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IRIS-T missile team fixes firing fault

The six-nation consortium developing the IRIS-T short-range air-to-air missile believes it has resolved the problem with the weapon's motor that caused it to eject debris during a test last November.

The firing, at the Swedish air force's Vidsel test centre, was the first separation of an IRIS-T from a Saab JAS39 Gripen. The procedure was successful, but downrange the missile deviated from the test profile and the thrust vectoring vanes on the rocket motor exhaust were expelled from the missile, says an IRIS-T consortium source. Part of the exhaust may also have been ejected from the missile. The source adds: "The firing's purpose [safe separation from a Gripen] was achieved but there was a malfunction."

An investigation revealed that the propellant liner detached from the rocket motor casing, which either choked the nozzle or increased the propellant burning area. Increasing the internal pressure by restricting the nozzle area or enlarging the fuel's burning area, as would happen once it detached from the liner, increases thrust, which in turn would account for the nozzle damage, says the source.

The consortium ceased test firings after the incident and conducted a series of bench trials of the motor, which is built by Norway's Nammo and Italy's Fiat Avio.

The failed flight-test missile used a European-sourced liner for the first time. A subsequent test reverted to a US-supplied liner that had been used for three earlier air firings from a Lockheed MartinF-16 over Crete and three ground launches on Sardinia.

The IRIS-T consortium is led by BGT with participation from companies in Canada, Greece, Italy, Norway and Sweden. The missile will be integrated with a range of fighters when it enters service - comprising the Boeing F/A-18A/B Hornet, Eurofighter, F-16, Gripen, McDonnell Douglas F-4 Phantom and Panavia Tornado.

IRIS-T has also been short-listed in Switzerland where it is competing against the Raytheon AIM-9X.