An ATSB investigation as to how two jets left Melbourne Airport and played a dangerous and unintended game of tag in 2010 when a faster following airliner rose up under the slower leading jet has lead to a shake up of deficient procedures that were being used by air traffic controllers.
The inquiry also found that similar deficiencies came into play in another instance of two airliners getting too close to each other after leaving Melbourne last year.
This is how the ATSB summaries its inquiries, which have resulted in AirServices Australia changing its procedures to eliminate the risk they posed to public safety.
On 5 December 2010, at 1422 Eastern Daylight-saving Time, a breakdown of separation occurred between a Boeing Company B737-7Q8 (737), registered VH-VBF, and a Boeing Company B767-338 (767), registered VH-OGU, on departure from Melbourne Airport, Victoria. The flight crew of the 737 had reduced their aircraft’s speed in order to meet a height requirement of the Standard Instrument Departure. The following 767 aircraft climbed at a faster speed.
When the aircraft were transferred from the aerodrome controller to a departures controller, there was 3.4 NM (about 6.3 km) separation between them. The departures controller expected them to climb at a similar speed, and did not recognise the loss of separation assurance. The controller’s actions to manage the compromised separation were not fully effective. At one point, radar separation had reduced to 1.9 NM (3.5 km) and vertical separation to 500 ft.
On 12 October 2011, a similar breakdown of separation occurred at Melbourne between an Airbus A320-232 and a Boeing Company 737-8BK. This incident involved different controllers to those involved in the 5 December 2010 incident.
The ATSB identified a safety issue in that the procedures for takeoffs at Melbourne Airport allowed for aircraft to depart relatively close to each other, with no documented requirements to ensure jet aircraft would maintain a set climb speed or to require flight crews to advise air traffic control if that speed could not be achieved. Although the Melbourne procedures were based on those used in Sydney, the Sydney procedures specified a minimum climb speed. The safety assessment report for the Melbourne procedures did not include a detailed comparison of the procedures used in the two locations. In response to the identified safety issue, Airservices Australia has commenced action to establish a standard speed profile for use at radar terminal area aerodromes in Australia, and to ensure that pilots of jet aircraft notify air traffic control when operating at a significantly lower speed than stipulated in that profile.
The jets involved in the 2010 tag match were a Virgin Australia 737-700 and a Qantas Cityflyer 767-300. In the 2011 incident the jet on top was a Jetstar A320, being overtaken by a Virgin Australia 737-800.
This is how the ATSB summarises the main safety factors involved in the 2010 incident.
- The Departures North controller expected the two aircraft to climb at similar speeds, did not recognise the loss of separation assurance, and assigned both aircraft the same flight level.
- The Auto Release procedures at Melbourne Airport allowed for aircraft to be departed at or close to the separation minima, with no documented requirements to ensure jet aircraft would maintain a set climb speed or flight crews would advise air traffic control if the speed could not be achieved. [Significant safety issue]
The ATSB says that it is satisfied with the remedial safety actions taken by AirServices Australia. The safety investigator doesn’t examine the questions arising from such a dangerously inadequate set of procedures having been adopted at for Melbourne Airport in the first place, and it would be fair to say that such questions would be appropriate to a thorough independent inquiry into the processes, priorities and competencies of the air navigation services provider.
The full ATSB report can be downloaded here.