At about 0700 Western Standard Time on 16 August 2010, a Fairchild Industries Inc. SA226-TC (Metro II) aircraft, registered VH-NGX, departed Perth Airport on a charter flight to Fortnam Mine, Western Australia. On board the aircraft were the pilot and 10 passengers.
The aircraft was climbing through flight level 205 when the right cockpit side window suddenly failed and the cabin rapidly depressurised. The pilot put on his oxygen mask, activated the passenger oxygen system and transmitted a distress call to air traffic control. He commenced an emergency descent to 9,000 ft and returned to Perth. There were no reported injuries to the aircraft occupants and the aircraft sustained minor airframe damage as a consequence of the window failure.
The investigation determined that the window failed as a result of cracks that had propagated laterally between the retainer holes along the upper edge of the window and significantly weakened its structural integrity.
Inspection of the aircraft logbooks determined that the failed window was fitted as an outer window in 2006 by the previous aircraft owner. However, the investigation identified that the window was manufactured and supplied as an inner window only, was of reduced material thickness, and was not designed to safely withstand cabin pressurisation loads.
The work practices during the installation of the incorrect window and its reduced material thickness contributed to the window's deterioration and failure under pressurisation loads.
The investigation did not identify any organisational or systemic issues that might adversely affect the future safety of aviation operations. Notwithstanding, the aircraft operator and Civil Aviation Safety Authority initiated proactive safety action to minimise the risk of a recurrence of the window failure.