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Flutter and crack discoveries put F-2 tests behind schedule

Completion of Japan Defence Agency (JDA) flight testing of the MitsubishiF-2A/B has slipped by nine months, following the discovery of excessive flutter and structural cracking of the fighter's composite wing.

A three-year, four-phase flight test programme by the JDA's Technical Research and Development Institute (TRDI) and Japan Air Self-Defence Force (JASDF) had been scheduled for completion by March 1999. This has now been extended through to the end of the year.

"The schedule has been delayed because we need to do more computer simulation testing," says the JDA. "Some parts, mainly in the wing, were found to have weak points near the pylons, so we will be conducting more tests on the F-2's main wing." it adds.

The wing cracks were discovered in one of two test articles undergoing 6,000h of fatigue and structural load testing at the TRDI's Tachikawa facility. The F-2's composite wing has also displayed an excessive amount of flutter when carrying four pylon mounted Mitsubishi ASM-2 anti-ship missiles, each of 530kg (1,170lb).

Efforts are now focused on reinforcing the wing for heavy weapon carriage and high g manoeuvring. The Mitsubishi-developed wing is fabricated from co-cured carbonfibre composites, and is designed to reduce the need for fasteners, trim weight and add strength.

The wing is co-produced by Mitsubishi and Lockheed Martin. The US manufacturer is under contract to supply 80% of all left-hand wing boxes.

The F-2's wing is 25% larger than that of the Lockheed Martin F-16, on which the Japanese aircraft's design is based, and features two additional underwing hardpoints. Two XF-2A and two tandem-seat XF-2B prototypes are engaged in a 1,000 sortie flight test programme at the TRDI's Gifu airbase. This was scheduled to include some 330 sorties for flutter and vibration testing.

According to the JDA, the extended flight test programme is not anticipated to impact on production of the 28 F-2s so far ordered out of a total of 130 eventually planned.

The first squadron deliveries to JASDF's Misawa AB are to begin in March 2000.