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| Date: | Sunday 15 October 2017 |
| Time: | 11:52 |
| Type: |  Airbus A320-216 |
| Owner/operator: | Indonesia AirAsia |
| Registration: | PK-AXD |
| MSN: | 3182 |
| Year of manufacture: | 2007 |
| Engine model: | CFMI CFM56-5B6 |
| Fatalities: | Fatalities: 0 / Occupants: 152 |
| Other fatalities: | 0 |
| Aircraft damage: | None |
| Category: | Serious incident |
| Location: | north of Perth, WA -
 Australia
|
| Phase: | En route |
| Nature: | Passenger - Scheduled |
| Departure airport: | Perth Airport, WA (PER/YPPH) |
| Denpasar-Ngurah Rai Bali International Airport (DPS/WADD) | |
| Investigating agency: | ATSB |
| Confidence Rating: |  Accident investigation report completed and information captured |
Indonesia AirAsia flight QZ535, an Airbus A320, initiated an emergency descent from flight level FL330 to 10,000 ft. during a flight from Perth, Australia, to Bali, Indonesia.
Earlier at about 11:22, the aircraft departed Perth Airport, with two flight crew, four cabin crew and 146 passengers on board. On departure, the flight crew were issued with a clearance from air traffic control to climb to FL 340. At about FL 250, the crew noticed a system 1 (SYS 1) fault for the pressurisation system appear and then disappear. At about 11:48, just after passing FL 300, the master caution activated for the opening of the pressurisation system safety valve(s) (SAFETY VALVE OPEN). The flight crew selected manual control (MAN) for the pressurisation system and, noting a cabin pressurisation rate of climb of 1,100 ft per minute, they attempted to close the outflow valve to reduce the cabin rate of climb. The first officer also noted the cabin differential pressure was 8.3 pounds per square inch and the cabin altitude was 8,900 ft. Before the checklist actions could be completed the master caution cleared.
At about 11:51, the master warning activated intermittently for a high cabin altitude. The excess cabin altitude warning (EXCESS CAB ALT) initially activated intermittently and then remained on.
At about this time, the cabin crew noted intermittent activations of the cabin seat belt signs and emergency lighting. The flight crew informed the cabin crew manager that they were going to conduct an emergency descent, donned their emergency oxygen masks and started the descent. Shortly after, the cabin crew manager reported to the flight crew that the emergency oxygen masks in the cabin were not deployed and the flight crew then manually deployed them. The cabin crew reported that they secured the cabin and instructed the passengers in accordance with their emergency descent procedures.
The flight crew informed air traffic control that they were conducting an emergency descent with pressurisation problems and requested a clearance to return to Perth Airport at 10,000 ft. After some initial communications difficulties, air traffic control issued the respective clearances for a descent to 10,000 ft and return to Perth Airport where the aircraft landed safely at about 12:48.
Some of the crew members reported some ear discomfort just prior to the emergency descent, but none reported any indications of hypoxia. During the descent there was an intermittent activation of the master caution for cabin low differential pressure (LO DIFF PR).
There were no reported injuries and the aircraft was not damaged. The post-flight maintenance tests identified the cabin pressure controller 1 as at fault.
Contributing factors
• During climb, the active cabin pressure controller produced a series of intermittent faults, which led to the cabin over-pressurising and the safety valve(s) opening. The malfunctioning controller then produced a series of intermittent excess cabin altitude alerts, which resulted in the flight crew performing the emergency descent in accordance with the procedure.
• The source of the cabin pressurisation system faults was isolated to the main circuit board in cabin pressure controller 1, which was the master controller. Cabin pressure controller 1 declared itself in failure after the flight crew had selected manual control of the cabin pressurisation system and therefore cabin pressure controller 2 did not take control.
• The operator had not incorporated two of the aircraft manufacturer's non-mandatory service bulletins for more reliable cabin pressure control, which likely would have facilitated the automatic changeover from cabin pressure controller 1 to cabin pressure controller 2, thereby preventing escalation of the malfunction.
Accident investigation:
 |
|
Sources:
https://flightaware.com/live/flight/AWQ535/history/20171015/0335Z/YPPH/YPPH
https://www.atsb.gov.au/publications/investigation_reports/2017/aair/ao-2017-098/
Images:
Revision history:
| Date/time | Contributor | Updates |
|---|---|---|
| 15-Oct-2017 18:38 | harro | Added |
| 17-Dec-2017 08:43 | AF5541 | Updated [Total occupants, Source, Narrative, ] |
| 17-Dec-2017 08:48 | harro | Updated [Source, Damage, Narrative, ] |
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