Date:	Friday 16 August 1991
Time:	12:46
Type:	Boeing 737-2A8 Advanced
Owner/operator:	Indian Airlines
Registration:	VT-EFL
MSN:	21497/504
Year of manufacture:	1977
Total airframe hrs:	29729 hours
Cycles:	33574 flights
Engine model:	Pratt & Whitney JT8D-17A
Fatalities:	Fatalities: 69 / Occupants: 69
Aircraft damage:	Destroyed, written off
Category:	Accident
Location:	38 km SW of Imphal Municipal Airport (IMF) -   India
Phase:	Approach
Nature:	Passenger - Scheduled
Departure airport:	Calcutta-Netaji Subhas Chandra Airport (CCU/VECC)
Destination airport:	Imphal Municipal Airport (IMF/VEIM)
Confidence Rating:	Accident investigation report completed and information captured

Narrative:
Indian Airlines flight 257 departed Calcutta at 11:54 on a scheduled 60-minute flight to Imphal, India.
The crew contacted Imphal at 12:34. The flight was cleared to descent to from FL290 to 10,000 feet and asked to report overhead the VOR for ILS runway 04.
At 12:39 the crew reported 12 miles inbound at 10,000 feet. The pilot then asked the air traffic controller as to whether they could set course directly outbound for let down. This was approved. Two minutes later the flight reported approaching overhead the VOR, although it was still 14 miles out. The controller then queried: "understand you are proceeding on a radial 217 for ILS". This was confirmed by the crew.
At 12:42 Imphal ATC cleared the flight to proceed outbound for an ILS approach to runway 04 descending to 5,000 feet. At 12:44 the flight reported commencing the procedure turn. This was the last contact with the flight.
The airplane impacted Thangjing Hill, in inclement weather conditions with low clouds and occasional rain.

PROBABLE CAUSE: "The accident occurred by reason of a grave error on the part of the Pilot-in-Command in not adhering to the operational flight plan and ILS let down chart and not realizing that his early descent to 10,000 feet and turning right for outbound leg without reporting overhead VOR would result in loss of time
reference and as such misplace him in the hilly terrain. The Pilot-in-Command's action may have been influenced by his extreme familiarity with the terrain".

Civil aviation aircraft accident summary for the year 1991 (DGAC India)

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