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On 25 June 2005, a Bombardier Aerospace Dash 8-315 (Dash 8) aircraft and three Aero Commander Div Shrike Commander aircraft (Aerocommander) were in an arrival sequence of seven aircraft to runway 15 at Cairns Airport. At 1705 Eastern Standard Time, when the Dash 8 was on final approach at about 6 nautical miles (NM) from the airport, the crew received a traffic alert and collision avoidance system (TCAS) traffic advisory. The crew saw an Aerocommander to the left at about 3 NM, and observed on the TCAS display an aircraft in close proximity. Very shortly after, the crew of the Dash 8 received a TCAS resolution advisory to climb their aircraft, which they followed. The crew reported as they were climbing, they saw a second Aerocommander pass to the left of the Dash 8.

An Airservices Australia (Airservices) investigation of the occurrence found that the occurrence was due to the following factors:

  • the approach controller made an error of judgement in assessing the new traffic sequence
  • the aerodrome controller used non-standard coordination phraseology that was misinterpreted by the approach controller
  • the use of sight and follow procedures for the number of aircraft involved increased controller workload
  • the approach controller's lack of recent familiarisation with tower visual separation procedures.

The Airservices report made four recommendations to Cairns Terminal and two recommendations to Cairns Tower, for action.

 

On 25 June 2005, a Bombardier Aerospace Dash 8-315 (Dash 8) aircraft was being operated on a scheduled passenger service from Weipa to Cairns, Qld, while three Aero Commander Div Shrike Commander aircraft (Aerocommander) were tracking to Cairns from Cooktown, Qld. The four aircraft were in an arrival sequence of seven aircraft tracking to runway 15. Visual meteorological conditions existed during the period of the aircrafts' arrivals.

Based on the aircrafts' estimated arrival time, the Dash 8 was 3 minutes behind the three Aerocommanders. The Aerocommanders were maintaining 1,000 ft above mean sea level, and the Dash 8 was on descent from 5,000 ft. The Cairns approach controller estimated that low level headwinds would delay the Aerocommanders more than the Dash 8. Consequently, the controller re-ordered the landing sequence to place the Dash 8 ahead of the Aerocommanders for landing. The approach controller notified the aerodrome controller of the change in the landing sequence.

At 1705 Eastern Standard Time, when the Dash 8 was on final approach at about 6 nautical miles1 (NM) from the airport, the crew received a traffic alert and collision avoidance system (TCAS) traffic advisory. The crew saw an Aerocommander to the left at about 3 NM, and observed on the TCAS display another aircraft in close proximity. Very shortly after, they received a TCAS resolution advisory to climb their aircraft, which they followed. The crew reported that as they were climbing, they saw an Aerocommander pass to the left of the Dash 8.

The four aircraft were being operated on instrument flight rules category flights that required separation by air traffic control. Controllers could use a 3 NM radar separation standard, a vertical separation standard of 1,000 ft, visual separation by the aerodrome controller, or require a pilot to sight and follow another aircraft. The approach controller's intention was to separate the aircraft using sight and follow procedures.

As the aircraft approached the airport the aerodrome controller used non-standard coordination phraseology that was misunderstood by the approach controller. The approach controller subsequently instructed the crew of the Dash 8 and the three Aerocommanders to transfer to the aerodrome controller's radio frequency. The resultant traffic situation presented to the aerodrome controller was difficult to resolve using visual separation or sight and follow procedures.

The TCAS events occurred as the first Aerocommander turned right to track behind the Dash 8 on the final approach to runway 15. The Aerocommanders were from the same operator and often used sight and follow procedures between company aircraft on arrival.

An Airservices Australia (Airservices) investigation found that the occurrence was due to the following factors:

  • the approach controller made an error of judgement in assessing the new traffic sequence
  • the aerodrome controller used non-standard coordination phraseology that was misinterpreted by the approach controller
  • the use of sight and follow procedures for the number of aircraft involved increased controller workload
  • the approach controller's lack of recent familiarisation with tower visual separation procedures.

The Airservices report made six recommendations and the following action has been taken in regard to the recommendations:

  • tower and approach/departure controllers were reminded to use standard coordination phraseology to reduce the possibility of ambiguity
  • a tower and approach/departure area familarisation program has been implemented that requires participating controllers to complete a project paper
  • letters of agreement regarding sight and follow procedures have been finalised with two local operators.

  1. A nautical mile is equal to 1852 metres.
 
General details
Date: 25 June 2005 Investigation status: Completed 
Time: 1705 EST  
Location   (show map):Cairns, Aero. Investigation type: Occurrence Investigation 
State: Queensland Occurrence type: Loss of separation 
Release date: 13 April 2006 Occurrence class: Airspace 
Report status: Final Occurrence category: Incident 
 Highest injury level: None 
 
Aircraft 1 details
Aircraft manufacturer: Aero Commander 
Aircraft model: 500 
Aircraft registration: VH-YJI 
Serial number: 3130 
Type of operation: Air Transport Low Capacity 
Damage to aircraft: Nil 
Departure point:Cooktown, QLD
Destination:Cairns, QLD
Aircraft 2 details
Aircraft manufacturer: Bombardier Inc 
Aircraft model: DHC-8 
Aircraft registration: VH-SBB 
Serial number: 539 
Type of operation: Air Transport High Capacity 
Damage to aircraft: Nil 
Departure point:Weipa, QLD
Departure time:1600
Destination:Cairns, QLD
 
 
 
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Last update 16 February 2016