Aviation safety investigations & reports

Breakdown of separation between GAF Nomad N22C, VH-ATO and two Boeing 737s, VH-VZA and VH-TJY, 17 km north-east of Melbourne Airport, Vic. on 16 February 2012

Investigation number:
AO-2012-029
Status: Completed
Investigation completed

Summary

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What happened

On 16 February 2012, a Government Aircraft Factory N22C, registered VH‑ATO (ATO), was conducting a survey flight north-east of Melbourne Airport, Victoria when it was involved in two losses of separation with two Boeing 737 aircraft. The 737s, registered VH‑VZA (VZA) and VH‑TJY (TJY), were on approach to runway 27 at Melbourne Airport. All of the aircraft were in receipt of an air traffic control service.

What the ATSB found

Although air traffic control intended that the pilot of ATO should keep his aircraft separate from VZA and TJY using visual observation (visual (pilot) separation), not all the prerequisites for using this separation method were met. As a result, the onus remained on air traffic control to maintain either a vertical separation standard of 1,000 ft or a surveillance separation standard of 3 NM (5.6 km). Losses of separation occurred when separation between ATO and VZA reduced to 1.5 NM (2.8 km) and 300 ft, and between ATO and TJY when separation reduced to 1.7 NM (3.2 km) and 700 ft.

The ATSB also identified that the controller was not aware of how specific aspects of the survey operation were to be conducted and therefore could not be assured that separation would be maintained.

Additionally, the ATSB identified that limited guidance and training was provided to controllers operating outside the towered environment in the application of the visual (pilot) separation standard, increasing the risk of the incorrect application of the standard.

What's been done as a result

In response to these occurrences, Airservices Australia amended the Manual of Air Traffic Services to include a number of factors to be considered by air traffic controllers prior to assigning visual (pilot) separation. In addition, the training package for Melbourne Airport arrivals controllers was reviewed and updated to ensure that visual separation, transfer of separation responsibilities and associated phraseologies were adequately addressed. Finally, the controller checking regime was strengthened to ensure that any identified training and/or knowledge deficiencies in relation to assigning visual separation, and their impact on controller performance, were addressed.

Safety message

The use of visual (pilot) separation transfers responsibility for separation between aircraft operating in controlled airspace from the air traffic controller to the flight crew of one of the aircraft. This occurrence highlights that, for the standard to be effective, all parties must have a shared understanding. Correct application of the visual (pilot) separation standard ensures that all involved flight crew are aware of their responsibility, thereby assuring that aircraft will not come into unsafe proximity.

Download final report
[Download  PDF: 2.29MB]
 
 
 
General details
Date: 16 February 2012   Investigation status: Completed  
Time: 1319 ESuT   Investigation level: Complex - click for an explanation of investigation levels  
Location   (show map): 17 km north-east of Melbourne Airport    
State: Victoria   Occurrence type: Loss of separation  
Release date: 29 August 2014   Occurrence category: Serious Incident  
Report status: Final   Highest injury level: None  

Aircraft 1 details

Aircraft 1 details
Aircraft manufacturer Government Aircraft Factories  
Aircraft model N22  
Aircraft registration VH-ATO  
Serial number 108  
Type of operation Aerial Work  
Sector Turboprop  
Damage to aircraft Nil  
Departure point Essendon, Vic.  
Destination Essendon, Vic.  

Aircraft 2 details

Aircraft 2 details
Aircraft manufacturer The Boeing Company  
Aircraft model 737  
Aircraft registration VH-TJY  
Serial number 28151  
Operator Qantas  
Type of operation Air Transport High Capacity  
Sector Jet  
Damage to aircraft Nil  
Departure point Adelaide, SA  
Destination Melbourne, Vic.  

Aircraft 3 details

Aircraft 3 details
Aircraft manufacturer The Boeing Company  
Aircraft model 737  
Aircraft registration VH-VZA  
Serial number 34195  
Operator Qantas  
Type of operation Air Transport High Capacity  
Sector Jet  
Damage to aircraft Nil  
Departure point Brisbane, Qld  
Destination Melbourne, Vic.  
Last update 14 November 2018