Description

On 5 December 2010 a Boeing 767-300 being operated by Qantas and departing Melbourne for Sydney in day Visual Meteorological Conditions (VMC) was following a Boeing 737-800 being operated by Virgin Australia which had also just departed Melbourne for Brisbane on the same SID and a loss of prescribed separation occurred. ATC became aware that the 767 was catching up with the 737 but were aware that it was in visual contact and therefore took no action to ensure separation was maintained. No Airborne Collision Avoidance System (ACAS) activation occurred.

Investigation

An Investigation by the Australian Transport Safety Bureau (ATSB) established that 737 had reduced speed in order to meet a height requirement of the SID being flown which had led to the 767 climbing at a significantly faster speed. It was noted that on transfer from TWR to radar departures, there was 3.4 nm separation between the two aircraft. However, the departures controller expected them to climb at a similar speed and “did not recognise the loss of separation assurance”. Once the problem was identified, the controller’s response was judged to have been “not fully effective” and separation reduced to 1.9 nm horizontally when 500 feet apart vertically. However, as the closing speed was relatively low, it was considered that there had been “a significant period for the problem to be detected and rectified”.