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A333 / A319, en-route, east of Lashio Myanmar, 2017

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On 3 May 2017, an Airbus A330 and an Airbus A319 lost prescribed separation whilst tracking in opposite directions on a radar-controlled ATS route in eastern Myanmar close to the Chinese border. The Investigation found that the response of the A330 crew to a call for another aircraft went undetected and they descended to the same level as the A319 with the lost separation only being mitigated by intervention from the neighbouring Chinese ACC which was able to give the A319 an avoiding action turn. At the time of the conflict, the A330 had disappeared from the controlling ACCs radar.
Event Details
When May 2017
Actual or Potential
Event Type
Air-Ground Communication, Human Factors, Loss of Separation
Day/Night Day
Flight Conditions Not Recorded
Flight Details
Aircraft AIRBUS A-330-300
Operator Sichuan Airlines
Domicile China
Type of Flight Public Transport (Passenger)
Origin Chengdu
Intended Destination Dubai International Airport
Take off Commenced Yes
Flight Airborne Yes
Flight Completed Yes
Flight Phase Cruise
Flight Details
Aircraft AIRBUS A-319
Operator China Southern Airlines
Domicile China
Type of Flight Public Transport (Passenger)
Origin Kathmandu/Tribhuvan International Airport
Intended Destination Guangzhou Baiyun International Airport
Take off Commenced Yes
Flight Airborne Yes
Flight Completed Yes
Flight Phase Cruise
Location En-Route
Origin Chengdu
Destination Dubai International Airport
Approx. approximately 9nm from LINSO
Loading map...

Tag(s) Extra flight crew (no training),
Event reporting non compliant,
Delayed Accident/Incident Reporting
Tag(s) Call Sign Confusion,
Incorrect Readback missed
Tag(s) Procedural non compliance
Tag(s) Required Separation not maintained,
ATC Error
Damage or injury No
Causal Factor Group(s)
Group(s) Aircraft Operation,
Air Traffic Management
Safety Recommendation(s)
Group(s) Aircraft Operation,
Air Traffic Management
Investigation Type
Type Independent


On 3 May 2017, an Airbus A330-300 (B-5960) being operated by Sichuan Airlines on a scheduled international passenger flight from Chengdu to Dubai as CSC603 with 253 persons on board and an opposite direction Airbus A319 (B-6202) being operated by China Southern Airlines on a scheduled international passenger flight from Kathmandu to Guangzhou as CSN 6068 with 119 persons on board lost prescribed separation in daylight whilst passing each other on ATS route A599 in eastern Myanmar. The prevailing weather conditions were not recorded.

An AIP extract showing the cover of Mandalay Radar including ATS route A599 on which the conflict occurred. [Reproduced from the Official Report]


An Investigation was carried out by the Myanmar Accident/Incident Investigation Bureau (MAIB). Examination of data from the FDR and CVR of the two aircraft involved and the prevailing weather conditions were both recorded by the Investigation as "not applicable".

The 40 year-old A319 Captain had accumulated 15,752 total flying hours which included 10,688 hours on type and their 29 year-old First Officer had accumulated 6,174 total flying hours which included 2,091 hours on type. The total flying hours of the 48 year-old A330 Captain were not recorded but they included 5,448 hours whilst employed at Sichuan Airlines on the A320 made up of 1181 hours on the A320 and 4,267 hours on the A330. There were two First Officers on the A330 flight deck, the 28 year-old had accumulated 1,797 total flying hours made up of 807 hours on the A320 and 740 hours on the A330 and the 34 year-old had accumulated 2640 total flying hours made up of 1,229 hours on the A320 and 1,161 hours on the A330. The 34 year-old Controller and their 45 year-old Shift Manager were both working a 12 hour day shift which had 3¾ hours to run at the time of the investigated event and had 11 and 21 years work experience respectively.

It was established that the A330 had been transferred to Yangon ACC by Kunming ACC 8nm prior to the Chinese/Myanmar border at waypoint LINSO. When overhead this waypoint, the crew called Yangon ACC and advised that they were maintaining FL 360. A few seconds later, without acknowledging this initial call, the controller transmitted to another aircraft identified as "MJC" that they were identified and should report LSO and descend to FL350 as FL370 was not available due traffic. The A330 crew then responded to the call made to "MJC" without including their callsign but confirming the next reporting point and seeking confirmation of the descent instruction to which the controller replied "affirm descend FL 350" also without including the callsign and the A330 crew responded with "603, next report LSO and right now descend to FL 350". This was followed immediately by the Controller with "MJC, affirmative descend FL 350" to which the A330 crew responded to with "Descend to FL 350, next report position LSO thank you CSC 603".

The A330 began descent from FL 360 to FL 350, the level which the A319 was maintaining in accordance with its clearance. At this time, the radar display being used by the controller did not show the A330. About a minute later, a Predicated Conflict Alert (PCA) was annunciated on the Kunming ACC radar display showing that the A330 was descending to the level already occupied by the eastbound A319. The Kunming Controller "tried to coordinate with Yangon ACC" and meanwhile called (the A319) and told its crew to make an immediate right turning onto a heading of 125° to avoid the opposite A330 which resolved the conflict. As the two aircraft passed, the ADS-B data from the A330 appeared on the radar screen at Yangon ACC showing it at FL 352 as it passed within about 2.5 nm of the A319 at FL 350 which was in the instructed right turn and passing through 101°. Thirty seconds later, the radar track of the A330 reappeared on the Yangon radar display showing that the A330 was now climbing through FL 357 and the A319 was still in the right turn.

The Investigation found that although the radar controller involved had been working in the Yangon ACC for "about four years", he had never completed the ACC radar course which meant that he was "unlicensed" in respect of the applicable regulatory requirements. It was noted that neither he nor the A330 crew had conducted their RTF communications in accordance with the procedures for use of callsigns. The A330 crew had failed to listen out with sufficient care and the controller had failed in the same way to listen carefully to readbacks and challenge any that were incomplete or incorrect.

The formally-documented Findings of the Investigation included a description of the RTF communications performance of both the duty controller and the A330 crew as "careless" in respect of both their transmissions and their listening, especially in respect of callsigns. In addition, it was found and that the Yangon ACC radar coverage of A599 in the area where the conflict had occurred was "not good enough" and it was noted that the event under investigation had not been reported to the MAIB by either the A330 pilots or the duty controller who had been the direct cause of it.

The Primary Cause of the conflict was formally documented as "the duty air traffic controller and the pilot from (the A330) listened carelessly to their conversation in their radio communication especially not concentrating on the aircraft Call Sign".

A Contributory Factor was also identified as follows:

  • The radar coverage on air route A599 between LSO and LINSO was intermittently not working properly and not good enough for radar operation around the time of occurrence.

A total of 5 Safety Recommendations were made as a result of this Investigation as follows:

  • that Duty Air Traffic Controllers should be more careful to and concentrate on the read back of pilots and then acknowledge by using standard radio telephony procedures.
  • that Pilots should listen more carefully to and concentrate on the call sign of their own aircraft and follow the ATC instructions accordingly (when in doubt ask again) by using standard radio telephony procedures.
  • that Radar Coverage on ATS Route A599 between LSO and LINSO should be upgraded and enhanced.
  • that the Duty Controller Involved should be sent on an Area Control Surveillance Training Course.
  • that Air Traffic Controllers and Pilots should send notification of accidents and incidents to the Myanmar Accident Investigation Bureau with minimum delay and using the most suitable and quickest means available.

The Final Report of the Investigation was released on 8 September 2017. It did not make any mention of TCAS 2 in respect of either of the aircraft involved.

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