Wizz A320 and Vueling A320 at Barcelona on Sep 24th 2014, loss of separation, no TCAS advisories

Last Update: October 2, 2015 / 15:31:19 GMT/Zulu time

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Incident Facts

Date of incident
Sep 24, 2014

Classification
Incident

Airline
Wizz Air

Flight number
W6-1963

Destination
Barcelona, Spain

Aircraft Registration
HA-LPL

Aircraft Type
Airbus A320

ICAO Type Designator
A320

A Wizzair Airbus A320-200, registration HA-LPL performing flight W6-1963 from Poznan (Poland) to Barcelona,SP (Spain), was on approach to Barcelona's runway 07L descending along standard arrival route BISBA4S.

A Vueling Airbus A320-200, registration EC-LZF performing flight VY-8306 from Barcelona,SP (Spain) to Amsterdam (Netherlands), had departed runway 07R and was climbing along standard departure route OKABI2R.

The two standard routes intersect at a point northeast of Sabadell VOR (SLL).

Spain's CIAIAC reported that the two aircraft lost required separation, which reduced to 400 feet vertical and 1.3nm horizontal, neither aircraft received TCAS traffic or resolution advisories. The air traffic controller however issued an instruction to HA-LPL to turn left and subsequently direct to Sabadell VOR to re-establish required separation.

Radar data show HA-LPL turned sharply right instead of left aggravating the conflict initially.

The Wizzair A320 continued for a safe landing on runway 07L, the Vueling A320 continued to Amsterdam for a safe landing.

On Oct 2nd 2015 the CIAIAC released their final report in Spanish concluding the probable causes of the incident were:

The lack of adherence to standard phraseology by the air traffic controller with respect to maneouvering instructions which led the Wizzair crew to understand to turn instead of continuing to SLL VOR/DME.

Contributing factors were:

- Lack in understanding or monitoring of readbacks by the air traffic controller, who did not detect the discrepancy between the received read back and the issued instructions

- inadequate or delayed conflict management, once the conflict was detected the controller did not issue instructions to avoid or reduce the conflict but insisted on the instructions already issued.

The CIAIAC reported that HA-LPL was instructed to follow the standard arrival route BISBA4S which would take the aircraft overhead SLL. EC-LZF was following the standard departure route OKABI2R, the two standard instrument procedures intersect at SLL VOR.

The controller issued following instruction: "Wizzair niner five one due to traffic over sierra lima lima make a tree sixty on your right" which was read back as: "Tree sixty on the right Wizzair niner five one", the crew initiated the 360 immediately afterwards. Subsequently the controller repeated his instruction four times over a period of 56 seconds while the separation between the aircraft was eroding to 400 feet vertical and 1.3nm horizontal. Seconds later the Wizzair crew, monitoring their navigation display and detecting the position of EC-LZF, stopped their turn and turned left back onto track to SLL and just informed the controller about them turning left, from this moment the distance between the aircraft increased again. The crew subsequently requested vectors back on route to SLL and received vectors taking them back onto the standard arrival route. There was no TCAS resolution advisory.

The CIAIAC analysed that according to ICAO the correct wording for the instruction to do the 360 would have been: "WZZ951 over SLL make a three sixty turn right due traffic", putting the justification/reason of the instruction at the end. Instead, with the wording used during the instruction, the crew understood, that there was traffic over SLL and therefore they had to do an immediate 360 to the right.

The read back indicating the immediate execution of the 360 was missed by the controller. The controller later stated that he decided to not provide deconflicting instructions expecting TCAS resolution advisories, which he didn't want to interfere with. It was therefore the crew of HA-LPL who detected and corrected the developing conflict.
Incident Facts

Date of incident
Sep 24, 2014

Classification
Incident

Airline
Wizz Air

Flight number
W6-1963

Destination
Barcelona, Spain

Aircraft Registration
HA-LPL

Aircraft Type
Airbus A320

ICAO Type Designator
A320

This article is published under license from Avherald.com. © of text by Avherald.com.
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