THY A321 and SunExpress B738 at Stuttgart on Oct 23rd 2023, loss of separation

Last Update: February 1, 2024 / 18:26:00 GMT/Zulu time

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Photo of THY Turkish Airlines TC-JSZ, Airbus A321 — THY Turkish Airlines TC-JSZ, Airbus A321 (Photo credit: Alec BHX/KKC / Flickr / License: CC by-sa)

Incident Facts

Date of incident
Oct 23, 2023

Classification
Incident

Cause
Loss of separation

Airline
THY Turkish Airlines

Flight number
TK-1706

Departure
Stuttgart, Germany

Destination
Istanbul, Turkey

Aircraft Registration
TC-JSZ

Aircraft Type
Airbus A321

ICAO Type Designator
A321

Airport
Stuttgart Airport, Stuttgart

Airport ICAO Code
EDDS

A THY Turkish Airlines Airbus A321-200, registration TC-JSZ performing flight TK-1706 from Stuttgart (Germany) to Istanbul (Turkey), was departing Stuttgart's runway 07.

A SunExpress Boeing 737-800, registration TC-SOR performing flight XQ-154 from Antalya (Turkey) to Stuttgart (Germany), was on final approach to Stuttgart's runway 07 and went around.

Germany's BFU reported, the occurrence was rated a serious incident due to the loss of separation in flight. The BFU is investigating the occurrence.

According to ADS-B data the landing aircraft was about 4.4nm before the runway threshold when the departing aircraft lined up for departure. Subsequently the landing aircraft touched down and went around with the departing aircraft still on the runway with the horizontal distance between the aircraft being about 0.9nm. The separation during climb out was 300 feet vertical and about 0.8nm horizontal when the landing aircraft turned left onto a diverging trajectory.

On Feb 1st 2024 the BFU reported in their preliminary report summarizing the sequence of events (all times in local time):

The Airbus A321 was on a flight from Stuttgart to Istanbul, Turkey. At 1946:25 hrs, the flight crew of the A321 standing on taxiway K contacted the tower controller and reported holding point of runway 07.

The Boeing 737 was on a flight from Antalya, Turkey, to Stuttgart and on approach to land. At 1948:14 hrs, the Boeing flight crew reported: “Tower good evening […] established ILS zero seven”. At 1948:21 hrs, the tower controller requested the A321 flight crew to line-up runway 07 after a landing A319.

The tower controller instructed the Boeing 737 flight crew at 1948:38 hrs: “[…] reduce speed one seven zero knots or less“. This was confirmed.

At 1948:51 hrs, the tower controller established radio contact with an Embraer EMB500 business jet coming from the General Aviation Terminal and taxiing on taxiway H towards the runway. The Embraer flight crew answered: “Yeah hello tower […] approaching hotel, ready for departure“. The controller answered: “Roger […] call you shortly“. Four seconds later the Embraer flight crew reported: “Holding hold short hotel […]“. At 1949:05 hrs, as the A319 touched down on the runway, the controller said: “[…] via hotel line-up runway zero seven“ (Fig. 1). This was confirmed.

At 1949:13 hrs, the controller told the A321 flight crew: “[…] you are number two for departure there is intersection departure ahead“. The flight crew confirmed this instruction and the A321 standing at the CAT 1 holding point began to move. At 1949:25 hrs, the EMB500 crossed the CAT 1 holding point on taxiway H and entered runway 07.

At 1949:22 hrs, the controller contacted the flight crew of the Boeing 737 about 6.5 NM away: “[…] reduce final approach speed“. At the time, the airplane had a speed of 171 KIAS and the flight crew answered: “Reducing final approach speed […]”. Within about 37 seconds, speed decreased to about 150 KIAS.

At 1949:29 hrs, the controller told the rolling A319: “[…] expedite vacating via delta“. The flight crew answered: “Vacate via delta […]“. The controller requested the flight crew to change to Stuttgart Ground frequency. At 1949:41 hrs, the flight crew confirmed the instruction.

At 1949:48 hrs, the controller told the Embraer flight crew: “[…] out of hotel no delay please wind zero six zero degrees two knots runway zero seven cleared for take-off”. At the time, the EMB500 was on taxiway H short of the intersection with the runway.

At 1949:55 hrs, the flight crew answered: “Cleared take off immediately […] runway zero seven […]”. At the time, the previously landed A319 crossed the CAT 1 holding point at taxiway D. The approaching Boeing 737 was about 5 NM away from the runway threshold and had a speed of 151 KIAS.

At 1950:02 hrs, the controller contacted the A321 flight crew with the words: “[…] be ready as soon as I call you“. This was confirmed.

At 1950:13 hrs, the EMB500 was aligned with the runway, began take-off run and lifted off about 28 seconds later.

At 1950:55 hrs, the controller told the A321 flight crew: “[…] after departure stop climb altitude four thousand feet and stay on my frequency wind zero one zero degrees one knot runway zero seven cleared for take-off”. This was confirmed.

At 1950:58 hrs, the EMB500 flew over the end of runway 07. On the radar display, the controller saw that the A321 had begun the take-off run and informed the flight crew of the Boeing 737, which was about 1.9 NM away from the threshold at 1951:15 hrs: “[…] departure is rolling, wind check zero nine zero degrees one knot“. At 1951:49 hrs, the controller told the Boeing 737 flight crew: “[…] wind one zero zero degrees one knot runway zero seven go […] go go around please left turn“ as the airplane was about 0.63 NM away from the threshold of runway 07 in descent at 200 ft in relation to the threshold. In the following approximately 17 seconds, vertical speed changed from -768 ft/min to 384 ft/min. Within 14 seconds, altitude decreased to 18 ft above the threshold. At 1951:54 hrs, the Boeing 737 overflew the threshold of runway 07 at this altitude. At the same time, the A321 was about 1,600 m (0.8 NM) from the threshold, abreast of the intersection with taxiway E.

At 1951:55 hrs, the A321 had a speed of about 160 kt, two seconds later, it lifted off.

At 1951:54 hrs, the controller instructed the Boeing 737 flight crew: “[…] turn left heading three five zero Airbus three two one departing”. From 1951:58 hrs on, the altitude of the Boeing 737 began to increase. At 1952:01 hrs the controller said again: “[…] left turn now please heading three five zero”. The crew confirmed the left-hand turn to a heading of 350°. At 1952:09 hrs, the controller added: “Turn left now“.

At 1952:10 hrs, the A321 overflew the end of runway 07.

At 1952:14 hrs, the Boeing 737 began to turn left away from the departure track so that the heading of the two aircraft diverged. At the time, the lateral distance to the A321 was 0.92 NM.

At 1952:15 hrs, the controller instructed the A321 flight crew to continue the climb to 5,000 ft AMSL and to change to the radio frequency of Langen Radar.

From 1952:22 hrs on, lateral distance between the two airplanes became larger again.

At 2004 hrs, the Boeing 737 landed on runway 07 of Stuttgart Airport.

Metars:
EDDS 231950Z AUTO 30006KT CAVOK 12/09 Q1009 NOSIG=
EDDS 231920Z AUTO 29008KT CAVOK 12/09 Q1008 NOSIG=
EDDS 231850Z AUTO 33004KT 320V020 CAVOK 11/09 Q1007 NOSIG=
EDDS 231820Z AUTO VRB02KT CAVOK 12/09 Q1007 NOSIG=
EDDS 231750Z AUTO 05004KT CAVOK 11/08 Q1007 NOSIG=
EDDS 231720Z AUTO 06003KT CAVOK 11/08 Q1007 NOSIG=
EDDS 231650Z AUTO 08006KT CAVOK 11/09 Q1007 NOSIG=
EDDS 231620Z AUTO 09005KT 070V140 CAVOK 12/09 Q1007=
EDDS 231550Z AUTO 08006KT CAVOK 12/09 Q1008 NOSIG=
EDDS 231520Z AUTO 06006KT CAVOK 13/09 Q1008 NOSIG=
EDDS 231450Z AUTO 07006KT 9999 -RA NSC 13/09 Q1008 NOSIG=
EDDS 231420Z AUTO 07005KT CAVOK 13/10 Q1009 NOSIG=
EDDS 231350Z AUTO 07004KT CAVOK 13/10 Q1009 NOSIG=
EDDS 231320Z AUTO VRB01KT 9999 -DZ NSC 13/08 Q1010 NOSIG=