On November 17 last year, two aircraft of India’s largest airline IndiGo came in perilous proximity to each other while taking off at Delhi’s Indira Gandhi International (IGI) Airport, which led to the emergency alert to avoid the collision. The event is being probed by the Aircraft Accident Investigation Bureau (AAIB) which termed it a ‘serious incident”.
The incident involved two planes viz Airbus A321 with the registration VT-IUO, and the other was an Airbus A320 (VT-ISO). The A321 was flying from Delhi to Hyderabad, while the A320 was en route to Raipur from the national capital.
“At the time of the closest vertical separation (400 feet), lateral separation was 1.2 NM. At the time of the closest lateral separation (0.2 NM), the vertical separation was 800 feet. There was no injury to any of the occupants on board in both aircraft. There was no damage,” AAIB mentioned in its preliminary incident report.
Traffic Alert and Collision Avoidance System
TCAS (Traffic Alert and Collision Avoidance System) onboard the airplanes alerted pilots and both planes averted the collision. Notably, TCAS in the aircraft gives out an alert when there is a presence of another aircraft in proximity beyond the permitted levels. Both vertical and lateral separation between the two planes went below the minimum permissible levels in the Nov 17 incident.
It is noteworthy that as per the norms, aircraft must maintain a minimum vertical separation of 1,000 feet and lateral separation of 5 nautical miles while airborne. IndiGo has not commented on the incident or the AAIB investigation yet.
Thorough investigation underway
As part of the ongoing investigation, AAIB has accessed the data from CVR (Cockpit Voice Recorder) and flight data recorder for further analysis.
Further, manuals related to operations were obtained from the airline and airport besides securing flight folders and METAR (Meteorological Aerodrome Report) details. Besides, the initial statements from the crew and air traffic controllers have been recorded, the report said.
