A December 5 report published by the Australian Transport Safety Bureau reviewed a May 17, 2012 unstable approach to Western Australia’s Laverton Aerodrome from the cockpit of a de Havilland Canada Dash 8.
The aircraft, operated by Skippers Aviation, was executing a circling approach to Runway 07 at Laverton in patchy fog. The crew positioned the aircraft on a close base leg to maintain visual reference with the runway, which led to a steep final approach and a high rate of descent. At approximately 900 feet agl the aircraft was still in a 25-degree right bank descending at 1,400 fpm with the power at flight idle.
These conditions triggered enhanced ground proximity warning system (EGPWS) alerts that also exceeded Skipper Aviation’s stable approach criteria, but the crew continued the approach. Later, the crew admitted they heard the EGPWS but assumed it had been triggered by the high sink rate, rather than an unstable approach. Nonetheless, they landed the aircraft safely.
During the investigation, the first officer said he did not think the sink rate was too high, but he acknowledged that he never looked at the instruments, just mainly out the window. He assumed the captain would mention a problem if it occurred, which he did not. The captain was looking out the windshield too because of the high sink rate, which essentially left no one monitoring inside the cockpit.
After this incident, Skippers Aviation refined its stabilized approach criteria and formulated a method of incorporating realistic EGPWS warning events in the Dash 8 simulator training to enhance crews’ ability to accurately recognize and respond to proximity alerts.