Defensive concept Development of a guided air-to-air missile began in 1946.
Hughes Aircraft was awarded a contract for a
subsonic missile under the project designation
MX-798, which soon gave way to the
supersonic MX-904 in 1947. The original purpose of the weapon was as a self-defense weapon for
bomber aircraft, which would carry a magazine of three missiles in the rear fuselage, and fire them through a long tube that led through the area that normally held the tail turret. In the case of the
B-52, the missile contained a tuner for the bomber's A-3 rear-facing radar, and would follow the signal being reflected off the target aircraft using a
semi-active radar homing (SARH) system.
Anti-bomber development At the same time that the original MX-798 had been released, a specification for a forward-firing missile for
fighter aircraft had been released as MX-799. This had progressed to the point of testing prototype rounds, as the
AAM-A-1 Firebird, when its subsonic speed and
manual guidance were realized to be serious problems. The project was cancelled, and the recently released MX-904 was redirected to replace Firebird in the anti-bomber role. At this stage the weapon was still designed to be fired out of a tube, now leading from a weapon bay behind the nose-mounted radar with the launch tube exiting below the radar antenna. Instead of a magazine with multiple missiles, three missiles were placed in the tube tip-to-tail. Housing in a tube presented several problems, but primary among them was that there was no way for the missile's seeker to
lock-on before launch. The original concept would be firing against
interceptor aircraft that were slowly approaching the B-52 and would be somewhere fairly close to directly behind the aircraft. In the case of a fighter, the target might not be so conveniently located, and with no way to know if it could see the target while inside the tube, this meant it might never lock-on properly. Eventually, it was decided to abandon the tube-launched concept and mount the missile on the wings or in weapon bays that would point the missile at the target prior to launch. This change also allowed the seeker to use
infrared homing as well as SARH. Interchangeable seekers were developed, allowing an aircraft to carry either type, or both. Additionally, freed from the tube, the missile's wings were allowed to grow larger and took on the long delta form that it and its various descendants would carry into the 2000s.
Testing and service The first test firings took place in 1949, at which time it was designated
AAM-A-2 and given the popular name
Falcon. A brief policy of assigning fighter and bomber designations to missiles led it to be redesignated
F-98 in 1951. In 1955, the policy changed again, and the missile was again redesignated
GAR-1. The initial
GAR-1 and
GAR-2 models entered service in 1956. It armed the
Northrop F-89 Scorpion,
McDonnell F-101B Voodoo and
Convair F-102 Delta Dagger and
F-106 Delta Dart interceptors. The only other users were Canada, Finland, Sweden and Switzerland, whose
CF-101 Voodoo,
Saab 35 Draken and
Dassault Mirage IIIS carried the Falcon. Canada also hoped to use them on the
Avro Canada CF-105 Arrow interceptor; however, this was never realized because of the Arrow's cancellation. Fighters carrying the Falcon were often designed with internal weapons bays for carrying this missile. The Scorpion carried them on wingtip pods, while the Delta Dagger and Delta Dart had belly bays with a trapeze mechanism to move them into the airstream for launch. The F-101B had an unusual bay arrangement where two were stored externally, and then the bay door would rotate to expose two more missiles. It is likely the
General Dynamics F-111's internal bay would have accommodated the missile as well, but by the time of service the Air Force had already dropped the Falcon for use against fighters, as well as the idea of using the F-111 as an air combat fighter. The GAR-1 had
semi-active radar homing (SARH), giving a range of about . About 4,000 missiles were produced. It was replaced in production by the
GAR-1D (later
AIM-4A), with larger control surfaces. About 12,000 of this variant were produced, the major production version of the SARH Falcon. The
GAR-2 (later
AIM-4B) was a heat-seeker, generally limited to
rear-aspect engagements, but with the advantage of being a '
fire and forget' weapon. As would also be
Soviet practice, it was common to fire the weapon in salvos of both types to increase the chances of a hit (a heat-seeking missile fired first, followed moments later by a radar-guided missile). The GAR-2 was about 1.5 in (40 mm) longer and 16 lb (7 kg) heavier than its SARH counterpart. Its range was similar. It was replaced in production by the
GAR-2A (later
AIM-4C), with a more sensitive
infrared seeker. A total of about 26,000 of the infrared-homing Falcons were built. weapons handlers with an AIM-4C, 1972. All of the early Falcons had a small 7.6 lb (3.4 kg) warhead, limiting their lethal radius. Also limiting them tactically was that Falcon lacked a
proximity fuze: the fuzing for the missile was in the leading edges of the wings, requiring a direct hit to detonate. In 1958, Hughes introduced a slightly enlarged version of the Falcon, initially dubbed
Super Falcon, with a more powerful, longer-burning rocket engine, increasing speed and range. It had a larger warhead (28.7 lb / 13 kg) and better guidance systems. The SARH versions were
GAR-3 (
AIM-4E) and the improved
GAR-3A (
AIM-4F). The infrared version was the
GAR-4A (
AIM-4G). About 2,700 SARH missiles and 3,400 IR Super Falcons were produced, replacing most earlier versions of the weapon in service. The Falcon was redesignated
AIM-4 in September 1962. The final version of the original Falcon was the
GAR-2B (later
AIM-4D), which entered service in 1963. This was intended as a fighter combat weapon, combining the lighter, smaller airframe of the earlier GAR-1/GAR-2 weapon with the improved IR seeker of the GAR-4A/AIM-4G. An effort to address the limitations of AIM-4D led to the development in 1970 of the
XAIM-4H, which had a laser
proximity fuze, new warhead, and better maneuverability. It was cancelled the following year without entering service. A larger version of the Falcon carrying a
0.25-kiloton nuclear warhead was developed as the
GAR-11 (later designated the
AIM-26 Falcon), while a long-range version was developed for the
North American XF-108 Rapier and
Lockheed YF-12 interceptors as the
GAR-9 (later
AIM-47 Falcon). ==Operational history==