Thai Airways International Flight 311 (TG311/THA311) was a flight from Bangkok, Thailand's Don Mueang International Airport to Kathmandu, Nepal's Tribhuvan International Airport. On Friday, 31 July 1992, an Airbus A310-304 on the route, registration crashed on approach to Kathmandu. At 07:00:26 UTC (12:45:26 NST; 14:00:26 ICT), the aircraft crashed into the side of a mountain north of Kathmandu at an altitude of and a ground speed of , killing all 113 passengers and crew members on board. This was both the first hull loss and the first fatal accident involving the Airbus A310.
Aircraft and crew
The aircraft's first flight was on 2 October 1987, and it entered service with Canadian airline Wardair under the registration C-FGWD. Wardair was acquired by Canadian Airlines International in 1989 and their operations consolidated and integrated under the Canadian Airlines banner. This Airbus A310 formally entered service with Canadian Airlines from 15 January 1990 (with the same registration). It was shortly thereafter sold to Thai Airways International, which took delivery on 9 May 1990 and had it re-registered as HS-TID. The aircraft was powered by two General Electric CF6-80C2A2 turbofan engines.
At the time of its destruction on 31 July 1992, the aircraft had been in commercial operations for less than five years. It was piloted by Captain Preeda Suttimai (41), who had logged 13,200 flight hours including 4,400 on A310 and 1,700 hours as Pilot In Command. and First Officer Phunthat Boonyayej (52), who had logged 14,600 flight hours including 4,200 on the A310. The cabin crew consisted of 12 flight attendants, looking after 99 passengers.
Accident
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 (ATC) 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 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 Before ATC could reply, the flight rescinded their previous transmission.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 . 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 (partly due 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 ATC 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, so he cleared the aircraft to , an altitude that would have been safe in the area south of the airport. The flight descended back to 11,500 ft, went through a 360° turn, and passed over the airport northbound.
Seconds before impact, the ground proximity warning system (GPWS) activated, and sounded alarms warning the crew of the imminent collision with the mountains. First Officer Boonyayej warned Captain Suttimai and urged him to turn the aircraft around, but possibly due to his frustration from the communications with ATC, Suttimai erroneously stated the GPWS was just giving false reports. The aircraft crashed into a steep rock face in a remote area of the Langtang National Park at an altitude of , killing all 113 people on board.