Aviation safety investigations & reports

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

Investigation number:
Status: Completed
Investigation completed


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.


Although the controller was off duty for the 2 days before the shift, it is possible that the early time of day and the duration at the control position contributed to fatigue. Also, it is likely that the controller relaxed as the number of aircraft under his control declined and he may not have been as diligent as usual in his conflict assessment. Consequently, he did not appreciate the potential for conflict.

The situation shows that controllers performance may lapse during night shifts and that they need to be aware of the effects of low arousal levels at that time of the morning. A shorter duration at the control position by each controller might help them maintain a level of arousal better suited to the task.

The use of system functions to assist controllers to detect potential conflicts would be beneficial especially for controllers working during the early morning.

Safety Action

Local safety action

As a result of their investigation into the occurrence, Airservices Australia Northern District is reviewing the use of the flight plan conflict probe.

The Australian Transport Safety Bureau is reviewing air traffic control fatigue issues. Any safety output resulting from the review will be published in the quarterly safety deficiency report.

General details
Date: 16 October 2000   Investigation status: Completed  
Time: 1811 hours UTC    
Location   (show map): Sapda, (IFR)    
State: International   Occurrence type: Loss of separation  
Release date: 09 July 2001   Occurrence category: Incident  
Report status: Final   Highest injury level: None  

Aircraft 1 details

Aircraft 1 details
Aircraft manufacturer The Boeing Company  
Aircraft model 747  
Aircraft registration 9V-SMQ  
Type of operation Air Transport High Capacity  
Damage to aircraft Nil  
Departure point SINGAPORE  
Destination Sydney, NSW  

Aircraft 2 details

Aircraft 2 details
Aircraft manufacturer The Boeing Company  
Aircraft model 747  
Aircraft registration N481EV  
Type of operation Air Transport High Capacity  
Damage to aircraft Nil  
Departure point Melbourne, VIC  
Destination Jakarta, INDONESIA  
Last update 07 March 2016