Lack of ATC coordination among probable causes for airprox incident in Indian airspace in May: AAIB

New Delhi: Lack of coordination due to increased workload and delayed action involving air traffic controllers at Muscat and Mumbai led to two aircraft coming closer than permitted separation in the Indian airspace on May 4, according to AAIB.

UAE-based Air Arabia's Airbus A320 (ABY405) and German cargo carrier AeroLogic's Boeing B777F (BOX622) were involved in an airprox incident or loss of permitted longitudinal separation between the two planes that happened at 2.30 am (IST) on May 4 while the aircraft were flying to Mumbai.

In its 23-page report, dated October 14, the Aircraft Accident Investigation Bureau (AAIB) said conflict alert was not generated at the OCC (Oceanic Control Centre) Mumbai despite the loss of separation.

"Review suggested that the Flight Plan (FPL) of aircraft BOX622 may not have been present in the system, although automation was reportedly functioning normally," it said.

AAIB noted that the transferring controller managed the Planner position while also imparting On-the-Job Training (OJT) while in Mumbai OCC (North), the coordinator was unavailable resulting in the controller having to attend hotline for exchanging estimates.

Also, the recordings of the Mumbai-Muscat hotline was not available.

The coordination failure wherein the transferring controller (Muscat control) missed climbing ABY405 to the coordinated level FL370 prior to transfer "due to increased workload" and the delayed action at the Mumbai OCC has been cited as a probable cause for the airprox incident.

AAIB mentioned the accepting controller was engaged in handling estimate coordination over the hotline in the absence of a dedicated coordinator, which led to reduced monitoring of the Controller's Work Position (CCWS) and hence a delayed response in resolving traffic.

Air Traffic Controllers (ATCs) in Muscat and Mumbai were 39 years old.

Among the safety recommendations, AAIB has asked the Airports Authority of India (AAI) to issue a Standard Operating Procedure (SOP) mandating the implementation of an alternate recording mechanism in cases where the primary recording system remains unserviceable for an extended period at an ATS (Air Traffic Service) facility.

"At Mumbai (ATC) the working position of the OSS (Operational Support Specialist) should be bifurcated to improve the handling of error queues. This arrangement should remain in effect until the current automation system is upgraded or replaced to minimise the generation of frequent error messages," the report said.

For the Oman's Air Navigation Services (ANS), AAIB has recommended that during periods of increased traffic complexity, all ATC positions should be adequately manned to ensure that the Executive Controller can focus solely on traffic management without distraction, thereby maintaining safety standards.

"To ensure safety, instructors must not be assigned dual roles during On-the Job Training (OJT), enabling them to focus solely on both training and the management of air traffic," it said.