ASN Wikibase Occurrence # 190910
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| Date: | Tuesday 2 October 2012 |
| Time: | 13:45 |
| Type: |  Boeing 737-838 |
| Owner/operator: | Qantas |
| Registration: | VH-VXM |
| MSN: | 33483/1177 |
| Year of manufacture: | 2002 |
| Fatalities: | Fatalities: 0 / Occupants: |
| Aircraft damage: | None |
| Category: | Incident |
| Location: | 26 km south of Darwin, NT -
 Australia
|
| Phase: | En route |
| Nature: | Passenger - Scheduled |
| Departure airport: | Darwin Airport, NT (DRW/YPDN) |
| Melbourne-Tullamarine Airport, VIC (MEL/YMML) | |
| Investigating agency: | ATSB |
| Confidence Rating: |  Accident investigation report completed and information captured |
A loss of separation (LOS) occurred between a descending Boeing 717 aircraft, registered VH-NXQ, operating a scheduled passenger service from Alice Springs to Darwin, Northern Territory, and a climbing Boeing 737, registered VH-VXM, operating a scheduled passenger service from Darwin to Melbourne, Victoria. The LOS occurred about 14 NM (26 km) south of Darwin, and the aircraft were under the jurisdiction of Department of Defence air traffic control (ATC) at the time of the occurrence.
Prior to the LOS, a predicted conflict alert was activated within the Australian Defence Air Traffic System (ADATS). After a short delay, the Approach controller instructed VXM’s flight crew to stop their climb at 9,000 ft. NXQ’s flight crew advised the controller of conflicting traffic below them and the controller instructed them to maintain 10,000 ft. Separation between the aircraft reduced to about 900 ft vertically as NXQ passed directly overhead VXM on a crossing track. The required separation standards were either 1,000 ft vertical separation or 3 NM (5.6 km) radar separation.
Contributing factors
- A previously-assigned transponder code was allocated to the Boeing 717 (VH-NXQ) in the Australian Defence Air Traffic System, which resulted in the 717’s radar return having a limited data block label and its call sign being incorrectly correlated to an overflying C130 Hercules aircraft.
- The Darwin Planner controller did not crosscheck the coordinated transponder code for the Boeing 717 with the code assigned in the Australian Defence Air Traffic System (ADATS), which resulted in the incorrect code remaining allocated in ADATS.
- The Australian Defence Air Traffic System (ADATS) did not automatically process all system messages generated by The Australian Advanced Air Traffic System. In cases where transponder code changes were not automatically processed, the risk controls in place were not able to effectively ensure that the changes were identified and manually processed. [Safety issue]
- Due to local contextual factors and confirmation bias, the Darwin Approach controller and Approach Supervisor assumed that the radar return labelled as VH-NXQ in the Australian Defence Air Traffic System (ADATS) was correct, and they did not identify the problem with this assumption until after the ADATS predicted conflict alert activated.
- The limited data block radar return displayed for the Boeing 717 was not observed by Darwin Approach until about the time a predicted conflict alert activated in the Australian Defence Air Traffic System.
- Darwin Approach controllers were routinely exposed to green (limited data block) radar
returns that were generally inconsequential in that Approach control environment, leading to a high level of expectancy that such tracks were not relevant for aircraft separation purposes. Refresher training did not emphasise the importance of scanning the green radar returns. [Safety issue]
Accident investigation:
 |
|
Sources:
https://www.atsb.gov.au/publications/investigation_reports/2012/aair/ao-2012-131/
Revision history:
| Date/time | Contributor | Updates |
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