Fairchild SA227-DC, VH-WBA

The Australian Transport Safety Bureau did not conduct an on-scene investigation of this occurrence. The report presented below was derived from information supplied to the Bureau.

While en route from the Jundee mine site to Perth, cruising at FL220, the crew of the Fairchild Industries Inc Metro 23, registration VH-WBA, saw the cabin altitude gauge indication climbing at a rate of about 8,000 ft/minute. The crew, suspecting a pressurisation failure, donned oxygen masks and directed the passengers to do the same. They contacted Melbourne Centre air traffic control and received a clearance to immediately descend to 14,000 ft. Once level at the amended cruise altitude, the use of passenger oxygen masks was discontinued and the flight proceeded to Perth.

Company maintenance investigation could not detect the reason for the pressurisation fault. Extensive trouble shooting was carried out in accordance with the manufacturer's maintenance manual, followed by ground runs and a test flight. The aircraft and its systems performed normally.

The aircraft was placed on a maintenance watch and returned to service where it has since operated without incident.