AIM-120 AMRAAM – Advanced Medium-Range Air-to-Air Missile
PANAGYURISHTE — The AIM-120 medium-range air-to-air guided missile (UR), originally designated AMRAAM [Advanced Medium-Range Air-to-Air Missile], was developed by Hughes Aircraft Co. This missile replaced the Sparrow missile of a similar class and was adopted by the US Air Force in 1991. Compared to the Sparrow missile, the AIM-120 achieved a significant reduction in the launch weight and dimensions of the missile, increasing the effectiveness of the fight against both high-altitude energetically maneuvering and low-flying targets in conditions of intensive electronic warfare.
This became possible thanks to modern achievements in the theory of aircraft control, radio electronics and computer technology, propulsion systems, and combat equipment. Currently, it is in service with the US Air Force, Germany, Great Britain, and several other NATO member countries.
About AIM-120 AMRAAM
The AIM-120 missile is made according to the normal aerodynamic scheme and consists of three compartments: head, warhead [warhead], and tail. It has a cruciform wing of a small area, which provides fairly good maneuverability at low flight speeds, and cruciform rudders in the tail section. The UR body is made of steel with a gray color, which can withstand significant kinetic heating.
The main part of the autonomous guidance equipment is concentrated in the head compartment, which is carried out using a combined system – command-inertial in the initial and middle sections of the flight path and active radar in the final. The equipment of the command-inertial system includes a cardless inertial platform and a command-line receiver located in the nozzle block of the tail section of the UR. The weight of the platform, in which miniature high-speed gyroscopes are used, is less than 1.4 kg.
A high-performance microcomputer operating at a clock frequency of 30 MHz is common for command-inertial and radar systems. It performs all the functions of control, command communication, signal processing of radar equipment and fuses, as well as built-in control when checking the operability of the main components and blocks of equipment. The introduction of such a micro-computer made it possible to significantly increase the number of parameters used to calculate the most optimal guidance trajectory, depending on the relative position of the missile and the target at the meeting point, their speeds, and flight directions.
For example, based on the measured range and angle of the target’s line of sight, as well as the rates of their change, the microcomputer calculates the target’s acceleration, and with a known own acceleration obtained using an inertial platform, it calculates its possible maneuvers. This computer can choose such a guidance trajectory in which the missile will overtake the target at an angle that gives the greatest effect for hitting the warhead.
The command line receiver is used if it is necessary to correct the missile’s flight path in the middle section. Active radar equipment, which provides fully autonomous missile guidance after a reliable target acquisition, includes an antenna with high-frequency receiver stages and a transmitter. The radar equipment antenna is placed under a radio-transparent fairing [length 530 mm, diameter at the base 17V mm] made of ceramic reinforced with fiberglass.
The warhead compartment contains the actual warhead, non-contact radar fuse, as well as elements of the safety-actuator and pyrotechnic circuit. Directional fragmentation type warhead, in which finished fragments are scattered in a narrow circular or limited sector. Moreover, the latter is possible only when the missile approaches the target from a strictly defined angle. With a direct hit on the target, a contact fuse is triggered. The propulsion system is a dual-mode solid-propellant rocket engine with a high specific impulse, operating on low-smoke, alumina-free fuel weighing 45 kg.
A typical missile guidance trajectory is divided into three sections: command-inertial, autonomous inertial, and active radar. Targets are detected using the airborne radar of the weapon control system of the carrier aircraft.
On the F-18 fighter, the AN / APG-65 station can highlight the ten most important targets by characteristics such as range and approach speed and continuously accompany them when scanning [eight of them are displayed on the indicator in the cockpit]. After the pilot selects a target, its coordinates are automatically entered into the inertial platform of the missile, and then, up to the launch, the coordinate system common to the missile defense and carrier aircraft is used, in which all calculations necessary for interception are carried out. After the missile is launched, the current coordinates of the target are recorded only in the onboard equipment of the carrier aircraft, and if it does not maneuver, the missile is guided using the inertial system, and then the active radar starts to work.
When the target makes maneuvers, its coordinates are corrected, entered into the inertial equipment of the rocket before launch. To do this, the corresponding correction commands are transmitted through the side lobes of the radar antenna of the carrier aircraft with the frequency of scanning the antenna pattern. These commands are perceived on board the UR by the command line receiver. Such command-inertial guidance is possible simultaneously for eight AIM-120 missiles when they are launched against different targets. At the same time, the aircraft indicator displays the value of the remaining flight time of each missile until its active radar equipment is turned on, which allows the pilot to timely stop transmitting correction commands to the missiles that have switched to the homing mode. Such a stop in the transmission of correction commands can also be carried out in the event of termination of target maneuvering when the missile is capable of being guided using its inertial equipment until the transition to homing.
The above guidance methods are used only in the absence of deliberate interference. If the target is setting up active interference, then the onboard equipment of the missile in the middle and final sections of the flight path can repeatedly switch to the mode of guidance to the source of interference. In close air combat, when the target is visually visible, the active radar homing mode is used.
AIM-120 can be hung on launchers of two types: with rail guides and with forced separation using squibs. The former is designed in such a way that “Sidewinder” missiles can also be placed on them. Devices of the second type are slightly modified existing LAU-17 and LAU-92 launchers, which are equipped with F-14, F-15, and F-18 aircraft. They are designed for the suspension of both UR “Sparrow” an AIM-120. Devices of both types will allow the suspension of seven SDs on the F-14 aircraft, six on the F-15, F-16, F-18, and Tornado-P.2, four on the Fantom F-4F.
Currently, three modifications of the AIM-120 rocket are known:
- AIM-120A – the first version of the missile, produced before 1994;
- AIM-120B – an upgraded version with the ability to reprogram the control system via a cable connector directly in the shipping container.
- AIM-120C – a missile that has been in production since 1996, modified to be placed on a promising F-22 aircraft, featuring reduced dimensions and improved performance in terms of speed, maneuverability, and target interception range.
- AIM-120D – The AIM-120D is an upgraded version of the AMRAAM with improvements in almost all areas, including 50% greater range 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 range of the AIM-120D is classified, but is thought to extend to about 100 miles (160 km)
|Carrier aircraft||F-4, F-5, F-14, F-15, F-16, F-18, F-22, F-35, “Tornado”, Hawk 200, Eurofighter Typhoon, KAI Ka-50, JAS 39 Gripen|
|Missile flight speed||Mach 4|
|Rocket length, mm||3660|
|Rocket body diameter, mm||178|
|Rudder swing, mm||627|
|Starting weight, kg||150.7|
|Warhead weight, kg||22|
AIM-120 AMRAAM is using in follow countrie: Australia, Belgium, Behrain, Bulgaria, Canada, Chile, Czech Republic, Denmark, Finland, Germany, Greece, Hungary, Indonesia, Israel, Italy, Japan, Jordan, Kuwait, Malaysia, Morocco, Netherlands, Norway, Oman, Pakistan, Poland, Qatar, Romania, Saudi Arabia, Singapore, South Korea, Switzerland, Spain, Sweden, Taiwan, Thailand, Turkey, United Arab Emirates, United Kingdom, United States.
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