Lauda Air Flight 004 (NG004/LDA004) was a regularly scheduled international passenger flight from Bangkok, Thailand to Vienna, Austria. On May 26, 1991, the Boeing 767-300ER 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 midair breakup, killing all 213 passengers and ten crew members on board. It is the deadliest aviation accident involving the Boeing 767, and the deadliest aviation accident in Thailand's history. The crash marked the 767's first fatal incident and third hull loss.[1][2][3] Formula One world motor racing champion Niki Lauda, who founded and ran Lauda Air, was personally involved in the accident investigation.

Lauda Air Flight 004
OE-LAV, the aircraft involved in the accident, in 1989
Date26 May 1991 (1991-05-26)
SummaryIn-flight breakup following uncommanded thrust-reverser deployment caused by possible design flaws and electrical failure
SitePhu Toei National Park, Suphan Buri province, Thailand
14°56′48″N 99°27′10″E / 14.94667°N 99.45278°E / 14.94667; 99.45278
Aircraft typeBoeing 767-3Z9ER
Aircraft nameMozart
OperatorLauda Air
IATA flight No.NG004
ICAO flight No.LDA004
Call signLAUDA 4
Flight originKai Tak Airport, British Hong Kong
StopoverDon Mueang International Airport, Bangkok, Thailand
DestinationVienna International Airport, Vienna, Austria

Aircraft edit

The aircraft involved was a Boeing 767-300ER, the 283rd Boeing 767 built,[4] that was powered by Pratt & Whitney PW4060 engines and was delivered new to Lauda Air on 16 October 1989.[5] The aircraft was registered OE-LAV and named Mozart.[4]: 21  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.[4]: 4 

Accident edit

Image of the plane disintegrating in mid-air

At the time of the accident, Lauda Air operated three weekly flights between Bangkok and Vienna.[6] At 23:02 ICT on 26 May 1991, the Boeing 767-3Z9ER operating as Flight 4 (originating from Hong Kong's Kai Tak Airport) departed Don Mueang International Airport in Bangkok 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).[4]: 4 [7][8][9][10][11] Both pilots were regarded as very competent. At 23:08, Welch and Thurner received a visual warning indication on the EICAS display that a possible system failure would cause the thrust reverser on the No. 1 engine to deploy in flight. After consulting the aircraft's Quick Reference Handbook, they determined that the alert was "coming on and off" and that it was "just an advisory thing." The pilots took no remedial action, possibly believing that the indication was false, but also with the knowledge that the 767 could stop with only one operational reverser.[1]

At 23:17, the No. 1 engine reverser deployed while the plane was over mountainous jungle terrain in the border area between the Suphan Buri and Uthai Thani provinces in Thailand. Thurner's last recorded words were, "Oh, reverser's deployed."[12][4]: 55  Moments later, 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 because of the aerodynamic plume formed during the engine's rundown to idle thrust and resulted in a 25% loss of lift and 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: "Jesus Christ" in response to the rapid rolling sensation, "here, wait a minute" as he shut down the engine and finally, "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, had already exceeded the aircraft's structural limits and destroyed the weakened rear fuselage along with the rest of the damaged flight surfaces. The loss of the tail caused further negative loading of the wings as the airplane nosed over vertically, reaching a speed of at least Mach 0.99 (the highest value that the aircraft's sensors could record), breaking the sound barrier.

The wings then failed and separated at the trailing edges, engulfing the remains of the falling aircraft in flames before impacting mountainous wooded terrain and exploding.[13] Most of the wreckage was scattered over a remote forest area roughly one square kilometre in size, at an elevation of 600 m (2,000 ft), in what is now Phu Toei National Park, Suphan Buri. The wreckage site is about 6 kilometres (4 mi; 3 nmi) north-northeast of Phu Toey, Huay Kamin (Thai: ห้วยขมิ้น), Dan Chang district, Suphan Buri province,[4] about 100 kilometres (62 mi; 54 nmi) northwest of Bangkok, close to the Burma-Thailand border.[6][14] Rescuers found Welch's body still in the pilot's seat.[15]

Recovery edit

Volunteer rescue teams and local villagers looted the wreckage, taking electronics and jewellery,[16] so relatives were unable to recover personal possessions.[17] The bodies were taken to a hospital in Bangkok, but the storage was not refrigerated and the bodies decomposed. Dental and forensic experts worked to identify bodies, but 27 were never identified.[18]

Speculation circulated that a bomb may have destroyed the aircraft, as some eyewitnesses had reported seeing a large fireball surrounding the aircraft, the result of the disintegration of the right wing during the dive. However, a terrorist motive was believed unlikely, as Austria was politically neutral with a reputation of avoiding international conflicts such as the recent Gulf War.[19]

Investigation edit

Niki Lauda travelled to Thailand to assist in the investigation

The flight data recorder was completely destroyed, so only the cockpit voice recorder could be analysed. Thailand's Air Safety Division head Pradit Hoprasatsuk stated that "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."[20] Upon hearing of the crash, Niki Lauda traveled to Thailand. He examined the wreckage and estimated that the largest fragment was about five metres (16 ft) by two metres (6.6 ft), which was about half the size of the largest piece resulting from the Lockerbie bombing.[21] Lauda attended a funeral for 23 unidentified passengers in Thailand and then traveled to Seattle to meet with Boeing representatives.

The official investigation, led by Thailand's Aircraft Accident Investigation Committee, lasted approximately eight months and resulted in a conclusion of probable cause: "The Accident Investigation Committee of the Government of Thailand determines the probable cause of this accident to be [an] uncommanded 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."[22] Multiple possibilities were investigated, including a short circuit in the electrical system. However, the destruction of much of the wiring meant that investigators could not arrive at a definitive reason for the activation of the thrust reverser.[4]

As evidence began to implicate the thrust reversers as the cause of the accident, Lauda conducted simulator flights at Gatwick Airport that appeared to show that deployment of a thrust reverser was a survivable condition. Lauda said that the thrust reverser could not be the sole cause of the crash.[23] However, the accident report states that the "flight crew training simulators yielded erroneous results"[4]: 21  and that recovery from the loss of lift from the reverser deployment "was uncontrollable for an unexpecting flight crew."[4]: 41 

The incident prompted 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.[4][24] Aviation writer Macarthur Job has stated 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."[12]

Lauda's visit with Boeing edit

Lauda stated: "What really annoyed me was Boeing's reaction once the cause was clear. Boeing did not want to say anything."[22] He asked Boeing to fly the scenario in a simulator using data different to that which Lauda had employed in his tests at Gatwick Airport.[25] 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 company's legal department replied that 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 a 767 with two pilots and have the thrust reverser deploy in air. Boeing told Lauda that it was not possible, so he persuaded Boeing to issue a statement saying that such a scenario would not be survivable. Lauda then added that "this was the first time in eight months that it had been made clear that the manufacturer [Boeing] was at fault and not the operator of the aeroplane [or Pratt and Whitney]."[22]

Previous testing of thrust reversers edit

When the U.S. Federal Aviation Administration (FAA) asked Boeing to test activating the thrust reverser in flight,[26] 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 in which the aircraft was flown at 10,000 feet (3,000 m) and then slowed to 250 knots (460 km/h; 290 mph; 130 m/s), and the test pilots then deployed the thrust reverser. The control of the aircraft was not jeopardized, and the FAA accepted the results of the test.[27]

The Lauda aircraft was travelling at a TAS speed of (400 knots (740 km/h; 460 mph)) at 24,700 feet (7,500 m) in the climb to 30,000 feet (9,100 m)[28] when the left thrust reverser deployed, causing the pilots to lose control of the aircraft. James R. Chiles, author of Inviting Disaster, said: "[T]he point here is not that a thorough test would have told the pilots Thomas J. Welch and Josef Thurner 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."[29]

Passengers and crew edit

Nation Passengers Crew Total
Austria 74 9 83
Hong Kong 52 0 52
Thailand 39 0 39
Italy 10 0 10
Switzerland 7 0 7
China 6 0 6
Germany 4 0 4
Portugal 3 0 3
Taiwan 3 0 3
Yugoslavia 3 0 3
United States 2 1[a] 3
Hungary 2 0 2
Philippines 2 0 2
United Kingdom 2 0 2
Australia 1 0 1
Brazil 1 0 1
Poland 1 0 1
Turkey 1 0 1
Total 213 10 223

The passengers and crew included 83 Austrians: 74 passengers and nine crew members.[30][31] Other nationalities included 52 Hong Kong residents,[31][32] 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 Turk.[31][33]

First officer Josef Thurner had once flown as a copilot with Niki Lauda on a Lauda Air 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.[34] Captain Thomas J. Welch lived in Vienna[31] but originated from Seattle, Washington.[33]

Notable victims included:

Aftermath edit

Flight 004 Memorial near Suphanburi

About a quarter of the airline's carrying capacity was destroyed as a result of the crash.[39] Following the crash of OE-LAV, the airline operated no flights to Sydney on 1, 6 and 7 June. Flights resumed with another 767 on 13 June.[40] Niki Lauda said that the crash and the ensuing period constituted the worst time in his life, even worse than the recovery from injuries that he had sustained after a crash in the 1976 German Grand Prix.[22] After the Flight 004 crash, bookings from Hong Kong decreased by 20%, but this was offset by an increase in bookings by passengers based in Vienna.[32]

In early August 1991, Boeing issued an alert to airlines stating that more than 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.[41]

At the crash site, which is accessible to national park visitors, a shrine was erected to commemorate the victims.[42] Another memorial and cemetery is located at Wat Sa Kaeo Srisanpetch, about 90 kilometres (56 mi; 49 nmi) away in Mueang Suphan Buri district.[43]

In popular culture edit

The crash of Flight 004 was featured in the second episode of Season 14 of the Canadian documentary television series Mayday, titled "Testing the Limits."[44]

See also edit

Notes edit

  1. ^ The captain.

References edit

  1. ^ a b Accident description at the Aviation Safety Network
  2. ^ Ranter, Harro. "Boeing 767". Aviation Safety Network. Retrieved 6 March 2019.
  3. ^ Ranter, Harro. "Thailand air safety profile". Aviation Safety Network. Retrieved 6 March 2019.
  4. ^ a b c d e f g h i j "Accident Report". Aircraft Accident Investigation Committee. Archived from the original on 7 June 2011. Retrieved 14 February 2014.
  5. ^ – Boeing 767 – MSN 24628 – OE-LAV retrieved 3 July 2016
  6. ^ a b Tummachartvijit, Tavorn. "Cause of airliner explosion Sought". Associated Press The Dispatch. 27 May 1991. 1A and 6A.
  7. ^ "Excerpts from Lauda News Conference on Crash of Boeing 767 With AM-Thailand Crash". AP NEWS. Associated Press. Retrieved 25 May 2020.
  8. ^ Lewis Jr M.D, Joseph W. (28 October 2016). Last and Near-Last Words of the Famous, Infamous and Those In-Between. AuthorHouse. ISBN 978-1-5246-4787-2.
  9. ^ "Two Doomed 767S Were Partners On Assembly Line". The Seattle Times. Retrieved 25 May 2020.
  10. ^ "Lauda 004 air crash". Retrieved 25 May 2020.
  11. ^ "Lauda Air 004 CVR Transcript". Retrieved 25 May 2020.
  12. ^ a b Job, Macarthur (1996). Air Disaster Volume 2, Aerospace Publications, ISBN 1-875671-19-6: pp.203–217
  13. ^ Chiles, p. 309.
  14. ^ "More Than 200 Believed Killed As Plane Crashes in Thai Jungle". Associated Press. 27 May 1991. Retrieved on 27 January 2013.
  15. ^ a b "UN drug man 'not Thai bomb target'". The Independent. Thursday 30 May 1991. Available on LexisNexis.
  16. ^ Johnson, Sharen Shaw. "Scavengers complicate crash probe". USA Today. 29 May 1991. News 4A.
  17. ^ Krausz, Tibor (10 December 2019). "Pilgrimage to Thai plane crash site for aunt killed 28 years ago: 'I'm here for you. You're no longer alone.'". South China Morning Post. Retrieved 10 December 2019.
  18. ^ Finlay, Victoria. "Relatives return to crash site for memorial service". South China Morning Post. Tuesday 25 May 1993. Retrieved 26 May 2013.
  19. ^ "Looting May Hurt Jet-crash Probe; Airline Chief Denies Extortion Plot". Inquirer Wire Services at The Philadelphia Inquirer. 1. Retrieved on 26 May 2013.
  20. ^ Archive. Associated Press. 31 August 1993. Retrieved on 16 March 2014.
  21. ^ "Looting may have hidden clues to crash". The Advertiser. Thursday 30 May 1991.
  22. ^ a b c d 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.
  23. ^ "Owner Rejects Thrust as Cause of Air Crash". The New York Times. 7 June 1991. Retrieved 26 January 2013.
  24. ^ Acohido, Byron. "Boeing Thrust Reversers Had History Of Glitches". Chicago Tribune.
  25. ^ Williamson, Hank (2011). Air Crash Investigations: Suddenly Falling Apart The Crash Of Lauda Air Flight NG 004, ISBN 9781257505401: p. 40.
  26. ^ Chiles, p. 112113.
  27. ^ Chiles, p. 113.
  28. ^
  29. ^ Chiles, p. 114.
  30. ^ Traynor, et al. "Crash teams investigate plane blast". The Independent. 28 May 1991.
  31. ^ a b c d Wallace, Charles P. "'All Evidence' in Thai Air Crash Points to Bomb". Los Angeles Times. 28 May 1991. 2. Retrieved 15 February 2013.
  32. ^ a b Finlay, Victoria. "Jet tragedy families wait on pay". South China Morning Post. 25 May 1993. Retrieved 27 January 2013.
  33. ^ a b "Pilots' Final Words". Associated Press]. The Seattle Times. 6 June 1991. Retrieved 15 February 2013.
  34. ^ 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 Reader's Digest [...]"
  35. ^ "Lauda Air-Absturz in Thailand jährt sich zum 20. Mal." [Lauda Air Crash in Thailand marks its 20th anniversary] (in German) Die Presse. 26 May 2011. Retrieved on 14 February 2013.
  36. ^ Parschalk and Thaler, p. 394(in German) "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."]
  37. ^ รายนามผู้ดำรงตำแหน่งผู้ว่าราชการจังหวัดเชียงใหม่ [List of incumbent governor of Chiang Mai Province]. (in Thai). Retrieved 17 March 2017.
  38. ^ "Special Messages from 8 U.S. Consuls General in Chiang Mai". (Archive) United States Department of State. Retrieved on 15 February 2013. Thai version, Archive
  39. ^ Traynor, Ian. "Lauda's driving ambition brings triumph and disaster in tandem". The Independent. 28 May 1991.
  40. ^ Aircraft, Volume 71. p. 44. "LAUDA AIR/LDA: Following the still unexplained loss of B767-329ER OE-LAV [24628] Mozart, there were no flights to Sydney by the Austrian carrier on 1, 6 and 7 June. Services resumed on 13 June with B767-3T9 (ER) OE-LAU [23765 xN6009F]
  41. ^ Lane, Polly and Acohido, Byron. "Boeing Tells 757 Owners To Replace Part – Faulty Thrust-Reverser Valve Blamed In 767 Accident That Killed 223". The Seattle Times. Monday, 9 September 1991. Retrieved on 15 February 2013.
  42. ^ "Truly Unseen: Phu Toei National Park | Thai Blogs". Archived from the original on 8 December 2010.
  43. ^ "Lauda Air Crash, 26 May 1991: Thailand's Worst Ever | Thai Blogs". Retrieved 29 September 2019.
  44. ^ "Mayday - Niki Lauda: Testing the Limits (Lauda Air Flight 004) -". Retrieved 3 March 2022.

Citations edit

Further reading edit

External links edit