Lauda Air Flight 004

Lauda Air Flight 004 was a regularly scheduled international passenger flight from Bangkok, Thailand, to Vienna, Austria. On May 26, 1991, the Boeing 767-300ER operating the service crashed, following an uncommanded midair deployment of the thrust reverser on the No.1 engine, causing the aircraft to enter an aerodynamic stall, uncontrolled dive, and break up midair, killing all 213 passengers and ten crew members on board. It is the deadliest aviation incident involving the Boeing 767, the deadliest of its kind, and the deadliest aviation incident in Thailand's history as of 2022. The crash marked the aircraft type's first fatal incident and third hull loss. Formula One world motor racing champion Niki Lauda, who founded and ran Lauda Air, was personally involved in the accident investigation.

Aircraft

The aircraft involved was a Boeing 767-300ER that was powered by Pratt & Whitney PW4060 engines and delivered new to Lauda Air on 16 October 1989. The aircraft was registered OE-LAV, was named ''Mozart'' and was the 283rd Boeing 767 built. At the time of the incident, the No.2 engine had been on the airframe since assembly of the aircraft (7,444 hours and 1,133 cycles) whereas the No.1 engine (with the faulty thrust reverser) had been on the aircraft since October 3, 1990 and had accumulated 2,904 hours and 456 cycles.

Accident

At the time of the accident, Lauda Air operated three weekly flights between Bangkok and Vienna.Tummachartvijit, Tavorn. "Cause of airliner explosion Sought". Associated Press '' The Dispatch''. 27 May 1991. 1A an
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At 23:02 ICT, on 26 May 1991, Flight 4 (originating from Hong Kong's Kai Tak Airport), the Boeing 767-3Z9ER took off from Don Mueang International Airport for its passenger service to Vienna International Airport with 213 passengers and ten crew, under the command of American Captain Thomas J. Welch (48) and Austrian First Officer Josef Thurner (41). Both pilots were regarded as very competent. At 23:08, Welch and Thurner received a visual warning indication on the EICAS display telling them that a possible system failure would cause the thrust reverser on the number one engine to deploy in flight. Having already consulted the aircraft's quick reference handbook, they determined that it was "coming on and off", and that it was "just an advisory thing" and took no action, possibly believing that the indication was false, and because the 767 could stop with only one operational reverser.

At 23:17, the number one engine reverser deployed while the plane was over mountainous jungle terrain in the border area between Suphan Buri and Uthai Thani Provinces in Thailand. Thurner's last recorded words were, "Oh, reverser's deployed". Job, Macarthur (1996). ''Air Disaster Volume 2'', Aerospace Publications, : pp.203–217 Just after, the cockpit voice recorder (CVR) recorded a shuddering sound, followed closely by a snap. Because of the reverser design, the lift on the aircraft's left wing leading edge became disrupted due to the aerodynamic plume formed during the engine's rundown to idle thrust, and resulted in a 25 percent loss of lift, resulting in an aerodynamic stall.

The aircraft immediately began a diving left turn. The CVR recorded a second snapping sound, followed by various alerts such as overspeed and master caution, and Welch's last recorded words, which were, "Jesus Christ," in response to the rapid rolling sensation, followed by "here, wait a minute", as he shut down the engine, and then, "damn it". Following this, the CVR recorded an increase in background noise, followed by several loud bangs. Maneuvering overloads produced by the pilots' attempts to regain pitch control, in combination with the velocity during the dive, already had exceeded the aircraft's structural limits, and destroyed the weakened rear fuselage, taking the rest of the damaged flight surfaces with it. The loss of the tail caused further negative loading of the wings as the airplane nosed over vertically, reaching a recorded speed of Mach 0.99 (The highest value onboard sensors were capable of recording), breaking the sound barrier.

At that point, the wings failed and sheared off at the trailing edges, engulfing the remains of the falling aircraft in flames before impacting mountainous wooded terrain and exploding. Most of the wreckage was scattered over a remote forest area roughly one square kilometre in size, at an elevation of , in what is now Phu Toei National Park, Suphan Buri. The wreckage site is about north-northeast of Phu Toey, Huay Kamin ( th, ห้วยขมิ้น), Dan Chang district, Suphan Buri province, about northwest of Bangkok, close to the Burma-Thailand border.More Than 200 Believed Killed As Plane Crashes in Thai Jungle
. Associated Press. 27 May 1991. Retrieved on 27 January 2013. Rescuers found Welch's body still in the pilot's seat."UN drug man 'not Thai bomb target'". ''The Independent''. Thursday 30 May 1991. Available on LexisNexis.

Recovery

Volunteer rescue teams and local villagers looted the wreckage, taking electronics and jewellery, 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 decomposed. Dental and forensic experts worked to identify bodies, but twenty-seven were never identified.Finlay, Victoria.
Relatives return to crash site for memorial service
. ''South China Morning Post''. Tuesday 25 May 1993. Retrieved 26 May 2013.

Speculation circulated that a bomb may have destroyed the aircraft, largely due to eyewitness reports of the large fireball surrounding the aircraft that had resulted from the disintegration of its right wing during the dive. ''The Philadelphia Inquirer'', citing wire services it did not identify, stated that "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.""Looting May Hurt Jet-crash Probe; Airline Chief Denies Extortion Plot". Inquirer Wire Services at ''The Philadelphia Inquirer''
1
Retrieved on 26 May 2013.

Investigation

The flight data recorder was completely destroyed, so only the cockpit voice recorder was of use. Pradit Hoprasatsuk, the head of the Air Safety Division of the Thailand Department of Aviation, stated, "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". Upon hearing of the crash, Niki Lauda traveled to Thailand. He examined the wreckage and estimated that the largest fragment was about by , which was about half the size of the largest piece in the Lockerbie crash. In Thailand, Lauda attended a funeral for 23 unidentified passengers, and then traveled to Seattle to meet with Boeing representatives.

The official investigation, led by Thailand's Aircraft Accident investigation Committee, took about eight months, and was released with the "probable cause" stating: "The Accident Investigation Committee of the Government of Thailand determines the probable cause of this accident to be nuncommanded in-flight deployment of the left engine thrust reverser, which resulted in loss of flight path control. The specific cause of the thrust reverser deployment has not been positively identified." 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 15 February 2013. Different possibilities were investigated, including a short circuit in the system. Due in part to the destruction of much of the wiring, no definitive reason for the activation of the thrust reverser could be found.

As evidence started to point towards the thrust reversers as the cause of the accident, Lauda 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. Owner Rejects Thrust as Cause of Air Crash
. ''The New York Times''. 7 June 1991. Retrieved 26 January 2013. However the accident report states that the "flight crew 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. Aviation writer Macarthur Job has said that "had that Boeing 767 been of an earlier version of the type, fitted with engines that were controlled mechanically rather than electronically, then that accident could not have happened".

Lauda's visit with Boeing

Lauda stated, "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 that used different data as compared to the one that Lauda had performed tests on at Gatwick Airport.Williamson, Hank (2011). Air Crash Investigations: Suddenly Falling Apart The Crash Of Lauda Air Flight NG 004, : p. 40. Boeing initially refused, but Lauda insisted, so Boeing granted permission. 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. 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 not be survivable, and Boeing issued it. Lauda then added, "this was the first time in eight months that it had been made clear that the manufacturer oeingwas at fault and not the operator of the aeroplane r Pratt and Whitney"

Previous testing of thrust reversers

When the US Federal Aviation Administration (FAA) asked Boeing to test activating the thrust reverser in flight, the FAA had allowed Boeing to devise the tests. Boeing had insisted that a deployment was not possible in flight. In 1982 Boeing conducted a test wherein the aircraft was flown at , then slowed to , and the test pilots then deployed the thrust reverser. The control of the aircraft was not jeopardized. The FAA accepted the results of the test.

The Lauda aircraft was traveling at a high speed () and at almost when the left thrust reverser 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 what to do. A thrust reverser deploying in flight might 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 of Lauda Flight 004, additional safety features such as mechanical positive locks were mandated to prevent thrust reverser deployment in flight.

Passengers and crew

The passengers and crew included 83 Austrians: 74 passengers and nine crew members.Traynor, et al. "Crash teams investigate plane blast". ''The Independent''. 28 May 1991.Wallace, Charles P. "'All Evidence' in Thai Air Crash Points to Bomb". ''Los Angeles Times''. 28 May 1991
2
Retrieved 15 February 2013. Other nationalities included 52 Hong Kong residents,Finlay, Victoria.
Jet tragedy families wait on pay
. ''South China Morning Post''. 25 May 1993. Retrieved 27 January 2013. 39 Thai, 10 Italians, seven Swiss, six Chinese, four Germans, three Portuguese, three Taiwanese, three Yugoslavs, two Hungarians, two Filipinos, two Britons, three Americans (two passengers and the captain), one Australian, one Brazilian, one Pole, and one Iranian Turk girl who boarded the aircraft with a Turkish passport.Pilots' Final Words
. Associated Press]. ''The Seattle Times''. 6 June 1991. Retrieved 15 February 2013.

Josef Thurner, the copilot, once flew as a co-pilot with Niki Lauda on a Lauda Boeing 767 service to Bangkok, a flight that was the subject of a '' Reader's Digest'' article in January 1990 that depicted the airline positively. Macarthur Job stated that Thurner was the better known of the crew members. Thomas J. Welch, the captain, lived in Vienna, but originated from Seattle, Washington.

Notable victims include:
* Clemens August Andreae, an Austrian economics professor,Lauda Air-Absturz in Thailand jährt sich zum 20. Mal
" auda Air Crash in Thailand marks its 20th anniversary '' Die Presse''. 26 May 2011. Retrieved on 14 February 2013. was leading a group of students from the University of Innsbruck on a tour of the Far East.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." [English: Six of the ten victims of South Tyrol are students of the Innsbruck Faculty of Economics from Klausen, Val Gardena, Olang, Mals and Kiens, who had participated in an excursion to the Far East under the guidance of Clemens August Andreae. The other four South Tyrolean fatalities - all from Bolzano - are two civil servants and a professional musician with his Chinese wife and the Bolzano-born daughter of the two."]
* 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."

Aftermath

About a quarter of the airline's carrying capacity was destroyed as a result of the crash. Following the crash of OE-LAV, the airline had no flights to Sydney, 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, even worse than the recovery from his injuries after his crash in the 1976 German Grand Prix. After the crash, bookings from Hong Kong decreased by 20% but additional passengers from Vienna began booking flights, so there were no significant changes in overall bookings.

In early August 1991, Boeing issued an alert to airlines stating that over 1,600 late model 737s, 747s, 757s, and 767s had thrust reverser systems similar to that of OE-LAV. Two months later, customers were asked to replace potentially faulty valves in the thrust reverser systems that could cause reversers to deploy in flight.

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 at Wat Sa Kaeo Srisanpetch, about away in Mueang Suphan Buri district.

Twenty-eight years later, Niki Lauda passed away at the age of 70, on 20 May 2019.

In popular culture

The crash of Flight 004 was featured in the Canadian documentary television series Mayday, in season fourteen, episode two, titled "Testing the Limits".

See also

* Sudan Airways Flight 2241
* TAM Transportes Aéreos Regionais Flight 402
* Pacific Western Airlines Flight 314
* Atlantic Southeast Airlines Flight 2311

Notes

References

Accident Report — Lauda Air Flight 004
— 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, 8 July 2008. , 9780061734588.
* Job, Macarthur. ''Air Disaster, Volume 2''. Aerospace Publications, 1996. , 9781875671199.
* Parschalk, Norbert and Bernhard Thaler. ''Südtirol Chronik: das 20. Jahrhundert''. Athesia, 1999.

Further reading

* Gilbert, Andy.
Lauda Air
. ''South China Morning Post''. Thursday 26 May 1994.
* ''Aviation Week & Space Technology''. 1991-10-03 (32), 1991-10-06 (28–30)

External links

Lauda Air Crash 1991: still too many open questions
nbsp;— Austrian Wings — Austrias Aviation Magazine

การสอบสวนอากาศยานประสบอุบัติเหต
Department of Civil Aviation
Archive


Ministry of Transport & Communications Thailand (in English)


. ( ttps://web.archive.org/web/20140327234142/http://www.rvs.uni-bielefeld.de/publications/compendium/incidents_and_accidents/lauda_air_b767.html Archive Bielefeld University. 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)
nbsp;— ''Austrian Wings'' — Austria's Aviation Magazine
Cockpit Voice Recorder transcript and accident summary

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