Thai Smile A320 and Mann AT72 at Yangon on Dec 18th 2017, loss of separation on runway due to operational error

Last Update: June 26, 2018 / 16:21:24 GMT/Zulu time

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Incident Facts

Date of incident
Dec 18, 2017

Classification
Report

Flight number
TG-302

Aircraft Registration
HS-TXB

Aircraft Type
Airbus A320

ICAO Type Designator
A320

A Thai Smile Airlines Airbus A320-200, registration HS-TXB performing flight TG-302 from Yangon (Myanmar) to Bangkok (Thailand) with 51 passengers and 6 crew, was cleared to line up runway 21 and wait and had taxied into position.

A Mann Yadanarpone Airlines Avions de Transport Regional ATR-72-212A, registration XY-AJP performing flight 7Y-417 from Sittwe to Yangon (Myanmar) with 71 passengers and 4 crew, was on final ILS approach to Yangon's runway 21 about 7nm from touch down when TG-302 was cleared to line up runway 21.

About 50 seconds after TG-302 had taxied into position the crew advised ATC: "Thai Smile 302, standby for takeoff clearance.", the controller replied: ""Thai Smile 302, behind landing aircraft on final, line up and wait behind.", the crew reported: "We already line up runway-21, Thai smile 320."

Another controller stepped in and cleared TG-302 for takeoff, the crew commenced their takeoff roll while 7Y-417 continued for touchdown.

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

The breakdown in separation between the A320 (HS-TXB) and the ATR 72-600 (XY-AJP) was the result of the instruction given by the tower controller to the A320 (HS-TXB) "behind landing aircraft on final, line up and wait" when the A320 (HS-TXB) had already lined up and waited on runway-21 of the Yangon International Airport.

- ATC did not inform Aircraft Accident Investigation Bureau of Myanmar of the incident.

The AAIBM reported it was estimed the separation between the aircraft reduced to about 1.2nm horizontal and 50 feet vertical, the landing aircraft crossed the threshold runway 21 when the departing aircraft had not yet vacated the runway.

The AAIBM complained that the occurrence was not reported to them until Dec 29th 2017.

The AAIBM reported that tower and approach were staffed by trainee controllers supervised by senior controllers.

The senior controller monitoring tower reported the traffic was light, the weather was good, there was one outbound aircraft and one inbound aircraft at 7DME, she went for a coffee to the coffee bar just prior to the occurrence, she did not hear the conversation between trainee and the aircraft because the trainee used a head set.

The trainee tower controller reported that she had instructed TG-302 to line up runway 21 and wait but then forgot about the aircraft. When after her instruction to line up behind the landing traffic the crew reported they were already lined up she didn't know what to do, her supervising controller wasn't with her. One of the approach controllers stepped in and cleared TG-302 for takeoff to resolve the conflict.

The trainee approach controller was sitting side by side with the trainee tower controller, observed the A320 in position on the runway and cleared TG-302 for takeoff to resolve the developing conflict while instructing the arriving 7Y-417 to continue the approach.

The AAIBM analysed: "From the radar play-back, it was confirmed that another landing aircraft (MYP 417A) had crossed the runway threshold on its final approach before the preceding departing aircraft (THD 302) was clear of the runway-in-use. That was contrary to the control of arriving aircraft as per Clause 7.10 of ICAO Doc 4444 as well as control of arriving aircraft as per Manual of Air Traffic Service of Myanmar."

With respect to standard operating procedures for ATC the AAIBM analysed:

Control of Arriving Aircraft

Separation of landing aircraft and preceding landing and departing aircraft using the same runway.

A landing aircraft will not normally be permitted to cross the runway threshold on its final approach until the preceding departing aircraft has crossed the end of the runway-in-use, or has started a turn, or until all preceding landing aircraft are clear of the runway-in-use.

Runway Incursion or Obstructed Runway

In the event the aerodrome controller observes, after a take-off clearance or a landing clearance has been issued, any obstruction on the runway likely to impair the safety of an aircraft taking off or landing, such as a runway incursion by an aircraft or vehicle, or animals or flocks of birds on the runway, appropriate action shall be taken as follows:

a) cancel the take-off clearance for a departing aircraft;

b) instruct a landing aircraft to execute a go-around or missed approach;

c) in all cases inform the aircraft of the runway incursion or obstruction and its location in relation to the runway.

Note.- Animals and flocks of birds may constitute an obstruction with regard to runway operations. In addition, an aborted take-off or a go-around executed after touchdown may expose the aeroplane to the risk of overrunning the runway. Moreover, a low altitude missed approach may expose the aeroplane to the risk of a tail strike. Pilots may, therefore, have to exercise their judgement in accordance with Annex 2, 2.4, concerning the authority of the pilot-in-command of an aircraft.

Following any occurrence involving an obstruction on the runway or a runway incursion, pilots and controllers shall complete an air traffic incident report in accordance with the ICAO model air traffic incident report form.
Incident Facts

Date of incident
Dec 18, 2017

Classification
Report

Flight number
TG-302

Aircraft Registration
HS-TXB

Aircraft Type
Airbus A320

ICAO Type Designator
A320

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