Flydubai B738 and El Al B738 near Kiev on Jun 13th 2018, many ATC spoil the separation, TCAS at the rescue

Last Update: June 18, 2019 / 14:39:13 GMT/Zulu time

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Incident Facts

Date of incident
Jun 13, 2018

Classification
Report

Airline
Flydubai

Flight number
FZ-727

Aircraft Registration
A6-FES

Aircraft Type
Boeing 737-800

ICAO Type Designator
B738

A Flydubai Boeing 737-800, registration A6-FES performing flight FZ-727 (callsign FDB15Z) from Dubai (United Arab Emirates) to Kiev Zhulyany (Ukraine), was descending through about FL277 towards Kiev cleared to descend to FL160 while entering Kiev's control zone BV2.

An El Al Boeing 737-800, registration 4X-EKO performing flight LY-2652 from Kiev Boryspil (Ukraine) to Tel Aviv (Israel), was climbing through about 9000 feet and was cleared to climb to FL350 by Kiev control BV2.

The two aircraft were on a head to head heading, separation was lost when several ATC controllers attempted to issue instructions to BV2 of how to salvage the separation and TCAS subsequently issued resolution advisories to both flight crews when the aircraft were both descending through FL210 at a horizontal distance of 4.2nm, the 1000 feet vertical separation was restored when the horizontal separation had reduced to 1.3nm. After being clear of conflict both aircraft continued to their destinations.

Israel's AIAI released their final report in Hebrew (editorial note: based on the English report by Ukraine's NBAAI, which was attempted to be attached to the PDF file however, was not included in that PDF and so far was not released on NBAAI's website. To serve the purpose of global prevention of the repeat of causes leading to an occurrence an additional timely release of all occurrence reports in the only world spanning aviation language English would be necessary, a Hebrew only release does not achieve this purpose as set by ICAO annex 13 and just forces many aviators to waste much more time and effort each in trying to understand the circumstances leading to the occurrence, in particular as no reasonable translation software is available and the use of native Hebrew translators is almost needed to make sense of the report. Aviators operating internationally are required to read/speak English besides their local language, investigators need to be able to read/write/speak English to communicate with their counterparts all around the globe)

The report concluded the probable causes of the serious incident were:

The Major Incident Cause (violation of the horizontal and vertical separation minima that led to TCAS RA operation and aircraft maneuvers according to recommendations of the traffic alert and collision avoidance systems) became coincidence of the following factors:

- control instructions on the continuous climb and descent with no sufficient air picture analysis and aircraft trajectory monitoring after alignment of routes of two head-on aircraft;

- transfer of responsibility for FDB 15Z aircraft control from TMA Kyiv BVO to TMA Kyiv BV2 at the level different from the agreed 11700 ft level;

- wrong decision on the method for resolution of the potentially conflict situation between two head-on aircraft by increasing the vertical speed ofFDB 15Z aircraft;

- non-performance by the FDB 15Z aircraft pilot of the controller's instructions on maintaining the vertical speed of descent and termination of descent on FL220.

- ATC instructor's insufficient control of the trainee controller's actions and failure to provide him with the correct decision for the conflict situation resolution;

Concurrent Factors:

failure to use the AATCS technical capabilities for analysis of the conflict situation between the aircraft;

- FDB 15Z aircraft crew's failure to report of impossibility to stop on the FL220.

The AIAI/NBAAI reported the horizontal separation at the time both aircraft were at FL210 was 4.2nm, by the time 1000 feet vertical separation was re-established the horizontal distance had reduced to 1.3nm.

The AIAI/NBAAI reported Kiev control zone BV2 was staffed by a trainee controller to be checked out for Kiev ACC services at the control desk and an instructor at the planner's desk. About two minutes prior to the hand off of Fly Dubai to BV2 the controller of the adjacent sector began coordinating with BV2. The trainee recognized a potential conflict between the arriving and departing flights and thus instructed the adjacent controller at Kiev BVO sector to hand the aircraft off at the sector boundary already at FL160.

The AIAI/NBAAI analysed:

The BVO controller cleared FZ-727 to descend to FL160, however, did not instruct the flight to be level at FL160 at the sector boundary. As result the crew performed a relatively shallow descent at about 1000 fpm and crossed the sector boundary at FL277.

About 6 minutes after BVO cleared FZ-727 to descend to FL160 flight LY-2562 reported on BV2 frequency climbing through 4300 feet and being cleared to climb to 9000 feet. The trainee controller identified the aircraft and cleared them to climb to FL270. The NBAAI wrote: "The instruction to climb to FL270 would not have created the potentially conflict situation between two aircraft in case of performance of the conditions, which had been agreed between controllers of TMA Kyiv BVO and BV2 on descent of FDB 15Z aircraft down to FL160 for the boundary of acceptance-and-transfer of the responsibility for control between the TMAs." The El Al crew requested to climb to FL350 and was cleared to climb to FL350.

About 22 seconds after the trainee cleared LY-2562 to climb to FL350, the crew of FZ-727 reported on frequency descending through FL277 to FL160. The NBAAI wrote: "The air picture, which developed, indicates that neither the controller of TMA Kyiv BVO, nor the controller of TMA Kyiv BV2 conducted monitoring of the FDB 15Z aircraft movement with use of surveillance systems." and subsequently added: "The very fact that the TMA Kyiv BVO controller did not meet the condition of TMA Kyiv BV2 and handed over the control of FDB 15Z aircraft at the level of FL277, instead of FL160, has created conditions for emergence of the potentially conflict situation, which required resolution. Two aircraft moved on head-on crossing tracks, and the vertical distance between them was being reducing."

The trainee identified FZ-727 and cleared the flight to descend to FL120. The NBAAI wrote: "Existence of the potentially conflict situation was not detected neither by the trainee controller, nor ATC instructor for two and a half minutes." Then the trainee detected the potential conflict, LY-2562 was climbing through FL164 and FZ-727 descending through FL254, the horizontal distance between the two aircraft was 33.1nm at that point. The trainee consulted with the instructor, then instructed the Flydubai to increase their descent to 2000fpm or greater. The NBAAI annotated: "The controllers' decision to apply the continuous climb (descent) to two head-on aircraft contradicted to the instruction of the ACC flight operations director, which was given at the briefing of the duty shift (see the scheme of step-by-step development of near-collision threat.)"

According to radar data FZ-727 did not increase their descent and still descended at about 1000 fpm average over the next almost 60 seconds, the trainee then instructed FZ-727 to increase their descent to at least 2500 fpm and provided traffic information about the head on aircraft, now at 17nm horizontal distance. The trainee did not provide traffic information to LY-2562 which was in violation of the ATC handbook requiring traffic information to both aircraft involved in a potential conflict situation.

Flight FZ-727 gradually increased their descent to 2500fpm over the next 10 seconds and above, 42 seconds after the instruction to increase descent to 2500fpm the aircraft was descending at 3900 fpm.

The short term collision alert activated at the ATC facilities alerting trainee, instructor, senior shift controller and supervisors (ACC flight operations director), which provided for a reaction time of about 120 seconds before loss of separation, in this particular case the reaction time was 68 seconds. The NBAAI wrote: "According to the ground recorders data, the STCA function operated 68 seconds prior to the violation of the established separation distances, which was sufficient for resolution of the potentially conflict situation." The shift controller recommended to turn both aircraft, after consulting with his instructor the trainee instructed FZ-727 to turn right onto a heading of 090 degrees. In the meantime the supervisor instructed BV2 to stop the climbing aircraft at FL210 and the descending aircraft at FL220.

The trainee relayed the instruction to FZ-727 to stop the descent at FL220, the crew read the instruction back. The aircraft was descending through FL220 at that very moment at a rate of descent in excess of 3900 fpm, the crew did not report they were just descending through FL220 at high rate and could not stop the descent at FL220 anymore however.

The trainee instructed LY-2562 to stop their climb at FL210, the crew read back the instruction and stopped the climb at FL210.

In interviews with the investigation the pilots of FZ-727 reported that upon receiving the instruction to stop descent at FL220 they pressed ALT HOLD immediately, however, the autopilot could not level off at FL220, the aircraft crossed FL215. The NBAAI wrote: "Having crossed FL220, at 10:50:09, the pilot requested clearance to turn to the right. The crew did not report to the controller about crossing FL220 and impossibility to follow the instruction (clearance) of the controller, as defined by paragraph 12.3.1.2 ICAO Doc 4444."

The NBAAI continued: "In the circumstances occurred, the instruction of the flight operations director to stop the aircraft on adjacent flight levels was late and not effective. FDB 15Z aircraft was in such configuration, when it could not any more follow timely the control instruction and stop on FL220. The vertical speed of descent of FDB 15Z aircraft decreased slowly. During crossing FL212, the FDB 15Z TCAS RA system operated with the recommendation to descend. The pilot fulfilled the TCAS recommendation."

Flight LY-2562 received a TCAS resolution advisory to climb and crossed FL210 at a climb rate of 1800 fpm, at the same time FZ-727 crossed through FL210 at a sink rate of 1400 fpm, the horizontal distance between the aircraft was 4.2nm at that point. 18 seconds later 1000 feet vertical separation was restored between the aircraft at a horizontal distance of 1.3nm. The headings of both aircraft did not change.

Both aircraft continued to their destinations without further incident.

The investigation released numerous safety recommendations to Ukraine's ATC provider as well as Ukraine's Civil Aviation Authority and also released one safety recommendation to Flydubai: "Focus on FDB 15Z crew's failure to carry out the controller instructions on maintenance of the vertical speed of descent and FL220 maintenance. In case of impossibility to carry out a controller instruction, a crew should report to the controller with the ICAO Doc 4444 specified phraseology, using the word "UNABLE" with indication of the cause."
Incident Facts

Date of incident
Jun 13, 2018

Classification
Report

Airline
Flydubai

Flight number
FZ-727

Aircraft Registration
A6-FES

Aircraft Type
Boeing 737-800

ICAO Type Designator
B738

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