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The report presented below was prepared principally from information supplied to the Bureau.

Reported Information

At 2040 eastern standard time on 7 December 2004, approximately 18 km north of Gayndah, Qld, the crew of a Bombardier Learjet 45 aircraft, registered VH-SQR, advised air traffic control that the aircraft pressurisation system had failed and that they were conducting an emergency descent to 10,000 ft. At the time, the aircraft was passing flight level 200 (20,000 ft) on descent to Maroochydore after a training flight from Townsville. The crew advised that they expected to make a normal approach and landing and that emergency services were not required. The aircraft landed at Maroochydore at 2102.

The crew subsequently reported that the aircraft's number-1 integrated computer had failed during cruise and that during descent the cabin pressure altimeter indicated a steady increase in cabin altitude. When it became apparent that the cabin altitude could not be controlled manually, and as the cabin altitude approached 10,000 ft, the crew donned oxygen masks and initiated an emergency descent to 10,000 ft. The crew advised that the maximum indicated cabin altitude was slightly above 13,000 ft.

The aircraft operator subsequently reported that extensive troubleshooting by company engineers was unable to identify any fault. As a precaution, the cabin pressure controller, the number-1 integrated computer, and the number-1 air data computer were changed and the removed items forwarded to the manufacturer for testing.

The aircraft was returned to service with no further reported faults. The operator subsequently reported that the manufacturer had found no fault in any of the components that might have contributed to the occurrence.

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