FIM-43 Redeye


The General Dynamics FIM-43 Redeye is a man-portable surface-to-air missile system. It uses passive infrared homing to track its target. Production began in 1962 andin anticipation of the Redeye II, which later became the FIM-92 Stingerended in the early 1970s after about 85,000 rounds had been built. The Redeye was withdrawn gradually between 1982 and 1995 as the Stinger was deployed, though it remained in service with various armed forces of the world until quite recently, being supplied via the Foreign Military Sales program. It was initially banned from being sold overseas, to avoid missiles falling into the hands of terrorist organizations. However, after the export ban was lifted, the weapon was never actually used by terrorists against civil aircraft, in contrast with other MANPADS. While the Redeye and 9K32 Strela-2 were similar, the missiles were not identical. Nonetheless, the CIA concluded that the Soviet SA-7 had benefited from the Redeye's development.

Development

Post-war developments

In May 1946, the War Department Equipment Board published a report on the future of infantry weapons. They called for the development of new weapons that would be the best in the world, while also being able to be separated into loads of no more than. When considering anti-aircraft weapons, they concluded that the M45 Quadmount mounting four M2 Browning machine guns would not be capable against future high-performance aircraft. They published a new requirement for a weapon suitable for engagements between against targets flying up to.
In response, in June 1948 the United States Army Ordnance Corps began development of the "Stinger" system, essentially an updated version of the Quadmount mounting four T17 machine guns firing the more powerful 0.60 round and aimed by an automated radar system. Development on this system continued until 1951, when the requirement was extended to, which could not be met by the 0.60 round. A new concept using a revolver cannon firing a new 37 mm round emerged, but proved too complex and was cancelled.

Porcupine and Octopus

At the 1950 Tripartite Conference in London, the US, UK and France agreed that the M2 would remain effective up until about 1960, but new weapons would be needed after that time. This led to development of the Porcupine and Octopus concepts in the US. Porcupine, started in 1951, was a 64-barrel rocket launcher firing salvos of Folding-Fin Aerial Rockets at an effective rate of 6,000 rounds per minute. The system was never built in complete form, and cancelled in February 1956. Octopus, from 1953, re-examined the.50 and.60 rounds, as well as the emerging 20 mm round based on the latter. This project also failed to deliver an operational system.
By the mid-1950s, new medium and high-altitude surface-to-air missile were rendering higher altitude flight increasingly dangerous, and attack aircraft were now expected to fly at low altitudes. This led to a 1954 requirement for a lightweight system able to engage targets from 0 to, and larger weapons that raised the ceiling to. In order to improve its capability in poor visibility, it was suggested that the weapon be aimed using infrared homing.

Redeye emerges

In 1955, Convair, recently purchased by General Dynamics, began examining a weapon that would fill both of these requirements. When initial studies proved promising, in January 1956 the company began an 11-month study which they named "Redeye" due to its infrared seeker. To lower prototype costs, the missile would initially be based on the unguided FFAR, which was already in widespread production. This would be turned into a missile by replacing the contact-fused warhead of the FFAR with a new seeker system and smaller warhead. Convair's prototype initially used a miniaturized version of the AIM-9 Sidewinder seeker and was small, weighing, a gripstock/launch tube weighing. The overall weight of the prototype was, while unit cost was initially estimated at $700 compared to about $3000 for a Sidewinder missile.
The resulting concept mockups were demonstrated to the Army and Marine Corps in November 1956. Simulations suggested that it would have an average miss distance of, and a direct-hit probability of 0.35 to 0.40. The design proved extremely interesting, and in 1957 official requirements were formulated. This led to the Army's Redstone Arsenal receiving several unsolicited proposals for similar weapons from other companies:
The competing designs were rejected for being too heavy, while US Army engineers deemed that while the Redeye design was the most promising, it also needed further substantial studies on the IR seeker before development could begin. They also concluded that improvements on the IR seeker were necessary for the system to perform as claimed on the proposal. Convair objected to the Army evaluation, stating that it already performed exhaustive research in private, while the United States Marine Corps were more enthusiastic about the Redeye and insisted that the weapon was ready for development, offering an initial funding of $1 million to accelerate the program.
On 14 April 1958, the development contract was released and Convair was awarded a contract to start development of the system.

Testing

The original design consisted of a simple tube with a clip-on grip system. The operator would simply point the tube in the general direction of the target, and fire when he heard the seeker make its "growl" sound, indicating it was locked onto the target. In May 1958 six unguided launches were conducted by US Marines at Twentynine Palms proving ground and Camp Pendleton, California, to assess human factors and ergonomics of the new weapon, as well as a trooper's capability to aim and launch a missile from the shoulder safely and accurately towards an imaginary target. In June 1958 the flight test phase of the feasibility demonstration program began.
The first test launches were conducted with unguided missiles, while in March 1959 the first tests with guided missiles were conducted. After these tests proved that the basic concept was feasible, engineering development phase began in October 1960. Convair contracted the Philco Corporation and the Atlantic Research Corporation to work on the development of the seeker and the two-stage rocket motor respectively.
The US Army evaluation proved to be prescient: development was more difficult than expected, stretching to seven years, research costs tripled, and the Redeye weight increased from to. Early testing also revealed technical problems with the propulsion system and pop-out tail fins. The uncooled lead-sulfide IR detector performance was also disappointing, with a 2−2.7μm sensitivity band it could only lock on the hot exhaust of jet aircraft, making the missile a tail-chaser only. After experimenting with thermoelectric cooling and a Hughes-designed gas-cooled seeker, the US Army eventually decided to eschew uncooled detectors in favor of a next-generation gas-cooled seeker, which gave the missile a limited ability to target other portions of the aircraft other than the tail. Another change introduced during development was turning the detachable gripstock and the launcher tube into a single piece. Once fired the single-piece launcher could be recycled and reloaded at the nearest supply depot up to eight times. Teething problems were gradually solved by 1963. During fiscal year 1963, 75 test launches were conducted against drones, with the first successful hit being made on 14 December 1962, against a QF-9F Panther jet drone flying at. In October 1963, 13 missiles were fired, with 11 direct hits while the remaining two within from the thermal source. In light of these successes, the US Army was convinced to start the industrialization phase of the program.
Limited production began in June 1963 as XM41 Redeye Block I. The missile was designated XMIM-43A and included the Mod 60 thermoelectrically cooled seeker. 300 systems were then evaluated between September 1965 and May 1966. After the Block I missiles were expended during engineering and service tests, the Block II systems designated XM41E1 came next, the improved missile being designated XMIM-43B and included a Mod 60A gas-cooled infrared detector cell. Deliveries of the missiles began in April 1966 alongside the final Block I missiles. In February 1967, the first Block II missiles were issued to US Army units for familiarization. A total of 1,743 XFIM-43B missiles were built for engineering tests and troop training.
The final Redeye Block III configuration, designated as the M41 Block III was a major redesign of the Redeye. The FIM-43C missiles retained the gas-cooled seeker from the Block II missile, but incorporated new components and electronics, including the new and improved M115 rocket motor, and M222 warhead. The new M171 launcher was fitted with a folding optical sight. The new missile could turn at up to 3g. The missile achieved a kill probability against F9F Panthers travelling at at an altitude of of 51%. From this it was calculated that the kill probability versus a Mikoyan-Gurevich MiG-21 at similar altitude would be 40.3%, and 53% against helicopters. Kill probability against larger propeller driven aircraft like the Antonov An-12 was estimated at 43%. Production of the Block III systems began in May 1967, with the first deliveries to the US Army and US Marine Corps starting in March 1968, but it was only cleared up for service in extreme climates in October 1968. On 18 December 1968, the M41 Block III was formally standardized as the FIM-43C, roughly six years behind schedule.