What happened
On 30th January 2014, a serious air proximity incident occurred in the airspace near Mumbai. The event involved an Air India Boeing 787-8, registration VT-ANE, and a Sesa Goa Ltd. P68C, registration VT-TLE.
The incident began when the P68C departed Juhu Aerodrome for Pune. After contacting Mumbai Approach Control, the aircraft was cleared to proceed direct to DOGAP. This specific routing placed the aircraft on a path that intersected the takeoff trajectory of Runway 14 at Mumbai’s Chhatrapati Shivaji International Airport (CSIA), approximately 4.5NM from the runway end.
Shortly after, the Air India Boeing 7/8-8 departed Runway 14 at CSIA for Delhi. As the Boeing 787-8 climbed through 2100ft, the approach controller attempted to manage the converging paths by issuing various altitude and heading changes to both aircraft. However, the rapid performance difference between the heavy jet and the smaller piston-propeller aircraft made separation difficult. At 04:37:03 UTC, the crew of VT-ANE received a TCAS Resolution Advisory (RA), prompting an immediate evasive descent. The aircraft successfully maneuvered to avoid the conflict, and both flights eventually proceeded to their destinations without injury or damage.
The investigation
An inquiry by AAIB India examined the sequence of events, the controller's instructions, and the technical performance of the aircraft involved. The investigation focused on the routing provided to the P68C and the timing of the controller's intervention. Investigators reviewed ATC communications, which revealed several instances of non-standard and ambiguous phraseology.
The investigation also looked into the functionality of the ATC automation system, noting that the Predicted Conflict Warning (PCW) failed to alert the controller to the impending collision. Furthermore, the investigation found that the controller had not delayed the departure of the Air India flight despite the known conflict created by the P68C's assigned route.