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The crew of the Dash 7, registered VH-UUM, were cleared to track visually via Kuranda. The crew of the Cessna 310, registered VH-XXT, were cleared to track visually via Stoney Creek. Both aircraft had flight planned IFR and were entitled to positive air traffic control separation. Such separation was not provided and the required radar separation standard of 3 NM between the two aircraft was infringed. The investigation revealed that the strategy for separation employed by the approach controller did not provide a separation standard. Radar separation was an option, in accordance with the Manual of Air Traffic Services (MATS), 9-2-1, paragraph 19, if the departing aircraft had been issued a standard radar departure. Such a departure was not provided. Moreover, because vertical separation had not been employed, the controller had to rely on lateral separation to ensure the aircraft did not conflict. However, lateral separation would not exist if both aircraft were simultaneously east of a line Stoney Creek-Kuranda. There was no separation assurance. MATS 4-1-1, paragraphs 4-6 place significant emphasis on the need for controllers to apply separation assurance techniques. Realising the potential confliction after take-off, the controller attempted to establish a visual sighting of the departing aircraft by the crew of the arriving aircraft. The visibility was reduced due to smoke haze, making a sighting unlikely. If a sighting had been achieved, it would have allowed the transfer of separation responsibility from the controller to the pilot. The crew of the arriving aircraft were unable to sight the departing aircraft. The controller then requested the crew of the arriving aircraft to make a right orbit but the crew were unable to comply due to high terrain. The crew suggested a left orbit, which was agreed to by the approach controller. The left orbit however, further reduced the distance between the two aircraft. The crew of the departing aircraft then sighted the arriving aircraft, with the assistance of the aircraft's TCAS, and were able to visually maintain separation. Vertical separation was reduced to 100 ft when the aircraft were 1.5 NM apart. The required radar separation was 3 NM or 1,000 ft vertically.

As a result of this and other occurrences, the Australian Transport Safety Bureau, formerly the Bureau of Air Safety Investigation, is currently investigating a safety deficiency. The deficiency relates to aspects of separation assurance techiques within air traffic control. Any safety output issued as a result of this analysis will be published in the Bureau's Quarterly Safety Deficiency Report.
General details
Date: 17 November 1999 Investigation status: Completed 
Time: 1728 hours EST  
Location   (show map):13 km WSW Cairns, Aero. Investigation type: Occurrence Investigation 
State: Queensland Occurrence type: Loss of separation 
Release date: 24 December 1999 Occurrence class: Airspace 
Report status: Final Occurrence category: Incident 
 Highest injury level: None 
Aircraft 1 details
Aircraft manufacturer: de Havilland Canada 
Aircraft model: DHC-7 
Aircraft registration: VH-UUM 
Serial number: 043 
Type of operation: Charter 
Damage to aircraft: Nil 
Departure point:Cairns, QLD
Destination:Mareeba, QLD
Aircraft 2 details
Aircraft manufacturer: Cessna Aircraft Company 
Aircraft model: 310 
Aircraft registration: VH-XXT 
Serial number: 310R1617 
Type of operation: Unknown 
Damage to aircraft: Nil 
Departure point:Mareeba, QLD
Destination:Cairns, QLD
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Last update 13 May 2014