Loss of separation involving a Short Bros SD360-500, VH-FCU and Boeing 737-377, VH-CZM, 35 km north of Brisbane, Queensland, on 3 November 1993

VH-FCU was enroute Gladstone-Brisbane and was being radar vectored for a left base for runway 01. VH-CZM had departed Brisbane on a standard instrument departure off runway 01. This involves the aircraft intercepting and tracking the 360 degree radial from Brisbane and, at 10 DME Brisbane, turning left and tracking for Kilcoy. Both aircraft were under the control of Brisbane Approach. At the time of the occurrence, the Approach position was occupied by a trainee controller under the supervision of a training officer.

The training officer alerted the trainee to the potential confliction between the two aircraft as VH-CZM turned left for Kilcoy. However, as the trainee was about to instruct VH-FCU to turn, a number of radio transmissions prevented him transmitting the instruction until a loss of separation was unavoidable. The aircraft came within four miles of one another while vertical separation did not exist. The trainee was an experienced approach controller from another centre and had only recently begun training in Brisbane. The training officer was aware of the trainee's experience level and delayed his intervention on this basis.

The following factors were considered relevant to this occurrence:

1. The Approach position was occupied by a trainee controller under the supervision of a training officer.

2. The training officer delayed his intervention in the process because of the trainee's previous experience.

3. Other radio traffic delayed the trainee issuing instructions to the aircraft which would have ensured separation.