What happened
On 22 March 2021, a VH-XGW flight from Dubbo to Bankstown was conducting an instrument approach to runway 11C under instrument flight rules. During the approach, the aircraft began to drift from its assigned track. By the time it reached the final approach fix, the aircraft had exceeded the allowable track tolerance of 0.3 NM. This deviation placed the aircraft in an area where obstacle clearance had not been surveyed for its current altitude, which was significantly below the Bankstown 15 NM minimum safe altitude of 2,500 ft.
Rather than performing the published missed approach procedure, the pilot requested a circling approach while continuing the descent. Although the pilot reported establishing visual contact with the airport, the aircraft entered a rain shower, prompting a left turn away from the runway. During these maneuvers, the aircraft descended to approximately 400 ft and moved outside the CAT B circling area. Despite receiving terrain alerts from ATC, the pilot continued the approach, eventually losing visual reference to the runway environment due to the aircraft's structure and deteriorating visibility.
The investigation
The investigation focused on the aircraft's deviation from the instrument approach path and the subsequent descent below minimum altitudes. Investigators examined flight surveillance data, which confirmed that the aircraft descended below the altitude required to maintain terrain separation. The inquiry also reviewed the pilot's decision-making regarding the transition from an instrument approach to a visual circling maneuver and the failure to initiate a missed approach when tracking tolerances were exceeded or when visual contact with the runway was lost.