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The crews of all four aircraft had planned to use the same air route between Port Macquarie and Taree. VH-IMA and VH-TQO were arriving at Port Macquarie while VH-IMH and VH-SVV were departing. Due to minor deviations in track-keeping, all four aircraft were to the west of the nominal track.

Weather conditions were such that a layer of cloud existed upwards from approximately 7,000 ft.

Although the flight service officer provided a timely and up-to-date directed traffic information service to all crews, radio communications between the crews of IMA and IMH, and between IMH and SVV were insufficient to ensure self-separation between their aircraft. The high number of radio transmissions on the various frequencies, when combined with the frequency management requirements of each crew, limited the opportunities for adequate radio contact.

The crews of IMA and IMH maintained altitudes in Class "G" airspace without broadcasting their intentions on the flight service frequency. In addition, while both crews were maintaining a listening watch on the flight service frequency for 8 minutes prior to their aircraft passing, neither crew made radio contact with the other.

Analysis of the recorded radar data indicated that the aircraft passed within 1,000 m horizontally and 200 ft vertically while IMA was maintaining 8,000 ft.

None of the aircraft were fitted with an Airborne Collision Avoidance System (ACAS). An ACAS would, most probably, have improved the situational awareness of the crews to the extent that a more effective traffic management plan may have been undertaken.

The lack of adequate situational awareness of the crews of IMA and IMH resulted in two regular public transport aircraft coming into relatively close proximity without either crew carrying out a positive separation plan.

The investigation identified safety deficiencies in respect to timely conflict alerting and self-separation procedures and contains seven recommendations to the Civil Aviation Safety Authority addressing those deficiencies.

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General details
Date: 28 April 1999 Investigation status: Completed 
Time: 2006 hours EST Investigation type: Occurrence Investigation 
Location   (show map):37 km S Port Macquarie, Aero. Occurrence type:Separation issue 
State: New South Wales Occurrence class: Airspace 
Release date: 02 May 2001 Occurrence category: Incident 
Report status: Final Highest injury level: None 
 
Aircraft 1 details
Aircraft manufacturer: Beech Aircraft Corp 
Aircraft model: 1900 
Aircraft registration: VH-IMH 
Serial number: UE-230 
Type of operation: Air Transport Low Capacity 
Damage to aircraft: Nil 
Departure point:Port Macquarie, NSW
Departure time:2002 hours EST
Destination:Williamtown, NSW
Aircraft 2 details
Aircraft manufacturer: Beech Aircraft Corp 
Aircraft model: 1900 
Aircraft registration: VH-IMA 
Serial number: UE-7 
Type of operation: Air Transport Low Capacity 
Damage to aircraft: Nil 
Departure point:Sydney, NSW
Departure time:1930 hours EST
Destination:Port Macquarie, NSW
Aircraft 3 details
Aircraft manufacturer: Piper Aircraft Corp 
Aircraft model: PA-31 
Aircraft registration: VH-SVV 
Serial number: 31-7405175 
Type of operation: Charter 
Damage to aircraft: Nil 
Departure point:Port Macquarie, NSW
Departure time:1959 hours EST
Destination:Sydney, NSW
 
 
 
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Last update 13 May 2014