Sun Express Germany B738 over Bulgaria on Aug 12th 2018, climb without clearance causes loss of separation
Last Update: September 8, 2020 / 17:45:15 GMT/Zulu time
Incident Facts
Date of incident
Aug 12, 2018
Classification
Incident
Airline
Sun Express Germany
Flight number
XG-3208
Departure
Burgas, Bulgaria
Destination
Frankfurt/Main, Germany
Aircraft Registration
D-ASXP
Aircraft Type
Boeing 737-800
ICAO Type Designator
B738
A Go2Sky Boeing 737-800 on behalf of Smartwings Slovakia, registration OM-GTF performing flight 6D-6129 from Antalya (Turkey) to Bratislava (Slovakia), was enroute at FL240 between waypoints ETUBA and NAVOD tracking ATS route T226 and did not want to change their flightlevel.
In preparation for the climb ATC instructed XG-3208 to turn left onto a heading 270. The crew however read back "Climb FL270", which was not picked up by ATC. The crew selected FL270 into their Selected Altitude, which was duely transmitted by Mode-S to the controller's desk, where a disagree message appeared between cleared and assigned altitude. The aircraft began to climb, about 15 seconds later the radar issued a short term conflict alert (STCA) between XG-3208 and 6D-6129 while XG-3208 was climbing through FL223.
In reaction to the STCA ATC instructed XG-3208 to descend back to FL220 immediately, 4 seconds later the crew read that instruction back. In the meantime the aircraft already climbed through FL236 at 2900 fpm. The separation reduced to 0 feet vertically and 2.6nm horizontally and the aircraft continued to climb reaching FL250 re-establishing vertical separation. ATC thus instructed XG-3208 to continue the climb to FL260.
6D-6129 complained: "We have a traffic very close to us, now 5 miles, I suppose. This was well below the minimum". ATC confirmed the minimum horizontal distance had been 2.5nm.
Both aircraft continued to their destinations without further incident.
On Sep 8th 2020 Bulgaria's AAIU released their final report concluding the probable causes of the serious incident were (EXE: executive radar controller, PLN: planning air traffic controller):
- Misunderstanding by the flight crew of SXD7BY of the ATC clearance issued by EXE air traffic controller, that lead to climb to FL 270 instead to turn left onto heading 270°
- EXE and PLN air traffic controller did not detect the discrepancy between the received readback and the issued instructions.
- EXE and PLN air traffic controller did not detect and interpret the deviation message in the track label of SXD7BY for the difference between the Selected Altitude downlinked Mode S parameter and the cleared flight level.
The AAIU reported there had been no imminent risk of a collision, neither crew received a TCAS traffic or resolution advisory.
The AAIU analysed:
The flight crew (XG-3208) reported that they are flying at FL200 and willing to climb. Initially, EXE ATCO issued climb instruction to FL220. At this point, if the EXE ATCO was issued the instruction for climbing to a higher FL (FL380 in accordance with the flight plan), a potential conflict with TVQ6129 will occur, flying on FL240 in parallel heading in a horizontal distance of less than 5 NM.
The EXE ATCO, after agreeing with the PLN ATCO, changed the plan to avoid potential conflict by issuing an instruction for turning left to heading 270° “SXD7BY turn left heading 270”. The flight crew wrongly repeated the instruction “Climb FL270, SXD7BY”. The EXE ATCO and PLN ATCO did not react to the wrongly repeated instruction by the flight crew, after that the aircraft started a climb.
Immediately after that, SATCAS visualized a deviation massage in the track label of SXD7BY for an existing difference between the CFL introduced by the ATCO and the SAL by flight crew, this was not noticed and for this reason, there was no reaction by EXE ATCO and PLN ATCO. After 21s, SATCAS generated a STCA between SXD7BY and TVQ6129. The EXE ATCO reacted to the alert and issued instructions to SXD7BY to avoid the conflict and avoid the separation infringement. It should be noted that ATCO had twice instructed the crew of SXD7BY to descent immediately to FL220, and once to fly on heading 270 for preserving the separation and the crew correctly replied but did not performed the instructions at all. The aircraft continued to climb, crossing FL236 with a vertical speed of 2900 ft/min and reached FL250. In view of the provided vertical separation between the two aircraft of 1000ft, the EXE ATCO correctly adjusted the instruction to SXD7BY to continue a climb to FL260.
In accordance with the third aspect of the possible inefficient implementation of procedures by ATCO when conducting radiotelephone communication, it could be concluded that the EXE ATCO and PLN ATCO did not correct the flight crew of SXD7BY for the wrongly understood instruction and did not detect and interpret the deviation massage in the track label of SXD7BY, thus creating conditions for a dangerous convergence.
Incident Facts
Date of incident
Aug 12, 2018
Classification
Incident
Airline
Sun Express Germany
Flight number
XG-3208
Departure
Burgas, Bulgaria
Destination
Frankfurt/Main, Germany
Aircraft Registration
D-ASXP
Aircraft Type
Boeing 737-800
ICAO Type Designator
B738
This article is published under license from Avherald.com. © of text by Avherald.com.
Article source
You can read 2 more free articles without a subscription.
Subscribe now and continue reading without any limits!
Read unlimited articles and receive our daily update briefing. Gain better insights into what is happening in commercial aviation safety.
Send tip
Support AeroInside by sending a small tip amount.
Related articles
Sun Express Germany B738 at Stuttgart on Jul 31st 2016, runway excursion on landing
A Sun Express Germany Boeing 737-800, registration D-ASXO performing flight XG-3264 from Varna (Bulgaria) to Stuttgart (Germany), landed on…
Sun Express B738 at Dusseldorf on Jul 16th 2018, flaps problem
A Sun Express Germany Boeing 737-800, registration D-ASXA performing flight XG-2830 from Fuerteventura,CI (Spain) to Dusseldorf (Germany) with 188…
Sun Express Germany B738 at Dusseldorf on May 17th 2012, sudden stop before hold short line injures two cabin crew
A Sun Express Germany Boeing 737-800, registration D-ASXH performing flight XG-1215 from Dusseldorf (Germany) to Bodrum Milas (Turkey), was taxiing…
Newest articles
Condor A320 near Lausanne on Apr 21st 2024, hydraulic problem
A Condor Airbus A320-200, registration D-AICA performing flight DE-1412 from Munich (Germany) to Fuerteventura,CI (Spain), was enroute at FL340 near…
United B763 near Providence on Apr 22nd 2024, suspected fuel leak
A United Boeing 767-300, registration N644UA performing flight UA-108 from Washington Dulles,DC (USA) to Munich (Germany), was enroute at FL330 about…
Subscribe today
Are you researching aviation incidents? Get access to AeroInside Insights, unlimited read access and receive the daily newsletter.
Pick your plan and subscribePartner
A new way to document and demonstrate airworthiness compliance and aircraft value. Find out more.
ELITE Simulation Solutions is a leading global provider of Flight Simulation Training Devices, IFR training software as well as flight controls and related services. Find out more.
Your regulation partner, specialists in aviation safety and compliance; providing training, auditing, and consultancy services. Find out more.
AeroInside Blog
Popular aircraft
Airbus A320Boeing 737-800
Boeing 737-800 MAX
Popular airlines
American AirlinesUnited
Delta
Air Canada
Lufthansa
British Airways