Loss of separation between a Boeing 737, VH-VXC and a Boeing 777, 9V-SVH, on 25 January 2006

On 25 January 2006, a Boeing Company 777-200 (777) was en route from Christchurch, NZ, to Singapore at flight level (FL) 360. A Boeing Company 737-838 (737) was en route from Alice Springs, NT, to Sydney, NSW, on a reciprocal track at FL370. At 0422.30 Coordinated Universal Time the two aircraft passed each other in the vicinity of waypoint APOMA, in the Melbourne Flight Information Region.

The pilots of the 777 had requested a clearance to climb to FL380. The separation standard that was applicable between the two aircraft, before the air traffic controller could authorise climb for the 777, was a ten minute longitudinal standard. That standard required the controller to calculate the estimated time the two aircraft would pass, using a method approved in the Manual of Air Traffic Services. Once that estimated time of passing was established, ten minutes either prior to, or after, that time of passing had to be applied. In the circumstances, a vertical separation standard needed to exist from the estimated time of passing plus the ten minutes. The crew of the 777 had been instructed to climb to FL380 at the estimated time of passing plus 8.5 minutes. There was an infringement of separation standards.

The air traffic controller's initial scan of the air situation display was incomplete and did not detect that a procedural separation standard would not exist between the 737 and the 777, or that he needed to calculate the time that the 10 minute longitudinal separation standard was established. A more comprehensive initial scan of the air situation display by the controller may have facilitated timely action to avoid an infringement of separation standards.