Thai Airways International Flight 311

Thai Airways International Flight 311

HS-TID, the aircraft involved in the accident seen at Don Mueang International Airport in April 1992
Accident summary
Date	31 July 1992
Summary	Controlled flight into terrain
Site	Langtang National Park, Nepal
Passengers	99
Crew	14
Fatalities	113 (all)
Survivors	0
Aircraft type	Airbus A310-304
Operator	Thai Airways International
Registration	HS-TID
Flight origin	Don Mueang International Airport, Bangkok, Thailand
Destination	Tribhuvan International Airport, Kathmandu, Nepal

Thai Airways International Flight 311 was a flight from Bangkok, Thailand's Don Mueang International Airport to Kathmandu, Nepal's Tribhuvan International Airport. On Friday, 31 July 1992, an A310-304 on the route, registration HS-TID, crashed on approach to Tribhuvan. At 07:00:26 UTC (12:45:26 NST; 14:00:26 ICT), the aircraft crashed into the side of a mountain 37 kilometres miles north of Kathmandu at an altitude of 11,500 feet and a ground speed of 300 nautical miles per hour, killing all 99 passengers and 14 crew members.

Flight 311 departed Bangkok at 10:30 local time. It was scheduled to arrive in Kathmandu at 12:55 Nepal Standard Time. After crossing into Nepalese airspace the pilots contacted air traffic control and were cleared for an instrument approach from the south called the "Sierra VOR Circling Approach" for Runway 20. Nepalese ATC at the time was not equipped with radar.

Shortly after reporting the Sierra fix ten miles south of the Kathmandu VOR, the aircraft called ATC asking for a diversion to Calcutta, India because of a "technical problem". Before ATC could reply, the flight rescinded their previous transmission. The flight was then cleared for a straight-in Sierra approach to Runway 02 and told to report leaving 9,500 feet (2,896 m). The captain asked numerous times for the winds and visibility at the airport, but ATC merely told him that Runway 02 was available.

A number of frustrating and misleading communications (due partly to language problems and partly to the inexperience of the air traffic controller, who was a trainee with only nine months on the job) ensued between air traffic control and the pilots regarding Flight 311's altitude and distance from the airport. The captain asked four times for permission to turn left, but after receiving no firm reply to his requests he announced that he was turning right and climbed the aircraft to flight level 200. The controller handling Flight 311 assumed from the flight's transmissions that the aircraft had called off the approach and was turning to the south, and he therefore cleared the aircraft to 11,500 feet (3,505 m), an altitude that would have been safe in the area south of the airport. The flight descended back to 11,500 feet, went through a 360-degree turn, passed over the airport northbound, and crashed on a steep rock face in a remote area of the Langtang National Park at an altitude of 11,500 feet.