What happened
A scheduled flight departed from Calcutta-Dum Dum Airport at 11:54, bound for Imphal, Manipur. During the approach phase, the flight crew encountered adverse weather conditions characterized by low visibility. After receiving clearance to descend to 10,000 feet, the crew was permitted to fly a direct outbound course toward an ILS approach for runway 04.
While maneuvering to align with the approach path, the aircraft's Ground Proximity Warning System (GPWS) activated for 6.3 seconds, indicating insufficient altitude. Shortly thereafter, the aircraft type struck the slope of Mt Thangjing, situated approximately 39 km southwest of the runway 04 threshold. The impact caused the plane to disintegrate. There were 69 fatalities among the occupants.
Findings
The investigation determined that the accident was driven by a significant deviation from established flight procedures by the pilot-in-command. Specifically, the pilot failed to follow the operational flight plan and the ILS let-down charts. By descending to 10,000 feet prematurely and executing a right turn for the outbound leg without reporting the overhead VOR, the crew lost their necessary time references. This error led to the aircraft being positioned incorrectly relative to the surrounding hilly terrain. It was noted that the pilot's high level of familiarity with the local landscape may have contributed to this lapse in procedural adherence.