The Cessna 152, VH-IVT was on a dual training flight, and was carrying out right hand circuits on runway 11 right. The Beech 58, VH-EUA was carrying out training circuits, also on runway 11 right, and had nominated right hand circuits during taxi. On the second circuit, when the aircraft was established on the downwind leg, the pilot of VH-EUA reported "downwind touch-and-go". The Tower controller instructed the pilot to follow VH-IVT which was turning onto final approach. After this touch-and-go, the pilot of VH-EUA was offered a left hand circuit by the Tower controller. The pilot declined the offer as this was to be his last circuit. The option of a left circuit was suggested to assist in providing separation between the two aircraft which had vastly different performance. Two other aircraft were in the circuit (a Robinson R22 VH-HER, and a Cessna 152 VH-HCG) but both had been issued landing instructions for completion of their flights. The occupants of the tower cab, the Tower controller and the Tower Coordinator, were monitoring the circuit traffic in the normal manner.
They had noted that VH-IVT and VH-EUA were approximately half a circuit apart when an additional aircraft, a Beech 76, VH-JWX called inbound to the Bankstown circuit. The pilot of that aircraft was asked to report at Warwick Farm. The controllers could not see this aircraft at the time, and both moved to the rear of the tower in an attempt to sight VH-JWX which was approaching from a westerly direction. While this was occurring, VH-EUA had completed the touch and go and was in a climbing right turn onto downwind. The pilot reported "downwind full stop" and the controllers, who had now obtained visual contact with VH-JWX, turned their attention back to the south-eastern circuit area. The pilot of VH-IVT called downwind touch and go at that time and as they looked up at the downwind position they saw VH-IVT in a steep turn and diverging from what appeared to be very close proximity with VH-EAU. When the Tower controller checked with the pilot of VH-EUA to confirm that they were following VH-IVT the pilot replied "we didn't even see him". The pilot flying VH-EUA from the left hand control seat reported that he saw VH-IVT at his 10 o'clock position and increased his bank angle to avoid the other aircraft. The pilot in the right hand control seat of VH-EUA was operating the radio and had not seen VH-IVT. The instructor in the right hand control seat of VH-IVT stated that after completing the turn onto downwind he sighted the other aircraft slightly below and about 50 feet away. He immediately took over and commenced a climbing turn to the right. The instructor said that the other aircraft would not have been visible from the left and seat, and a collision may have occurred if avoiding action had not been taken.
Significant Factors
The Tower Controller and the Coordinator were distracted by an inbound aircraft and did not recognise the potential confliction between VH-EAU and VH-IVT. The pilot in command of VH-EAU did not adequately monitor the position of the aircraft ahead, VH-IVT, before he commenced a turn onto downwind.