Английская Википедия:British Airways Flight 38

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Файл:190fe - British Airways Boeing 777-236ER, G-YMMM@LHR,05.10.2002 - Flickr - Aero Icarus.jpg
G-YMMM, the aircraft involved in the accident in May 2002

British Airways Flight 38 was a scheduled international passenger flight from Beijing Capital International Airport in Beijing, China, to London Heathrow Airport in London, United Kingdom, an Шаблон:Convert trip. On 17 January 2008, the Boeing 777-200ER aircraft operating the flight crashed just short of the runway while landing at Heathrow.[1][2][3] No fatalities occurred; of the 152 people on board, 47 sustained injuries, one serious.[4] It was the first time in the aircraft type's history that a Boeing 777 was declared a hull loss, and subsequently written off.[5][6]

The accident was investigated by the Air Accidents Investigation Branch (AAIB) and a final report was issued in 2010. Ice crystals in the jet fuel were blamed as the cause of the accident, clogging the fuel/oil heat exchanger (FOHE) of each engine. This restricted fuel flow to the engines when thrust was demanded during the final approach to Heathrow.[7] The AAIB identified this rare problem as specific to Rolls-Royce Trent 800 engine FOHEs. Rolls-Royce developed a modification to the FOHE; the European Aviation Safety Agency (EASA) mandated all affected aircraft to be fitted with the modification before 1 January 2011.[4][8] The US Federal Aviation Administration noted a similar incident occurring on an Airbus A330 fitted with Rolls-Royce Trent 700 engines and ordered an airworthiness directive to be issued, mandating the redesign of the FOHE in Rolls-Royce Trent 500, 700, and 800 engines.[9]

Aircraft

The aircraft involved in the accident was a Boeing 777-236ER, registration Шаблон:Nowrap (manufacturer's serial number 30314, line number 342), powered by two Rolls-Royce Trent 895-17 engines.[10] The aircraft first flew on 18 May 2001 and was delivered to British Airways on 31 May 2001.[11] It had a seating capacity of 233 passengers.[4]Шаблон:RP On board were 16 crew members and 136 passengers. The crew consisted of Captain Peter Burkill (43), Senior First Officer John Coward (41), First Officer Conor Magenis (35), and 13 cabin crew members. The captain had 12,700 total flight hours, with 8,450 in Boeing 777 aircraft. The senior first officer had 9,000 total flight hours, with 7,000 in Boeing 777 aircraft. The first officer had 5,000 total flight hours, with 1,120 in Boeing 777 aircraft.[4]Шаблон:RP

Accident

Файл:BA38 map close.PNG
A map showing the location of the plane (blue dot) after landing and sliding through the field on the runway safety area – route marked in red
Файл:BA 38 Accident Path facing west.png
Path of G-YMMM from first ground contact until it came to rest in the taxiway at the corner of the approach end of runway 27L. Note the red ILS antenna array in the foreground, which was narrowly missed by the aircraft.

Flight 38 departed from Beijing at 02:09 Greenwich Mean Time (GMT), flying a route that crossed Mongolia, Siberia, and Scandinavia, at altitudes between flight level 348 and 400—approximately Шаблон:Convert, and in temperatures between Шаблон:Cvt and Шаблон:Cvt.[4]Шаблон:RP Aware of the cold conditions outside, the crew monitored the temperature of the fuel, with the intention of descending to a lower and warmer level if any danger of the fuel freezing arose.[4]Шаблон:RP This did not prove necessary, as the fuel temperature never dropped below Шаблон:Cvt, still well above its freezing point.[Note 1]

Although the fuel itself did not freeze, small quantities of water in the fuel did.[Note 2] Ice adhered to the inside of the fuel lines, probably where they ran through the pylons attaching the engines to the wings.[4]Шаблон:RP This accumulation of ice had no effect on the flight until the final stages of the approach into Heathrow, when increased fuel flow and higher temperatures suddenly released it back into the fuel.[4]Шаблон:RP This formed a slush of soft ice that flowed forward until it reached the fuel/oil heat exchangers (FOHEs)[Note 3] where it froze once again, causing a restriction in the flow of fuel to the engines.[4]Шаблон:RP[4]Шаблон:RP

The first symptoms of the fuel-flow restriction were noticed by the flight crew at an altitude of Шаблон:Convert and Шаблон:Convert from touchdown, when the engines repeatedly failed to respond to a demand for increased thrust from the autothrottle. In attempting to maintain the instrument landing system glide slope, the autopilot sacrificed speed, which reduced to Шаблон:Convert at Шаблон:Convert.[1] The autopilot disconnected at Шаблон:Convert, as the co-pilot took manual control.[4]Шаблон:RP Meanwhile, the captain reduced the flap setting from 30 to 25° to decrease the drag on the aircraft and stretch the glide.[4]Шаблон:RP[13]

At 12:42, the 777 passed just above the residential street of Myrtle Avenue,[14] then immediately after overflew traffic on the A30 and the airport's Southern Perimeter road and landed on the grass about Шаблон:Convert short of runway 27L.[4]Шаблон:RP The captain declared an emergency to air traffic control a few seconds before landing. The decision to raise the flaps allowed the plane to glide beyond the ILS beacon within the airport perimeter, thus avoiding more substantial damage.[4]Шаблон:RP

During the impact and short slide over the ground, the nose gear collapsed, the right main gear separated from the aircraft, penetrating the central fuel tank and the passenger oxygen supply, causing a major fuel leak and the release of oxygen gas from adjacent compartments.[4]Шаблон:RP The right main landing gear also penetrated the cabin space, causing the sole serious injury in this accident to a passenger in seat 30K. The left main gear was pushed up through the wing, as it was designed to do in case of failure due to excessive vertical load. The aircraft came to rest on the threshold markings at the start of the runway. Шаблон:Cvt of fuel leaked, but no fire started.[4]Шаблон:RP One passenger received serious injuries (concussion and a broken leg), and four crew members and eight passengers received minor injuries.[1][2][3]

Aftermath

The London Ambulance Service stated that three fast response cars, nine ambulances, and several officers were sent to the scene to assess the casualties. Those injured were taken to the nearby Hillingdon Hospital.[15]

Willie Walsh, the British Airways chief executive, released a statement praising the actions of the "flight and cabin crew [who] did a magnificent job and safely evacuated all of the 136 passengers ... The captain of the aircraft is one of our most experienced and has been flying with us for nearly 20 years. Our crews are trained to deal with these situations."[16] He also praised the fire, ambulance, and police services.

All flights in and out of Heathrow were halted for a short time after the accident. When operations resumed, many long-haul outbound flights were either delayed or cancelled, and all short-haul flights were cancelled for the rest of the day. Some inbound flights were delayed, and 24 flights were diverted to Gatwick, Luton, or Stansted. In an attempt to minimise further travel disruptions, Heathrow Airport received dispensation from the Department for Transport to operate some night flights.[2] Even so, the following day (18 January), 113 short-haul flights were cancelled because crews and aircraft were out of position.[17]

On the afternoon of 20 January 2008, two cranes lifted the aircraft onto wheeled platforms and removed it from its resting place.[18] It was towed towards Heathrow's BA maintenance hangars base for storage and further inspections by the AAIB. After assessment of the damage and repair costs, the aircraft was declared to be damaged beyond economic repair (despite still being largely intact) and written off, becoming the first Boeing 777 hull loss in history.[19] It was broken up and scrapped in the spring of 2009. The dismantling and disposal was handled by Air Salvage International.[20]

During a press conference the day after the accident, Captain Peter Burkill said that he would not be publicly commenting on the cause of the incident while the AAIB investigation was in progress. He revealed that Senior First Officer John Coward was flying the aircraft, and that First Officer Conor Magenis was also present on the flight deck at the time of the accident.[21] Coward was more forthcoming in a later interview, stating: "As the final approach started I became aware that there was no power ... suddenly there was nothing from any of the engines, and the plane started to glide."[22]

Burkill and Coward were grounded for a month following the crash while they were assessed for post-traumatic stress disorder. Five months after the accident, Burkill flew again, taking charge of a flight to Montreal, Canada. He remained "haunted" by the incident, and took voluntary redundancy from British Airways in August 2009.[23] Burkill subsequently established a blog and wrote a book, Thirty Seconds to Impact, that denounced BA's treatment of the situation following the crash.[24] In November 2010, Burkill rejoined British Airways, stating, "I am delighted that the discussions with British Airways, have come to a mutually, happy conclusion. In my opinion, British Airways is the pinnacle of any pilot's career, and it is my honour and privilege to be returning to an airline that I joined as a young man."[25]

All 16 crew were awarded the BA Safety Medal for their performance during the accident. The medal is British Airways' highest honour.[26] On 11 December 2008 the crew received the President's Award from the Royal Aeronautical Society.[27]

British Airways continues to use the flight 38 designation on its Beijing to Heathrow route,[28] operating out of Beijing Daxing International Airport, usually with a Boeing 787 Dreamliner.

Initial speculations

Mechanical engine failure was not regarded as a likely cause given the very low probability of a simultaneous dual engine failure.[29] An electronic or software glitch in the computerised engine-control systems was suggested as possible causes of the simultaneous loss of power on both engines.[29] Both engine and computer problems were ruled out by the findings of the February Special Bulletin.[1]

Some speculation indicated that radio interference from Prime Minister Gordon Brown's motorcade, which was leaving Heathrow after dropping the Prime Minister off for a flight to China, was responsible for the accident. This interference was also eliminated as a cause.[4]Шаблон:RP

Initial analysis from David Learmount, a Flight International editor, was that "The aircraft had either a total or severe power loss and this occurred very late in the final approach because the pilot did not have time to tell air traffic control or passengers." Learmount went on to say that to land in just Шаблон:Convert, the aircraft must have been near stalling when it touched down.[30][31] The captain also reported the aircraft's stall warning system had sounded.[32]

A METAR issued twenty minutes before the crash indicated that the wind was forecast to gust according to ICAO criteria for wind reporting.[33] The possibility of a bird strike was raised, but there were no sightings or radar reports of birds.[29] Speculation had focused on electronics and fuel supply issues.[34] A few weeks after the accident, as suspicion started to fall on the possibility of ice in the fuel, United Airlines undertook a review of their procedures for testing and draining the fuel used in their aircraft, while American Airlines considered switching to a different type of jet fuel for polar flights.[35]

Investigation

The Department for Transport's AAIB investigated the accident, with the US National Transportation Safety Board, Boeing, and Rolls-Royce also participating.[4]Шаблон:RP The investigation took two years to complete, and the AAIB published its final report on 9 February 2010. Three preliminary reports and 18 safety recommendations were issued during the course of the investigation.[4]Шаблон:RP

The flight data recorder (FDR) and the cockpit voice recorder (CVR), along with the quick access recorder (QAR), were recovered from the aircraft within hours of the accident, and they were transported to the AAIB's Farnborough headquarters, some Шаблон:Convert from Heathrow.[36] The information downloaded from these devices confirmed what the crew had already told the investigators, that the engines had not responded when the throttles were advanced during final approach.[37][38]

Fuel system

Файл:BA 38 Cavitation explained.jpg
Illustration of cavitation in the high pressure fuel pumps used in the Trent 800 engines on the Boeing 777. When fuel flowing into the pump falls to very low pressure, gas bubbles form in the fuel. Bubble collapse on the high pressure side can cause damage to the pump's outlet ports.
Файл:Cavitation in a gear pump.ogv
This video shows cavitation in a gear pump similar to that used in the Boeing 777.
Файл:Fuel system mock-up for BA 38 investigation.jpg
Mock-up of G-YMMM's fuel delivery system

In its Special Bulletin of 18 February 2008, the AAIB noted evidence that cavitation had taken place in both high-pressure fuel pumps, which could be indicative of a restriction in the fuel supply or excessive aeration of the fuel, although the manufacturer assessed both pumps as still being able to deliver full fuel flow. The report noted the aircraft had flown through air that was unusually cold (but not exceptionally so), and concluded that the temperature had not been low enough to freeze the fuel. Tests were continuing in an attempt to replicate the damage seen in the fuel pumps and to match this to the data recorded on the flight. A comprehensive examination and analysis was to be conducted on the entire aircraft and engine fuel system, including modelling fuel flows, taking account of environmental and aerodynamic effects.

The AAIB issued a further bulletin on 12 May 2008, which confirmed that the investigation continued to focus on fuel delivery. It stated, "The reduction in thrust on both engines was the result of a reduced fuel flow and all engine parameters after the thrust reduction were consistent with this." The report confirmed that the fuel was of good quality and had a freezing point below the coldest temperatures encountered, appearing to rule out fuel freezing as a cause. As in the aforementioned February bulletin, the report noted cavitation damage to the high-pressure fuel pumps of both engines, indicative of abnormally low pressure at the pump inlets. After ruling out fuel freezing or contamination, the investigation then focused on what caused the low pressure at the pump inlets. "Restrictions in the fuel system between the aircraft fuel tanks and each of the engine HP pumps, resulting in reduced fuel flows, is suspected." The fuel delivery system was being investigated at Boeing, and the engines at manufacturer Rolls-Royce in Derby.

The AAIB issued an interim report on 4 September. Offering a tentative conclusion, it stated:[39]

Шаблон:Cquote

The report summarised the extensive testing performed in an effort to replicate the problem suffered by G-YMMM. This included creating a mock-up of G-YMMM's fuel delivery system, to which water was added to study its freezing properties. After a battery of tests, the AAIB had not yet succeeded in reproducing the suspected icing behaviour and was undertaking further investigation. Nevertheless, the AAIB believed its testing showed that fuel flow was restricted on G-YMMM and that frozen water in the jet fuel could have caused the restriction, ruling out alternative hypotheses such as a failure of the aircraft's FADEC (computerised engine control system). The hypothesis favoured in the report was that ice had accreted somewhere downstream of the boost pumps in the wing fuel tanks and upstream of the engine-mounted fuel pumps. Either enough ice had accumulated to cause a blockage at a single point, or ice throughout the fuel lines had become dislodged as fuel flow increased during the landing approach, and the dislodged ice had then formed a blockage somewhere downstream.

Because temperatures in flight had not dropped below the 777's designed operating parameters, the AAIB recommended Boeing and Rolls-Royce take interim measures on Trent 800-powered 777s to reduce the risk of ice restricting fuel delivery.[40] Boeing did so by revising the 777 operating procedures so as to reduce the opportunities for such blockages to occur, and by changing the procedure to be followed in the event of power loss to take into account the possibility that ice accumulation was the cause.[7]Шаблон:Update after

The report went on to recommend that the aviation regulators (FAA and EASA) should consider whether other aircraft types and other engines might be affected by the same problem, and to consider changing the certification process to ensure that future aircraft designs would not be susceptible to the newly recognised danger from ice formation in the fuel.[41]

The report acknowledged that a redesign of the fuel system would not be practical in the near term, and suggested two ways to lower the risk of recurrence. One was to use a fuel additive (FSII) that prevents water ice from forming down to Шаблон:Cvt. Western air forces have used FSII for decades, and although it is not widely used in commercial aviation, it is nonetheless approved for the 777.

Rejected theories

The Special Bulletin of 18 February, stated "no evidence of a mechanical defect or ingestion of birds or ice" was found, "no evidence of fuel contamination or unusual levels of water content" was seen within the fuel, and the recorded data indicated "no anomalies in the major aircraft systems". Some small foreign bodies, however, were detected in the fuel tanks, although these were later concluded to have had no bearing on the accident.[4]Шаблон:RP

The Special Bulletin of 12 May 2008 specifically ruled out certain other possible causes, stating: "There is no evidence of a wake vortex encounter, a bird strike, or core engine icing. There is no evidence of any anomalous behaviour of any of the aircraft or engine systems that suggests electromagnetic interference." [42]

Probable cause

Файл:BA 38 Fuel system ice buildup.jpg
Accreted ice in a fuel system test rig used to investigate the crash of BA Flight 38 (G-YMMM). This ice accumulation did not cause the failure. It was when this ice was released at a warmer temperature and higher fuel flow that it flowed downstream, blocking fuel flow into the fuel/oil heat exchangers (FOHE) in both engines.

The AAIB issued a full report on 9 February 2010. It concluded: Шаблон:Cquote

Other findings

The AAIB also studied the crashworthiness of the aircraft during the accident sequence. It observed that the main attachment point for the main landing gear was the rear spar of the aircraft's wing; because this spar also formed the rear wall of the main fuel tanks, the crash landing caused the tanks to rupture. The report recommended that Boeing redesign the landing gear attachment to reduce the likelihood of fuel loss in similar circumstances.

The report went on to note that the fire extinguisher handles had been manually deployed by the crew before the fuel shut-off switches. The fire extinguisher handles also have the effect of cutting off power to the fuel switches, meaning that the fuel may continue to flow – a potentially dangerous situation. The report restated a previous Boeing Service Bulletin giving procedural advice that fuel switches should be operated before fire handles. It went on: "This was not causal to the accident, but could have had serious consequences in the event of a fire during the evacuation." Indeed, the need to issue Safety Recommendation 2008–2009, affecting all 777 airframes, which had yet to incorporate the Boeing Service Bulletin (SB 777-28-0025) – as was the case with G-YMMM – was given as the main reason for issuing the first special bulletin, well before the accident investigation itself was complete.[1]

Similar incidents

Файл:Ice-Trent-800-Heat-Exchanger.PNG
Laboratory duplication of ice crystals clogging the FOHE on a Rolls-Royce Trent 800 series engine taken from the NTSB report[7] addressing the incidents of BA Flight 38 and DL Flight 18.
Файл:N862DA (4396842208).jpg
N862DA, the aircraft involved in Delta Air Lines Flight 18, seen in 2009

On 26 November 2008, Delta Air Lines Flight 18 from Shanghai to Atlanta, another Trent 800-powered Boeing 777, experienced an "uncommanded rollback" of one engine while in cruise at Шаблон:Convert. The crew followed manual recovery procedures and the flight continued without incident. The US NTSB assigned one of the investigators who worked on the BA Flight 38 investigation to this incident, and looked specifically for any similarity between the two incidents.[43] The NTSB Safety Recommendation report[44] concluded that ice clogging the FOHE was the likely cause. The evidence was stronger in this case since data from the flight data recorder allowed the investigators to locate where the fuel flow was restricted.

In early 2009, Boeing sent an update to aircraft operators, linking the British Airways and Delta Air Lines "uncommanded rollback" incidents, and identifying the problem as specific to the Rolls-Royce engine FOHEs.[8] Originally, other aircraft were thought to be unaffected by the problem.[8] However, in May 2009, another similar incident happened with an Airbus A330 powered by a Trent series 700 engine.[45]

The enquiries led Boeing to reduce the recommended time that the fuel on 777 aircraft equipped with Rolls-Royce Trent 800-series engines be allowed to remain at temperatures below Шаблон:Cvt from three to two hours.[46]

On 11 March 2009, the NTSB issued urgent safety recommendation SB-09-11 calling for the redesign of the FOHEs used on Rolls-Royce Trent 800 Series engines. A build-up of ice from water naturally occurring in the fuel had caused a restriction of the flow of fuel to the engines of G-YMMM. Rolls-Royce had already started on redesigning the component, with an in-service date of March 2010 at the latest. All affected engines were to be fitted with the redesigned component within six months of its certification.[47] In May 2010 the Airworthiness Directive was extended to cover the Trent 500 and 700 series engines, as well.[45]

Lawsuit

In November 2009, 10 passengers were announced to be suing Boeing over the incident in the Circuit Court of Cook County in Illinois, United States.[48] Each of the ten plaintiffs reportedly could receive up to US$1,000,000 (about £600,000 at the time) compensation. The lawsuit alleged that the design of the aircraft was "defective and unreasonably dangerous", that Boeing "breached their duty of care", and also breached their "warranties of merchantability and fitness".[49] Claims were settled out of court in 2012.[50]

In popular culture

The Discovery Channel Canada / National Geographic TV series Mayday featured the incident in a season-10 episode titled "The Heathrow Enigma".[51]

See also

Шаблон:Portal

Notes

Шаблон:Reflist

References

Шаблон:Reflist

External links

Шаблон:External media Шаблон:Commons category-inline

Шаблон:Aviation accidents and incidents in 2008 Шаблон:Aviation accidents and incidents in the United Kingdom Шаблон:International Airlines Group

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  1. ↑ 1,0 1,1 1,2 1,3 1,4 Шаблон:Cite news
  2. ↑ 2,0 2,1 2,2 Шаблон:Cite news
  3. ↑ 3,0 3,1 Шаблон:Cite news
  4. ↑ 4,00 4,01 4,02 4,03 4,04 4,05 4,06 4,07 4,08 4,09 4,10 4,11 4,12 4,13 4,14 4,15 4,16 4,17 4,18 4,19 4,20 4,21 Шаблон:Cite web
  5. ↑ Шаблон:Cite news
  6. ↑ Шаблон:Cite news
  7. ↑ 7,0 7,1 7,2 Шаблон:Cite web
  8. ↑ 8,0 8,1 8,2 Шаблон:Cite web
  9. ↑ Шаблон:Cite web
  10. ↑ Шаблон:Cite web
  11. ↑ Шаблон:Cite web
  12. ↑ Шаблон:Cite web
  13. ↑ Шаблон:Cite news
  14. ↑ Шаблон:Cite web
  15. ↑ Шаблон:Cite press release
  16. ↑ Шаблон:Cite news
  17. ↑ Шаблон:Cite news
  18. ↑ Шаблон:Cite news
  19. ↑ Шаблон:Cite news
  20. ↑ Шаблон:Cite web
  21. ↑ Шаблон:Cite news
  22. ↑ Шаблон:Cite web
  23. ↑ Шаблон:Cite news
  24. ↑ Шаблон:Cite news
  25. ↑ Шаблон:Cite web
  26. ↑ Шаблон:Cite web
  27. ↑ Шаблон:Cite web
  28. ↑ Шаблон:Cite web
  29. ↑ 29,0 29,1 29,2 Шаблон:Cite news
  30. ↑ Шаблон:Cite news
  31. ↑ Шаблон:Cite news
  32. ↑ Шаблон:Cite newsШаблон:Cbignore
  33. ↑ EGLL 171220Z 21014KT 180V240 9999 SCT008 BKN010 09/08 Q0997 TEMPO 21018G28KT 4000 RADZ BKN008 – translation here, issued by BAA Heathrow Wunderground.com
  34. ↑ Шаблон:Cite web
  35. ↑ Шаблон:Cite news
  36. ↑ Шаблон:Cite news
  37. ↑ Шаблон:Cite news
  38. ↑ Шаблон:Cite news
  39. ↑ Шаблон:Cite news
  40. ↑ Шаблон:Cite news
  41. ↑ Шаблон:Cite news
  42. ↑ Шаблон:Citation
  43. ↑ Шаблон:Cite web
  44. ↑ Шаблон:Cite web
  45. ↑ 45,0 45,1 Шаблон:Cite web
  46. ↑ Шаблон:Cite web
  47. ↑ Шаблон:Cite press release
  48. ↑ Шаблон:Cite news
  49. ↑ Шаблон:Cite news
  50. ↑ Шаблон:Cite news
  51. ↑ Шаблон:Cite episode


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