A332, northwest of Phuket Thailand, 2012
A332, northwest of Phuket Thailand, 2012
Summary
On 20 December 2012, a PW4168A-engined Airbus A330-200 was climbing through FL220 after departing Phuket at night when sudden uncontained left engine failure occurred. Engine shutdown and initiation of a return was followed by consequential loss of the green and then blue hydraulic systems. Shortly after this, a relatively uneventful landing followed with only minor damage but “without pilot assessment or knowledge of the safety margin”. As the findings of the Investigation raised still-relevant concerns about the way this multiple failure scenario was handled, it was still felt to be useful to publish the 148-page Final Report eleven years later.
Flight Details
Aircraft
Operator
Type of Flight
Public Transport (Passenger)
Flight Origin
Intended Destination
Actual Destination
Take-off Commenced
Yes
Flight Airborne
Yes
Flight Completed
Yes
Phase of Flight
Climb
General
Tag(s)
Air Turnback,
Inadequate Aircraft Operator Procedures,
Non Precision Approach,
PIC aged 60 or over
HF
Tag(s)
Distraction,
Inappropriate crew response - skills deficiency,
Inappropriate crew response (technical fault),
Procedural non compliance,
Dual Sidestick Input
LOC
Tag(s)
Significant Systems or Systems Control Failure,
Loss of Engine Power,
Flight Management Error
EPR
Tag(s)
MAYDAY declaration
AW
System(s)
Engine - General
Contributor(s)
OEM Design fault,
Component Fault in service,
Ejected Engine Failure Debris
Outcome
Damage or injury
Yes
Aircraft damage
Minor
Non-aircraft damage
No
Non-occupant Casualties
No
Off Airport Landing
No
Ditching
No
Causal Factor Group(s)
Group(s)
Aircraft Operation
Aircraft Technical
Safety Recommendation(s)
Group(s)
None Made
Investigation Type
Type
Independent
Description
On 20 December 2012, an Airbus A330-200 (D-ABXA) being operated by Air Berlin was on an international passenger flight from Phuket to Abu Dhabi as AB7425 when the left PW4168A engine failed at night. It was set to idle but only shut down when doing so did not diminish automatic flight capability. The First Officer agreed to take over as PF at the request of the Captain but the ongoing management of system serviceability and performance issues raised by the failure was not in accordance with related procedures. An approach and relatively uneventful overweight landing just over half an hour after the engine failure had occurred was made without any prior review of landing performance. After touchdown, there were several opposing dual control inputs and some minor damage to the aircraft occurred, principally but not only involving deflated main gear tyres. The 241 passengers and 10 crew members disembarked onto the runway using mobile airstairs. Debris from the left engine failure was found to have damaged both the engine cowling and the inner wall of its thrust reverser as well as the engine pylon.
Investigation
A Serious Incident Investigation was carried out by the German Federal Bureau of Accident Investigation (BFU). The CVR and FDR were removed and their data were successfully downloaded. Relevant data was also recovered from the FMS.
The 60 year-old Captain had a total of 14,811 hours flying experience which included 2,219 hours on type. The 49 year-old First Officer had a total of 10,429 hours flying experience which included 3,921 hours on type.
What Happened
Thirteen minutes after a night takeoff and climb in benign weather conditions with the Captain acting as PF, the aircraft was climbing through FL220 when a loud bang was heard and strong vibration began. The left engine N1 was observed to have decreased to about 38% whilst the N2 and EGT had increased. The Master Warning was triggered and the Captain called “Engine Failure”. The ECAM overlimit warnings for the left engine EGT and N2 were displayed. The left thrust lever was reduced to flight idle and the EGT decreased. The First Officer, with the Captain’s agreement, declared a MAYDAY and it was decided to return to Phuket. ATC and the cabin crew were advised accordingly.
Five minutes after the left engine malfunction, it was shut down and the APU was started. A non-precision RNAV approach to the 3,000 metre long, 45 metre wide runway 09 was set up. The Captain then announced that he would like the First Officer to take over as PF as he had not landed an aircraft for eight weeks. The First Officer accepted and the Captain then advised ATC that they would like to track the airport VOR and fly “a kind of holding pattern“ at 6,000 feet before possibly starting an approach. Shortly after this and 21 minutes after the engine failure, a green hydraulic system leak was annunciated although no significant loss of green system pressure was observed. The First Officer then took over as PF allowing the Captain to consult the ECAM and the system pages in respect of malfunctions. A flaps 2 fault then appeared on the ECAM followed by a blue hydraulic system low pressure warning. Flaps 2 was selected and the landing gear was successfully extended. This was followed by a warning of low pressure in both hydraulic systems and having seen a “green reservoir low level” requested “ECAM action” and “Green electric pump”. The AP was then disconnected and the planned RNAV approach to runway 09 was commenced noting that no approach lighting was available. During the approach, the Captain “tried to obtain clarity regarding the technical condition of the aircraft” and voiced his concern about the likely effectiveness of the braking system, deducing that at least accumulator-fed emergency braking should be available.
According to FDR data, as the aircraft descended through approximately 2,000 feet, engine control reverted to ‘Alternate Law’. As the final approach continued, the Captain “voiced information concerning the rate of descent and the need to descend further” and just before touchdown, the first of five dual sidestick inputs was recorded with four more following after touchdown. During the landing, the wheel brakes, spoilers and the reverser of the still operating right engine were used with brake pressures of 1,920psi (left) and 1,700 psi (right) were recorded. Several tires were damaged and deflated and the aircraft came to a stop after about 1,630 metres ground roll.
The Captain made the standard alerting call of “cabin crew to stations” followed two minutes later by advice of a normal disembarkation onto the runway for bus transport to the terminal. The airport remained closed for around six hours until the disabled aircraft could be removed.
Why It Happened
It was determined that the left engine had been rendered inoperative by the failure of vanes in a single cluster of the 4th stage of the Low Pressure Turbine (LPT) due to “deviation of the component geometry caused by flawed casting moulds” with similar deviations having previously led to engine failures. It was accepted that subsequent actions by the engine manufacturer should prevent more vane cluster failures. Whilst the airworthiness origins of this event were important and have since been addressed, the main still-relevant thrust of the Investigation was the response of the flight crew to it and the aircraft operator context for that response. However, before progressing to that aspect, the illustrations below show which part of the engine was involved and what happened to it.
The PW 4168A engine showing the location of the LPT fan blade failure. [Reproduced from the Official Report]
The LPT 4th guide vane stage showing the location of the two missing vane clusters. [Reproduced from the Official Report]
Although the ECAM actions at that time would not have resulted in engine shut-down, the applicable FCOM procedure for an ‘EGT OVER LIMIT’ annunciation required this. It was considered probable that the engine vibrations when it failed had loosened the Case Drain Line of the green hydraulic system Engine Driven Pumps (EDP) causing it to leak fluid. Such a leakage could have been stopped by closing the Fire Shut Off Valve (SOV) but “the technical features in the aircraft did not allow the location of the leakage which had occurred to be determined” so that ECAM action and procedures in the FCOM/QRH to stop a leakage were not suitable for this particular situation and the continuing leak was inevitably going to lead to system failure when the level in the fluid reservoir became too low.
The blue hydraulic system then failed because the EDP was no longer functioning once the left engine was shut down and windmilling of the fan decreased. Failure of both the green and blue hydraulic systems meant that parts of the control surfaces were no longer actuated and the wheel brakes reverted to alternate braking powered by a hydraulic accumulator and without antiskid. The leading edge slats, intended to reduce the stall speed near the ground, did not travel to their intended final position.
The flight crew did not carry out the procedures as described in the FCOM and the applicable ECAM actions were either not completed at all or only partially. In particular, the landing checklist was not completed and an effective FORDEC approach to the situation which occurred was absent and insufficient communication resulted in ineffective solutions of problems with the flight crew “unable to gain a thorough overview over the technical problems” encountered.
Taking an overview of the response to the engine failure and its subsequent consequences, it was concluded that the time available for the return to land had been characterised by repeated interruptions by both pilots of intended/agreed/instructed action which resulted in “procedures not being properly implemented” and “constructive workload management not being performed”. The actions of both pilots, especially their deviation from applicable procedures was considered to have prevented them from obtaining an overview of their situation and from making optimum use of the airborne time they made available. In particular it was considered that applied CRM had “not resulted in the recognition of deficits and therefore they were not remedied”. Ultimately, in the final stages of the flight, the flight crew “was no longer in full control of the situation” which “in combination with the degraded aircraft performance had resulted in a higher probability of an accident”. It was, however, accepted that such a combination of technical problems, human factors, and deficits in teamwork is not limited to this occurrence. Of more systemic concern was the fact that even though the flight crew met all the recurrent training performance requirements and the operator had established an SMS, the multi-failure scenario in the investigated event “could not be managed on an acceptable level”.
The Causes of the occurrence were formally recorded as follows:
Immediate Causes:
- A leak in the green hydraulic system following an engine failure in circumstances where the available information and the associated procedure would not have been suitable to stop the leakage and thus maintain the functionality of this hydraulic system for the remainder of the flight.
- The limited capability of the flight crew to assess the developing situation and manage it.
Systemic Cause:
The fact that the established procedures to ensure flight safety, especially the existing SMS and the training syllabus of the operator, were not adequate to prepare the flight crew for this multiple failure scenario.
Safety Message
Whilst no Safety Recommendations were made, the following four ‘Safety Messages’ were documented based on the findings of the Investigation:
- The training of flight crews in regard to unexpected complex situations should include interruptions by third parties (e.g. ATC).
- The assessment of simulator check flights should be designed in a way that Crew Resource Management (CRM) of the pilots during unexpected complex situations is assessed at length.
- Air Traffic Services (ATS) should ensure that the number of calls to flight crews made by Air Traffic Control (ATC) is as limited and as coherent as possible. The Air Traffic Management, Doc 4444, Chapter 15 of the International Civil Aviation Organisation (ICAO) should be considered.
- Air Traffic Services (ATS) should ensure that an aircraft involved in an emergency should receive another (“own”) frequency, if an improved service can be provided to the aircraft concerned. The Air Traffic Management Doc 4444, Chapter 15 of the International Civil Aviation Organisation (ICAO) should be considered.
The Final Report was eventually completed on 1 August 2023 and released on 1 December 2023. The aircraft operator involved ceased operating in 2017.
