What happened
On 7 January 2022, two IndiGo Airbus A320 aircraft, VT-ITD and VT-ISV, were involved in a serious airprox incident near Kempegowda International Airport, Bengaluru. At the time, air traffic control was transitioning from segregated parallel operations—where one runway is used for arrivals and the other for departures—to single runway operations.
During this transition, both aircraft were cleared for takeoff simultaneously from parallel runways 09L and 09R. The flight paths for the two departures were designed to merge at a specific waypoint. As the aircraft climbed, the Approach Departure controller identified a potential conflict and issued immediate heading changes to both crews. Despite the intervention, the separation between the two aircraft dropped to approximately 0.9 NM horizontally and 100 feet vertically, significantly below the required 3 NM horizontal and 1000 feet vertical separation standards.
The investigation
An investigation by the AAIB examined radar recordings, radio communications, and flight data from both aircraft. The inquiry established that the simultaneous departures from the two runways had not been approved by the DGCA. Investigators found that the controllers in the tower were communicating on different frequencies, which prevented the flight crews from having situational awareness regarding the other aircraft. Furthermore, the investigation revealed that the Short-Term Conflict Warning (STCA) system had been inhibited at lower altitudes to prevent frequent nuisance alerts, meaning the automated system did not trigger a warning during the encounter.
Findings
- The primary cause was that ATC allowed simultaneous departures from two parallel instrument runways that were not authorized for such operations at this airport.
- The existing Standard Instrument Departure (SID) designs were unsuitable for managing the risks associated with simultaneous departures from these specific runways.
- There was a significant lack of coordination between the North and South tower controllers during the transition between operational modes.
- Inadequate staffing and a lack of teamwork during the shift contributed to the loss of situational awareness.
- Safety risk assessments had failed to identify simultaneous departures as a potential hazard, leaving no mitigations in place.
Safety action
Following the investigation, several recommendations were directed toward the Airports Authority of India (AAI). These include reviewing the design of SIDs to support independent instrument departures, reviewing the areas where conflict warnings are inhibited, and implementing comprehensive checklists and coordination procedures for transitioning between different runway operation modes. Additionally, the AAIB emphasized the need for improved Team Resource Management (TRM) training for controllers.