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Summary

Summary

FACTUAL INFORMATION An instrument flight rules (IFR) Piper Chieftain (PA-31-350) departed Wynyard for Moorabbin on climb to 8,000 ft. Five minutes later an IFR Beechcraft Baron (D55) departed Smithton for Bankstown, tracking via East Sale, on climb to 9,000 ft. The intended tracks of the aircraft crossed at a position approximately 50 NM north of Wynyard. The PA-31-350 was operating a regular transport flight while the D55 was on a charter flight. The visibility was in excess of 20 km and there was no cloud below 10,000 ft. Both aircraft were operating in uncontrolled, class G, airspace. The crews of IFR aircraft operating in class G airspace are required to be provided with information on other IFR traffic by the responsible air traffic services (ATS) operator. The area in which the flights were operating was the responsibility of the Melbourne Sector 3 Low controller. The Sector 3 Low controller had been rated in the position for approximately five months. Traffic levels were high and there was a considerable number of radio transmissions that required her attention. The controller advised traffic information, with the exception of the PA-31-350, to the pilot in command (PIC) of the D55 when that aircraft was taxiing at Smithton. She had previously advised traffic information on four other IFR aircraft to the PIC of the PA-31-350. Flight details of all aircraft were available to the controller on flight progress strips. The controller endeavoured to plot the tracks of the two aircraft on a chart to assess whether they would conflict. However, she was distracted by radio transmissions and by the need to conduct co-ordination with other ATS positions and was unable to complete the plot. There was provision for a planner controller, adjacent to the Sector 3 Low controller's position, but it was not occupied. The normal practice was to staff the Sector 3 Low position with a single operator. The team leader was available to assist the controller but the controller was satisfied with the situation and did not think assistance was required. The PIC of the PA-31-350 had maintained his aircraft at 5,000 ft to avoid two other aircraft inbound to Wynyard on the route. As he recommenced climb to his planned level of 8,000 ft he sighted an aircraft to his left. This aircraft appeared to be on climb and was at a distance of approximately 2 NM. The PIC of the PA-31-350 was aware that the converging aircraft was the D55, as he had previously heard the PIC of that aircraft arranging separation with the crews of other aircraft. The PIC of the PA-31-350 established communications with the PIC of the D55 who advised that he had the PA-31-350 in sight and would restrict his climb to pass below that aircraft. The two aircraft passed with approximately 300 ft vertical separation. ANALYSIS The controller was not sure whether the tracks and levels of the two aircraft would cause them to conflict and had endeavoured to plot the tracks to clarify the situation. A more experienced controller, faced with the same concern in a high workload period, may have passed traffic information to the two crews in lieu of increasing the complexity of the task by plotting the tracks. This action would have required little effort in comparison to drawing and assessing a plot of the intended tracks. In addition, the immediate provision of traffic information would have been more expeditious and would have ensured that the pilots received the information in sufficient time to co-ordinate their mutual separation. The operation of the position by a single controller was adequate for the majority of traffic situations. However, the supervisor should have recognised the increasing complexity of the situation and offered the inexperienced controller some assistance during the high workload period when she was probably becoming task saturated. The limited experience level of the controller probably prevented her from recognising her own level of task saturation. The situational awareness and visual scan of the pilot in command of the PA-31-350 assisted him in sighting and co-ordinating separation with the other aircraft. SIGNIFICANT FACTORS 1. The Sector 3 Low controller's limited level of experience. 2. The complexity of the traffic situation due to the high number of radio transmissions. 3. Inadequate monitoring of the controller's workload by the supervisor.
 
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