In Australia, between 2012 and 2016, 179 wake turbulence occurrences were reported to the ATSB, with 78 of these occurring at Sydney Airport.
In addition, seven of the eight minor injuries reported as being a result of a wake turbulence occurrences were at Sydney. Further, when compared with other major Australian airports (Adelaide, Brisbane, Melbourne and Perth), an aircraft was more likely to have a missed approach or go‑around, a ground proximity alert, or have control issues following a wake turbulence encounter at Sydney Airport.
Sydney Airport is the only major Australian airport currently with parallel runways. The distance between these runways is such that they are treated as individual runways and do not require the application of the wake turbulence separation standard for aircraft operating to a single runway.
The investigation found that at Sydney Airport, when the time between arriving aircraft (including those operating on parallel runways) is less than one per minute, the likelihood of encountering wake turbulence increased substantially, with Runway 34 Right (the shorter of the parallel runways) the most likely to be affected.
Evidence indicates that wake turbulence generated by aircraft arriving on one runway can affect aircraft arriving on the parallel runway, especially under certain wind conditions. Aircraft arriving on Runway 34 Left were found to be the most likely cause for more than half of the Runway 34 Right arrival wake turbulence occurrences. A leading Airbus A380 (a super heavy aircraft) probably generated more than one‑third of these occurrences.
The rate of reported wake turbulence occurrences by arriving aircraft following an Airbus A380 was more than double that of any other aircraft type arriving at Sydney. All A380 wake turbulence occurrences took place outside peak arrival periods (one or more aircraft arrivals per minute). Medium weight aircraft, such as a Bombardier DHC-8 or Boeing 737, were more likely to report an encounter with wake turbulence than larger aircraft. No light aircraft reported encountering wake turbulence at the airport.
There were no reported wake turbulence occurrences at Sydney Airport between 2012 and 2016 that occurred during a reported loss of separation (breach of the wake turbulence separation standard). In contrast to wake turbulence occurrences, the rate of other turbulence occurrences at Sydney Airport is consistent with other major Australian airports.
What is wake turbulence
For fixed-wing aircraft, wake turbulence is the combined effect of jet blast or propeller wash with wake vortices. Wake vortices are the primary contributor to wake turbulence. The initial strength of the vortices is primarily dependent upon the generating aircraft’s speed, weight and wingspan. These vortices decay with time and largely become non‑hazardous—depending on atmospheric conditions—within several minutes.
The wake vortices can affect following aircraft in a similar way to flying through weather-related turbulence. More specifically, aircraft encountering wake turbulence may experience an induced roll, which can increase safety risk, especially during phases of flight close to ground such as arrivals and departures. The risk of an injury resulting from a wake turbulence encounter is higher for cabin crew than passengers, who are generally secured in their seats earlier during arrivals.