Thai Airways International Flight 311

1992 Thai Airways International Flight 311

HS-TID, the aircraft involved in the accident seen at Don Mueang International Airport in April 1992
Accident
Date	31 July 1992
Summary	Controlled flight into terrain due to pilot error, ATC error, and loss of situation awareness in inclement weather
Site	Langtang National Park, Nepal
Aircraft type	Airbus A310-304
Aircraft name	Buri Ram
Operator	Thai Airways International
Registration	HS-TID
Flight origin	Don Mueang International Airport, Bangkok, Thailand
Destination	Tribhuvan International Airport, Kathmandu, Nepal
Passengers	99
Crew	14
Fatalities	113
Survivors	0

1992 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 Kathmandu. At 07:00:26 UTC (12:45:26 NST; 14:00:26 ICT), the aircraft crashed into the side of a mountain 37 kilometres 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. This was both the first hull loss and the first fatal accident involving the Airbus A310.^[1][2]

Aircraft and crew

The aircraft involved was a five-year-old Airbus A310-304 registered as HS-TID. The aircraft's first flight was on 2 October 1987, and was delivered to Wardair with the registration C-FGWD. The aircraft was then owned and operated by Canadian Airlines on 15 January 1990 (with the same registration), following CA's acquisition of Wardair in 1989. The aircraft was then delivered to Thai Airways on 9 May 1990 and given its registration as HS-TID.^[1]

The flight crew consisted of Captain Preeda Suttimai (41), First Officer Phunthat Boonyayej (52), and a cabin crew of 12 flight attendants.

Accident

Flight 311 departed Bangkok at 10:30 local time. It was scheduled to arrive in Kathmandu at 12:55 Nepal Standard Time.^[3] 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.^[4]

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".^[5] 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.

Memorial park in Kakani, Nepal

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, and passed over the airport northbound.

Seconds before impact, the ground proximity warning system 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 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 11,500 feet, killing all 113 people on board.

Investigation

Investigators from the Nepalese aviation authority, Airbus Industrie, and the Transportation Safety Board of Canada (which assisted with technical details) determined that the aircraft had experienced a minor fault in the workings of the inboard trailing flaps just after the aircraft reached the Sierra reporting fix. Concerned that the complex approach into Kathmandu in instrument conditions would be difficult with malfunctioning flaps and frustrated by ATC and his first officer's inconclusive and weak answers to his questions, the captain decided to divert to Calcutta.^[6] The flaps suddenly began to work properly, but the captain was forced to resolve more aspects of the difficult approach himself due to his first officer's lack of initiative. Only after numerous extremely frustrating exchanges with ATC was the captain able to obtain adequate weather information for the airport, but by that time he had overflown Kathmandu and the aircraft was headed towards the Himalayas.^[6]

Crash site of Flight 311, between Ghopte and Tharepati Pass, Nepal

Nepalese authorities found that the probable causes of the accident were the captain's and controller's loss of situational awareness; language and technical problems caused the captain to experience frustration and a high workload;^[6] the first officer's lack of initiative and inconclusive answers to the captain's questions; the air traffic controller's inexperience, poor grasp of English, and reluctance to interfere with what he saw as piloting matters such as terrain separation; poor supervision of the inexperienced air traffic controller; Thai Airways International's failure to provide simulator training for the complex Kathmandu approach to its pilots; and improper use of the aircraft's flight management system.^[4]

Victims

Nationality	Passengers	Crew	Total
Australia	1	-	1
Belgium	5	-	5
Canada	2	-	2
Finland	5	-	5
Germany	4	-	4
Israel	2	-	2
Japan	17	-	17
Nepal	23	-	23
New Zealand	1	-	1
South Korea	2	-	2
Spain	3	-	3
Thailand	21	14	35
United Kingdom	2	-	2
United States	11	-	11
Total	99	14	113[7]

Aftermath

Flight 311 was retired after the accident, including its outbound flight 312 to Bangkok. They were both reassigned to flights 319 and 320, respectively and were still operated by Airbus A310. They now use the Boeing 777 aircraft after the Airbus A310 fleet were phased out by the airline in 2001. The remains of the aircraft can still be seen in Langtang National Park on the trek from Ghopte to the Tharepati Pass.

Dramatization

The crash of Thai Airways International Flight 311 is featured in the Tenth Episode on the Season 17 of Mayday (Air Crash Investigation). The episode is titled "The Lost Plane".

See also

• Aviation safety
• Controlled flight into terrain
• List of accidents and incidents involving commercial aircraft
• Pakistan International Airlines Flight 268
• UPS Airlines Flight 1354

References

External links

• Media related to Thai Airways International Flight 311 at Wikimedia Commons
• Google Books description: "Thai Airways International Ltd. Airbus Industrie A310-304, HS-TID, Near Kathmandu, Nepal, 23NM NNE, 31 July 1992." Commission for the Accident Investigation of TG311, 1993.
• "Conclusions from report on CFIT accident near Kathmandu" (DjVu). ICAO Journal. Montreal: International Civil Aviation Organization. 48 (7): 23–26. September 1993. ISSN 0018-8778. Retrieved 2 May 2014.
• Pre-crash photos of HS-TID from Airliners.net

Coordinates: 28°03′09″N 85°27′03″E / 28.05250°N 85.45083°E / 28.05250; 85.45083