AIM-9 Sidewinder

The AIM-9 Sidewinder is a heat-seeking, short-range, air-to-air missile (AAM) carried by fighter aircraft and some helicopters. The Sidewinder was the first effective air-to-air missile. New variants and upgrades have kept the AIM-9 Sidewinder in active service with many air forces, five decades after its introduction. The development of the Sidewinder missile began in 1946 at the Naval Ordnance Test Station, Inyokern, California, now the Naval Air Weapons Station China Lake. A prototype Sidewinder, the XAAM-N-7 (later AIM-9A), was first fired successfully in September 1953. The initial production version, designated AAM-N-7 (later AIM-9B), entered operational use in 1956, and has been improved upon steadily since.About 110,000 Sidewinders have been built, of which perhaps one percent have been used in combat, resulting in some 250-300 kills world-wide to date.

AIM-9 Sidewinder
Class Missile
Type Air to Air
Manufacturer Raytheon Missile Systems
Origin United States of America
Country Name Origin Year
United States of America 1956
Country Name Operational Year Retirement Year
Argentina View
Australia View
Austria View
Belgium View
Brazil View
Canada View
Chile View
Denmark View
Egypt View
Ethiopia View
Finland View
France View
Germany View
Greece View
Honduras View
Indonesia View
Iran (Persia) View
Israel View
Italy View
Japan View
Jordan View
Kenya View
Korea View
Kuwait View
Malaysia View
Mexico View
Morocco View
Netherlands View
Oman (Muscat) View
Pakistan View
Philippines View
Portugal View
Saudi Arabia View
Singapore View
Spain View
Sudan View
Sweden View
Switzerland View
Thailand (Siam) View
Tunisia View
Turkey (Ottoman Empire) View
United Arab Emirates View
United Kingdom - UK (Great Britain) View
United States of America 1956 View
Venezuela View
Vietnam View
Yemen View
ManufacturerName Production From Production To Quantity
Raytheon Missile Systems 1949 View
Lockheed Missiles and Space Company View
Loral Corporation View

The AIM-9 is made up of a number of different components manufactured by different companies, including Aerojet and Raytheon. The missile is divided into four main sections: guidance, target detector, warhead, and rocket motor.

The guidance and control unit (GCU) contains most of the electronics and mechanics that enable the missile to function. At the very front is the IR seeker head utilizing the rotating reticle, mirror, and five CdS cells or “pan and scan” focal-plane array (AIM-9X), electric motor, and armature, all protruding into a glass dome. Directly behind this are the electronics that gather data, interpret signals, and generate the control signals that steer the missile. An umbilical on the side of the GCU attaches to the launcher, which detaches from the missile at launch. To cool the seeker head, a 5,000 psi (35 MPa) argon bottle (TMU-72/B or A/B) is carried internally in Air Force AIM-9L/M variants, while the Navy uses a rail-mounted nitrogen bottle. The AIM-9X model contains a Stirling cryo-engine to cool the seeker elements. Two electric servos power the canards to steer the missile (except AIM-9X). At the back of the GCU is a gas grain generator or thermal battery (AIM-9X) to provide electrical power. The AIM-9X features high off-boresight capability; together with JHMCS (Joint Helmet-Mounted Cueing System), this missile is capable of locking on to a target that is in its field of regard said to be up to 90 degrees off boresight. The AIM-9X has several unique design features including built-in test to aid in maintenance and reliability, an electronic safe and arm device, an additional digital umbilical similar to the AMRAAM and jet vane control.

Next is a target detector with four IR emitters and detectors that detect whether the target is moving farther away. When it detects this action taking place, it sends a signal to the warhead safe and arm device to detonate the warhead. Versions older than the AIM-9L featured an influence fuze that relied on the target's magnetic field as input. Current trends in shielded wires and non-magnetic metals in aircraft construction rendered this obsolete.

The AIM-9H model contained a 25-pound (11 kg) expanding rod-blast fragmentary warhead. All other models up to the AIM-9M contained a 22-pound (10 kg) annular-blast fragmentary warhead. The missile's warhead rods can break rotor blades (an immediately fatal event for any helicopter).

Recent models of the AIM-9 are configured with an annular-blast fragmentation warhead, the WDU-17B by Argotech Corporation. The case is made from spirally wound spring steel filled with 8 pounds (4 kg) of PBXN-3 explosive. The warhead features a safe/arm device requiring five seconds at 20 g (~200 m/s²) acceleration before the fuze is armed, giving a minimum range of approximately 2.5 kilometers.

The Mk36 solid-propellant rocket motor provides propulsion for the missile. A reduced-smoke propellant makes it difficult for a target to see and avoid the missile. This section also features the launch lugs used to hold the missile to the rail of the missile launcher. The forward of the three lugs has two contact buttons that electrically activate the motor igniter. The fins provide stability from an aerodynamic point of view, but it is the "rollerons" at the end of the wings providing gyroscopic precession to free-hinging control surfaces in the tail that prevent the missile from spinning in flight. The wings and fins of the AIM-9X are much smaller and control surfaces are reversed from earlier Sidewinders with the control section located in the rear, while the wings up front provide stability. The AIM-9X also features vectored thrust or jet vane control to increase maneuverability and accuracy, with four vanes inside the exhaust that move as the fins move. The last upgrade to the missile motor on the AIM-9X is the addition of a wire harness that allows communication between the guidance section and the control section, as well as a new 1760 bus to connect the guidance section with the launcher’s digital umbilical.

The Sidewinder incorporated a number of innovations over the independently developed World War II-era Madrid IR range fuze used by Messerschmitt's Enzian experimental surface-to-air missile, that enabled it to be successful.[citation needed] The first innovation was to replace the "steering" mirror with a forward-facing mirror rotating around a shaft pointed out the front of the missile. The detector was mounted in front of the mirror. When the long axis of the mirror, the missile axis and the line of sight to the target all fell in the same plane, the reflected rays from the target reached the detector (provided the target was not very far off axis). Therefore, the angle of the mirror at the instant of detection (w1) estimated the direction of the target in the roll axis of the missile.

The yaw/pitch (angle w2) direction of the target depended on how far to the outer edge of the mirror the target was. If the target was further off axis, the rays reaching the detector would be reflected from the outer edge of the mirror. If the target was closer on axis, the rays would be reflected from closer to the centre of the mirror. Rotating on a fixed shaft, the mirror's linear speed was higher at the outer edge. Therefore if a target was further off-axis, its "flash" in the detector occurred for a briefer time, or longer if it was closer to the center. The off-axis angle could then be estimated by the duration of the reflected pulse of infrared.

The Sidewinder also included a dramatically improved guidance algorithm. The Enzian attempted to fly directly at its target, feeding the direction of the telescope into the control system as it if were a joystick. This meant the missile always flew directly at its target, and under most conditions would end up behind it, "chasing" it down. This meant that the missile had to have enough of a speed advantage over its target that it did not run out of fuel during the interception.

The Sidewinder is not guided on the actual position recorded by the detector, but on the change in position since the last sighting. So if the target remained at 5 degrees left between two rotations of the mirror, the electronics would not output any signal to the control system. Consider a missile fired at right angles to its target; if the missile is flying at the same speed as the target, it should "lead" it by 45 degrees, flying to an impact point far in front of where the target was when it was fired. If the missile is traveling four times the speed of the target, it should follow an angle about 11 degrees in front. In either case, the missile should keep that angle all the way to interception, which means that the angle that the target makes against the detector is constant. It was this constant angle that the Sidewinder attempted to maintain. This "proportional pursuit" system is very easy to implement, yet it offers high-performance lead calculation almost for free and can respond to changes in the target's flight path, which is much more efficient and makes the missile "lead" the target.

However, this system also requires the missile to have a fixed roll-axis orientation. If the missile spins at all, the timing based on the speed of rotation of the mirror is no longer accurate. Correcting for this spin would normally require some sort of sensor to tell which way is "down" and then adding controls to correct it. Instead, small control surfaces were placed at the rear of the missile with spinning disks on their outer surface; these are known as rollerons. Airflow over the disk spins them to a high speed. If the missile starts to roll, the gyroscopic force of the disk drives the control surface into the airflow, cancelling the motion. Thus the Sidewinder team replaced a potentially complex control system with a simple mechanical solution.

Combat debut: Taiwan Strait, 1958

The first combat use of the Sidewinder was on September 24, 1958, with the air force of the Republic of China (Taiwan), during the Second Taiwan Strait Crisis. During that period of time, ROCAF North American F-86 Sabres were routinely engaged in air battles with the People's Republic of China over the Taiwan Strait. The PRC MiG-17s had higher altitude ceiling performance and in similar fashion to Korean War encounters between the F-86 and earlier MiG-15, the PRC formations cruised above the ROC Sabres, immune to their .50 cal weaponry and only choosing battle when conditions favored them. In a highly secret effort, the United States provided a few dozen Sidewinders to ROC forces and an Aviation Ordnance Team from the U. S. Marine Corps to modify their Sabres to carry the Sidewinder. In the first encounter on 24 September 1958, the Sidewinders were used to ambush the MiG-17s as they flew past the Sabres thinking they were invulnerable to attack. The MiGs broke formation and descended to the altitude of the Sabres in swirling dogfights. This action marked the first successful use of air-to-air missiles in combat, the downed MiGs being their first casualties.

During the Taiwan Strait battles of 1958, a Taiwanese AIM-9B hit a Chinese MiG-17 without exploding; the missile lodged in the airframe of the MiG and allowed the pilot to bring both plane and missile back to base. Soviet engineers later admitted that the captured Sidewinder served as a "university course" in missile design and substantially improved Soviet air-to-air capabilities. They were able to reverse-engineer a copy of the Sidewinder, which was manufactured as the Vympel K-13/R-3S missile, NATO reporting name AA-2 Atoll. There may have been a second source for the copied design: according to Ron Westrum in his book Sidewinder, the Soviets obtained the plans for Sidewinder from a Swedish Air Force Colonel, Stig Wennerström. (According to Westrum, Soviet engineers copied the AIM-9 so closely that even the part numbers were duplicated, although this has not been confirmed from Soviet sources.)

The Vympel K-13 entered service with Soviet air forces in 1961.

In 1972, when the Finnish Air Force started using Sidewinder (AIM-9P) in their Saab 35 Draken fighters, they were already using Soviet-made Atoll in their MiG-21s; Finns found the two so similar that they tested Sidewinders in MiGs and Atolls in Drakens.

Development during early 1960s

The Sidewinder subsequently evolved through a series of upgraded versions with newer, more sensitive seekers with various types of cooling and various propulsion, fuse, and warhead improvements. Although each of those versions had various seeker, cooling, and fusing differences, all but one shared infrared homing. The exception was the U.S. Navy AAM-N-7 Sidewinder IB (later AIM-9C), a Sidewinder with a semi-active radar homing seeker head developed for the F-8 Crusader. Only about 1,000 of these weapons were produced, many of which were later rebuilt as the AGM-122 Sidearm anti-radiation missile.

USAF adoption from 1964

The original USAF nomenclature for the Sidewinder was the GAR-8, although it too later adopted the name AIM-9. Although originally developed for the USN and a competitor to the USAF AIM-4 Falcon, the Sidewinder was subsequently introduced into USAF service. The US DoD directed that the F-4 Phantom be adopted by the USAF. The Air Force originally borrowed F-4B model Phantoms, which were equipped with AIM-9B Sidewinders as the short-range armament.

The first production USAF Phantoms were the F-4C model, which carried the AIM-9B Sidewinder, from December 1964. During the 1960s the USN and USAF pursued their own separate versions of the Sidewinder, but cost considerations later forced the development of common variants beginning with the AIM-9L.

Vietnam War service 1965–1973

When air combat started over North Vietnam in 1965, Sidewinder was the standard short range missile carried by the US Navy on its F-4 Phantom and F-8 Crusader fighters and could be carried on the A-4 Skyhawk and on the A-7 Corsair for self-defense. The US Air Force also used the Sidewinder on its F-4C Phantoms and when MiGs began challenging strike groups, the F-105 Thunderchief also carried the Sidewinder for self-defense. The USAF opted to carry only AIM-4 Falcon on their F-4D model Phantoms introduced to Vietnam service in 1967, but disappointment with combat use of the Falcon led to a crash effort to reconfigure the F-4D so that it could carry Sidewinders.

Performance of the 454 Sidewinders launched during the war, and the AIM-7 Sparrow was not as satisfactory as hoped. Both the USN and USAF studied the performance of their aircrews, aircraft, weapons, training, and supporting infrastructure. The USAF conducted the classified Red Baron Report while the Navy conducted a study concentrating primarily on performance of air-to-air weapons that was informally known as the "Ault Report". The impact of both studies resulted in modifications to the Sidewinder by both services to improve its performance and reliability in the demanding air-to-air arena.

US Navy develops AIM-9D/G/H

The Navy Sidewinder design progression went from the early production B model to the D model that was used extensively in Vietnam. The G and H models followed with new forward canard design improving ACM performance and expanded acquisition modes and improved envelopes. The "Hotel" model followed shortly after the "Golf" and featured a solid state design that improved reliability in the carrier environment where shock from catapult launches and arrested landings had a deteriorating effect on the earlier vacuum tube designs. The Ault report had a strong impact on Sidewinder design, manufacture, and handling.

US Air Force develops AIM-9E/J/N/P

Once the Air Force adopted the Sidewinder as part of its arsenal, it developed the AIM-9E, introducing it in 1967. The "Echo" was an improved version of the basic AIM-9B featuring larger forward canards as well as a more aerodynamic IR seeker and an improved rocket motor. The missile, however still had to be fired at the rear quarter of the target, a drawback of all early IR missiles. Significant upgrades were applied to the first true dogfight version, the AIM-9J, which was rushed to the South-East Asia Theatre in July 1972 during the Linebacker campaign, in which many aerial encounters with North Vietnamese MiGs occurred. The Juliet model could be launched at up to 7.5g (74 m/s²) and introduced the first solid state components and improved actuators capable of delivering 90 lb·ft (120 N·m) torque to the canards, thereby improving dogfight prowess. In 1973, Ford began production of an enhanced AIM-9J-1, which was later redesignated the AIM-9N. The AIM-9J was widely exported. The J/N evolved into the P series, with five versions being produced (P1 to P5) including such improvements as new fuzes, reduced-smoke rocket motors, and all-aspect capability on the latest P4 and P5. BGT in Germany has developed a conversion kit for upgrading AIM-9J/N/P guidance and control assemblies to the AIM-9L standard, and this is being marketed as AIM-9JULI. The core of this upgrade is the fitting of the DSQ-29 seeker unit of the AIM-9L, replacing the original J/N/P seeker to give improved capabilities.

General Information
Developed by USA
Deployed by (all versions)Argentian, Australia, Austria, Bahrain, Belgium, Brazil, Canada, Chile, Denmark, Egypt, Ethiopia, Finland, France, Germany, Greece, Honduras, Indonesia, Iran, Israel, Italy, Japan, Jordan, Kenya, Korea, Kuwait, Malaysia, Mexico, Morocco, Netherlands, New Zealand, Norway, Oman, Pakistan, Philippins, Portugal, Saudi Arabia, Singapore, Spain, Sudan, Sweden, Switzerland, Taiwan, Thailand, Tunisia, Turkey, UAE, UK, USA, Venezuela, Vietnam, Yemen
Development Year 1949
Deployment Year 1956(9B)
Platform many western fighters and attack aircrafts
Launcher LAU-7/A Sidewinder launcher
Number manufactured 150,770(48,850 all version, through 1999, including 48,850 export)
Contractor Raytheon Co., Raytheon Systems, Lockheed Martin Corp., Loral Space Div.

Dimensions and Performance
Length 2.85m(,AIM-9L), 2.85m(AIM-9M), 3.07m(AIM-9P), 2.85m(AIM-9R)
Body Diameter 12.7cm
Wing/Fin span 63cm, 63cm, 56cm, 63cm
Launch Weight 85.3kg, 86.0kg, 78.0kg, 87.0kg
Range 17.7km, 17.7km, 17.7km, 19.3km
Speed Mach 2.5+

Components
Propulsion solid propellant
Engine Atlantic Research, Thiokol and Hercules Mk16, Mk36 Mod11 or Bermite/Rocketdyness TX-683 (AIM-9L/M)
Warhead 9.4kg annular blast, preformed-rod sheth, HE fragmentation warhead
Guidance passive infrared homing (except for AIM-9C/9R)

End notes