In December 2019, Bengaluru’s Kempegowda International Airport (KIA), as per a media release from its owner BIAL, became the first airport in the country to operate independent parallel runways that enable aircraft to land or take-off simultaneously on both runways.

The Airports Authority of India (AAI) informed its stakeholders (airlines, air navigation service providers, the airline regulator, etc) of this through an aeronautical information regulation and control aeronautical information publication supplement dated October 10, 2019, regarding the commissioning of a new runway, south of the existing runway, with the two runways being given the nomenclature RWY 09L/27R and RWY 09R/27L.

Even today, KIA has the singular distinction of being the only airport South of the Vindhyas to operate parallel runways. On the morning of January 7, however, a near dangerous scenario played out involving the same parallel runways. Two Airbus A 320 IndiGo aircraft — 6E 455 departing for Kolkata and flight 6E 246 for Bhubaneswar — were cleared for take-off almost simultaneously. Even as they were airborne, both aircraft flew dangerously close to each other with a high risk of a ‘breach of separation’, potentially risking a mid-air collision and jeopardising the lives of around 430 passengers and crew.

A ‘breach of separation’ occurs when two aircraft traverse the minimum mandatory vertical or horizontal distance in an airspace envelope. What saved the day was the alertness of an approach radar controller who, on noticing the trajectory or flight path proximity of the two commercial aircraft and the fact that they were headed nearly towards each other, alerted the aircrew who were until then operating their respective aircraft unaware of the impending danger. The two Airbus A320s pilots were directed to quickly change course; flight 6E 455 was asked to swerve to left and flight 6E 246 was asked to swerve right, thereby avoiding what could have been a catastrophe.

‘Overly hyped’ incident

While the Directorate General of Civil Aviation (DGCA) told this correspondent that the DGCA was investigating the incident and would “take the strictest action against those found delinquent,” it brings to question whether airports across the country are equipped to handle such emergencies. Airports with parallel runways are not a novelty, though there may not be many in the country.

Some senior pilots that BusinessLine spoke to, however, played down the incident. A senior IndiGo pilot said, “The incident has been overly hyped up. There is a fairly large lateral separation between both runways. The standard operating procedure at Bengaluru airport requires pilots to change over to the radar frequency soon after take-off and radar control is exercised. (This was) a relatively small SOP lapse with no serious consequences.”

Pilots also averred that the traffic alert and collision avoidance system (TCAS), would have been activated and there was no need to unnecessarily panic over the incident. But at low altitude, the TCAS has limitations; it cannot, for example, tell a pilot to descend or pitch down. As aviation expert Capt Mohan Ranganathan said, “The TCAS doesn’t want to disturb the pilot at say 500 feet when he /she is still engaged in stabilising the aircraft after take-off.”

Safety procedures

Capt Amit Singh, pilot and expert/consultant on airline safety, said, “Technically, the airport doesn’t have an independent parallel runway mode and works on either a segregated model (2 runways) with one runway used for landing and the other for departure, or a simple single runway mode.”

“The airport is in proximity to Yelahanka airport to the south, which is a defence airport. The new runway was built to the south of the existing runway, which placed it even closer to Yelahanka and its airspace. The design requirements of parallel runways require aircraft departing from the southern runway to turn right by 45 degrees whereas those departing simultaneously from the northern runway can fly straight out. This assures that the two aircraft have diverging flight paths soon after take-off.

“Kempegowda International Airport cannot allow a right turn after take-off from the southern runway since it would transgress Yelahanka Airspace. So, a left turn has been promulgated with a restriction on simultaneous departures from the two runways. When you have a non-standard instrument departure that converges (flights paths), you cannot release both aircraft simultaneously. The use of a segregated mode or the single mode, and standard operating procedures (SOPs) on implementing these modes of operation, are designed to mitigate just this risk. The SOP is the safety barrier,” he said.

The question is what happens if the SOP fails as it did in this incident.

The safety risk assessment is a continuous process that has a feedback loop. An SOP cannot last a lifetime and needs to be reviewed with a fresh pair of eyes each time.

Published on January 24, 2022