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History of the flight

The Boeing 717 (717) aircraft, registered VH-VQD, was being operated on a scheduled passenger service under the instrument flight rules from Brisbane to Mackay, with an expected arrival time of 2030 EST. There were rain showers and scattered low cloud in the area at the time and the air traffic controller had issued the crew with a clearance to conduct a runway 14 VOR/DME approach at Mackay. The pilot in command was the handling pilot for the sector.

Late in the cruise segment, the pilot in command asked the copilot to obtain the predicted altitude of the aircraft when it would pass overhead Mackay. The copilot said that he cleared the Mackay altitude constraint (2,500 ft) in the active flight plan page on the multi-function control and display unit (MCDU) of the flight management system (FMS). This enabled the unit to display the predicted altitude. The system displayed 5,100 ft and the copilot conveyed that information to the pilot in command.

The copilot then reinstated the previously set 2,500 ft altitude constraint into the active flight plan. The crew could not positively recall checking the altitude constraint against the Mackay waypoint at the end of that process. Passing overhead Mackay, the copilot entered the minimum descent altitude for the approach (430 ft) in the mode control panel altitude window. The aircraft was being operated on automatic pilot, with profile, navigation and manual speed modes engaged for the VOR/DME approach.

As the aircraft descended on the outbound leg of the approach, the crew noticed that the predicted track for the inbound turn on the map display screen showed a break between the inbound turn and the inbound track. During the inbound turn, the pilot in command became concerned that the aircraft was not going to intercept the inbound radial by the final approach fix at 5 NM by Distance Measuring Equipment (DME), and he and the copilot directed their attention to the aircraft's tracking profile.

A short time later, the pilot in command noted that the aircraft was descending through 1850 ft. Believing that they were too low for that segment of the approach, he asked the copilot to confirm the minimum step altitude. The copilot advised 2,200 ft. The crew then heard the Mackay Tower controller suggest that they 'check altitude', and that the aircraft was 'low on profile'. The pilot in command responded by selecting the autopilot vertical speed mode, commanding the aircraft to climb until it was above 2,200 ft. The crew then continued flying the approach to runway 14 and intercepted the inbound radial at about 6.6 DME.

The minimum crossing altitude at the final approach fix for the runway 14 VOR/DME approach was 760 ft. As the aircraft passed the final approach fix, it was at 1,427 ft, in the landing configuration, and established on the final approach track. The pilot in command indicated that he was 'a bit in shock' at that time over what had happened during the inbound turn but had not considered conducting a missed approach.

At about 800 ft, the copilot said that the runway was to the right. Visibility was satisfactory and the windshield wipers were off. The pilot in command said that he saw the lights the copilot was referring to and began to turn towards them, even though he felt that there was 'something not right', and he could not see the visual approach slope indicator system (T-VASIS) runway approach guidance lighting.

A short time later, the tower controller instructed the crew to climb, adding that the aircraft was 'well off centreline'. The pilot in command said that he was surprised by that instruction and initially did not react. However, when the controller repeated the instruction, about 2 seconds later, the pilot in command initiated a climb straight-ahead.

The pilot in command said that he had commenced the missed approach before the aircraft reached 500 ft on final approach. This was consistent with the information from the flight data recorder. The operator's procedures required the crew to check that the aircraft was aligned with the runway and on glideslope passing 500 ft on final approach.

The recorded flight data showed that the aircraft's track began to diverge right from about 138 degrees when the aircraft was descending through 620 ft at 3 DME on final approach. The missed approach was initiated 25 seconds later when the aircraft was tracking about 177 degrees as it passed 2.3 DME.

After the crew reported level at 2,500 ft during the missed approach, the controller instructed them to turn left when ready and track direct to the VOR. A short time later, the controller advised the crew that if the turn was not initiated, the aircraft would be required to climb to 3,100 ft; the minimum sector altitude. The crew turned the aircraft left and landed at Mackay following a second VOR/DME approach to runway 14.

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