A Fokker 50 was conducting a practice Instrument Landing System (ILS) approach for runway 24 at Perth, with an intended overshoot to Cunderin. A Cessna 172 was tracking via Northam to Perth with an intended overshoot to Jandakot. Other traffic in the area at the time was a helicopter tracking from Perth to Mundijong.
At 1133 Western Standard Time the crew of the Fokker was conducting the overshoot onto a radar heading which placed the aircraft in close proximity to the Cessna. The pilot of the Cessna sighted the Fokker and turned and descended to avoid that aircraft.
Perth Air Traffic Control had two runway specific traffic management plans. These were North-East (duty runways 03/06) and South-West (duty runways 21/24). Airspace ownership changed dependent on the plan in use and the airspace was divided as Terminal Control Area South (TMA S) and Terminal Control Area North (TMA N), the division occurring along the 281/077 radials from the Perth VOR. At the time of the occurrence the plan placed North-East and TMA S under the control of approach (APP) and TMA N under the control of departures (DEP).
The Perth Aerodrome Controller (ADC) had assumed responsibility for the Aerodrome control position approximately 10 minutes prior to the occurrence. The departure controller had received a handover 10 minutes prior to the incident and was unaware that the Fokker would turn back towards the Cessna.
The relative positions and intended tracks of both the Fokker and the Cessna were such that the departure controller was required to maintain vertical separation until within approximately 5 NM of the aerodrome, with the Fokker passing under the Cessna near Parkerville.
The aerodrome controller coordinated with the approach controller for departure instructions for the helicopter. The approach controller issued the instruction "right unrestricted you separate all the inbounds". The aerodrome controller accepted this and the instructions were issued without reference to the departure controller. The aerodrome controller subsequently coordinated with the approach controller for the overshoot instructions for the Fokker. The approach controller issued the instruction "left 120 unrestricted", but shortly after revised the instruction to, "separate with the helicopter, or keep him on runway heading for a bit to get him above". The aerodrome controller advised that the left turn onto a heading of 120 degrees would suffice. The approach controller issued the overshoot instruction without reference to the departure controller.
Coordination between the tower controllers and the Terminal Control Area controllers utilises the Operational Data Information contained within the radar label display. Coordination between approach and departures is via hotline communications.
Temporary Local Instruction (TLI) SDW/98/160 page 47 Section 5 paragraph 12.3 provides a choice of units to coordinate for aircraft overshooting Perth with the proviso "as appropriate." That section was contained in a letter of agreement between the Tower and Terminal Control Area and specifically dealt with overshooting aircraft.
The same TLI at page 65 Section 6 paragraph 2.1.1 advised that "In all instances the next call must be to DEP". This instruction was headed "Management of Departing IFR Aircraft-Perth" and dealt with Perth Departures from the non-duty runway. That paragraph specifically required the aerodrome controller to coordinate with the departures controller for departure instructions on aircraft departing from the non-duty runway but did not mention the procedure to be followed for overshooting aircraft from the non-duty runway.
The information flow between the approach and departures controllers was not in accordance with local instructions, because approach was issuing overshoot instructions for an aircraft that would require a clearance from departures. The aerodrome controller, by coordinating with approach instead of departures, compounded this and may have reduced the departures controllers' situational awareness.
The use of Operational Data Information for coordination between units was accepted as a standard operating procedure. On some occasions the overuse and over reliance on Operational Data Information coordination may lead to a lack of situational awareness. Controllers were aware of what was intended to happen after the overshoot but there were no visual cues as to what the aircraft was doing. The approach and departures controllers coordinated via hotline for Departures to retain the Cessna on frequency and place the aircraft on a close right downwind. However there was no way for the aerodrome controller to know this unless the controller had queried the aircraft's current clearance. This may have led the approach controller to discount the Cessna from his mental traffic picture.
- The approach controller, by issuing departure instructions without reference to the Departures controller, did not comply with local instructions.
- The aerodrome controller accepted overshoot instructions that placed the two aircraft in close proximity.
- The aerodrome controller did not provide assistance to the departure and approach controllers with regard to aircraft operating within close proximity to the aerodrome.
- The sole reliance on the use of Operational Data Information for coordination left room for ambiguity to exist in the controllers understanding of an aircraft's intended track.
Local safety action
Following the investigation, Airservices Australia has:
- Withdrawn the use of OPD coordination between the tower and TMA and, restricted the use of Local Instruction 8-22-TM for use between TMA positions.
- Briefed controllers to pass sequence information to tower as per Local Instructions 8-23TM in a timely manner and to ensure that handover/takeover procedures are carried out as per local instructions 1-5-TM.
- Instructed TWR and TMA Team Leaders to promote team work across streams at all times and ensure each unit provides back up support at all times, especially during quiet periods.
- Added a section to local instructions for the control of overshooting aircraft including an instruction to provide a "next" call to DEP for all aircraft conducting overshoot at Perth.
- Instructed controllers to pass the current clearance issued to aircraft operating within 5nm of Perth airport to the ADC by the TMA controllers. However this does not absolve the ADC from obtaining information which may be pertinent to separation responsibilities.
|Date:||19 January 1999||Investigation status:||Completed|
|Time:||1130 hours WST|
|Location:||4 km E Perth, Aero.|
|State:||Western Australia||Occurrence type:||Loss of separation|
|Release date:||12 May 2000||Occurrence category:||Incident|
|Report status:||Final||Highest injury level:||None|
Aircraft 1 details
|Aircraft manufacturer||Fokker B.V.|
|Type of operation||Air Transport High Capacity|
|Damage to aircraft||Nil|
|Departure point||Perth, WA|
Aircraft 2 details
|Aircraft manufacturer||Cessna Aircraft Company|
|Type of operation||Flying Training|
|Damage to aircraft||Nil|
|Departure point||Wongan Hills, WA|