Thai Airways International Flight 311

Aircraft and crew

Aircraft

The aircraft involved was an Airbus A310-304, manufactured by Airbus Industrie in 1987 and registered as HS-TID with serial number 438. It was powered by two General Electric CF6-80C2A2 turbofan engines.

Crew

At the time of the accident, the aircraft had been in commercial operations for 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. The First Officer was 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 (03:30 UTC). It was scheduled to arrive in Kathmandu at 12:55 Nepal Standard Time (07:10 UTC). 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. The captain was evidently uncomfortable with this approach, as he did not want to fly so near to the higher northern mountain range and turn around in poor visibility.

Shortly after reporting the Sierra fix 10 km south of the Kathmandu VOR, the aircraft called ATC asking for a diversion to Calcutta, India, because of a "technical problem" (while attempting to extend the flaps, they had become stuck, making the steep descent into Kathmandu unsafe). Before ATC could reply, the flight rescinded their previous transmission; they retracted and re-extended the flaps properly. The flight was then cleared for a straight-in Sierra approach to Runway 02 and told to report leaving 9500 ft. The captain asked numerous times for the winds and visibility at the airport, but ATC merely told him that Runway 02 was available.

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, intending to turn back to point Romeo and re-attempt the straight-in approach. 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 11500 ft, an altitude that would have been safe in the area south of the airport. The flight descended back to 11,500 ft, unintentionally went through a nearly 360° turn (rather than a 180-degree one to return to southern point Romeo), 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 11500 ft and with a ground speed of 300 kn, killing all 113 people on board.

Investigation

Investigators from the Civil Aviation Authority of Nepal, 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.

Nepalese authorities found that the probable causes of the accident were the captain and air traffic controller's loss of situational awareness; language and technical problems which caused the captain to experience frustration and a high workload;

While trekking up the Himalaya mountain to the crash site, a British investigator from Airbus, Gordon Corps (62), died due to altitude sickness. Corps had over 11,500 flight hours and was a senior test pilot for Airbus.

Victims

Notable deaths

• Uzi Peres was an Israeli film director, screenwriter and film producer.

Aftermath

Thai Airways retired the flight number 311 after the accident, along with its counterpart flight number 312, which had been used for the outbound flight from Kathmandu to Bangkok. These were replaced by flight numbers 319 and 320, respectively. These redesignated flights continued to be operated by Airbus A310 aircraft until this type was retired by the airline and replaced with Boeing 777 aircraft in 2001. The remains of the aircraft can still be seen in Langtang National Park on the trek from Ghopte to the Tharepati Pass.

Fifty-nine days after the Flight 311 disaster, Pakistan International Airlines Flight 268 crashed on approach to Kathmandu, killing all 167 on board, the deadliest accident in the country's history.

Dramatization

The crash is featured in Season 17, Episode 10 of Mayday (Air Crash Investigation). The episode is titled "The Lost Plane".

Notes

References

References

1. Ranter, Harro. "Accident Description". [[Flight Safety Foundation]].
2. "KOIRALA v. THAI AIRWAYS INTERNATIONAL LTD".
3. (1992-07-31). "Thai jetliner crashes in Nepal". United Press International.
4. (1992-07-31). "Thai Airliner Crashes In Nepal's Himalayan Foothills; 113 Aboard -- 11 Americans Are Listed As Among The Passengers". The Seattle Times.
5. (2 August 1992). "Rescue Teams Fail to Find Thai Jet That Crashed With 113 Aboard". The New York Times.
6. (1996). "Cockpit-Cabin Communication: The Impact of National and Occupational Cultures". [[San Jose State University]].
7. (4 August 1992). "British pilot dies on Airbus mission". The Herald.
8. (5 August 1992). "Test pilot dies". [[The Independent]].
9. (5 August 1992). "High Altitude Claims Life of Probe Leader". Deseret News.
10. (1 August 1992). "113 Feared Dead in Nepal Crash; Thai jetliner slams into Himalayan hillside during heavy monsoon rains.". Los Angeles Times.
11. {{ASN accident
12. (25 September 2023). "Mayday: Air Disaster - Investigating the Unlikely Crash Site of Thai Airways Flight 311 In The Himalayas".