The Advanced Medium Range Air-to-Air Missile (AMRAAM)
AIM-120 development programme was started in 1975, with
a joint US Air Force and US Navy study. Two
contractors, Hughes and Raytheon, competed in a three
year validation phase and in 1981 Hughes was awarded
the full-scale development contract. Development
problems forced a complete programme review in 1985,
the development phase was extended by two years and the
in-service date delayed from 1986 to 1989, with further
evaluation problems resulting in entry to service in
1991. AMRAAM was designed to follow on and improve upon
the performance of AIM-7 Sparrow and to be carried on
the F-14, F-15, F-16 and F/A-18 aircraft. Performance
improvements over the Sparrow include higher speed,
greater range, increased manoeuvrability, better
resistance to electronic countermeasures, an active
radar terminal seeker and improved reliability and
maintainability. The active radar terminal seeker
together with track-while-scan radar on the launch
aircraft provides a capability simultaneously to track
multiple targets, launch several missiles and manoeuvre
to avoid counter attacks. As a result of the 1985
programme review, a number of design changes was
identified to reduce the high production costs of some
assemblies.
DESCRIPTION:
The AMRAAM missile is 3.65 m long, has a body diameter
of 178 mm and a fin span of 0.63 m. The fixed central
wings have a span of 0.53 m. The missile weighs 157 kg
and has a low smoke solid propellant boost and
sustainer motor. A maximum range of about 50 km could
be expected against head-on targets, reducing to 10 km
or less against receding targets. The design
incorporates extensive built-in test capability for the
missile, the launcher and the associated aircraft
weapon system, and aims to achieve impressive storage
and captive-carry reliability requirements. The warhead
weight is around 22 kg, with directed fragments
initiated by an active radar proximity fuze. Control is
by four rear fuselage-mounted fins, moved by
electrically powered actuators. The command link
receiver antennas are at the rear of the missile, to
receive guidance updates on target position and
manoeuvre from the launch aircraft. There are three
guidance modes for the missile, depending upon the
launch range and conditions. In a typical engagement
the missile is launched and first guided by on-missile
inertial navigation with command guidance updates from
the launch aircraft. The missile then goes into
autonomous mode and continues to guide by inertial
navigation only. Finally, the terminal mode is selected
when the target is within range of the missile's active
monopulse radar seeker, which then guides the missile
onto the target aircraft. In short range engagements,
which can be made down to a few hundred metres, the
missile guides all the way by its onboard active radar
seeker.
SPECIFICATIONS:
Length: 3.65 m
Body diameter: 178 mm
Wingspan: 0.53 m
Launch weight: 157 kg
Warhead: 22 kg HE directed fragmentation
Fuze: Active radar
Guidance: Command, inertial and active radar
Propulsion: Solid propellant
Range: 50 km
