Mumbai airport glitch: AAI says ATC official, Air India pilot at fault

A grab from the viral video showing the two aircraft on the same runway. PIC/X

The Airports Authority of India (AAI) has issued a circular regarding the glitch on the Mumbai airport runway stating that a preliminary investigation suggests a violation of rules. AAI began its investigation after a viral video from Mumbai airport showed an IndiGo aircraft landing just seconds after an Air India Airbus A320 lifted off the runway. Both aircraft had just 509 metres of separation. The preliminary investigation suggests that the Air India pilot and the ATC operator are at fault as the former spent a longer duration on the runway than he was supposed to.

ATC, Air India pilot at fault

"The ATC official involved in the incident violated the SOP for time-based spacing between arrivals at Mumbai airport," a senior AAI official said. "According to the listed SOPs, in the recent incident, the Air India A320 took longer to depart. In this scenario, the ATC should have cancelled the departure and instructed the arriving IndiGo aircraft to execute a go-around and come back again for landing. On investigation, it was found that the separation between the two aircraft was just 509 metres and could have caused a catastrophic outcome had the Air India pilot rejected take off," the official disclosed.

Violation of ATC procedure

The AAI has reissued a directive urging the ATC officials at Mumbai airport to follow the standard operating procedures (SOPs) to ensure proper spacing between departing and arriving traffic. Explaining the methods of separation used by ATC, the senior AAI official said, "ATC operators use majorly two methods to ensure separation between aircraft. At non-busy airports, they use distance-based separation, while at busy airports time-based separation is utilised. At Mumbai airport, controllers often use the time-based separation method."

According to the official, using the time-based method, aircraft are separated based on time intervals rather than any established physical distance. "ATC operators calculate the time required for one aircraft to safely follow another, considering factors such as speed and performance, characteristics of the aircraft. This method allows them to accommodate more traffic at busy airports," the official said, adding that Mumbai is the busiest single-runway-equipped airport in Asia.

Provisions in new circular

"In 2023, AAI issued an SOP, which listed all the norms and procedures for time-based separation. The duration it takes for an aircraft to descend and pass the runway threshold is a variable figure and can be influenced by various factors like wind directions and aircraft speed. While ensuring separation through this method, the ATC involved needs to make decisions in a split second and issue instructions to aircraft, if either departing or arriving traffic makes a mess," said another senior AAI official.

The circular, whose copy was obtained by mid-day, states: "In case the mentioned SOP for time-based separation is breached, controllers are instructed to halt departures and instruct arriving aircraft to execute a go-around. Utmost precaution should be exercised in doing so." Earlier, the DGCA had de-rostered the ATC official involved in the incident, pending the outcome of the investigation.