Serious incident to the Embraer ERJ170 registered F-HBXK operated by Hop! and to the Airbus A320 registered OO-SNE operated by Brussels Airlines on 21/10/2020 at Paris -[...]

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The landing and take-off operations at Paris-Charles de Gaulle airport were taking place on the south parallel runways, in particular weather conditions, with a strong crosswind and moderate to severe turbulence below 1,500 ft.

The ERJ170 was at 500 ft on short final on runway 26L when the crew of the A320 were cleared to take-off from runway 26R.

At a height of 200 ft, a Windshear warning was triggered on board the ERJ170. The crew applied the procedure associated with this warning by interrupting the approach and keeping the
wings level.

After eight seconds, when the ERJ170 flew through 580 ft in climb, the Windshear warning stopped. The crew identified the end of the windshear situation when the aeroplane flew through 1,000 ft, 11 s after the end of the warning. The crew continued complying with the procedure by keeping the wings level for a further eight seconds up to an altitude of 1,500 ft, in accordance with the operator's operational instructions for the ERJ170 (refer to paragraph 2.3.3 note 5). They then notified the controller of the windshear and the go-around.

Due to compliance with the Windshear procedure and the strong crosswind, the ERJ170 deviated northwards and closed in on the A320 taking off from runway 26R.

The controller attempted to resolve the conflict by using the emergency phraseology to order the ERJ170 to turn onto a heading of 240°, around 10 s after the ERJ170 had reported the go-around. The crew read back the instruction but the controller's order to change the heading was not followed. In fact, complying with the TCAS procedure, the crew stopped the turn as they passed through a heading of 250° which resulted in a track of 263°. The crew of the ERJ170 did not immediately inform the controller of the TCAS resolution advisory due to the frequency being busy.

The controller then asked the crew of the A320 to stop climbing without using the emergency phraseology. The latter replied that they were following a resolution advisory emitted by
their TCAS.

The crew of the ERJ170 then ambiguously informed the controller that they had also had a TCAS resolution advisory.

The crews followed the orders of the resolution advisory provided by their respective TCAS systems. The minimum separation reached during the incident was 0.09 NM and 460 ft.

Neither of the crews informed the controller of the end of their respective TCAS resolution advisories using the standard message set out in the phraseology rules. The use of the past tense in the non-standard message made by the crew of the ERJ170 stating that they had also had a TCAS may have led the controller to believe that the resolution advisory had ended. The controller therefore issued orders to the crews despite the ongoing resolution advisories.

The BEA issues 4 safety recommendations:

- Recommendations FRAN-2023-013 et FRAN-2023-014 / Risk of abnormal proximity in the event of a go-around during specialised simultaneous operations, in the case of an aircraft complying with a Windshear procedure and strong crosswind situations:

The distance between the centrelines of the south parallel runways at Paris-Charles de Gaulle airport is below the minimum centreline-to-centreline value set out in the RCA in the case of specialised simultaneous operations.

However, this regulation stipulates that parallel runways with a centreline-to-centreline distance below this value can be used simultaneously subject to the approval by the competent air traffic services authority, of a study taking into consideration the geometry of the runway layout and the associated control means.

The BEA has no knowledge of a study that takes into account the combined risk associated with an aircraft flying a missed approach due to a windshear warning and a strong crosswind situation when specialised operations were introduced at Paris-Charles de Gaulle.

Due to the implementation in March 2022 of requirement ATS.TR.255 of Regulation (EU)
No 2017/373 laying down common requirements for providers of air traffic management/air navigation services, the French air navigation service provider (DSNA) submitted the Alternative Means of Compliance (AltMOC) 2022/06/21-IR ATM/ANS-AMOC FR No 015 to demonstrate an equivalent level of safety in the particular runway configuration at Paris-Charles de Gaulle. This file was approved by the French civil aviation safety directorate (DSAC) in June 2022.

The arguments for demonstrating compliance presented in the DSNA AltMOC are undermined by this event in the specific case of a missed approach due to a windshear situation.

In such a situation, in accordance with the operational procedure, the crew must keep the wings level and the horizontal profile of the aircraft's flight path will depend on the surrounding conditions. Due to strong crosswind, the aeroplane's track will deviate from the published go-around path. This deviation could result in a loss of separation with an aeroplane taking off from the parallel runway. This situation may become critical when runway spacing is below the standards prescribed by ICAO and the European regulation.

The BEA has brought to light at least three loss-of-separation events that occurred over the last five years and presenting similar factors.

Consequently, the BEA recommends that:

• whereas while complying with a Windshear procedure, the crew must keep the wings level and cannot respond to any possible lateral vectoring instruction issued by the controller;
• whereas the arguments for demonstrating compliance presented in the Alternative Means of Compliance (AltMOC) file 2022/06/21-IR ATM/ANS-AMOC FR No 015 to demonstrate an equivalent level of safety in the particular runway configuration at Paris-Charles de Gaulle are undermined in the specific case of a missed approach due to a windshear situation;

the DSNA revise the demonstration of compliance with regulatory requirement ATS.TR.255 of Regulation (EU) No 2017/373, in particular the point relating to the minimum distance between runway centrelines and the divergence between departure and go-around paths for specialised simultaneous operations, so that it takes into account the observations highlighted by this incident; [Recommendation FRAN 2023-013]

the DSAC reassess its decision to approve the AltMOC submitted by the DSNA on the specific issue of the alternative means of compliance to AMC4 ATS.TR.255. [Recommendation FRAN 2023-014]

- Recommandation FRAN-2023-015 / Adaptation of specialised operations:

In the documents that it has published on parallel or near-parallel runway operations, the International Civil Aviation Organisation (ICAO) recommends that independent parallel approaches to parallel runways spaced by less than 1,525 m between their centre lines shall be suspended under certain meteorological conditions, as prescribed by the appropriate ATS authority (windshear, turbulence, downdrafts, crosswind and significant meteorological conditions such as thunderstorms) which might otherwise increase final approach track deviations to the extent that safety may be impaired.

It does not make an equivalent recommendation for the case of specialised operations on parallel or near-parallel runways.

The serious incident of this report shows that weather conditions can be the cause of path deviations that can result in losses of separation between traffic during specialised operations on parallel or near-parallel runways.

The BEA has brought to light at least three loss-of-separation events that occurred over the last five years and presenting similar factors.

Although the runway centreline-to-centreline distance at Paris-Charles de Gaulle is less than the ICAO recommended standard, a similar scenario is still possible for operations on runways meeting this standard. In such a case, the runway centreline-to-centreline distance provides greater margins, but the BEA is not aware of any study that demonstrates that the loss of separation would be avoided regardless of the runway centreline-to-centreline distance and weather conditions.

Consequently, the BEA recommends that:

1. ICAO assess the appropriateness of recommending the adaptation of specialised simultaneous operations when certain meteorological conditions prescribed by the appropriate ATS authorities (windshear, turbulence, downdrafts, crosswind or other significant meteorological conditions such as thunderstorms) might cause an increase in deviations from the published flight paths to the extent that safety may be impaired. [Recommendation FRAN 2023-015]

The recommendations are being processed

The status of the recommendations is available at SRIS2: click here

___________________________________________________________________

Note: in accordance with the provisions of Article 17.3 of Regulation No 996/2010 of the European Parliament and of the Council of 20 October 2010 on the investigation and prevention of accidents and incidents in civil aviation, a safety recommendation in no case creates a presumption of fault or liability in an accident, serious incident or incident. The recipients of safety recommendations report to the issuing authority in charge of safety investigations, on the measures taken or being studied for their implementation, as provided for in Article 18 of the aforementioned regulation.

General information

Local date	21/10/2020
Responsible entity	France - BEA
Scope of Investigation	Full (Annex 13) type investigation
State or area of occurrence	Europe and North Atlantic - France - 95 Val-d'Oise
Location	Paris Charles-De-Gaulle AD
Human consequences	None
Aircraft consequences	None
Occurrence class	Serious incident
Occurence category	MAC: Airprox/ ACAS alert/ loss of separation/ (near) midair collisions
File number	BEA2020-0471

Flight Information

Aircraft category	Fixed Wing - Aeroplane - Large Aeroplane - Large Aeroplane
Operator	France - HOP!
Manufacturer / Model	EMBRAER - ERJ170
Aircraft Registration	F-HBXK
State of registry	France
Last departure point	France - LFRB (BES): Brest Bretagne
Planned destination	France - LFPG (CDG): Paris Charles-De-Gaulle
Flight phase	Approach
Serial number	17000008
Operator Type AG
Operation Type	Commercial Air Transport - Passenger - Airline

Second aircraft involved

Aircraft category	Fixed Wing - Aeroplane - Large Aeroplane - Large Aeroplane
Operator	Belgium - Brussels Airlines N. V.
Manufacturer / Model	Airbus - A320
Aircraft Registration	OO-SNE
State of registry	Belgium
Last departure point	France - LFPG (CDG): Paris Charles-De-Gaulle
Planned destination	Belgium - EBBR (BRU) : Brussels/Brussels-National (Brussels Airport)
Flight phase	Take-off
Serial number	4243
Operator Type AG
Operation Type	Commercial Air Transport - Passenger - Airline

BEA is the French air safety investigation authority for civil aviation. The sole objective of the investigation is to improve air safety. It is intended neither to apportion blame nor to assess responsiblity.

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