PIA B772 and Emirates B773 near Karachi on Jan 7th 2020, loss of separation

Last Update: August 4, 2020 / 17:37:59 GMT/Zulu time

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Incident Facts

Date of incident
Jan 7, 2020

Classification
Incident

Flight number
PK-301

Aircraft Registration
AP-BGY

Aircraft Type
Boeing 777-200

ICAO Type Designator
B772

A PIA Pakistan International Airlines Boeing 777-200, registration AP-BGY performing flight PK-301 from Islamabad to Karachi (Pakistan) with 309 passengers and 12 crew, had been enroute at FL400, reached the top of descent into Karachi about 140nm northeast of Karachi and was in the initial descent.

An Emirates Boeing 777-300, registration A6-EPS performing flight EK-516 from Dubai (United Arab Emirates) to Delhi (India) with 355 passengers and 17 crew, was enroute at FL350 about 50nm northeast of Karachi tracking into a northeasterly heading.

About 90nm northeast of Karachi the Emirates Boeing received a TCAS resolution advisory to descend due to the PIA Boeing descending at high sink rate, the Emirates crew complied with the advisory, the PIA Boeing received a TCAS resolution advisory to reduce rate of descent about 110nm northeast of Karachi. The PIA Boeing continued to descend, descended to below FL360 about 106nm northeast of Karachi. According to ADS-B data the horizontal separation reduced to about 1nm at about 07:48:50Z while due to TCAS activations and compliance with the resolution advisories the vertical separation was kept at about 1000 feet. About 106m northeast of Karachi, about 45 seconds after point of closest approximation, the Emirates had returned to FL350, the PIA Boeing was descending through FL353, the horizontal separation between the aircraft had increased to 13nm again.

Pakistan's CAA reported a near collision occurred and suspended three air traffic controllers involved into the occurrence. An investigation has been opened.

On Aug 4th 2020 the CAA released their final report concluding the probable causes of the serious incident were:

Lack of situational awareness on part of Duty Air Traffic Controller (Area Radar Controller East) who while issuing descent clearance to PIA301 (From FL400 to FL180), keeping in mind another reciprocal traffic (PIA588 maintaining FL170) missed out another reciprocal traffic UAE516 (maintaining FL350). Upon activation of STCA (Violation Phase), his evasive maneuver was too late.

Contributing factors were:

Lack of coordination / assistance on the part of Duty Air Traffic Controller (Area Procedure Controller East) for not been able to anticipate the traffic conflict, contributed to the occurrence. Furthermore he missed the Flight Plan Alert and did not act upon the alert.

STCA (Violation Phase) activated directly, without giving any prediction / anticipation of conflict. The STCA (Prediction Phase) did not activate because of the parameters set by the user and deprived the controller a safety feature provided in the system of anticipation of conflict.

The CAA reported flight PK-301 had been cleared to descend to FL180 on pilots discretion, however, without requesting the crew to report leaving FL400. PK-301 left FL400 some time later.

According to radar data the minimum vertical separation was reached at about 400 feet vertical and 6.9nm horizontal separation. TCAS RAs to climb activated in PK-301 and to descend in EK-516. EK-516 descended to FL347 while PK-301 climbed up to FL369. A vertical separation of 1000 feet was re-established when both aircraft were about 4.1nm apart. The aircraft crossed each other with a minimum horizontal separation of 2.7nm with EK-516 at FL348 and PK-301 at FL369.

The CAA analysed:

PIA301 was operating from Islamabad to Karachi and came in contact with ATC Karachi (Area Radar Controller East) short of NH (Nawabshah). PIA301 was maintaining FL400. The aircraft was given Air Traffic Control clearance and asked to report ready for descend.

UAE516 was operating from Dubai to Delhi and came in contact with ATC Karachi (Area Radar Controller East) South West of Karachi maintaining FL350 and was proceeding direct to waypoint “BADUL”.

ATC Karachi instructed PIA301 “when ready descend to FL180”, same was acknowledged by PIA301. Area Radar Controller East instructions were contrary to the instructions contained in SATI.

For such descend clearance, the Area Radar Controller East and the Area Procedure Controller East were required to coordinate first. This prior descend coordination was not done for PIA301.

Flight plan alert was instantly generated when the current FPL of PIA301 was modified by Area Radar Controller East for descend to FL180. However the same was missed by Area Procedure Controller East, and he did not acted upon the alert.

After approximately 04 minutes later PIA301 started descend to FL180 and did not informed ATC Karachi of leaving FL400. At this moment UAE516 was maintaining FL350 and approx 70NM reciprocal to PIA301.

After 03 minutes 14 seconds of vacating FL400, PIA301 was passing FL359Ð. At that time the reciprocal traffic ie UAE516 was 15NM, and was still maintaining FL350.

The STCA (Violation Phase) generated at 07:47:52 UTC, whereas no STCA (Prediction Phase) was activated by the system.

As the configuration of ATM database for activation of STCA was set at horizontal distance of 17 NM when the vertical separation is less than or equals to 800 feet, the Prediction Phase alert was not generated. Subsequently STCA violation alert activated directly, without giving any prediction / anticipation of conflict. The prediction alert did not activate because of the parameters set by the user.

Area Radar Controller East once realizing the confliction between both aircraft (PIA301 passing FL355Ð for FL180 and UAE516 maintaining FL350 and approximately 09NM apart) initiated evasive maneuver by instructing UAE516 to turn left by 10 degrees for spacing. At this point both aircraft were 08-09NM reciprocal to each other. No traffic information was given with evasive action.

Both aircraft informed ATC Karachi that they have received TCAS – RA and initiated avoidance action. PIA301 stopped descend at FL354 and initiated climb whereas UAE516 started descend from FL350 due to TCAS – RA. At the time of minimum vertical separation of 400 ft, both aircraft (PIA301 & UAE516) were 06.91NM laterally separated. They crossed each other (lateral separation 0.54 NM) with a vertical separation of 1800ft as both had initiated TCAS – RA climb and descend respectively.

Duty Air Traffic Controller (Area Radar Controller East) while giving descend clearance to PIA301 from FL400, missed the reciprocal traffic UAE516 maintaining FL350.Duty Controller initiated evasive maneuver as soon as he realized that both the aircraft are getting close to each other, but it was little late, and could not be complied because of TCAS – RA.

Duty Air Traffic Controller (Area Procedure Controller East) was supervising a student. He too overlooked the conflict. Furthermore he also did not acted upon the activation of FPL Alert.
Incident Facts

Date of incident
Jan 7, 2020

Classification
Incident

Flight number
PK-301

Aircraft Registration
AP-BGY

Aircraft Type
Boeing 777-200

ICAO Type Designator
B772

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