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.