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Analysis

Summary

The aircraft was operating in an environment that was conducive to turbulent conditions. During the encounter with the severe turbulence between 1131 and 1133, the aircraft was located about 3 NM from the edge of a convective cell with a high base. The severe turbulence encountered by the aircraft was probably associated with strong convective outflows from that cell.

The crew considered that the meteorological information issued to them prior to departure from Sydney and also by the Alice Springs aerodrome controller, was sufficient for them to determine the weather conditions likely to be encountered during the approach to runway 30. The crew's decision to continue the approach near convective activity was based on their subjective assessment of that information and the actual weather conditions.

The provision of weather information to the flight crew by the aerodrome controller was in accordance with the requirements of the MATS. There were no current SIGMETs or AIRMETs during the descent and approach of the aircraft and therefore the aerodrome controller was not required to issue a hazard alert to the crew.

The transmission from the crew at 1134 referred to downbursts but this information was not clarified by the controller to determine whether a report of windshear conditions was required in the next terminal information broadcast. Information Golf, broadcast at 1136, did not contain any reference to pilot reports of severe turbulence in the circuit area.

There was no record that the crew's reports were passed on to BoM for processing. MATS was ambiguous and did not provide clear guidance as to what action should be taken by air traffic controllers following the receipt of a pilot report concerning severe turbulence in the terminal area. Despite the ambiguity, the controller assessed the reports, and he subsequently included them in information Hotel issued at 1201. The controller also alerted the crew of the next aircraft operating in the Alice Springs terminal area about the report.

This occurrence highlights the need for air traffic controllers and flight crews to be aware of the hazards associated with convective activity. It is the second occurrence in a twelve-month period involving high capacity aircraft operating into airports affected by convective activity. The first occurrence involved a windshear encounter at Brisbane Airport in January 2001. A more detailed analysis of the hazards associated with convective activity in terminal airspace is provided in ATSB Air Safety Occurrence Report 200100213.

 
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