Qantas B738 over Tasman Sea on Jan 18th 2023, engine shut down in flight

Last Update: August 3, 2023 / 06:12:43 GMT/Zulu time

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Photo of Qantas VH-XZB, Boeing 737-800 — Qantas VH-XZB, Boeing 737-800 (Photo credit: gordon.bevan@xtra.co.nz / Flickr / License: CC by-sa)

Incident Facts

Date of incident
Jan 18, 2023

Classification
Incident

Cause
Engine shut down in flight

Airline
Qantas

Flight number
QF-144

Departure
Auckland, New Zealand

Destination
Sydney, Australia

Aircraft Registration
VH-XZB

Aircraft Type
Boeing 737-800

ICAO Type Designator
B738

A Qantas Boeing 737-800, registration VH-XZB performing flight QF-144 from Auckland (New Zealand) to Sydney,NS (Australia) with 145 people on board, was enroute at FL360 about 300nm east of Sydney when the crew needed to shut the left hand engine (CFM56) down. The aircraft drifted down to FL200 and continued to Sydney for a safe landing on runway 34L about 70 minutes after leaving FL360.

Some Australian media were claiming the right hand engine was broken showing the engine with its thrust reverser deployed during the landing roll as "broken".

Passengers reported there had been a bang from the left hand engine.

On Jan 19th 2023 the ATSB announced they have dispatched three investigators on site and opened a safety investigation. FDR and CVR were "quarantained", their data are going to be downloaded.

On Aug 3rd 2023 the ATSB released their final report commenting "Trans-Tasman engine failure event highlights benefits of effective decision making" and concluding the probable causes of the incident were:

Contributing factors

- During cruise, separation of the radial driveshaft led to a mechanical discontinuity between the engine core and accessory gearbox. This resulted in loss of the accessory gearbox-driven main fuel pump pressure and uncommanded shutdown of the left engine. In addition, the failed driveshaft prevented the engine from being restarted in-flight.

Other findings

- Based on the more favourable forecast weather conditions and operational requirements, the flight crew decided to continue to Sydney rather than divert to Norfolk Island, which ensured that no additional risk was added to an already high workload situation.

- The cockpit voice recorder was inadvertently overwritten during maintenance activity following the incident flight. Although not critical to this investigation, this information could have provided direct evidence regarding the flight crew's coordination, check list management, and decision making throughout the flight.

The ATSB summarized the sequence of events:

After about 1 hour in the cruise, the flight crew transferred high frequency (HF) radio communications from Auckland to the en route controller at Brisbane Centre (en route controller).

Once the en route controller accepted monitoring of the aircraft, the flight crew requested to climb to FL 380. About 3 minutes later, and before the climb was authorised, the flight crew reported hearing a ‘pop’ sound, followed by the autopilot and auto throttle disengaging, with associated warning lights and horn. They then identified left (#1) engine was not operating. The flight crew broadcast MAYDAY,6 citing an engine failure and requested an immediate descent to FL 240. The en route controller enquired if it was a single or double engine failure, to which the flight crew confirmed a single-engine failure. About 1 minute later, the en route controller authorised a descent to FL 240 when ready.

At the same time, following the completion of cabin service, the cabin safety manager (CSM) heard a noise and felt the aircraft yawing in a manner they described as ‘not normal’. After confirming that the cabin crew member next to them had also experienced the event, the CSM advised that they called the flight deck. The captain answered and advised the CSM that they could not talk at that moment as an engine had just failed. The CSM then called the cabin crew team leader at the rear of the cabin to inform them of the situation.

About 5 minutes later, the captain called the CSM to the flight deck and explained the situation, in that the left engine had shut down uncommanded and they were unsure why. The captain further advised that the aircraft was operating safely on one engine, and they were working through the engine failure, and associated checklists. The captain requested that the CSM relay this information to the cabin crew, monitor the passengers and to advise the flight deck if anything changed in the cabin.

Soon after, the CSM advised the flight crew that the cabin was getting quite warm7 and power was not available to various galley equipment and the rear bathrooms.8 The APU had been selected to ‘on’ as part of the engine failure checklist, however, cabin airflow had been affected. The flight crew reported they then selected the temperature controller to minimum and conditions improved.

The flight crew continued working through the non-normal checklists, while on a slow descent. Following authorised descent to FL 200, and with all checklists completed, the flight crew decided to attempt the in-flight engine restart checklist. While the first few steps were accomplished, the engine start attempt had to be aborted when a designated parameter could not be achieved. The flight crew then consolidated their plan and prepared for a single-engine landing at Sydney.

Throughout the descent into Sydney, en route and Brisbane Centre air traffic controllers maintained contact with the flight crew, with scheduled check-in times to ascertain location details, operational status, and updates to any requirements in Sydney. Just prior to top of descent, the flight crew advised Brisbane Centre they were downgrading from a MAYDAY to PAN PAN10 but would still like aviation rescue fire-fighting services to attend and inspect the left engine before they proceeded to the terminal. Shortly after, air traffic control (ATC) communications were transferred to Sydney.

At about this time the captain made an announcement to the passengers, stating:
- they were to commence the descent into Sydney in a few minutes time
- acknowledging there were some issues with one engine that was affecting the air-conditioning and some electrical systems
- once on the ground, emergency services would attend the aircraft to inspect the engine, as a precaution, before they proceeded to the terminal
- reassuring them that everything was okay, and they would make another announcement once on the ground.

Following an uneventful landing at Sydney at 1526 local time, emergency services met the aircraft on the taxiway. Once cleared, the aircraft was taxied to the terminal, where engineering personnel conducted an additional inspection before the airbridge was positioned. At this point, the captain made a further announcement advising that they had experienced an engine failure about 1 hour out of Sydney. The captain thanked the passengers for their patience and understanding. In addition, the flight crew exited the flight deck and personally addressed each passenger as they disembarked.

The ATSB analysed:

While in cruise, about 1 hour and 24 minutes from departure and without command, the left engine shut down. The flight crew reported they did not detect any change in parameters, which may have alerted them to an impending engine issue. This was consistent with the recorded data, which showed there was no warning. In addition, recent maintenance was indicative of a normally operating engine. The reason for the uncommanded shutdown was later established as being the result of the separation of the radial driveshaft. The mechanical discontinuity between the engine core and accessory driveshaft resulted in loss of fuel pump pressure and the subsequent engine failure. The driveshaft failure also prevented the engine restart.

While Norfolk Island was closer at the time of the engine failure, a diversion required a deviation from their current track. In addition, Norfolk Island presented changeable weather and operational conditions. In contrast, Sydney Airport was on their direct route, had favourable weather conditions forecast, had an extensive emergency response, and a straight-in approach on a very long runway. The flight crew’s decision to continue to Sydney ensured no additional risk was added to an already high workload situation.

The ATSB publication Black box flight recorders highlights the benefits of aircraft flight recorders such as the cockpit voice recorder, by creating a record of the total audio environment in the cockpit area. This includes crew conversations, radio transmissions, aural alarms, and ambient cockpit sounds, check list management, and decision making. As highlighted in the ATSB’s publication, around 80% of aircraft accidents involve human factors, which means that crew performance may have contributed to some events. As a result, the cockpit voice recorder often provides accident investigators with invaluable insights into why an accident occurred. In this case, the recorded audio of this incident was inadvertently overwritten during maintenance operations. However, flight data was available and was found to be consistent with the flight crew’s recollections and ATC audio recordings.