On 15 October 2017, at about 1152 Western Standard Time,
1] the flight crew on board an Air Asia Airbus A320-216, registered PK-AXD, initiated an emergency descent from flight level (FL)
2] 330 to 10,000 ft.
Earlier at about 1122, the aircraft departed Perth Airport, Western Australia, for the planned destination of Bali, Indonesia, 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 1148, just after passing FL 300, the master caution activated for the opening of the pressurisation system safety valve(s)
3] (SAFETY VALVE OPEN). The flight crew selected manual control (MAN) for the pressurisation system and, noting a cabin pressurisation rate of climb
4] 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
5] 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 1151, 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,
6] 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 1248.
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). Figure 1 below depicts the activation of the alerts, and the descent from FL 330 to 10,000 ft, which was at an average rate of about 2,300 ft per minute. 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 (see
Aircraft pressurisation).
