A Saab SF340B aircraft (Saab) departed Tamworth aerodrome and was tracking to the southeast on climb to flight level (FL) 120. A Mooney Aircraft Corporation M20J (Mooney) was travelling in the opposite direction en route from Bankstown to Inverell via Scone and Tamworth at 8,500 ft. The Mooney was in Tamworth class "C" controlled airspace. The Saab crew received a traffic alert from that aircraft's traffic alert and collision avoidance system as the Saab was approaching 8,000 ft. The Saab crew levelled their aircraft at 8,200 ft and rolled the aircraft to the left to avoid the Mooney. The pilot of the Mooney did not request or obtain an airways clearance from the Tamworth Aerodrome Controller (ADC) to enter Tamworth control area prior to the occurrence. The Saab passed within 1.8 nautical miles (NM) horizontally and 300 ft vertically of the Mooney. The required separation standard was either 1,000 ft vertically or a minimum horizontal distance determined using the appropriate "Lateral Separation" table in the Manual of Air Traffic Services (MATS). There was an infringement of separation standards.
Tamworth Air Traffic Control (ATC) provided a non-radar, or procedural control, service to aircraft operating within the Tamworth control area and control zone (CTR). Controllers used non-radar information to establish and maintain procedural separation standards in accordance with MATS. Tamworth class "C" control area steps extended to 36NM when above 6,500 ft AMSL to the south-southeast of the Tamworth aerodrome in the area that encompassed the flight path of the Mooney. Class "G" non-controlled airspace surrounded the Tamworth CTR and control area.
The Saab crew was conducting a scheduled fare-paying passenger flight under instrument flight rules (IFR) and had been cleared by the Tamworth ADC to climb to FL120. The standard altitude Tamworth ATC could assign to aircraft leaving Tamworth control area and entering the overlying Brisbane sector in accordance with the letter of agreement between Tamworth ATC and Brisbane ATC, was FL120 (subject to other aircraft). Otherwise, a procedural separation standard was applied by Tamworth ATC and coordinated with the Brisbane sector controller, or responsibility for separation was specifically assigned to the Brisbane sector controller.
The pilot of the Mooney was an IFR pilot and was normally provided with radio frequency management instructions by ATC along the route. On this flight however, the pilot of the Mooney was operating under visual flight rules (VFR) and no such advice was provided. All aircraft crews that planned to enter class "C" controlled airspace, whether operating under IFR or VFR, were required to establish two-way radio contact with ATC and obtain an airways clearance prior to entering class "C" airspace. The Tamworth visual terminal chart (VTC) depicted the lateral boundaries of class "C" control area surrounding Tamworth aerodrome above 4,500ft AMSL. However, neither the VTC nor the Aeronautical Information Publication (AIP) En-Route Supplement Australia (ERSA) specified the vertical boundary between Tamworth control area and the overlying Brisbane sector. The pilot later reported that he had studied the Jeppessen low altitude en-route chart relevant to Tamworth, prior to the flight, and believed that he would not require an ATC clearance to enter Tamworth control area above 6,500ft AMSL.
Airservices Australia reported that the Brisbane sector controller had seen the occurrence on that controller's air situation display (ASD) in the Brisbane Air Traffic Services Centre and had received a short term conflict alert (STCA) from The Australian Advanced Air Traffic System (TAAATS). The Brisbane sector controller reported that STCA's between aircraft operating within Tamworth control area were common but did not necessarily indicate a potential infringement of separation standards. Short term conflict alerts, in those circumstances, occurred when the procedural separation standard being used by Tamworth ATC was less restrictive than the STCA activation parameters used in TAAATS.
Although the track symbol and a label, showing the secondary surveillance radar code and the altitude from the Mooney, were displayed to the Brisbane sector controller on the ASD, the Brisbane sector controller had no control or jurisdiction over the Mooney and was not aware that the pilot had not established two-way radio contact with Tamworth ATC. The Brisbane sector controller was also not aware that the pilot had not received an airways clearance to enter Tamworth control area. The Brisbane sector controller believed both aircraft were under the control of Tamworth ATC because both aircraft were within the Tamworth control area. The Tamworth ADC was unable to provide a separation service to the Saab in relation to the Mooney as he had no information on that aircraft.
The pilot of the Mooney was an IFR pilot who should have been able to establish, from the information available, that Tamworth control area was class "C" airspace above 4,500 ft. He should also have known that he required an airways clearance prior to entering class "C" airspace. Had the pilot requested a clearance on any of the frequencies referred to in the ERSA or depicted on the charts, he would have been provided with the correct Tamworth ATC frequency on which to establish two-way radio contact and obtain an airways clearance. Two-way radio contact between Tamworth ATC and the pilot of the Mooney would have enabled Tamworth ATC to apply separation standards in accordance with MATS.
The relevant AIP's did not specify the vertical boundary between Tamworth control area and the overlying Brisbane sector. That omission may have made it difficult for the Mooney pilot to determine the correct ATC frequency on which to establish two-way radio contact with Tamworth ATC.
The Brisbane sector controller did not provide traffic information to Tamworth ATC about the Mooney because he had no reason to suspect that the Mooney was in Tamworth controlled airspace without an airways clearance. Provision of facilities that would have enabled Tamworth ATC to better determine the disposition of aircraft within and around Tamworth controlled airspace may have assisted Tamworth ATC to provide a separation standard between the Mooney and the Saab.
- The Mooney pilot did not comply with AIP procedures.
Local safety actions
The ERSA was amended to advise frequency management instructions for crews entering Tamworth class "C" and "D" airspace from adjacent class "G" airspace.
During the course of this investigation Airservices Australia approved the installation of a tower situational awareness display (TSAD) in Tamworth Tower. The TSAD will display transponder equipped aircraft, within radar coverage, operating in the Tamworth control area and CTR. The TSAD is expected to be installed in July 2002.
Additionally, Airservices Australia has commenced a review of airspace boundaries on map displays with a view to reducing possible misinterpretation.
|Date:||05 July 2001||Investigation status:||Completed|
|Time:||0714 hours EST|
|Location:||12 km SSE Tamworth, (VOR)|
|State:||New South Wales||Occurrence type:||Loss of separation|
|Release date:||15 July 2002||Occurrence category:||Incident|
|Report status:||Final||Highest injury level:||None|
Aircraft 1 details
|Aircraft manufacturer||Mooney Aircraft Corp|
|Type of operation||Private|
|Damage to aircraft||Nil|
|Departure point||Bankstown, NSW|
Aircraft 2 details
|Aircraft manufacturer||S.A.A.B. Aircraft Co|
|Type of operation||Air Transport Low Capacity|
|Damage to aircraft||Nil|
|Departure point||Tamworth, NSW|
|Departure time||0710 hours EST|