Lauda Air Flight 004
|Date||26 May 1991|
|Summary||In-flight breakup caused by uncommanded thrust reverser deployment|
|Site||Phu Toei National Park
Amphoe Dan Chang, Suphanburi Province, Thailand
|Aircraft type||Boeing 767-3Z9ER|
|Flight origin||Kai Tak Airport
|Last stopover||Don Mueang International Airport
|Destination||Vienna International Airport
Lauda Air Flight 004, operated by a Boeing 767-300ER, was an international passenger flight that crashed 26 May 1991 in Thailand due to an uncommanded thrust reverser deployment of the Number 1 (left) engine in-flight, killing all 223 people on board. It remains to date the deadliest aviation accident involving a Boeing 767 and the deadliest on Thai soil. It was also the aircraft type's first fatal crash and first hull-loss.
It was the third serious accident involving an Austrian aircraft, after the crash in 1960 of an Austrian Airlines Vickers Viscount and the crash on 23 September 1989 of an Aero Commander AC 90 aircraft which claimed the life of Alfred Dallinger, the Austrian minister of social affairs.
History of the flight
At the time of the accident, Lauda Air operated three weekly flights between Bangkok and Vienna. On 26 May 1991, at 23:02 local time, Flight NG004 (originating from Hong Kong's Kai Tak Airport), a Boeing 767-3Z9ER, registration OE-LAV, ship name Mozart, took off from Old Bangkok International Airport (Don Mueang International Airport) for its flight to Vienna International Airport with 213 passengers and 10 crew, under the command of Captain Thomas J. Welch (American) and First Officer Josef Thurner (Austrian).
At 23:08, Welch and Thurner received a visual warning indicating that a possible system failure would cause the thrust reverser on the number 1 engine to deploy in flight. Having consulted the aircraft's Quick Reference Handbook, they determined that it was "just an advisory thing" and took no action.
At 23:17, the thrust reverser on the number 1 engine deployed while the plane was over mountainous jungle terrain in the border area between Suphanburi and Uthai Thani provinces in Thailand. Thurner's last recorded words were, "Oh, reverser's deployed!". The lift on the aircraft's left side was disrupted due to the reverser deployment, and the aircraft was placed in an immediate left diving turn. The aircraft went into a diving speed of .99 mach, which may have broken the sound barrier. The aircraft broke up in mid-air on the way down at 4,000 feet (1,200 meters). Most of the wreckage was scattered over a remote forest area roughly 1 km2 in size, at an elevation of 600 m above sea level, in what is now Phu Toei National Park, Suphanburi. The wreckage site is about three nautical miles north northeast of Phu Toey, Huay Kamin, Dan Chang District, Suphan Buri Province., about 100 miles (160 km) northwest of Bangkok, close to the Burma-Thailand border.
None of the 223 passengers and crew aboard the airliner survived. Rescuers found the body of Welch still in the pilot's seat. After the accident, scavengers collected electronics and jewellery.
Voluntary rescue teams and local villagers looted the remains of the flight, so relatives were unable to recover personal possessions. The bodies were taken to a hospital in Bangkok. The storage was not refrigerated and the bodies were decomposing. Dental and forensic experts worked to identify bodies. Twenty-seven bodies were never identified.
The looting had the potential to complicate the investigation. Speculation that a bomb may have destroyed the aircraft circulated. The Philadelphia Inquirer, citing wire services it did not identify, stated, "The search for a motive is difficult because politically neutral Austria has generally stayed out of most international conflicts – such as the Persian Gulf war – that have made other countries' airlines the targets of terrorist attacks." According to a security officer located at an embassy of a Western country a Lauda Air employee stationed in Bangkok had threatened to use a bomb to destroy a Lauda aircraft unless he was paid money. Lauda Air fired the employee but he was later hired by Thai Airways International, which handled luggage loading and uploading for Lauda Air in Bangkok. Niki Lauda, owner of the airline, said that the airline never received a threat.
The flight data recorder was damaged to the point of being unreadable, so only the cockpit voice recorder was usable. "The attempt to determine why the reverser came on was hampered by the loss of the flight data recorder, which was destroyed in the crash", said Pradit Hoprasatsuk, the head of the Department of Aviation's Air Safety Division. Upon hearing of the crash, Niki Lauda travelled to Thailand. He examined the wreckage and concluded that the largest fragment was about 5 metres (16 ft) by 2 metres (6.6 ft), "about half the size of the largest piece in the Lockerbie crash."  In Thailand Niki Lauda attended a funeral for 23 unidentified passengers, and then traveled to Seattle to meet with Boeing.
As evidence started to point towards the thrust reversers as the cause of the accident, he made simulator flights at Gatwick Airport which appeared to show that deployment of a thrust reverser was a survivable incident. Lauda said that the thrust reverser could not be the sole cause of the crash. The accident report states that the "flightcrew training simulators yielded erroneous results" and stated that recovery from the loss of lift from the reverser deployment "was uncontrollable for an unexpecting flight crew". The incident led Boeing to modify the thrust reverser system to prevent similar occurrences by adding sync-locks, which prevent the thrust reversers from deploying when the main landing gear truck tilt angle is not at the ground position.
The aviation writer Macarthur Job has noted that, "had that Boeing 767 been of an earlier version of the type, fitted with engines that were mechanically rather than electronically controlled, then that accident could not have happened." 
The investigation took about eight months.
Niki Lauda's visit with Boeing
Lauda said "What really annoyed me was Boeing's reaction once the cause was clear. Boeing did not want to say anything." Lauda asked Boeing to fly the scenario in a simulator. Boeing initially refused, but Lauda insisted. Lauda attempted the flight in the simulator 15 times, and in every instance he was unable to recover. He asked Boeing to issue a statement, but the legal department said it could not be issued because it would take three months to adjust the wording. Niki Lauda asked for a press conference the following day, and told Boeing that if it was possible to recover, he would be willing to fly on a 767 with two pilots and have the thrust reverser deploy in air. Boeing told Lauda that it was not possible, so he asked Boeing to issue a statement saying that it would be not survivable, and Boeing issued the statement. Lauda said "This was the first time in eight months that it had been made clear that the manufacturer was at fault and not the operator of the aeroplane."
Previous testing of thrust reverser
When the Federal Aviation Administration (FAA) of the United States asked Boeing to do tests on what would happen if the thrust reverser activated in flight, the FAA had allowed Boeing to establish the tests of the thrust reverser. Boeing had insisted that a deployment was not possible in flight. In 1982 Boeing established a test where the aircraft was slowed to 250 knots, and the test pilots then used the thrust reverser. The control of the aircraft had not been jeopardized. The FAA accepted the results of the test.
The Lauda aircraft was traveling at a high speed when the thrust reversers deployed, causing the pilots to lose control of the aircraft. James R. Chiles, author of Inviting Disaster, said "The point here is not that a thorough test would have told the pilots Thomas J. Welch and Josef Thumer [sic] what to do. A thrust reverser coming on in flight may not have been survivable, anyway. But a thorough test would have informed the FAA and Boeing that thrust reversers deploying in midair was such a dangerous occurrence that Boeing needed to install a positive lock that would prevent such an event." As a result of their findings during the investigation process of Lauda flight 004, additional safety features were mandated to prevent thrust reverser deployment in flight.[clarification needed]
Passengers and crew
|Final tally of passenger nationalities|
|People's Republic of China||6||0||6|
The passengers and crew included 83 Austrians, with 74 Austrian passengers and nine Austrian crew members. 52 Hong Kong residents were on board the aircraft. Other nationalities included 39 Thais, 10 Italians, 7 Swiss, 6 Chinese, 4 Germans, 3 apiece from Portugal, Taiwan, and Yugoslavia, 2 apiece from Hungary, the Philippines, the United Kingdom, and the United States, and one apiece from Australia, Brazil, Poland, and Turkey. In addition, an American was the aircraft's pilot.
Of the passengers, 125 had boarded in Hong Kong, while the rest boarded in Bangkok. Of the passengers who boarded in Bangkok, there were 38 Thai, 34 Austrians, 7 Swiss, 4 Germans, 2 Yugoslavs, 1 Australian, 1 Briton, and 1 Hungarian. Of the passengers who boarded in Hong Kong, most were Austrian or Chinese.
Of the passengers, 10 were from South Tyrol in Italy. Six of them were students of the University of Innsbruck School of Economics, and they originated from Val Gardena (Gröden), Kiens (Chienes), Klausen (Chiusa), Mals (Malles Venosta), and Olang (Valdaora). The other four were from Bolzano (Bozen), including two public officials/officers, a musician, and the musician's daughter. The musician was traveling with his Chinese wife.
- Donald McIntosh, a 43-year-old British senior United Nations anti-drug official posted in Bangkok. His death caused Austrian newspapers to post initial speculation stating that people bombed the airplane to kill him; a UN spokesperson said that he was not on a secret mission and could not have been a target of an assassination.
- Pairat Decharin, the governor of Chiang Mai Province, and his wife.Charles S. Ahlgren, the former U.S. consul general to Chiang Mai, said "That accident not only took their lives and that of many of Chiang Mai's leaders, but dealt a blow to many development and planning activities in the town."
- Clemens August Andreae, an Austrian economics professor, was leading a group of students from the University of Innsbruck on a tour of the Far East.
- Mom Sinuan Na Chiangmai (หม่อมศรีนวล ณ เชียงใหม่), the wife of Pairat Decharin and consort of Chao Ratchabut (Wongtawan Na Chiang Mai), the prince of Chiang Mai
- Winit Winitchaiyaphak (วินิจ วินิจฉัยภาค), the Deputy Principal Private Secretary
- Chao Phongkaeo Na Lamphun (เจ้าพงศ์แก้ว ณ ลำพูน), the daughter of Chao Ratchabut.
Josef Thurner, the copilot, once flew as a copilot with Niki Lauda on a Lauda Boeing 737 service to Bangkok, a flight that was the subject of a The Reader's Digest article in January 1990 that positively depicted the airline. Macarthur Job said that, as a result, Thurner was the better known of the crew members. Thomas P. Welch, the pilot, lived in Vienna, but originated from Seattle, Washington.
About one quarter of the airline's carrying capacity vanished as a result of the crash. Following the crash of OE-LAV, the airline had no flights to Sydney, Australia, on 1, 6, and 7 June. Flights resumed with another 767 on 13 June. Niki Lauda said that the crash in 1991 and the period after was the worst time in his life.
In early August 1991, Boeing gave an alert to airlines stating that over 1,600 late model 737s, 757s, 767s, and 747s had thrust-reverser systems common to that of OE-LAV. On Monday 9 September 1991 the Boeing Commercial Airplane Group asked its customers to replace a valve in the thrust reverser systems that may cause the thrust reverser to deploy in flight.
Fourteen months before 25 May 1993, Boeing and Lauda Air came to a joint settlement with most of the families of the deceased victims. By 25 May 1993, 20 families, which had children as claimants, had not yet received settlement money. The law firm Sinclair Roche represented almost all of the relatives of the Hong Kong residents who died in the crash.
Annual memorial services were scheduled for 26 May. A memorial service was scheduled for Wednesday 26 May 1993.
At the crash site, which is accessible to national park visitors, a shrine was later erected to commemorate the victims. Another memorial and cemetery is located near Ban Tha Sadet, some 90 km away in Amphoe Mueang Suphanburi.
- Tummachartvijit, Tavorn. "Cause of airliner explosion Sought." Associated Press at The Dispatch. Monday May 27, 1991. 1A and 6A.
- "Lauda Air-Absturz in Thailand jährt sich zum 20. Mal." Die Presse. 26 May 2011. Retrieved on 14 February 2013. "Das Unglück 1991 in Thailand war das dritte schwere, von dem ein österreichisches Verkehrsflugzeug betroffen war. Am 26. September 1960 hatte der Absturz einer "Vickers-Viscount"-Turboprop-Maschine der AUA beim Landeanflug auf den Moskauer Flughafen Scheremetjewo 31 Tote gefordert. Schuld war damals eine falsche Höhenmesser-Einstellung. Am 23. September 1989 war eine mit elf Personen besetzte "Commander AC 90" der Rheintal-Flug beim Landeanflug auf den Flughafen Altenrhein am schweizerischen Ufer des Bodensees bei dichtem Nebel in das Gewässer gestürzt. Dabei kam auch der damalige Sozialminister Alfred Dallinger (S) ums Leben." and "In Thailand starb der Innsbrucker Wirtschaftswissenschafter Univ.-Prof. Clemens August Andreae."
- Accident description at the Aviation Safety Network
- Job, Macarthur (1996). Air Disaster Volume 2, Aerospace Publications, ISBN 1-875671-19-6: pp.203-217
- Accident Report, Appendix A, page 55
- Chiles, p. 309.
- Accident Report
- "More Than 200 Believed Killed As Plane Crashes in Thai Jungle." Associated Press. May 27, 1991. Retrieved on January 27, 2013.
- "UN drug man 'not Thai bomb target'." The Independent. Thursday 30 May 1991. Available on LexisNexis.
- Johnson, Sharen Shaw. "Scavengers complicate crash probe." USA Today. 29 May 1991. News 4A.
- Finlay, Victoria. "Relatives return to crash site for memorial service." South China Morning Post. Tuesday 25 May 1993. Retrieved on 26 May 2013.
- "Looting May Hurt Jet-crash Probe; Airline Chief Denies Extortion Plot." Inquirer Wire Services at The Philadelphia Inquirer. 1. Retrieved on May 26, 2013.
- Lauda, Niki (interview by Maurice Hamilton). "Niki Lauda: 'People had lost their loved ones yet no one was telling them why'." Observer Sport Monthly at The Guardian. 29 October 2006. Retrieved on 15 February 2013. The quote "People always think that the worst time of my life must have been after the German Grand Prix crash in 1976, which put me in a coma and left me with severe burns. But it wasn't. In 1991, one of the planes from Lauda Air, the airline I had set up, crashed in Bangkok, killing 223 people." verifiably shows that Lauda said that the 1991 crash was the "worst" time in Lauda's life.
- "Looting may have hidden clues to crash." The Advertiser. Thursday 30 May 1991.
- "Rejects Thrust as Cause of Air Crash." The New York Times. June 7, 1991. Retrieved on January 26, 2013.
- Accident Report, section 2.3, page 21
- Accident Report, section 3.1, 9, page 41
- Lane, Polly; Acohido, Byron. "Boeing Tells 757 Owners To Replace Part -- Faulty Thrust-Reverser Valve Blamed In 767 Accident That Killed 223". The Seattle Times. Retrieved 2009-06-23.
- Chiles, p. 112-113
- Chiles, p. 113
- Chiles, p. 114.
- Traynor, Irian, Nick Cumming-Bruce, and Steve Vines. "Crash teams investigate plane blast." The Independent. 28 May 1991. Available on LexisNexis.
- Wallace, Charles P. "'All Evidence' in Thai Air Crash Points to Bomb." Los Angeles Times. May 28, 1991. 2. Retrieved on February 15, 2013.
- Finlay, Victoria. "Jet tragedy families wait on pay." South China Morning Post. Tuesday 25 May 1993. Retrieved on 27 January 2013.
- "Pilots' Final Words." Associated Press at The Seattle Times. Thursday June 6, 1991. Retrieved on February 15, 2013.
- Parschalk and Thaler, p. 394 "Sechs der zehn Südtiroler Opfer sind Studenten der Innsbrucker Fakultät für Wirtschaftswissenschaften aus Klausen, Gröden, Olang, Mals und Kiens, die unter der Leitung von Clemens August Andreae an einer Exkursion nach Fernost teilgenommen hatten. Die anderen vier Südtiroler Todesopfer - alle aus Bozen - sind zwei Beamte sowie ein Berufsmusiker mit seiner chinesischen Frau und dem in Bozen geborenen Töchterchen der beiden."
- "Special Messages from 8 U.S. Consuls General in Chiang Mai." (Archive) Department of State. Retrieved on February 15, 2013. Thai version, Archive
- "คอลัมน์: ผ่อ...เมืองเหนือ: อดีต ผู้ว่าฯ ไพรัตน์ เดชะรินทร์" [Column: Looking at the Northern Cities: Pairat Decharin, former governor]. Naew Na. 2009.02.17. Retrieved 2013-02-16. (Archive) "ข้อมูลนี้ผิดผู้ที่สร้างกำแพงเมืองและประตูเมืองขึ้นมาใหม่คือคุณชัยยา พูนศิริวงศ์ คนที่นั่งเครื่องบินเลาด้าแอร์ไลน์ตกตายหมู่คือคุณไพรัตน์ เดชะรินทร์ พร้อมคุณนาย ก็ต้องให้ความเป็นธรรมกับผู้ตายและคณะที่ตายพร้อมกับผู้ว่าฯไพรัตน์ เป็นคุณหญิงสองท่านคือ หม่อมศรีนวล ณ เชียงใหม่ ชายาเจ้าราชบุตร (วงค์ตะวัน) ณ เชียงใหม่ สายตรงพระเจ้ากาวิละ และเจ้าพงษ์แก้ว ณ ลำพูน ลูกสาวเจ้าราชบุตร นอกนั้นอีก 10 กว่าคนเป็นคหบดีชื่อดังของเชียงใหม่ทั้งสิ้น ทุกคนที่เสียชีวิต ล้วนแต่เป็นนักสังคมสงเคราะห์ช่วยเหลือประชาชนที่ยากไร้มานานไม่ต่ำกว่าคนละ 20 ขึ้นไป"
- "โศกนาฏกรรมนกเหล็ก จากอดีตถึงวันนี้" [Tragedies of the iron birds: From the past to the present]. Manager. 2009.08.05. Retrieved 2013-02-16. (Archive) "26 พฤษภาคม 2534 (สุพรรณบุรี) หากถามว่า เหตุการณ์เครื่องบินตกครั้งไหนรุนแรงและสยองขวัญที่สุดในเมืองไทย เชื่อว่าคงไม่หนีไม่พ้นอุบัติเหตุเครื่องบินของเลาด้าแอร์ตกอย่างแน่นอน เพราะในครั้งนั้นได้คร่าชีวิตผู้โดยสารไปถึง 223 คน โดยเป็นคนไทยจำนวน 39 คน ซึ่งหลายคนก็มีชื่อเสียง อย่างนายวินิจ วินิจฉัยภาค รองราชเลขาธิการ นายไพรัตน์ เดชะรินทร์ ผู้ว่าราชการจังหวัดเชียงใหม่ ฯลฯ"
- Job, p. 204. "Of all the crew, Josef Thurner was perhaps the better known thanks to having been copilot to Niki Lauda himself on a Boeing 737 service to Bangkok which became the subject of a highly affirmative article on the airline and its history in the January 1990 issue of The Reader's Digest[...]"
- Traynor, Ian. "Lauda's driving ambition brings triumph and disaster in tandem." The Independent. 28 May 1991.
- Aircraft, Volume 71. p. 44. "LAUDA AIR/LDA: Following the still unexplained loss of B767-329ER OE-LAV  Mozart, there were no flights to Sydney by the Austrian carrier on June 1, 6 and 7. Services resumed on June 13 with B767-3T9 (ER) OE-LAU [23765 xN6009F] Johann Strauss refers, departing Sydney with a joint Lauda Air and Air Malta/ AMC flight number. It routed back to Vienna via Bangkok and Luqa, Malta. Lauda Air[...]
- Lane, Polly and Byron Acohido. "Boeing Tells 757 Owners To Replace Part -- Faulty Thrust-Reverser Valve Blamed In 767 Accident That Killed 223." Seattle Times. Monday, 9 September, 1991. Retrieved on 15 February 2013.
- Paknam Web - Phu Toei National Park
- Paknam Web - Lauda Air Cemetery
- Accident Report - Lauda Air Flight 004 (Archive) - Aircraft Accident Investigation Committee, Ministry of Transport and Communications Thailand, Prepared for World Wide Web usage by Hiroshi Sogame (十亀 洋 Sogame Hiroshi), a member of the Safety Promotion Committee (総合安全推進 Sōgō Anzen Suishin) of All Nippon Airways
- Aircraft, Volume 71. Royal Aeronautical Society Australian Division, 1991.
- Chiles, James R. Inviting Disaster. HarperCollins, July 8, 2008. ISBN 0061734586, 9780061734588.
- Job, Macarthur. Air Disaster, Volume 2. Aerospace Publications, 1996. ISBN 1875671196, 9781875671199.
- Parschalk, Norbert and Bernhard Thaler. Südtirol Chronik: das 20. Jahrhundert. Athesia, 1999.
- Gilbert, Andy. "Lauda Air." South China Morning Post. Thursday 26 May 1994.
- Aviation Week & Space Technology. 03.06.1991 (32), 10.06.91 (28-30)
- "การสอบสวนอากาศยานประสบอุบัติเหต" Department of Civil Aviation (Thai) (Archive)
- "Computer-Related Incidents with Commercial Aircraft The Lauda Air B767 Accident." (Archive) University of Bielefeld. 26 May 1991.
- Lauda Air Flight 004 (Index of articles) - South China Morning Post
- "flugzeugabsturz_20jahre.pdf." (Archive) University of Innsbruck. -- Includes list of University of Innsbruck professors, assistants, and students who died on Flight 004
- Last flight of the Mozart (Der Todesflug der Mozart, German)." - Austrian Wings - Austrias Aviation Magazine
- PlaneCrashInfo.Com - Lauda Air Flight 004
- Grand Prix Hall of Fame - Biography on Niki Lauda (Contains information about Flight 004)