Electrical systems event involving Airbus A330, VH-EBL, near Curtin aerodrome, Western Australia on 14 May 2019

The occurrence

On 14 May 2020 at about 0030 Western Standard Time,^[1] an Airbus A330-203 aircraft registered VH-EBL, was operating as Qantas flight QF044, a scheduled passenger service between Sydney, Australia and Denpasar, Indonesia. While in the cruise at flight level 390^[2] and abeam the Royal Australian Air Force Curtin aerodrome near the West Australian coast, the first officer’s primary flight, navigation and multipurpose control displays lost power and went blank. Accompanying this, the autopilot disconnected, the cockpit Master Warning light illuminated with an aural alert and multiple electronic centralised aircraft monitor (ECAM) messages presented on the engine/warning display.

The flight crew assumed manual aircraft control and worked to complete the appropriate response checklists and to better understand the issue. At 0038, the crew made a PAN^[3] call to air traffic control (ATC) advising of the electrical problem and the possible need to divert. That decision was made at 0044 and the crew advised ATC that they would be diverting the aircraft to Broome – approximately 170 km from their position.

The flight crew reported that while some inoperative systems were restored during the diversion, other systems remained unavailable. All flight, navigation and multipurpose controls on the captain’s side of the flight deck remained functional throughout the flight. The approach to and landing on runway 10 at Broome was uneventful and the aircraft touched down at 0150.

Overview of the investigation

Following notification of the occurrence, the ATSB initiated an investigation under the Transport Safety Investigation Act 2003, for the purposes of examining the electrical systems event and the flight crew’s response. Information was obtained from the aircraft manufacturer and operator, including formal technical and operational investigation reports from both Airbus and Qantas. ATSB investigators interviewed both flight crew and the information thus provided was correlated against the technical and operational reports.

In summary, based on information gathered during the investigation, it was found that the electrical systems event had originated within the aircraft’s number-two integrated drive generator (IDG) and generator control unit (GCU) systems. The event produced abnormal behaviours in related electrical systems which were not immediately or definitively indicative of an IDG or GCU fault – making the task of fault diagnosis difficult. Indeed, engineering staff examining the aircraft after arrival in Broome and following relocation under special authority to Brisbane, were unable to replicate the systems behaviour reported by the flight crew.

Reasons for the discontinuation

Following a review of the investigation and the information gathered, the ATSB has discontinued its investigation of this occurrence as a result of the following principal considerations:

• The flight crew, despite receiving unclear information from the monitoring systems, recognised that the aircraft’s systems were significantly degraded and appropriately managed the risks by diverting to the nearest suitable airport.
• The aircraft flight crew’s responses to the system failures during the diversion effectively managed the risks presented by the degraded aircraft systems.
• The approach and landing at the diversion airport was appropriately managed and uneventful.
• The operator and manufacturer’s combined investigations into the technical origins of the electrical systems event, while unable to conclusively identify root cause, did isolate the areas of likely contribution.
• Both manufacturer and aircraft operator have undertaken proactive safety action in response to the technical failure areas of concern.
• The operator has similarly assessed the operational and logistical issues arising from the use of Broome as a diversionary destination.

As such, the ATSB considered it was unlikely that further independent investigation would identify any systemic safety issues or important safety lessons.

The evidence collected during this investigation remains available to be used in future investigations or safety studies. The ATSB will also monitor for any similar occurrences that may indicate a need to undertake a further safety investigation.

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1. Western Standard Time (WST): Coordinated Universal Time (UTC) + 8 hours.
2. Flight level: at altitudes above 10,000 ft in Australia, an aircraft’s height above mean sea level is referred to as a flight level (FL). FL 390 equates to 39,000 ft.
3. PAN PAN: an internationally recognised radio call announcing an urgency condition which concerns the safety of an aircraft or its occupants but where the flight crew does not require immediate assistance.