Simultaneous runway operations were being conducted at the time of the occurrence with departures from runway 16 and arrivals on runways 16 and 07. A busy traffic situation was creating high work load levels for the tower staff. Weather conditions were fine with light winds. The air traffic situation around the airport was further complicated by an overflying helicopter which had departed from Prince Henry hospital, located 8 km to the east, en-route to Bankstown via overhead Sydney Airport at 1,500 feet. VH-AJM taxied at 0744 EST and at 0747, reported ready for takeoff on runway 16, from the intersection with taxiway Foxtrot, 536 metres south of the runway 16 threshold. VH-MZM taxied at 0750 and was instructed to taxy to and hold at the holding point adjacent to the threshold of runway 16.
The planned departure sequence from runway 16 was VH-AJM followed by VH-MZM. The Tower Controller amended the departure sequence due to the presence of the overflying helicopter, as the departure track of VH-AJM placed that aircraft in potential confliction with the helicopter. He decided that VH-MZM should takeoff before VH-AJM. When VH-MZM was instructed to line up, the crew of VH-AJM mistakenly believed the instruction was addressed to them and commenced to taxi beyond the holding point into the runway strip. They recognised their error when VH-MZM was subsequently cleared for takeoff. Although the Tower Controller had not observed VH-AJM move beyond the holding point, as his view of taxiway Foxtrot was obscured by a structural roof support beam, the incursion was immediately noticed by the Tower Coordinator and the Surface Movement Controller who alerted the Tower Controller. The take-off clearance for VH-MZM was cancelled and both aircraft were instructed to vacate the runway to allow an aircraft on final approach for runway 16 to land.
Significant Factors
1 The crew of VH-AJM expected to depart before VH-MZM.
2 The Tower Controller amended the departure sequence due to overflying traffic in potential conflict with the departure track of VH-AJM
3 The crew of VH-AJM misinterpreted the call-sign when the Tower Controller issued a line up clearance to VH-MZM.