What happened
On September 2, 2013, at approximately 08:52 UTC, a serious air proximity incident occurred at Indira Gandhi International Airport, Delhi, involving a SpiceJet B737-800, registration VT-SPJ, and an IndiGo A320, registration VT-IEB.
At the time of the incident, VT-SPJ was on final approach to Runway 28. Simultaneously, VT-IEB was lined up on the same runway, prepared for takeoff. Due to expected wake turbulence from a preceding heavy aircraft, the takeoff for VT-Ieb was delayed. During this delay, air traffic controllers instructed VT-IEB to enter and line up on the active runway. Meanwhile, VT-SPJ continued its approach.
As VT-IEB began its takeoff roll, VT-SPJ reached the runway threshold at an altitude below 50 feet and was forced to execute a go-around because the runway was still occupied. As the SpiceJet aircraft climbed, the IndiGo aircraft rotated for takeoff, causing the two planes to converge in the departure path. The aircraft reached a point of near-collision with zero vertical separation and an estimated lateral separation of only 300 feet. The situation was only averted by a last-second visual avoidance maneuver by the crew of VT-SPJ.
The investigation
The AAIB India investigation examined flight data recorders, cockpit voice recordings, and ATC tower audio. The inquiry established that the Air Traffic Control (ATC) environment was compromised by improper handover procedures. At the time of the incident, three controllers were present on the frequency: a duty controller, an instructor, and a trainee. The investigation found that the duty controller had signed out of the logbook without a formal handover to the instructor, leaving a trainee controller handling the channel without active supervision. Furthermore, the instructor was not wearing a headset and was effectively offline.
Findings
- ATC procedural failures: The controller decided to hold VT-IEB on the active runway while allowing VT-SPJ to continue its approach, significantly reducing separation. There was also a failure to implement a formal command hierarchy or proper handover/takeover procedures.
- Pilot errors (SpiceJet): The crew of VT-SPJ continued the approach without landing clearance and failed to initiate a missed approach by the decision height. Additionally, the crew did not correctly interpret or comply with TCAS Resolution Advisories (RA).
- Pilot errors (IndiGo): The crew of VT-IEB failed to recognize the developing conflict and did not reject the takeoff despite the approaching aircraft performing a go-around.
- TCAS performance: While the TCAS systems issued alerts, the advisories were incorrectly interpreted or only partially followed by the crews.
- Infrastructure: The investigation noted that the ATC tower equipment was not ergonomically placed, and loose wiring presented operational hazards.