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A Beech 1900 (Beech) departed from runway 27 and was tracking via a STRATHBOGIE 8 standard instrument departure, on climb to 5,000 ft. Shortly after, a Boeing 767 (B767) departed from runway 34 on a DOSEL 8 standard instrument departure, on climb to 5,000 ft. The standard instrument departure tracks intersected approximately 2 NM north of the aerodrome. The departure north radar controller (departure controller) observed that the separation between the two aircraft was not going to be maintained and queried the aerodrome controller in relation to the separation procedure being applied. The aerodrome control position was being operated by a trainee under the supervision of a rated controller. The trainee advised that he thought the departure controller was providing separation. The departure controller instructed the Beech crew to turn left onto a heading of 310 degrees and the B767 crew to turn right onto a heading of 030 degrees. The two aircraft passed at the same altitude, with 1 NM lateral separation. The minimum separation required was either 3 NM laterally or 1,000 ft vertically. There was an infringement of separation standards. The B767 was fitted with a traffic alert and collision avoidance system and the crew received a traffic advisory just prior to the issue of the avoiding instructions from the departure controller.

The trainee and the aerodrome controller had been at the console for about 3 hours and the number of aircraft being managed had reduced slightly following a busy period. The runway mode was being changed from land and hold short operation (LAHSO) using runways 34 and 27, to dedicated departure runway arrangement using those runways. In LAHSO all aircraft depart from runway 27, while in the dedicated departure mode, departures to the south and west use runway 27 and those to the north and east use runway 34. In that configuration, the intersection of aircraft departure tracks is almost eliminated. It was recognised by experienced controllers that the transition period between runway modes required an increased awareness and careful consideration of the traffic management plan to ensure that potential conflicts for departing aircraft were minimised. The trainee was aware of potential problems for each mode but had not been alerted to the potential problems that may occur during a mode transition period. On taxi, the crew of the B767 requested and were approved to use runway 34. The trainee subsequently amended the departure order of the B767 and the Beech to eliminate a requirement to apply a 2 minute wake turbulence separation standard to the Beech aircraft.

The trainee did not appreciate that the aircraft's departure tracks converged north of the aerodrome. The aerodome controller reported that as the trainee was soon to be checked for a rating his monitoring of the trainee's control was less vigilant than normal. Local instructions stated that the aerodrome controller was responsible for the separation of departing aircraft within 5 NM of the aerodrome and that for departures from different runways, the aerodrome control and departure control positions were jointly responsible for coordinating a separation solution. The departure controller's preference was to depart the B767 before the Beech but he agreed to the trainee's request to change the departure order. Normal practice in this situation was that the aerodrome control position, having initiated the change, was responsible for the separation unless otherwise coordinated. The controllers neither coordinated a separation solution nor clearly established who was responsible for ensuring separation. Both assumed that the other was going to separate the two aircraft. The aerodrome controller was not aware of the developing situation and was only alerted to the infringement following the departure controller's query to the trainee.

The trainee had undergone tower control ab initio training, which included approximately 1 day of training on the vectoring of aircraft. The course did not provide any terminal area (TMA) control training. Controllers undergoing training for tower positions were able to undertake TMA familiarisation. But, the tower training syllabus did not require trainees to develop an understanding of, or to be familiar with, TMA operations. TMA familiarisation by tower trainees was conducted on an ad-hoc basis and there was no procedure to assess a trainee's level of understanding of TMA operations.

Melbourne Tower training publications did not provide advice of a preferred duration for training sessions that would maximise the training benefit. The publications did list aspects of critical safety that needed to be covered during training for both trainees or supervising controllers. But, the list did not include areas of known conflict for standard instrument departures or standard arrival routes. The publications did not include advice of the potential inherent complexity of runway mode transition.

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