In October 1988 the US Navy's Naval Air Systems Command (NAVAIR) awarded contracts to two industrial teams for a four year technology-validation phase of the AAAM. One team was a combination of Hughes and Raytheon, two rival companies which have come to dominate the US market for medium/long-range air-to-air missiles. The other links General Dynamics with Westinghouse.
Under a programme known as the Advanced Missile System (AMS), GD has studied technology for long range air-to-air missiles for more than a decade. The first practical results to emerge, in the late 1970s, were a new five-cavity klystron microwave tube, the construction of a demonstration integrated-guidance section and integrated missile receiver, and the testing of an experimental Interrupted Continuous Wave (ICW) transmitter.
The latter was strictly lab-test hardware —it filled a two-bay electronics rack—but provided the experience needed to propose ICW technology for the AAAM semi-active radar seeker. Using ICW technology, the launch aircraft can "time manage" its radar, switching the beam from one target to another in rapid succession so that this single illuminator can handle a multiple engagement.
By the end of the decade a full-scale airframe had been built. Looking rather like a stretched Standard surface-to-air missile (SAM), this featured long-chord cruciform wings and narrow-chord cruciform tail fins, plus a short tandem-rocket booster. The missile is 12ft long (3-65m), 5- 5in (140mm) in diameter, and weighs 386lb (175kg).
A first-generation seeker gimbal and a second-generation control section were tested in the early 1980s, while 1983 saw trials on a ground test stand of a heavy-walled prototype of the proposed rocket motor and thrust-vector control (TVC) system. Other tests checked the performance of the proposed warhead against what were described as "RA-5-size targets". A second series of wind tunnel tests on the missile airframe began in 1983. The EO guidance mode was tests carried out by day and night.
The GD/Westinghouse missile has folding wing and tail surfaces, and is delivered from the depot packed in a circular storage/launch tube. The team has released artwork showing how 12 of these tubes could be carried in two lateral rows of six under the fuselage of an F-14D.
Tomcat will also need to carry a multifunction airborne track illuminator (ATI) pod, either on one of its fuselage stations or an underwing pylon. This unit is 11ft 10in (3.6m) long, 16in (406mm) in diameter, and weighs 750lb (341kg). It is self-powered by a ram-air turbine whose vanes are located about a quarter of the way from the forward end. On the US Navy's next-generation fighter, currently expected to be a derivative of the USAF's Advanced Tactical Fighter, the functions of the ATI will be handled by the aircraft's Westinghouse-developed radar.
Targets would be detected initially either by the F-14D's APG-71 radar or by its infrared search and track system (IRST), then handed over to the ATI pod. This uses its front facing antenna to track the targets and compute the engagement envelope for each one. It also has a limited degree of search capability.
The aircrew selects the target to be engaged, then fires the missile. The round will leave the launch tube under the power of its tandem-mounted rocket booster. At burnout this will be jettisoned, and the main solid-propellant rocket motor (sustainer) ignited to power the round for the first stage of its flight out to the target. After launch, the crew is free to manoeuvre its aircraft to reduce the closure rate. There is no need to keep the aircraft pointed towards the target —a drawback to conventional semi-active radar- homing-missile attacks. The ATI pod even has a second rearward-facing antenna.
Like the Hughes AIM-120 AMRAAM, AAAM will fly an optimised trajectory under the control of an inertial midcourse guidance system. Uplink facilities are provided, so that the parent aircraft can transmit targeting updates should these be needed.
In the later stages of flight, the missile activates its terminal guidance seeker. Still later, the radome is jettisoned, allowing the missile's infrared seeker to begin operation. Home-on-jam attacks are also possible.
While the sustainer is burning, its jet-tab thrust vectoring control (TVC) system will supplement the missile's aerodynamic control surfaces. This will probably be of greatest importance when engaging targets flying at high altitude. In such cases, the sustainer is re-ignited for a second burn. This extra power, plus the use of TVC, is expected to allow the missile to have the same manoeuvrability at 100,000ft (30,500m) as today's Sparrow has at 20,000ft (6,000m).
