Loss of Separation Between Aircraft in Australian Airspace
Australian Transport Safety Bureau (ATSB). Aviation Research Investigation, AR-2012-034. Oct. 18, 2013. 97 pp. Appendixes, figures, glossary, tables.
Loss of separation (LOS) events involving aircraft under air traffic control (ATC) occur, on average, about once every three days in Australia, according to this ATSB study, conducted to evaluate the effectiveness of the national air traffic system.
Most LOS events — including the 531 events reported to ATSB in the period studied, between January 2008 and June 2012 — are not near-midair collisions, the report on the study said, noting that in 90 percent, “there was no, or a low, risk of aircraft colliding.” In fact, there has never been a midair collision in Australia between aircraft that were receiving a separation service from ATC, the report said.
Nevertheless, about six LOS events involving an elevated risk of collision are reported each year, the report said.
“Losses of separation occur across all controlled airspace types and types of separation standards, involve mostly aeroplanes (but of all types of operations, from large jet airliners to general aviation aircraft), and involve errors by both controllers and pilots,” the report said. “Although there are some areas … where future attention may be focused to enhance safety, the evidence available from a range of sources does not indicate fundamental deficiencies in the safety management of aircraft separation in Australia.”
About 80 percent of LOS events occur in airspace managed by Airservices Australia, which has jurisdiction over most of the country’s controlled airspace.
The remaining 20 percent of events occurred in airspace controlled by military air traffic services — “relatively high, considering the overall number of movements,” the report said, adding that the Department of Defence believes this is because military controllers do “not normally employ strategic separation mechanisms such as long-range flow control or traffic management plans, as these mechanisms do not allow the required degree of flexibility in service provision that military operations and training require.”
About half of the LOS events in the study were associated with actions of air traffic controllers, and about half were associated with pilot actions; in 9 percent of cases, the event involved actions by both a controller and a pilot, the report said.