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A320, en-route, Sydney Australia, 2007

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Summary
On 11 January 2007, an Air New Zealand Airbus A320 which had just departed Sydney Australia for Auckland, New Zealand was observed to have turned onto a heading contrary to the ATC-issued radar heading. When so advised by ATC, the crew checked the aircraft compasses and found that they were reading approximately 40 degrees off the correct heading.
Event Details
When January 2007
Actual or Potential
Event Type
AW, HF, LOS
Day/Night Day
Flight Conditions VMC
Flight Details
Aircraft AIRBUS A-320
Operator Air New Zealand
Domicile New Zealand
Type of Flight Public Transport (Passenger)
Origin Sydney Airport
Intended Destination Auckland Airport
Actual Destination Sydney Airport
Flight Phase Cruise
ENR
Location En-Route
Origin Sydney Airport
Destination Auckland Airport
Location
Approx. 28 km north-west of Sydney Airport
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General
Tag(s)
HF
Tag(s) Data use error
Distraction
Ineffective Monitoring
Procedural non compliance
LOS
Tag(s) Accepted ATC Clearance not followed
Lateral Navigation Error


Outcome
Damage or injury No
Causal Factor Group(s)
Group(s) Aircraft Operation
Aircraft Technical
Safety Recommendation(s)
Group(s) None Made
Investigation Type
Type Independent

Description

On 11 January 2007, an Air New Zealand Airbus A320 which had just departed Sydney Australia for Auckland, New Zealand on the first flight of the day was observed to have turned onto a heading contrary to the ATC-issued radar heading. When so advised by ATC, the crew checked the aircraft compasses and found that they were reading approximately 40 degrees off the correct heading and that a ‘GPS PRIMARY LOST’ message had appeared on the MFD and the NDs.

The crew then advised ATC that they had navigational difficulties and elected to return to Sydney for landing. When the aircraft returned to the departure gate, the flight crew noticed that the inertial reference system (IRS) had been aligned to the incorrect longitude. The operator subsequently found that the IRS had been aligned by maintenance staff prior to the crew boarding the aircraft. The incorrect alignment of the IRS was not detected during a number of subsequent checks prior to departure".

The ATSB Investigation Report was published in April 2008 and found that:

  • There was no aircraft systems anomaly that might have contributed to the development of the occurrence.
  • Maintenance personnel had inadvertently entered incorrect position information in the aircraft inertial reference system (IRS) prior to release to service for the incident flight.
  • The incorrect position data in the IRS remained undetected by the flight crew, despite four separate pre-take-off procedural defences where position verification should have occurred.

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