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The Airbus A320 on a flight from Hobart to Melbourne had commenced descent from flight level (FL) 350 to FL210 when the aircraft cabin altitude began to rise rapidly. The co-pilot was unable to control the cabin pressurisation manually.

The flight crew donned oxygen masks, and the pilot in command requested and was given a clearance by air traffic control for an immediate descent to 10,000 ft. During the descent, the passenger oxygen masks deployed. The aircraft subsequently made an uneventful approach and landing at Melbourne Airport.

The operator found that the electronic control of the pressurisation outflow control-valve had failed, allowing the valve to remain in the fully open position. The valve was changed and the aircraft returned to service. The valve has been returned to the manufacturer in France for further evaluation.


As a result of this occurrence, the Bureau of Air Safety Investigation is currently analysing two possible safety deficiencies. The deficiencies identified involve the use of oxygen masks and emergency descent profile awareness by cabin crew during cabin decompression, and the carriage of additional Passenger Service Unit tools in the mid cabin area of the aircraft.

General details
Date: 08 March 1998 Investigation status: Completed 
Time: 1105 hours ESuT  
Location   (show map):19 km SSE Wonthaggi, (VOR) Investigation type: Occurrence Investigation 
State: Victoria Occurrence type: Air/pressurisation 
Release date: 24 July 1998 Occurrence class: Technical 
Report status: Final Occurrence category: Incident 
 Highest injury level: Minor 
Aircraft details
Aircraft manufacturer: Airbus Industrie 
Aircraft model: A320 
Aircraft registration: VH-HYB 
Serial number: 023 
Type of operation: Air Transport High Capacity 
Damage to aircraft: Nil 
Departure point:Hobart, TAS.
Departure time:1023 hours ESuT
Destination:Melbourne, VIC.
Crew details
RoleClass of licenceHours on typeHours total
Minor: 013013
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Last update 13 May 2014