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AIM-120 AMRAAM Slammer - Design

Four wings, four fins (control surfaces), and the wiring harness cover are mounted externally, providing additional distinguishing features from other similar missiles, such as AIM-7 Sparrow. The AIM-120C utilizes "clipped" wings and fins in order to meet the internal carriage requirements of the F-22. AMRAAM consists of the following major sections: Guidance, Armament, Propulsion, and Control. Other components include a wiring harness, harness cover, Thermally Initiated Venting System (TIVS), and wing and fin assemblies.

Guidance Section, Weapons Guidance Unit. The Weapons Guidance Unit (WGU) consists of the radome, seeker, servo, transmitter-receiver, electronics unit, Inertial Reference Unit, Target Detection Device (TDD), the harnesses, and frame structure. All units except the TDD are contained within a sealed structure composed of the pyroceramic radome, titanium skin sections, and aluminum aft bulkhead. The TDD, RF and video processor, and the antennas are attached to the aft skin section as a complete testable assembly. Electronics group functions include radar signal processing, seeker servo control, and all of the computations performed in the central data processor. The WGU-16B is used on AIM-120A missiles, the WGU-41/B is used on AIM-120B missiles, and the WGU-44/B is used on AIM-120C missiles. Guidance sections on AIM-120B and AIM-120C missiles contain Electronic Erasable Programmable Read Only Memory which allow reprogramming of the missile software. Missile software versions are denoted by Tape and Revision Numbers, e.g., Tape 4 Revision 16.

Armament Section, Weapons Detonation Unit. The Weapons Detonation Unit (WDU)-33/B forms an integral part of the tactical missile airframe and includes the warhead, the FZU-49/B (modified Mk 3 Mod 5) safe-arm fuze device, and the Mk 44 Mod 1 booster. The armament section also includes the forward missile hook and hanger. The WDU-33/ B warhead meets the Insensitive Munitions (IM) program requirements.

Propulsion Section, Weapons Propulsion Unit. The Weapons Propulsion Unit (WPU)-6/B consists of an airframe, integral rocket motor, a blast tube and exit cone, and an Arm/Fire Device (AFD) with a visible safe-arm indicator. The high performance rocket motor utilizes a reduced smoke, hydroxyl terminated, polybutadiene propellant in a boost sustain configuration, an asbestos-free insulated case (an integral part of the airframe), and an integral aft closure, blast tube, and nozzle assembly with a removable exit cone to facilitate control section installation/removal. Wings are attached in wing sockets at the forward end of the propulsion section. Provisions are included within this section for mounting the filter rectifier assembly.

Control Section, Weapons Control Unit. The Weapons Control Unit (WCU)-11/B consists of four independently controlled electro-mechanical servo actuators, four lithium-aluminum batteries connected in parallel, and a steel fuselage section that is bolted to the propulsion section aft skirt. Each actuator consists of a brushless DC motor ballscrew, an infinite resolution potentiometer directly coupled to the output shaft, and pulse width modulated control electronics. The output shaft is engaged directly to a squib actuated lock so that it does not interfere with the fin (control surface) installation and removal. (5) Wiring Harness, Harness Cover, and Thermally Initiated Venting System.

The wiring harness cover extends from the aft end of the guidance section to the forward end of the control section. Its primary purpose is to provide protection for the wiring harness. The main wiring harness electrically connects the umbilical connector, guidance section, and control section. The wiring harness cover also houses the TIVS. The TIVS is designed to vent rocket motor pressure in the event the missile is exposed to a fuel fire.

The TIVS consists of an external thermal cord which, when ignited, triggers an Out-Of-Line Device (OOLD) that ignites a Linear Shape Charge that weakens the rocket motor, allowing the rocket motor to vent without exploding. The OOLD prevents the shaped charge from detonating should the booster in the OOLD inadvertently detonate due to causes such as high impact. The unit has an additional safety feature that causes it to "reset" within nine to thirteen units of gravity, such as the acceleration experienced during missile launch. This feature prevents the system from functioning during missile free flight so that the associated aerodynamic pressures do not inadvertently enable the TIVS and thereby degrade missile performance.

An indicator is on the wiring harness cover showing the condition of the TIVS, either "ENABLE" or "DISABLE". Only TIVS equipped missiles are deployed aboard Aircraft Carriers (CV/CVN). The WPU-6/B Propulsion Section (with TIVS) meets the fast cook-off and sympathetic detonation requirements of the IM program and the policy delineated in OPNAV Instruction (OPNAVINST) 8010.13B. The other requirements (bullet impact, fragment impact, and slow cook-off) have not been met with the current configuration. However, the WPU-6/B has been granted the appropriate waivers for shipboard use.

Wing and Fin Assemblies. Wing and fin assemblies provide for flight control of the missile. The four wings are detachable, stationary flight surfaces with ball fasteners to facilitate quick installation and removal. The four fins provide the movable control surfaces. The AIM-120C has "clipped" wings and fins which are not interchangeable with AIM-120A and AIM-120B missiles. The AIM-120C utilizes "clipped" wings and fins in order to meet the internal carriage requirements of the F-22.

Launchers. The AMRAAM system includes three new Missile Rail Launchers (MRLs): the LAU-127A/A, in conjunction with the LAU-115, used on the F/A-18C/D aircraft; the LAU-128A/A, and the LAU-129A/A, used on the F-15 and F-16 aircraft, respectively. Additional interface cables are not required between the aircraft and the launcher. The MRL can be installed and operated at all current AIM-9 Sidewinder positions on all candidate aircraft, except F/A-18C/D wing tip stations; and is also capable of launching AIM-9 Sidewinder missiles. The MRL supplements the Sidewinder launchers (except F/A-18C/D wing tip) on AMRAAM capable aircraft.

Power for Built-In-Test (BIT) of the pre-launch dormant missile is provided by converting aircraft power in the AMRAAM Electronic Control Unit. The filter rectifier assembly is mounted at the forward end of the missile propulsion section and provides the conversion of aircraft power required by the missile. Prior to launch, signal and data transfer between missile and aircraft is accomplished through a buffer connector that is in-line between the launcher cable and the missile umbilical connector. Similarly, the CFMRE interfaces with AMRAAM using the buffer connector and the missile umbilical connector, and supplies the power in lieu of the aircraft for off-aircraft BIT and reprogramming operations.

Organizational-level maintenance units receive AMRAAM as an AUR, four per container. Organizational-level maintenance is performed by Work Center 230 USN Aviation Ordnanceman (AO) with Navy Enlisted Classification (NEC) codes 8342 and 8842, and USMC personnel with Military Occupational Specialty (MOS) 6531. The AN/AWM-54 Aircraft Firing Circuit Test Set is used to test for stray voltage in aircraft weapons circuits prior to loading ordnance. The AN/AWM-96 Aircraft Weapons Control Test Set is used primarily by Aviation Electronics Technicians (ATs) to test the functionality of the aircraft weapons circuit prior to loading AMRAAM, but is also used by AOs in squadrons employing the Integrated Weapons Team concept. On-aircraft testing is accomplished using the BIT capability of the missile.

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