Cessna Aircraft 402C VH-RMI, Darwin Airport, 6 February 1998

After full flap was selected on late final approach, the pilot
heard a loud thud, the aircraft pitched nose up and the flaps
retracted rapidly. A go around was conducted while the pilot
established that the aircraft operated normally, apart from the
flaps. A flapless landing was carried out.

Examination of the flap system revealed a failure on the idler
gear of the flap drive gearbox. The gearbox had been in service for
12,546 hours, since the aircraft was manufactured. The manufacturer
had not specified any inspection schedules, the gearbox being
required "on condition".