Preliminary ATSB Report On Air NZ B767 Engine Failure Ex BNE.

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ACCIDENT & INCIDENT REPORTS - DETAIL

Preliminary Report


Occurrence Number: 200205780
Release Date: 23-Jan-03
Occurrence Type: Accident
Location: 30 km ESE Brisbane, Aero.
State: Queensland (QLD)
Occurrence Date: 08-Dec-02
Time/Zone: 1020 hours EST
Highest Injury Level: None
Investigation Category: 3
Injuries: Fatal Serious Minor None Total
Crew 0 0 0 10 10
Passenger 0 0 0 190 190
Ground 0 0 0 0 0
Total 0 0 0 200 200

Aircraft Details
Aircraft Manufacturer: Boeing Co
Aircraft Model: 767-219ER
Aircraft Registration: ZK-NBC
Serial Number:
Type of Operation: Air Transport, International

Damage to Aircraft: Substantial (Severe mechanical and structural damage to the number-one (left) engine and nacelle. Associated distortion and structural damage to the engine pylon. Surface damage to the number-five leading edge slat above the engine.)
Departure Time: 0012 hours EST
Departure Point: Brisbane, QLD
Destination: Auckland, NEW ZEALAND
Crew Details: Role Class of Licence Hours on Type Hours Total


FACTUAL INFORMATION
SAFETY ACTION

FACTUAL INFORMATION

While climbing through flight level 110 (FL110), the crew of a Boeing 767-219ER aircraft operating a regular passenger transport service between Brisbane and Auckland, heard what they reported as 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 according to the aircraft quick-reference handbook for `Engine Fire, Severe Damage or Separation'.

The captain declared a full emergency to air-traffic control, after which radar headings for a return to Brisbane airport and a clearance to descend were received. A visual assessment of the engine damage by the first officer found damage to the engine nacelle as well as the leading-edge flaps. In consideration of the flap damage, the crew elected to carry out the approach without using the leading edge flaps and using only partial extension of the trailing edge flaps. Late in the final approach, the first officer made a `brace' call to the passengers and cabin crew using the public address system. The aircraft approach and landing was uneventful.

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 forty centimetres and the number-two 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.

Preliminary examination of the failed turbine disk at the Canberra laboratories of the ATSB found that the fracture had occurred from an area of fatigue cracking, originating from the bottom of a turbine blade dovetail slot. The fatigue cracking had grown radially into the disk to a depth of around forty millimetres, with the remainder of the fracture being typical of rapid ductile overload. During the laboratory examination, two additional cracks were found at the bottom of other dovetail slots. Microscopic evaluation of the primary fracture and the largest of the other cracks found that both defects had initiated from the corner of the slot bottom where it transitioned onto the disk rear face.

At the time of failure, the turbine disk had accumulated 12,485 cycles since new and 4,579 cycles since last complete inspection.

The investigation is continuing.


SAFETY ACTION

Local Safety Action

At the time this report was prepared, the engine manufacturer indicated that it was working on revisions to service bulletin (SB) 72-0779 "Engine - HPT Rotor - Stage 1 Disk - Etch, FPI and Eddy Current Inspection of Dovetail Slot Bottoms". These revisions are planned to provide for new inspection thresholds for the engine first stage high-pressure turbine disk and are scheduled for implementation by the end of January 2003.

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WINGED KIWI PUTS THE WIND UP GE

The Australian
24-01-2003

A spectacular engine failure that forced an Air New Zealand Boeing 767 -200 to make an emergency landing in Brisbane on December 8 may be linked to wider problems with a General Electric engine part.

An Australian Transport Safety Bureau interim report released yesterday found fatigue cracking led to the failure of first-stage high-pressure turbine disk.

The ATSB said preliminary examination of the disk in its Canberra laboratories found the cracking originated from the bottom of a turbine blade dovetail slot.

The crack had grown radially to a depth of about 40mm before the the disk failed, smashing the engine and damaging the nacelle, the engine pylon and a section of wing.

Two more cracks were found at the bottom of other dovetail slots.

The airline has since stepped up inspections of its eight CF6-80A engines and the US Federal Aviation Administration has issued an airworthiness directive making improved inspections mandatory from January 28.

"The fact that they put out an airworthiness directive means it's not just Air New Zealand they're looking at," ATSB deputy director Alan Stray said.

"It has the potential to plague the world fleet and the fact that an AD has come out leads me to believe they've got evidence of other incidents. "

Investigators found the aircraft was climbing thorough 11,000ft en route to Auckland when the crew hear a loud bang and felt the aircraft lurch to the right.

The captain declared a full emergency and a visual assessment revealed damage to the engine nacelle as well as the leading edge flaps.

"In consideration of the flap damage, the crew elected to carry out an approach without using the leading edge flaps and using only a partial extension of the trailing edge flaps," the report says.

"Late in the final approach, the first officer made a `brace' call to passengers and cabin crew using the public address system. The aircraft approach and landing was uneventful".

Air New Zealand welcomed the ATSB report but said no obvious root cause of the failure had yet been determined.

"It is clear, however, that there are no concerns about the maintenance of the disk being a factor in the failure of the engine," said Air NZ vice- president, operations and technical, Craig Sinclair.

Mr Sinclair said the airline's enhanced inspection program, due to be completed in mid-April, exceeded the FAA directive and was also expected to be consistent with new inspection thresholds likely to be introduced worldwide by GE.

Further tests will be carried out on the failed disk in the US and the incident will be part of a a review of Air NZ by Boeing due to start next month, he said.