Safety issues

Following the advanced release of the safety recommendation, Airservices Australia informed the ATSB of the following: 

On 6 December 2018, Airservices issued a Temporary Local Instruction for Sydney requiring that the distance between successive arrivals on runway 16L and 16R [and runway 34L and 34R] increase from 4 NM to 5 NM. This instruction will be permanently incorporated into Sydney Operational Procedures (via Letter of Agreement 3183). 

While this instruction was issued to reduce the likelihood of go-around and loss of separation events at Sydney, it significantly reduces the likelihood of wake turbulence events. 

In addition, as it recognised that the potential for wake turbulence is more prevalent when the wind is from the north or northwest, to increase pilot awareness and caution, the following action is being taken. 

• Air traffic controllers will be required to place a standard caution on the Aeronautical Terminal Information Service (ATIS). This will be documented in Local Instructions. 
• A wake turbulence caution will be included in the local En Route Supplement Australia (ERSA). 

Temporary Local Instructions and a Notice to Air Men (NOTAM) will be issued on 16 February 2019 as interim measures ahead of publication of the above documents (see below). 

The increased distance between arrivals and improved awareness in the piloting community significantly reduces the risk of wake turbulence events at Sydney aerodrome. We will monitor wake turbulence events and pilot feedback, and intervene further if circumstances demand. 

Amend Letter of Agreement 3138 as follows: TLI to be issued 16/2/19 

10.3 WAKE TURBULENCE 

10.3.1 Parallel Approach Limitations 

When a super wake turbulence category aircraft is making an approach to a parallel runway provide wake turbulence distance separation to the adjacent runway when the aircraft making an approach to the adjacent runway has a MTOW less than 25 000kg. 

10.3.2 RWY 34R Traffic Requirements 

When ATIS notification of parallel wake turbulence applies, APP/DIR provide traffic information and a wake turbulence caution to aircraft on approach to 34R that will operate within the wake turbulence distance of a Heavy or Super aircraft making an approach to runway 34L. 

Example: 
'QFA501, TRAFFIC A380 SUPER RUNWAY LEFT 4 MILES AHEAD CAUTION WAKE TURBULANCE' 

Note: This traffic advice can be combined with other traffic information requirements of Independent Visual Approaches when applicable. 

This is in accordance with AIP (GEN 3.4-88) 

Amend Local Instruction as follows: TLI to be issued 16/2/19 

Local Instructions add a note regarding Wake Turbulence for inclusion on the ATIS. 

When the wind is unfavourable as stated below. "Caution possible W/T from parallel runway operations". 

Amend Local ERSA Entry as follows: NOTAM to be issued 16/2/19 then include in ERSA August publication 

"Due to the nature of operations at Sydney during 34// operations with wind from the west to northwest" CAUTION Wake turbulence may exist.

The ATSB agrees that the measures being implemented by Airservices have the potential to reduce the frequency of wake turbulence events at Sydney Airport, in particular: 

• increasing separation distances for arrivals from 4 NM to 5 NM on runways 16L/R and 34L/R 
• applying the single-runway wake turbulence standard to the parallel runways when the leading aircraft is a super heavy like an A380 and the following aircraft is light (under 25,000 kg). 

Furthermore, increasing pilot awareness of the potential for wake turbulence when the wind is from the north or northwest will provide an opportunity for crews to be prepared for wake turbulence in advance of any experience of it. While this could reduce the consequences of a wake turbulence encounter, it is unlikely to affect the likelihood of encountering wake turbulence. 

The analysis in this ATSB research investigation showed that over half of the wake turbulence occurrences at Sydney were attributable to one or more of the three factors outlined in the safety issue. Although the actions by Airservices have the potential to reduce some of the influence of some of these, they are somewhat limited. The 5 NM separation will only affect heavy aircraft following another heavy aircraft, and medium aircraft following another medium aircraft, as other aircraft already have at least 5 NM wake turbulence separation standard applied. The application of the wake turbulence separation standard to the parallel runways does address the worst-case combination of a super heavy aircraft leading and an aircraft below 25,000 kg following (which did not result in any wake turbulence events in the study period). However, it will not apply when the following aircraft is a medium above 25,000 kg or heavy aircraft (including most common passenger aircraft operating to Sydney). In addition, even through eliminating the influence of all three, Sydney Airport would likely still have a higher rate of wake turbulence events than other major airports. › 33 ‹ ATSB – AR-2017-011 

As such, the ATSB encourages Airservices to consider conducting their own quantitative analyses to explore other options that could further reduce the risk of wake turbulence for aircraft arriving into Sydney Airport.

 In accordance with Section 25(2) of the Transport Safety Investigation Act 2003, Airservices has accepted the safety issue AR-2017-011-SI -01 and accepted the associated recommendation AR-2017-01 1SR-OII in full. Consistent pervious correspondence on 11 February 2019, Airservices has implemented a broad range of actions to increase pilot awareness and caution in recognition of wake turbulence events at Sydney. Notwithstanding, they have acknowledged that the final report (AR-2017-011) encourages Airservices to conduct further quantitative analyses and explore other options that could reduce the risk of wake turbulence events at Sydney. In an effort to address the safety recommendation, Airservices is progressing with an internal quantitative analysis of wake turbulence events at Sydney. The analysis will utilise Airservices ODAS data and corresponding historical occurrence data to model the risk resulting from wake turbulence events at Sydney. The analysis may identify further improvements available at Sydney to reduce the risk of wake turbulence events. The Terms of Reference for this analysis was provided to the ATSB on 22 March 2019. 

ATSB acknowledges Airservices actions and agrees with the direction and scope of the planned quantitative analysis which will should further identify factors that increase the risk of wake turbulence at Sydney Airport. The ATSB will monitor the recommendation until Airsevices inform them of the analysis outcomes.

To address the safety issue, Airservices Australia conducted a comprehensive quantitative analysis of wake vortices for Sydney parallel approaches. This has resulted in the production of a computational model that enables Airservices to simulate wake vortex motion and strength, and interactions with following aircraft. This report also detailed Airbus A380 movements at Sydney Aerodrome since January 2019. The number of A380 movements at Sydney (for the most recent available data, May-July 2022) is around one-third of the average movements in 2019.

The ATSB has reviewed the analysis conducted by Airservices which has significantly increased the understanding of wake vortex generation/propagation at Sydney Aerodrome and the overall understanding of the factors contributing to wake turbulence occurrences.