A Piper Seminole was being flown from Essendon airport, which is
located 5 NM south-east of Melbourne airport, to Bendigo. The
extended centrelines of the respective northerly runways, which
were being used for arrivals and departures, are approximately 3 NM
apart. The wind at the time was northerly at 25 kts.
The pilot of the Seminole was instructed to maintain runway
heading of 350 degrees and climb to 6,000 ft. After take-off the
aircraft was identified on radar by the Melbourne departures north
(DEPN) controller.
Six minutes later the crew of a Boeing 767 (B767) was cleared to
take-off from runway 34 at Melbourne, for Sydney, and to maintain
runway heading on climb to 5,000 ft. After take-off the aircraft
was identified on radar by the DEPN controller who cleared the crew
to climb to flight level (FL) 200.
Traffic was light, with four departing and one arriving aircraft
being managed by the DEPN controller. The controller was aware of
the need to maintain either vertical or lateral separation between
aircraft departing from Melbourne and the Seminole, and was also
conscious that the present heading of the Seminole was not in the
direction of Bendigo. He had previously radar vectored a departing
Boeing 737 ahead of the Seminole, and planned to do the same with
the B767, however, he observed that the B767 did not appear to be
climbing as fast as he had expected. Consequently, the controller
would have to take both the B767 and the Seminole further to the
north before achieving sufficient vertical or lateral separation to
enable him to allow the aircraft to resume their respective planned
routes. The minimum required separation was either 3 NM lateral or
1,000 ft vertical.
When the B767 was approximately 7 NM to the south-west of the
Seminole the controller believed he could vector the B767 to pass
behind it, thus minimising any delay to both aircraft. The
controller did not issue instructions to ensure vertical separation
prior to turning the B767.
The B767 was vectored right, onto a heading of 040 degrees.
Shortly after, the Seminole was vectored left onto a heading of 270
degrees. The DEPN controller then instructed the B767 crew to
continue the right turn onto 060 degrees as the aircraft was
passing approximately 4,500 ft, and instructed the pilot of the
Seminole to turn right onto 290 degrees. The B767 crew was
requested to expedite the turn onto 090 degrees. Shortly after, the
crew reported receiving a traffic alert and collision avoidance
system (TCAS) resolution advisory, indicating the crew should
maintain the current altitude of approximately 5,400 ft due to a
conflicting aircraft. The crew complied, and advised the DEPN
controller accordingly. The controller advised the crew that they
had passed another aircraft that was to their left. Separation was
reduced to 1.5 NM lateral and 600 ft vertical. The B767 crew did
not sight the other aircraft.
The B767 crew subsequently reported that the wind at 5,000 ft
was westerly at 50 kts. This would have had the effect of
increasing the groundspeed of the B767 as it turned towards the
east. Consequently, the rate of closure between the B767 and the
Seminole would have been greater than anticipated by the
controller, and it was probably at that stage he became aware that
the aircraft might pass with less than the required separation.
However, his subsequent instructions were unable to rectify the
situation. Had the controller continued to employ separation
assurance techniques, the occurrence would probably not have
eventuated.