Sichuan A333 and China Southern A319 over Myanmar on May 3rd 2017, loss of separation enroute

Last Update: November 2, 2017 / 19:45:50 GMT/Zulu time

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Incident Facts

Date of incident
May 3, 2017

Classification
Incident

Airline
Sichuan Airlines

Flight number
3U-603

Departure
Chengdu, China

Destination
Dubai, United Arab Emirates

Aircraft Registration
B-5960

Aircraft Type
Airbus A330-300

ICAO Type Designator
A333

A Sichuan Airlines Airbus A330-300, registration B-5960 performing flight 3U-603 from Chengdu (China) to Dubai (United Arab Emirates) with 239 passengers and 14 crew, had been enroute at 11,000 meters (FL361) within China and descended to FL350 upon entering Myanmar's Airspace.

A China Southern Airbus A319-100, registration B-6202 performing flight CZ-6068 from Katmandu (Nepal) to Guangzhou (China) with 109 passengers and 10 crew, was enroute at FL350 about to enter Chinese Airspace from Myanmar and about 25nm from 3U-603 when 3U-603 began the descent to FL350.

Myanmar's Accident Investigation Board (AIB) reported that CZ-6068 needed to be immediately turned right onto a heading of 125 degrees in order to avoid the aircraft in opposite direction being handed off from Kunming Area Control Center (China). The occurrence was rated a serious incident and is being investigated by Myanmar's AIB.

Myanmar's Aircraft Investigation Bureau (MAIB) released their final report concluding the probable causes of the serious incident were:

Primary Cause

The duty air traffic controller and the pilot from CSC 603 listened carelessly to their conversation in their radio communication especially not concentrating on aircraft Call Sign.

Contributing Factors

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

The MAIB reported the eastbound A319 was handed off at FL350 from Myanmar's Yangon ACC to China's Kunming ACC while still inside Myanmar Airspace and established contact with Kunming ACC. About 3 minutes later Kunming ACC handed the A333 off to Yangon ACC at FL360 and established contact with Yangon ACC. Yangon ACC, after contact was established, told another aircraft that their requested FL370 was not available and they needed to descend to FL350, instructing that other flight to descend to FL350. However, the A333 mistook the instruction for them, acknowledged the instruction without the controller noticing the wrong aircraft was reading back and descended.

The MAIB reported the critical sequence of events:

08:38:26 (TC), CSN 6068 first contacted Kunming ACC on 125.75 MHz before LINSO, So the Kunming ACC controller instructed CSN 6068 to report over LINSO.
08:41:55 (UTC) CSC 603 maintaining FL 360 was transferred to Yangon ACC on 126.75 MHz at 15 KM east of LINSO.
08:42:05 (UTC) CSC 603 first contacted Yangon ACC maintaining FL 360 position at over LINSO.
08:42: 12 (UTC) the Controller of Yangon ACC contacted another aircraft MJC 683 saying "MJC 683, Identified, report LSO, level 370 is not available due traffic, descend FL 350"
08:42:25(UTC) CSC 603 read back, "next report LSO, confirm descend to 350"
08:42:29(UTC) the controller of Yangon ACC, acknowledged the read back, "Affirm descend FL350"
08:42:38(UTC) read back again,"603,next report report LSO and right now descend to FL350"
08:42:45(UTC) the Controller of Yangon ACC instructed "MJC, affirmative descend FL350"
08:42:53(UTC) CSC 603 read back, "Descend to Fl 350, next report position LSO thank you CSC 603"
08:43:15(UTC) CSC 603 commenced descending when passing LINSO, at that time the separation between both aircraft was 66KM.
08:43:56(UTC) there was Predicated Conflict Alert (PCA) on the Kunming ACC radar display, showed CSC 603 was descending with the distance 46Km to CSN 6068. The controller of Kunming ACC tried to coordinated with Yangon ACC, meanwhile, called CSN 6068 to make an immediate right turning on course 125 degree to avoid the opposite CSC 603.

The MAIB analysed with respect to the ATC controller: "Even though Licensing system is being executed for international operation as per Myanmar Civil Aviation Requirements, he was unlicensed. In the conversation between ATC controller and CSC 603 as per ATC record, he occasionally did not follow strictly the radio telephony procedures and acknowledged the readback from CSC 603 pilots without carefully listening to."

With respect to radar coverage the MAIB analysed: "The radar coverage of air route A 599 between LSO and LINSO was insufficient and did not work properly for that purpose of radar operation as per radar readback. According to the witness statements there has been such deficiencies for long time. Around the time of occurrence CSC 603 could not be seen because of lack of radar coverage."