Accident description
Last updated: 3 September 2014
Status:Final
Date:Sunday 8 December 2002
Time:10:12
Type:Silhouette image of generic B762 model; specific model in this crash may look slightly different
Boeing 767-219ER
Operator:Air New Zealand
Registration: ZK-NBC
C/n / msn: 23328/149
First flight: 1986-08-08 (16 years 4 months)
Total airframe hrs:68007
Cycles:20390
Engines: 2 General Electric CF6-80A
Crew:Fatalities: 0 / Occupants: 10
Passengers:Fatalities: 0 / Occupants: 190
Total:Fatalities: 0 / Occupants: 200
Airplane damage: Substantial
Airplane fate: Repaired
Location:30 km (18.8 mls) ESE of Brisbane, QLD (   Australia)
Phase: En route (ENR)
Nature:International Scheduled Passenger
Departure airport:Brisbane International Airport, QLD (BNE/YBBN), Australia
Destination airport:Auckland International Airport (AKL/NZAA), New Zealand
Narrative:
While climbing through FL110, the crew heard a loud 'bang' and felt the aircraft move to the right, followed by a progressive yaw to the left. After checking instrumentation, the failure of the left (number-one) engine was confirmed and the engine was shut down. An emergency was declared and the aircraft returned to Brisbane. An initial engineering examination of the left engine revealed a large rupture of the outboard core cowl and severe gouging and scoring of the outboard side of the engine strut above the cowl damage. The leading edge flap panel above the strut was extensively damaged over approximately 40cm and the no. 2 canoe fairing behind the engine sustained debris impact and puncture damage. Inspection of the engine core beneath the ruptured cowl revealed that the first-stage high-pressure turbine disk had failed and released a large segment of the disk rim and outer web. The engine casing around the disk had been completely severed and the central shaft fractured between the stage-one and stage-two high-pressure turbine disks.

FINDINGS:
- The technical investigation of the failed CF6-80A stage-1 high-pressure turbine disk (s/n. MPOP-8478) found that the disk failed as a result of the initiation and growth of fatigue cracking from the rear bottom corner of a turbine blade fir tree slot.
- The disk had developed a total of three slot bottom fatigue cracks at the time of ultimate failure.
- None of the cracks were attributable to any identified erroneous tool or handling damage to the slot bottoms.
- The disk had undergone a repair operation in August-October 1998. The repair was conducted to remove fir tree slot edge nicks and other damage and included
blending of the damage followed by shot-peening of the rear slot edges and other areas.
- All of the cracked fir tree slots and several other uncracked slots showed surface microstructural flow and damage that was attributable to the shot peening operation following the 1998 repair.
- The type of surface damage produced (specifically the formation of stress-raising defects known as ‘peened surface extrusion folds’) has been shown to be detrimental to the fatigue life of the affected component.
- The disk had operated for 7,838 hours and through 2,793 cycles following return to service after the August 1998 overhaul.
- The previous CF6-80C2 stage-1 HPT disk failure (September 2000) occurred 1,675 cycles after a similar blending and shot peening repair of disk slots and rear corners.
- The corrective action implemented after the September 2000 disk failure did not encompass the CF6-80A stage-1 HPT disks.

Sources:
» ATSB

Official accident investigation report
investigating agency: Australian Transport Safety Bureau (ATSB) - Australia
report status: Final
report number: ATSB report 200205780
report released:24-SEP-2004
duration of investigation:656 days (1 year 9.7 months)
download report: In-flight uncontained engine failure and air turn-back, Boeing 767-219ER, ZK-NBC (ATSB report 200205780)
cover

Follow-up / safety actions
As a result of the findings of the investigation, the engine manufacturer has
implemented several changes to the manufacturing and repair shot peening processes, to avoid the surface damage found on the failed disk. Other safety action taken included revising the inspection requirements for the CF6-80A disks to include the more thorough examination of the slot bottom and rear break-edge areas, as required for the CF6-80C series engines. The US Federal Aviation Administration (FAA) and the Australian Civil Aviation Safety Authority (CASA) have subsequently mandated the revised requirements. The aircraft operator, as part of its own investigation into the occurrence, has developed a series of recommendations aimed at addressing the crew communication deficiencies experienced during the return to Brisbane after the engine failure.

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Map
This map shows the airport of departure and the intended destination of the flight. The line between the airports does not display the exact flight path.
Distance from Brisbane International Airport, QLD to Auckland International Airport as the crow flies is 2288 km (1430 miles).

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