Loss of separation between a Boeing 747-400, 9V-SMQ and a Boeing 747, N481EV, 16 October 2000

A Boeing 747-400 (B747-400) was en route from Singapore to
Sydney at flight level (FL) 330 on air route A585, and a B747 was
tracking in the opposite direction at FL350 from Melbourne to
Jakarta on air route G222. The routes A585 and G222 converged at
SAPDA, a position approximately 720 NM north-west of Broome on the
boundary of the Australian and Indonesian flight information
regions (FIRs). Route G222 was north-east of route A585 and the
prescribed lateral separation point between the routes was 272 NM
south-east of SAPDA. The aircraft were under the control of the
Kimberley sector controller of the Brisbane centre.

The B747-400 was estimating SAPDA at 1811 Universal Coordinated
Time and the controller approved that crew at 1747 to climb to
FL350 at SAPDA. The Kimberley controller was advised at 1806 the
B747 was at METUM, a position 252 NM south-east of SAPDA, at 1805
maintaining FL350 and estimating SAPDA at 1836. At 1812, the
Kimberley controller received a SAPDA position report from the
B747-400 crew and shortly after recognised there was no separation
being applied between the aircraft. At 1813, the Kimberley
controller instructed the B747-400 crew to descend to FL330,
however there was an infringement of separation standards. The
B747-400 crew subsequently reported maintaining FL330 at 1819.

The estimated time of passing of the aircraft was 1824. The
Kimberley controller needed to establish the vertical separation
standard of 2,000 ft between the aircraft before 1809 to ensure
separation.

The Kimberley sector was a procedural sector operated by a
single controller. Communication between controllers and flight
crews could be by either:

- very high frequency (VHF) radio,

- controller pilot data link communication (CPDLC), or

- high frequency (HF) radio through a third-party radio
operator.

The controller was communicating with the B747-400 crew using
CPDLC and with the B747 crew by third-party HF radio. There was no
VHF radio coverage in the portion of the sector in which the
aircraft were operating.

The controller commenced the shift at 1300 (2300 Eastern
Standard Time) and worked till about 1530 when he had a break. He
returned to the position at 1610 and remained there until the
occurrence. Normally during the period from 1400 to 1800, the
number of aircraft in the sector gradually increased and after that
time, traffic numbers decreased. The controller reported that there
had been a busy period that had finished just before the
occurrence. That was the controller's first shift following a 2-day
break.

When the B747-400 crew requested approval to climb to FL350 via
CPDLC, the controller checked for conflicting aircraft on the air
situation display. At that stage, the B747 on G222 was over Western
Australia and the controller reported that he might have perceived
that aircraft as part of a group of aircraft on a more northerly
route. Consequently, he coordinated a change of level with the
adjacent Indonesian sector controller, and then instructed the
B747-400 crew to climb at SAPDA.

The air traffic system had a flight plan conflict probe (FPCP)
function to assist in the early identification of conflicts outside
radar coverage. However, the FPCP had not been included in the
commissioning of the new air traffic control system during 1998-99
and was not active.