Aviation safety issues and actions

Wake turbulence occurrences at Sydney Airport

Issue number: AR-2017-011-SI-01
Who it affects: Aircraft arriving at Sydney Airport
Issue owner: Airservices Australia
Operation affected: Aviation: Air transport
Background: Investigation Report AR-2017-011
Date: 15 February 2019

Safety issue description

Given the parallel runway configuration, there was a disproportionate rate of reported wake turbulence occurrences for aircraft arriving at Sydney Airport compared to other major Australian airports in the years 2012 to 2016. Wake turbulence occurrences at Sydney Airport were found to be primarily associated with three factors:

  • arrival densities of one or more aircraft per minute (including parallel runway arrivals), especially on flights that arrived on Runway 34 Right
  • wind direction from the west or north‑west for aircraft arriving on Runway 34 Right, especially when coinciding with a heavy or super heavy aircraft arriving on Runway 34 Left
  • arrivals following an Airbus A380 compared to other aircraft.

Response to safety issue by Airservices Australia

Received 19 November 2018

Airservices will publish an Aeronautical Information Circular (AIC) aimed at operators who operate into Sydney Airport. The AIC will advise industry of the injuries associated with wake turbulence for runway 34R as identified in the ATSB Report. The AIC will also recommend that cabin crew should be seated and secured in the earlier part of the approach.

Received 18 December 2019

…We consider that the action is proportionate to the likelihood and consequence of the risk when it is considered in the broader picture of Sydney operations. Consideration of other options, such as an attempt to increase the spacing on Runway 34R when an A380 lands on Runway 34L, would result in increased complexity for controllers and increased delays for industry. The operations are based on the runways being treated as independent operations and any requirement to change this interaction is likely to introduce other risk into the system…

…As the service provider, Airservices complies with the current wake turbulence separation ruleset as prescribed in CASR Part 172. Airservices Manual of Air Traffic Services (MATS) continues to meet all current regulatory requirements on wake turbulence separation. CASA have not raised any concerns over our application of wake turbulence standards at Sydney during recent surveillance events. If there is ongoing concern with the safety outcomes being achieved by the current ruleset, we request the ATSB consider readdressing the safety issue to the Civil Aviation Safety Authority (CASA)…

ATSB comment in response

The ATSB appreciates Airservices’ response to the identified safety issue regarding wake turbulence occurrences at Sydney Airport and acknowledges the proposed action to reduce the number of injuries associated with these occurrences. However, the ATSB does not consider that the proposed safety action adequately reduces the risk associated with the safety issue, primarily concerning the frequency of wake turbulence occurrence on arrival at Sydney Airport. The proposed safety action attempts to address only one aspect of the consequence (injury), and does not address temporary loss of control scenarios that can result from wake turbulence. Further, as wake turbulence related injuries on arrival to Sydney Airport during the study period all occurred during the descent phase of flight, the introduction of measures to have cabin crew seated in the earlier part of approach may have limited impact on preventing future injuries.

Recommendation

Action organisation: Airservices Australia
Action number: AR-2017-011-SR-011
Date: 15 February 2019
Action status: Released

The Australian Transport Safety Bureau recommends that Airservices Australia introduce measures to reduce the frequency of wake turbulence occurrence at Sydney Airport. Measures that could reduce the likelihood of these occurrences are primarily associated with:

  • arrival densities of one or more aircraft per minute (including parallel runway arrivals), especially on flights that arrived on Runway 34 Right
  • wind direction from the west or north west for aircraft arriving on Runway 34 Right, especially when coinciding with a heavy or super heavy aircraft arriving on Runway 34 Left
  • arrivals following an Airbus A380 compared to other aircraft.

Correspondence

Response from: Airservices Australia
Action status: Released
Response text:

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.

ATSB response:

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.

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.

Current issue status: Safety action pending
Last update 15 February 2019