History of Flight
On 17 November 2023, Indigo flight IGO2113 (A321-271NX, registration VT-IUO) departed Delhi for Hyderabad using runway 27 and SID AKRIB 6A. Indigo flight IGO2206 (A320-251N, registration VT-ISO) departed Delhi for Raipur using runway 29R and SID ITBAN 6C. Both aircraft were in the climb phase when a loss of separation occurred, leading to an airprox.
Injuries and Damage
No injuries were reported to crew, passengers, or cabin crew on either aircraft. No damage to either aircraft occurred.
Crew Information
Both pilots-in-command held ATPL licenses; both first officers held CPL licenses. Crew of IGO2113 and IGO2206 were qualified as per regulations.
Aircraft Information
Both aircraft were operated by M/s Interglobe Aviation (Indigo). VT-IUO is an Airbus A321-271NX, and VT-ISO is an Airbus A320-251N. Both are medium wake turbulence category, IFR flights.
Investigation and Analysis
The Aircraft Accident Investigation Bureau (AAIB) analyzed flight data recorders, cockpit voice recorders, and ATC communications. The analysis highlighted non-adherence to standard operating procedures by the crew of IGO2113, leading to an altitude deviation. The air traffic controller failed to issue a timely warning about the potential conflict. The ground-based safety net (STCA) issued warnings, but these were not effectively utilized.
Conclusion
The probable cause of the incident is the non-adherence to Standard Operating Procedures by the crew of IGO 2113 leading to altitude deviation and subsequent loss of separation with IGO 2206. The contributory factor was the failure of the Air Traffic Controller to issue a timely warning to the aircraft about the potential conflict.
Safety Recommendations
The AAIB issued safety recommendations addressing operational procedures, crew training, ATC training, and enhancement of safety nets to prevent recurrence.