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Two Boeing 737s land below minima after diverting due to fog at their destination

The original forecast at the time of departure for the intended destination of Adelaide, did not predict fog. During the flights, fog formed at Adelaide, preventing a normal landing. Both crews considered conducting an auto land at Adelaide but with better weather expected at Mildura they both chose to divert, only to find deteriorating conditions there too had left them with limited options.

As a result, both crew landed below minima at Mildura.

On 18 June 2013, two Boeing 737 aircraft, VH-YIR operated by Virgin Australia Airlines Pty. Ltd. as Velocity 1384 and VH-VYK operated by Qantas Airways Ltd. as Qantas 735, were on scheduled flights to Adelaide, South Australia.

On nearing Adelaide, the forecast improvement in weather conditions had not occurred and as a result, both aircraft commenced a diversion to Mildura, Victoria. Upon arrival at Mildura, the actual weather conditions were significantly different to those forecast, in particular with visibility reduced in fog.

The flight crew of Qantas 735 conducted an instrument approach and landed below minima. The flight crew of Velocity 1384 also conducted an instrument approach and landed below minima in fog and with fuel below the fixed reserve.

The ATSB found that the weather deterioration at Adelaide did not appear on the forecast when both aircraft departed their respective ports and furthermore the forecast duration of the fog in the later, amended forecast showed a clearance time earlier than actually occurred. This meant that Qantas 735 continued to Adelaide with the expectation that the fog would clear prior to their arrival, which did not occur. It also influenced the decision making of the Virgin Australia flight watch personnel, who did not pass this weather to the flight crew of Velocity 1384.

In relation to the weather at Mildura, the ATSB found that the deterioration was significantly worse than originally forecast. This resulted in the need for both Qantas 735 and Velocity 1384 to land in conditions that were below minima. The ATSB identified that both flight crew uploaded sufficient fuel for the originally-forecast conditions in accordance with their operators’ fuel policy and the Civil Aviation Safety Authority requirements.

The ATSB also found that in certain weather patterns and at certain locations, fog is both rare and difficult to forecast reliably.

In addition, the ATSB noted that the industry expectation for the provision of flight information services was not aligned with that provided by Airservices Australia (Airservices). Further, it was identified that in certain circumstances, pilots will not be made aware of a deterioration of weather at an airport that has an Automatic Weather Information Service or other Automatic Broadcast Service. These services did not provide for the recognition and active dissemination of special weather reports (SPECI) to pilots, thereby not meeting the intent of the SPECI alerting function provided by controller-initiated flight information service.

In response to this occurrence, Airservices advised that they would work with the Bureau of Meteorology to explore feasible options to provide information on significant deteriorations in weather conditions to address the very high frequency radio range limitations of the automated broadcast services. In the meantime, Airservices has updated the Manual of Air Traffic Services to ensure dissemination of weather information from locations with an Automatic Weather Information Service should that service be unavailable.

The Bureau of Meteorology advised of various system changes and improvements in response to this occurrence. This included to equipment used in forecasting.

Virgin Australia Airlines Pty. Ltd. (Virgin) advised of a review and benchmarking exercise as part of its examination of this occurrence. This resulted in enhancements to Virgin’s flight planning and flight following policies, re-organisation of the flight following section and expansion of communication infrastructure across the Virgin fleet. In addition, Virgin’s pilot weather requirements have been clarified and enhanced.

In response to this occurrence the ATSB issued a safety recommendation to Airservices. This recommended that Airservices, as the issue owner, work in collaboration with the Bureau of Meteorology to instigate a system change to reinstate the alerting function of SPECI reports currently not available through an Automatic Broadcast Service.

Safety message

Pilots are reminded of their responsibility for collecting all relevant information to support in‑flight decision making. This includes weather and operational information for the destination, which should be considered prior to a decision point or point of no return.

It is important that pilots understand what will be provided under Airservices’ provision of flight information service and that they are also able to request weather and operational information from air traffic control. In addition, pilots should note the potential benefits of informing the controller of a non-normal situation. These include increased monitoring and support as required and the potential to reduce pilot workload in stressful situations.

Read the full investigation report AO-2013-100

 

 
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Last update 31 May 2016