What happened
On April 21, 2017, at Indira Gandhi International Airport (Delhi), a serious air proximity incident occurred involving two scheduled commercial flights. A Jet Airways B737-800, registration VT-JGV, was performing a missed approach on Runway 11 after an exceptionally high-speed approach. Simultaneously, a Tata Singapore A320-232, registration VT-TTC, was cleared for takeoff from the same runway.
The Jet Airways flight was observed by radar to be maintaining ground speeds significantly above standard limits, recorded at 390 knots at 20 NM from touchdown and 3anchored at 350 knots at 13 NM. Despite multiple instructions from the Approach Radar Controller to reduce speed for landing, the crew maintained high velocities. As the aircraft reached approximately 5.5 NM from the runway, the ground speed remained at 320 knots, preventing the crew from extending flaps, as the speed exceeded the 250-knot limit for flap deployment.
During this high-speed arrival, the Tower Controller cleared the departing Tata Singapore aircraft for takeoff without coordinating with the Approach Radar Controller. The subsequent missed approach by the Jet Airways aircraft and the departure of the Airbus resulted in a breach of separation, with lateral distance dropping to 0.3 NM and vertical separation reaching only 400 feet.
The investigation
The AAIB India investigation examined flight data recorders (DFDR), air traffic control (ATC) voice recordings, and intercom transcripts between the Tower and Approach sectors. The inquiry scrutinized the operational status of the controllers and the adherence to standard operating procedures (SOPs) by both flight crews.
Investigators found that the Approach Radar Controller lost situational awareness regarding the feasibility of landing the aircraft at such high speeds. Furthermore, the investigation revealed that the Tower Controller failed to monitor the incoming high-speed traffic and released the departing flight without proper coordination. The inquiry also noted that the Approach Radar Controller's authorization for Tower and Area Control duties had lapsed, as they had not performed duties in those sectors for over 180 days.
Findings
- The crew of VT-JGV failed to adhere to published speed control procedures and standard cockpit protocols.
- The Approach Radar Controller failed to recognize the danger of an aircraft attempting to land at 310 knots of ground speed.
- The failure of the Tower Controller to coordinate with Approach Radar before releasing the departing aircraft was a primary factor in the separation breach.
- Coordination between the Tower and Approach sectors utilized non-standard language.
- The aircraft's high speed prevented the deployment of flaps, necessitating the go-around.