On 21 June 2012, a breakdown of separation occurred between a Qantas Airways Boeing Company B737-438, registered VH-TJS (TJS) and a Sharp Aviation Fairchild SA227, registered VH-MYI (MYI) near Melbourne Airport, Victoria. After being radar vectored from the north-east and given an assigned heading of 230˚, TJS was cleared to conduct an instrument approach to runway 27 at Melbourne Airport. However, instead of intercepting the runway 27 localizer, TJS maintained the assigned heading and passed through the localizer by about 1 NM. As a result the separation between TJS and MYI reduced to less than the required standard of 3 NM.
Although the reason for the clearance deviation could not be positively identified, it was likely that a higher than usual workload resulted in the flight crew not arming the appropriate approach mode or observing the aircraft’s closure relative to the runway 27 localizer. The occurrence highlights the need for flight crews to closely monitor the aircraft flight path and be ready to take prompt action in the event of any deviation from the cleared route.