Qantas A388 at Dubai on Mar 28th 2014, engine automatically shut down in flight

Last Update: April 18, 2017 / 13:51:23 GMT/Zulu time

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Photo of Qantas VH-OQL, Airbus A380-800 — Qantas VH-OQL, Airbus A380-800 (Photo credit: c38astra / Flickr / License: CC by-sa)

Incident Facts

Date of incident
Mar 28, 2014

Classification
Incident

Airline
Qantas

Flight number
QF-9

Departure
Dubai, United Arab Emirates

Destination
London Heathrow, United Kingdom

Aircraft Registration
VH-OQL

Aircraft Type
Airbus A380-800

ICAO Type Designator
A388

A Qantas Airbus A380-800, registration VH-OQL performing flight QF-9 from Dubai (United Arab Emirates) to London Heathrow,EN (UK) with 484 passengers and 19 crew, was climbing out of Dubai's runway 30R when the crew stopped the climb at FL060 reporting problems with engine #3 (inboard right hand, Trent 972). The aircraft returned to Dubai for a safe landing on runway 30L about one hour after departure.

The airline confirmed a #3 engine fault indicated by the instruments prompted the crew to return to Dubai.

A replacement Airbus A380-800 registration VH-OQI reached London with a delay of 14.5 hours.

On Apr 18th 2017 the United Arab Emirates GCAA released their final report concluding the probable causes of the incident were:

The Air Accident Investigation Sector determines that the cause of the inflight engine shutdown was the mechanical damage of the step aside gear box (SAGB) that had resulted in a loss of drive to the external gear box (EGB).

The loss of drive resulted in the uncommanded shutdown of the engine along with the disconnection of the fuel pump fuel, oil pumps and generators, which were driven from the EGB. The primary root cause was insufficient clamping load to prevent relative movement between the SAGB driven bevel gear shaft lower support bearing and the bearing support housing.

THe GCAA reported the aircraft was climbing through 2000 feet out of Dubai when the crew received an ECAM message "ENG FAIL" indicating the #3 engine had failed. The engine had shut down without being commanded to do so although all indications had been normal prior to the shut down. The crew stopped the climb at FL060, the crew attempted to re-start the engine without success, the crew observed no rotation of the high pressure spool. The crew therefore initiated a return to Dubai for a safe landing. Metallic particles were found on the engine's master chip detector confirming the engine had suffered an internal failure.

The GCAA reported that the #3 engine had undergone an engine shop visit for removal of the high pressure turbine due to expiry in June 2013, where the SAGB bearing support was found damaged and was replaced. Following the shop visit the engine had operated for 2,224 hours in 198 flight cycles, all on the occurrence aircraft.

The GCAA analysed:

Hardware was examined in the laboratory at the SAGB manufacturer (Avio Aero). A cracked lower bearing support from another engine was examined by Avio and Rolls-Royce in the Rolls-Royce laboratory. These examinations identified that crack had initiated from stress concentration features resulting from the wear step generated on the lower bearing support. Examination of the fracture surface in the scanning electron microscope (SEM) identified characteristic of propagation under a high cycle fatigue mechanism.

A stress review between Rolls-Royce and Avio Aero was performed. The difference between starting loads and engine running loads was agreed. Analysis of the bolted joint at the interface of the bearing with the lower bearing support found that the original, specified bolt torque did not produce a sufficient clamping load to prevent relative movement between the components during engine running. This was identified as the primary root cause.

The Angled Drive Shaft (ADS) imbalance condition was concluded to exacerbate the movement and was therefore a contributory factor that influenced the rate of wear. Any out-of-tolerance radial run-out of the ADS would also influence the out-of-balance at high shaft speeds and was therefore concluded to be contributory factor.

Further analysis, with increased bolt torque applied, demonstrated that the increased clamping load at the joint would prevent movement when a correctly balanced and in-tolerance ADS is installed. The analysis also indicated that there was reserve margin in the current design under these conditions.

The major quality investigation at Avio Aero identified the reason for the ADS unbalance condition. This resulted in effective, remedial processes being incorporated that addressed the imbalance condition and identified shafts with unacceptable radial run-out.