the missile is not released too early). It is also unlikely the enemy can outmaneuver the missile since the closure rate will be so great. In a tail-on engagement, the firing aircraft might have to close to between one-half and one-quarter maximum range (or maybe even closer for a very fast target) in order to give the missile sufficient energy to overtake the targets.

If the targets are armed with missiles, the fire-and-forget nature of the AMRAAM is invaluable, enabling the launching aircraft to fire missiles at the target and subsequently take defensive actions. Even if the targets have longer-range semi-active radar homing (SARH) missiles, they will have to chase the launching aircraft in order for the missiles to track them, effectively flying right into the AMRAAM. If the target aircraft fires missiles and then turn and runs away, their own missiles will not be able to hit. Of course, if the target aircraft have long range missiles, even if they are not fire-and-forget, the fact that they force the launching aircraft to turn and run reduces the kill probability, since it is possible that without the mid-course updates the missiles will not find the target aircraft. However the chance of success is still good and compared to the relative impunity the launching aircraft enjoy, this gives the AMRAAM-equipped aircraft a decisive edge. If one or more missiles fail to hit, the AMRAAM-equipped aircraft can turn and re-engage, although they will be at a disadvantage compared to the chasing aircraft due to the speed they lose in the turn, and would have to be careful that they're not being tracked with SARH missiles.

Similarly armed targets

The other main engagement scenario is against other aircraft with fire-and-forget missiles like the Vympel R-77 (NATO AA-12 "Adder") — perhaps MiG-29s, Su-27s or similar. In this case engagement is very much down to teamwork and could be described as "a game of chicken." Both flights of aircraft can fire their missiles at each other beyond visual range (BVR), but then face the problem that if they continue to track the target aircraft in order to provide mid-course updates for the missile's flight, they are also flying into their opponents' missiles. Although in this regard the RVV-AE (which is the missile's export name or R-77 the official Russian Air force designation) does have an advantage as it is faster and has a greater range than the AMRAAM. Meaning that the Russian airplane firing it can in fact fire first, although it still needs to lead the missile towards the target as the missiles own radar seeker has a limited range (under 10km, as on AMRAAM). This is why teamwork is so important and advanced missiles with guidance systems with hand-off capability can help overcome this problem. This is also part of the reason why most tactics dictate holding on to missiles "until you see the whites of their eyes," or holding on to them for as long as possible.

If the enemy fires missiles at maximum range, you will be able to defeat them easily without having surrendered valuable ordnance yourself. The other main tactic would be to sneak up behind the enemy aircraft and launch missiles without them noticing, giving the launching aircraft sufficient time to leave the danger zone of the enemy after launching. Even if the enemy detects the launch and turns around, the speed and possibly altitude it loses during the turn puts its missiles at an energy disadvantage which may be sufficient for the other aircraft to defeat it. This typically requires excellent ground-control intercept (GCI) or airborne radar (AWACS — Airborne Warning and Control System) facilities in order to be successful.

Variants and upgrades

Air-to-air missile versions

There are currently three variants of AMRAAM, all in service with the United States Air Force, USN, 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, and AIM-120C deliveries began in 1996.

The AIM-120C 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) can be partially offset with a longer-range AMRAAM, but note that the AMRAAM does not have a very-long range like the Phoenix missile.

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 recently 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.

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.

AMRAAM will continue to serve in the arsenal of the USAF, the U.S. Navy, and the U.S. Marine Corps until at least 2020 when the Joint Dual Role Air Dominance Missile (JDRADM) would potentially enter service. The -120A and -120B models are currently nearing the end of their service life while the -120D variant has just entered full production.

Ground-launched systems

Raytheon successfully tested launching AMRAAM missiles from a five-missile carrier on a HMMWV (hum-vee). 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 (probably the MPQ-64 Sentinel radar system or possibly a PATRIOT missile battery radar) and help to provide low-level, close-in defence while the PATRIOT system engages targets at higher altitudes and greater ranges. 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, proported to be an extended range AMRAAM and bearing a striking resemblance to the ESSM (Evolved Sea Sparrow Missile).

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, including Egypt. 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

Operational History

The AMRAAM was used for the first time on 27 December 1992, when an USAF F-16C shot down an Iraqi MiG-25 that violated the southern no-fly-zone. 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 Serbian J-22 Orao 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 using AIM-9 missiles. At that point three launches in combat resulted in three kills, so in the second half of the 1990s AMRAAM was informally named "Slammer". In 1998 and 1999 AMRAAMs were again fired by USAF F-15s at Iraqi aircraft violating the No-Fly-Zone, but this time they failed to hit their targets, probably because they were fired at their limit effective range so that Iraqi pilots were able to outmaneuver them. During the spring of 1999, AMRAAMs saw their main combat action during Allied Force, Kosovo 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 (even if the kill by the F-16C may have happened due to friendly fire by a SA-7 MANPADS fired by Serbian Infantry). In this campaign, NATO fighters fired more AIM-120 to their targets to achieve these 6 kills.

As of mid 2008, the AIM-120 AMRAAM has shot down nine enemy aircraft (six MiG-29, one MiG-25, one MiG-23, and one Soko J-21 Jastreb or J-22 Orao.

The AMRAAM was also involved in a friendly-fire incident when F-15 fighters patrolling the Southern No-Fly Zone inadvertently shot down a pair of U.S. Army Blackhawk helicopters

Operators

In 2005 Chile received AIM-120 AMRAAM missiles from the United States Air Force as part of the Peace Puma Plan which Chilean Air Force also received 10 F-16 D fighters as part of the plan. In 2006 Poland new F-16 Block52+ has Aim-120C-5.

In early 2006 the Pakistan Air Force ordered 500 AIM-120C-5 AMRAAM missiles as part of a $650mn F-16 ammunition deal to equip the PAF's F-16C/D Block 52+ and F-16A/B MLU.

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 $421 million USD. 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 (300 AIM-120C-7), Morocco and South Korea.

External links

See also

In service

Under development

Notes

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