Unstable approach involving de Havilland Canada Dash 8, VH-XFZ, Laverton Aerodrome, Western Australia, on 17 May 2012

What happened

On 17 May 2012, the flight crew of a de Havilland Canada Dash 8 aircraft, registered VH-XFZ and operated by Skippers Aviation Pty Ltd, was conducting a circling approach to runway 07 at Laverton Aerodrome, Western Australia. In conditions of low cloud, the crew positioned the aircraft on a close base leg to maintain visual reference with the runway threshold. This led to a steep final approach and a high rate of descent that triggered alerts from the aircraft’s Enhanced Ground Proximity Warning System (EGPWS) and exceeded the operator’s stable approach criteria. The crew heard some alerts from the EGPWS and knew they had a high rate of descent but at the time did not identify an unstable approach. The crew continued the approach and landed.

What the ATSB found

The ATSB found that at the time of the occurrence the flight crew did not have an adequate understanding of operational aspects of the aircraft’s EGPWS and the operator’s standard operating procedures in regard to mandatory go-arounds. Crew fixation on the runway environment at a time of higher than normal cognitive workload and an inadequate monitoring of the aircraft’s rate of descent resulted in the continuation of an unstable approach, contrary to the operator’s procedures. The ATSB also determined that the operator’s minimum height for achieving the criteria for a stable approach was lower than recommended by the International Civil Aviation Organization.

What has been done as a result

In response to this occurrence, the operator implemented a number of safety actions to refine their stabilised approach criteria and formulate a method of incorporating realistic EGPWS warning events in the Dash 8 simulator training program. The intent was to enhance crews’ ability to recognise and respond correctly and rapidly to EGPWS alerts.

Safety message

The ATSB continues to stress the risks associated with the handling of an approach to land. The Flight Safety Foundation cites a lack of go-arounds from unstable approaches as the number one risk factor in approach and landing accidents and the primary cause of runway excursions. This occurrence highlights the importance of crews adhering to standard operating procedures and correctly responding to cockpit warnings.