RAWALPINDI: The Iranian Civil Aviation Organisation (CAO), which investigated the July incident when two Pakistan International Airlines (PIA) planes flying over the Iranian territory narrowly escaped a mid-air collision, has found that one of the aircraft descended without Air Traffic Control (ATC) clearance.

Based on their findings, the Iranian authorities have suggested that the Pakistan Civil Aviation Authority (PCAA) take remedial action about the pilot’s “misunderstanding” for prevention of similar occurrences, according to a CAO report available with Dawn.

The matter was probed by the Aircraft Accident Investigation Board (AAIB) of Iran after the PIA had asked the Iranian aviation authorities to dig out facts behind the incident, allegedly caused by ‘wrong instructions’ by the [Iran] ATC to Peshawar-bound PK-286 that subsequently came in the way of Dubai-bound PK-211 flight.

On July 24, PIA flights PK-211 (Boeing 777), en route from Islamabad to Dubai, and another PK-286 (Airbus A320), flying from Doha to Peshawar, came dangerously close to each other, when their Traffic Collision Avoidance System (TCAS) — a system in the cockpit on all planes that automatically guides it by communicating with the TCAS of another aircraft — corrected their course. Sources said Captain Athar Haroon was flying the Boeing 777, while Captain Samiullah was flying Airbus A320.

Iranian incident report suggests remedial measures to prevent such a situation from occurring again

“Based on radar service within control area (airspace), the controller’s instructions and clearance for both traffics were correct, and the cause of TCAS/resolution advisory (RA) serious incident was the pilot’s misunderstanding, leading to mistakenly (PIA211) commence descent without receiving any clearance from Tehran [air traffic] controller,” the AAIB report stated about the cause.

In its report, the AAIB’s safety investigation panel concluded, “The flight PIA211 started to descend without ATC clearance. Details of the flight plan route for PIA211 were against Iran Traffic Orientation Scheme (TOS). Disclosure of the incident report details to public by Pakistan International Airlines spokesperson before issuing the Final Report was against international regulations.”

The report also issued safety recommendations to avert recurrence of such incidents. The Iranian authorities suggested the Pakistan CAA “take remedial action about pilot mistake based on the findings on the report for prevention of similar occurrences”. Simultaneously, it also wrote to the Iranian Airport and Air Navigation Company, “Even though the phraseology used by the controller was proper and correct, in order to prevent such an ambiguity or misunderstanding by pilots, it is recommended to make an inquiry from other States about similar and proper phraseology, for the purpose of substitution or amendment of current phraseology.”

The report recalled the on July 24, PIA’s flight PK-211 made a radio contact with Tehran air traffic controller, when it was identified by the Tehran radar controller. The pilot then requested the controller to advise any “level restriction at MOBET position, and the controller told him expect FL200 20 miles before PATAT, ‘report when ready for descent’. The granted message was acknowledged by the pilot accordingly”.

“Another flight, PIA286… on reciprocal track… was identified by the Tehran radar controller, and following the pilot’s request, this flight was instructed to proceed directly to NABOX waypoint. At 005107UTC, the controller instructed the PIA211 to proceed directly to PATAT waypoint and expect FL200, 20 [nautical miles] before PATAT and stand by for descent.

The pilot acknowledged the message correctly. At 005307UTC, the pilot of PIA286 declared TCAS/RA descending. Immediately, the controller told the PIA211, ‘You were told to stand by for descent’.

“At 005407 another flight on frequency told the PIA211 without expressing his call sign: ‘you were never given a clearance; you were told to call when ready’. At 005427UTC, the controller cleared PIA211 to descend FL200 and to maintain 20NM before PATAT waypoint. The message was acknowledged. [Later], PIA211 was handed over to the UAE radar... for further descent.

The report further said that on Jul 27, some parts of the above information were disclosed to social media by PIA.

Meanwhile, according to media reports, due to the alleged negligence of the Iranian ATC, which was said to have cleared the same altitude, the two planes came dangerously close to each other and averted a midair collision over Iranian territory near the UAE airspace.

A PIA spokesman was reported to have said: “The PIA is writing to Iranian ATC to investigate as it instructed the plane, but it was wrong.”

He had said the flight PK-211 was maintaining a 35,000-foot altitude when it came close to PK-268, which was flying at an altitude of 36,000 feet and was cleared to descend to 20,000 feet.

The descent would have come in the flight path of PK-211, the spokesman added. However, the aircraft’s TCAS corrected the course for both the planes and automatically guided them, he added.

A few days later, Iranian state media had reported the country it was investigating the claim of a near-miss in its airspace between the two passenger jets due to “human error” by air traffic controllers.

Published in Dawn, August 18th, 2022