A Cessna 560 medical transport jet entered an uncommanded left bank during a nighttime approach to Perth Airport, resulting in two EGPWS terrain alerts, before the aircraft exceeded its maximum angle of bank during a recovery climb, an ATSB investigation report details.
On 13 August 2025, the Cessna 560 (Citation 5) was operated by Avcair on a medical transport flight under the instrument flight rules from Learmonth to Perth, with 2 flight crew – the first officer who was the pilot flying and the captain was the pilot monitoring – and 3 passengers on board.
Nearing Perth Aiport after 8pm, air traffic control cleared the aircraft to conduct the instrument landing system approach to land on runway 24.
However, as the aircraft followed the instrument landing system localiser while being flown using the autopilot, it did not capture the glideslope.
As the flight crew attempted to correct the flight path using the automation system, the aircraft continued to descend, and the autopilot disconnected.
The aircraft then entered an uncommanded left bank, and the enhanced ground proximity warning system (EGPWS) issued two alerts shortly after.
When the aircraft was about 500 ft above the ground, the captain took control and initiated a recovery climb.
The ATSB found the glideslope was not captured because the flight crew had incorrectly set the approach decision altitude in the altitude selector before the autopilot captured it.
This, combined with the selected flight director modes, led the autopilot to command a continued descent towards terrain.
“During their response, because of a lighting fault the flight crew had trouble finding the required flight director mode button on the first officer’s selector panel,” ATSB Director of Transport Safety Dr Stuart Godley explained.
“A similar defect was observed in the preceding days, but no action had been taken.”
The ATSB found the flight crew had then become preoccupied with the flight director mode selection, and did not effectively monitor the aircraft’s state.
“The aircraft entered an uncommanded left bank as the descent continued and the crew then did not respond appropriately when the EGPWS issued two alerts,” Dr Godley said.
During the recovery, the aircraft reached a bank angle of about 50°, above the maximum bank angle and therefore entering an undesired aircraft state.
The airspeed then exceeded the operator’s stabilised approach criteria in the late stage of the approach, but the flight crew did not conduct a go-around.
The flight was then completed without further incident.
“This incident highlights how an unexpected disruption during an instrument approach can rapidly lead to a significant deviation from the intended flight path, and result in an undesired aircraft state,” Dr Godley said.
“In this scenario, effective crew resource management – where each pilot is performing their assigned role of flying or monitoring the aircraft – is essential.”
Dr Godley noted the adoption of EGPWS technology has reduced the number of controlled flight into terrain accidents globally.
“However, EGPWS is a last line of defence, and should be responded to immediately, as a delay can allow a developing terrain proximity event to place the aircraft at risk of a controlled flight into terrain accident.”
Read the final report: Descent below minimum sector altitude, ground proximity alert and unstable approach involving Cessna 560, VH-OHE, 23 km north-east of Perth Airport, Western Australia, on 13 August 2025