Aviation safety investigations & reports

Pressurisation event involving Airbus A320, PK-AXD, 160 NM (300 km) north of Perth, Western Australia, on 15 October 2017

Investigation number:
Status: Completed
Investigation completed
Phase: Final report: Dissemination Read more information on this investigation phase

Final Report

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What happened

On 15 October 2017, at about 1152 Western Standard Time, the flight crew on board an AirAsia Indonesia Airbus A320-216, registered PK-AXD, initiated an emergency descent from FL 340 to 10,000 ft in response to a malfunction of the aircraft’s pressurisation system. The aircraft returned to Perth Airport, Western Australia, with no reported injuries or damage.

What the ATSB found

The manufacturer of the cabin pressure controllers identified an intermittent rare fault with cabin pressure controller 1 circuit board, which resulted in incorrect control of the outflow valve. This led to the over-pressurisation of the aircraft cabin and activation of the cabin safety valve(s). Following the activation of the safety valve(s), several warnings of excess cabin altitude were generated, which ultimately resulted in the flight crew conducting the emergency descent procedure. The ATSB found that the operator had reviewed and elected not to incorporate the manufacturers recommended, but not mandatory, improvements to the pressurisation system. The improvements were communicated to the airline by service bulletins. Incorporating the bulletins would have likely prevented the emergency descent incident.

In accordance with the manufacturer’s procedure, the flight crew deployed the passenger oxygen masks. However, several units either did not deploy, or deployed but did not provide oxygen. Consequently, several passengers moved around the cabin to secure a spare oxygen mask. As passengers were moving around while the seat belt sign was illuminated, the cabin crew shouted commands such as ‘BRACE’, ‘GET DOWN’ and ‘CRASH POSITION’. This probably increased the level of confusion and panic amongst some passengers.

The ATSB conducted a passenger safety survey following the incident. About half the respondents indicated they were unsure if oxygen was flowing from their oxygen masks, and several responses indicated a misunderstanding of how the equipment operates.

What's been done as a result

The aircraft manufacturer, Airbus, reviewed their A320 emergency procedures related to the circumstances in which it would be appropriate for flight crew to manually change the active cabin pressure controller. Airbus advised they would recommend a manual cabin pressure controller changeover in case of abnormal cabin altitude. This modification was implemented in the A320 Quick Reference Handbook revision March 2019.

The ATSB has issued AirAsia Indonesia with a safety recommendation to review its current passenger pre-flight safety briefing and safety information card to ensure passengers are provided with clear instruction on how to activate the flow of oxygen from the passenger oxygen masks and that the bag may not inflate when oxygen is flowing.

Safety message

An important aspect of managing abnormal passenger responses is the cabin crew’s ability to recall and use the appropriate standard commands. In this case, the passengers generally responded well when appropriate commands were used, but incorrect commands resulted in some confusion and panic among the passengers. Cabin crew emergency procedures training that include role-playing of the full range of expected passenger behaviour, including panic and confusion, can better prepare cabin crew when exposed to more complex real-world scenarios.

Download final report
[Download  PDF: 1008KB]

The occurrence


Safety analysis


Safety issues and actions

General details

Sources and submissions


Safety Issue

Go to AO-2017-098-SI-01 -

Passenger oxygen mask instructions

The pre-flight safety briefing and safety information card did not include a clear instruction on how to activate the flow of oxygen from the passenger oxygen masks and that the bag may not inflate when oxygen is flowing. This resulted in some passengers not understanding whether or not there was oxygen flowing in the mask.

Safety issue details
Issue number: AO-2017-098-SI-01
Who it affects: Airline passengers
Status: Closed – Adequately addressed
General details
Date: 15 October 2017   Investigation status: Completed  
Time: 11:52 WST   Investigation level: Defined - click for an explanation of investigation levels  
Location   (show map): 300 km north of Perth   Investigation phase: Final report: Dissemination  
State: Western Australia   Occurrence type: Air/pressurisation  
Release date: 26 November 2019   Occurrence category: Serious Incident  
Report status: Final   Highest injury level: None  

Aircraft details

Aircraft details
Aircraft manufacturer Airbus  
Aircraft model A320-216  
Aircraft registration PK-AXD  
Serial number 3182  
Operator Indonesia AirAsia  
Type of operation Air Transport High Capacity  
Sector Jet  
Damage to aircraft Nil  
Departure point Perth, Western Australia  
Destination Denpasar, Indonesia  
Last update 27 November 2019