History of the Flight
On 29 November 2017, PIA flight 313, an Airbus A320 registration AP-BLV, was operating from Allama Iqbal International Airport, Lahore to Jinnah International Airport, Karachi on ATS route J112. Airblue flight ABQ 200, an Airbus A321 registration AP-BMW, was operating from Jinnah International Airport, Karachi to Benazir Bhutto International Airport, Islamabad.
At 02:52:27 UTC, PIA 313, maintaining FL340, contacted Karachi Area Control East (Radar Controller) and was cleared for the NAWABSHAH 2A STAR and informed to expect radar vectors for an ILS approach to Runway 25L at Karachi. At 02:53:24, ABQ 200, flying parallel to the ATS route, contacted the same controller, reporting climbing to FL310 and later stating FL350 as its final level. At 02:54:00, ATC cleared ABQ 200 to climb to FL350.
Sequence of Events
ATC shift changeover occurred at 03:00:00. The outgoing shift briefed the incoming controller. As both aircraft were on parallel tracks and no immediate action was required, the morning Radar Controller handed over traffic to the Procedure Controller due to a faulty headset.
At 03:08:03, when the aircraft were 10.89 NM apart on parallel tracks, the ATM system displayed a Short Term Conflict Alert (STCA). Realizing the conflict, ATC Karachi asked ABQ 200 to report heading to initiate radar vectors at 03:08:10. ABQ 200 replied reporting a TCAS Resolution Advisory (RA).
At 03:08:11, radar data showed ABQ 200 climbing through FL333, PIA 313 maintaining FL340, with lateral separation of 8.65 NM. At 03:08:20, ABQ 200 reported TCAS RA while passing FL335, with PIA 313 approximately 6.5 NM apart. At 03:08:23, ATC passed traffic information to PIA 313, which replied that the traffic was visual.
ABQ 200 then descended; at 03:08:31 it was passing FL334 descending, with lateral separation of 4.88 NM. At 03:08:46, ABQ 200 was maintaining FL334, PIA 313 maintaining FL340, lateral separation 4.33 NM. The minimum vertical separation was 500 ft, and lateral separation was 5.66 NM at that time.
Injuries and Damage
No damage to the aircraft or injuries to passengers or crew of either flight were reported.
Causes / Contributing Factors
The investigation stated that the TCAS RA alert might be erroneous; however, the incident may be considered a loss of separation due to lack of situational awareness on the part of Air Traffic Control.