British Airways Flight 38

British Airways Flight 38 (call sign Speedbird 38) was a scheduled flight from Beijing Capital International Airport which crash landed just short of the runway at its destination, London Heathrow Airport, on 17 January 2008 after an 8,100-kilometre (4,400 nmi; 5,000 mi) flight. . There were no fatalities but 47 people sustained injuries; one serious. The 150-tonne aircraft was the first Boeing 777 to be written off in the model's twelve-year history.

The cause of the accident was ice crystals in the fuel clogging the fuel-oil heat exchanger (FOHE) of each engine. This restricted fuel flow to the engines as thrust was demanded during the final approach to Heathrow. Boeing identified the problem as specific to the Rolls-Royce engine fuel-oil heat exchangers, and Rolls-Royce has subsequently developed a modification to its FOHE; the European Aviation Safety Agency (EASA) mandated that all affected aircraft were to be fitted with the modification before 1 January 2011. Boeing 777 aircraft powered by GE or Pratt & Whitney engines were not affected by the problem.

Accident


The aircraft used for the flight was Boeing 777-236ER G-YMMM (manufacturer's serial number 30314, line number 342), powered by two Trent 800 engines.

Flight 38's route took it over Mongolia, Siberia and Scandinavia, at an altitude which varied between 34,800' and 40,000' (FL348-400), and in temperatures between -65 and -74 °C. Aware of the cold conditions outside, the crew monitored the temperature of the fuel on board the plane, with the intention of descending to a lower, and warmer, level if there was any danger of the fuel freezing. In the event, this did not prove necessary, as the fuel temperature never dropped below -34 °C, still well above its freezing point..

Although the fuel itself did not freeze, small quantities of water in the fuel did freeze. Ice adhered to the inside of the fuel lines, probably in the section where they run through the struts attaching the engines to the wings. 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. This formed a slush of soft ice which flowed forward until it reached the Fuel/Oil Heat Exchangers (FOHEs). where it froze once again, causing a restriction in the flow of fuel to the engines. The first symptons of the fuel flow restriction were noticed by the flight crew at 720 feet (220 m) and 2 miles (3.2 km) 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 (ILS) glide slope, the autopilot sacrificed speed, which reduced to 108 knots at 200 feet (61 m). The autopilot disconnected at 150 feet (46 m), as the co-pilot took manual control. Meanwhile, the captain reduced the flap setting from 30 degrees to 25 degrees in order to decrease the drag on the aircraft and stretch the glide.

The plane passed above traffic on the A30 and the airport's Southern Perimeter road, including a car which had just dropped off the then British Prime Minister, Gordon Brown, and landed on the grass approximately 270 metres (890 ft) short of runway 27L. The captain declared an emergency to the control tower a few seconds before landing.

During the impact and short ground roll, the nose gear collapsed, the right main gear separated from the aircraft penetrating the central fuel tank and cabin space, and the left main gear was pushed up through the wing. The aircraft came to rest on the threshold markings at the start of the runway. A significant amount of fuel leaked, but there was no fire. Four crew members and eight passengers received minor injuries, and one passenger received serious injury – concussion and a broken leg.

Speculation
Because both engines failed to produce increased power when demanded, mechanical engine failure was not regarded as a likely cause given the very low probability of a simultaneous dual engine failure, Rather, it was considered that an electronic or software glitch in the computerised engine-control systems was more likely to have caused the simultaneous loss of power on both engines. Both engine and computer problems were ruled out by the findings of the February Special Bulletin.



Speculation that radio interference from the Prime Minister's motorcade was responsible for the accident was also eliminated as a cause.

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 350–400 metres, the aircraft must have been near stalling when it touched down.

Dr. Thurai Rahulan and Dr. Guy Gratton, both academics, speculated that the weather conditions made wind shear a possible cause. The METAR in force at the time indicated that the wind was forecast to gust according to ICAO criteria for wind reporting, but was not gusting at the time and wind shear had not been reported. The possibility of a bird strike was raised, but there were no sightings or radar reports of birds. Speculation had focused on electronics and fuel supply issues. In response to speculation that the cause of the accident was ice in the centre fuel tank, United Airlines and American Airlines took precautionary steps to ensure the quality of the fuel used in their aircraft.

Initial response
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.

Soon after the crash, the Civil Aviation Authority (CAA) announced that they were aware of the incident and that the "incident will be investigated by the Air Accidents Investigation Branch of the Department for Transport and the CAA is offering assistance to all organisations involved."

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 crew are trained to deal with these situations". He also praised the fire, ambulance and police services.

BAA Limited: Incident at Heathrow

We can confirm that flight BA38, a Boeing 777 arriving from Beijing, carried out an emergency landing at Heathrow Airport today at 12:42. Heathrow’s emergency services attended the scene and passengers were immediately evacuated and taken to a reception centre at the airport. The Air Accidents Investigation Branch is attending the scene.''

Heathrow Airport’s southern runway was closed immediately after the incident but has now re-opened for take-offs only. The northern runway is operating for arriving aircraft. ''

Passengers flying from Heathrow today should contact their airline regarding the status of their flight. Some arriving aircraft are being diverted to other airports, this is being done on a flight by flight basis.

Aftermath
As a consequence of the emergency services deployment to the accident all flights were halted for a short time. 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, and Heathrow Airport received dispensation from the Department of Transport to operate some night flights. On the following day (18 January) a total of 113 short haul flights were cancelled due to crews and aircraft being out of position.

On the afternoon of 20 January 2008, the aircraft was removed from its resting place with two cranes lifting it onto wheeled platforms.

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 Air Accident Investigation Branch (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. John 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."

Burkill and Coward were grounded for a month following the crash while they were assessed for posttraumatic stress disorder. Five months after the accident, Captain Burkill flew again taking charge of a flight to Montreal, Canada. However, he remained "haunted" by the incident, and took voluntary redundancy from British Airways in August 2009. Captain Burkill subsequently established a blog and wrote a book, "Thirty Seconds to Impact" that denounced BA's treatment of the situation following the crash. 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."

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

British Airways continues to use the Flight 38 designation on its Beijing to London (Heathrow) route, however it is now operated with a Boeing B777-300ER.

Investigation
The Air Accidents Investigation Branch (AAIB) investigated the accident, with the U.S. National Transportation Safety Board (NTSB), Boeing and Rolls-Royce also participating. The investigation took two years to complete, and the AAIB published its final report on 9 February 2010. A number of preliminary reports and eighteen safety recommendations were issued during the course of the investigation.

Initial report, 18 January 2008
The AAIB released an initial report on 18 January, which stated:

Initial indications from the interviews and Flight Recorder analyses show the flight and approach to have progressed normally until the aircraft was established on late finals for Runway 27L. At approximately 600 ft and 2 miles from touch down, the Autothrottle demanded an increase in thrust from the two engines but the engines did not respond. Following further demands for increased thrust from the Autothrottle, and subsequently the flight crew moving the throttle levers, the engines similarly failed to respond. The aircraft speed reduced and the aircraft descended onto the grass short of the paved runway surface.

Initial report update, 24 January 2008
An update was issued on 24 January:

As previously reported, whilst the aircraft was stabilised on an ILS approach with the autopilot engaged, the autothrust system commanded an increase in thrust from both engines. The engines both initially responded but after about 3 seconds the thrust of the right engine reduced. Some eight seconds later the thrust reduced on the left engine to a similar level. The engines did not shut down and both engines continued to produce thrust at an engine speed above flight idle, but less than the commanded thrust.

Recorded data indicates that an adequate fuel quantity was on board the aircraft and that the autothrottle and engine control commands were performing as expected prior to, and after, the reduction in thrust.

All possible scenarios that could explain the thrust reduction and continued lack of response of the engines to throttle lever inputs are being examined, in close cooperation with Boeing, Rolls Royce and British Airways. This work includes a detailed analysis and examination of the complete fuel flow path from the aircraft tanks to the engine fuel nozzles.

Special Bulletin, 18 February 2008
A further update, issued on 18 February, stated that there was "no evidence of a mechanical defect or ingestion of birds or ice", that there was "no evidence of fuel contamination or unusual levels of water content" within the fuel and that the recorded data indicated that there were "no anomalies in the major aircraft systems". Some small foreign bodies, however, were detected in the fuel tanks and these were to undergo further analysis.

The report 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 are 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 is to be conducted on the entire aircraft and engine fuel system including modelling fuel flows taking account of environmental and aerodynamic effects.

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 2008-009, 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 this special bulletin, well before the accident investigation itself was complete.

Special Bulletin, 12 May 2008
The AAIB issued a further bulletin on 12 May 2008 which confirmed that the investigation continued to focus on fuel delivery. It stated that "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 now focuses 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 Bulletin 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."

British Airways internal investigation
An internal investigation into the accident was conducted by British Airways. The report concluded that the actions of the flight crew prevented a worse outcome than actually occurred. It also stated that the emergency evacuation alarm was too quiet for one member of the cabin crew to hear.

Interim Report, 4 September 2008
The AAIB issued an interim report on 4 September. Offering a tentative conclusion, it stated:

The investigation has shown that fuel to both engines was restricted; most probably due to ice within the fuel feed system. The ice was likely to have formed from water that occurred naturally in the fuel whilst the aircraft operated for a long period, with low fuel flows, in an unusually cold environment; although, G-YMMM was operated within the certified operational envelope at all times.

The report detailed 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. 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 Air Accidents Investigations Branch (AAIB) recommended Boeing and Rolls-Royce take interim measures on Trent 800-powered 777s to reduce the risk of ice restricting fuel delivery.

The report's finding resulted in three safety recommendations:

Safety Recommendation 2008-047

It is recommended that the Federal Aviation Administration and the European Aviation Safety Agency, in conjunction with Boeing and Rolls-Royce, introduce interim measures for the Boeing 777, powered by Trent 800 engines, to reduce the risk of ice formed from water in aviation turbine fuel causing a restriction in the fuel feed system.

Safety Recommendation 2008-048

It is recommended that the Federal Aviation Administration and the European Aviation Safety Agency should take immediate action to consider the implications of the findings of this investigation on other certificated airframe / engine combinations.

Safety Recommendation 2008-049

It is recommended that the Federal Aviation Administration and the European Aviation Agency review the current certification requirements to ensure that aircraft and engine fuel systems are tolerant to the potential build up and sudden release of ice in the fuel feed system.

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 −40 °C. 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. The report also suggested that, because low fuel flows are conducive to ice formation, airlines could make operational changes to lessen the risk of a blockage forming shortly before landing.

Boeing revised the 777 operating procedures to keep such blockages from forming, and revised the procedure to be followed in the event of power loss to take into account the possibility that ice accumulation was the cause.

Final report, 9 February 2010
The AAIB issued a full report on 9 February 2010. It concluded : The investigation identified that the reduction in thrust was due to restricted fuel flow to both engines.

The investigation identified the following probable causal factors that led to the fuel flow restrictions:


 * 1) Accreted ice from within the fuel system released, causing a restriction to the engine fuel flow at the face of the FOHE, on both of the engines.
 * 2) Ice had formed within the fuel system, from water that occurred naturally in the fuel, whilst the aircraft operated with low fuel flows over a long period and the localised fuel temperatures were in an area described as the ‘sticky range’.
 * 3) The FOHE, although compliant with the applicable certification requirements, was shown to be susceptible to restriction when presented with soft ice in a high concentration, with a fuel temperature that is below −10 °C and a fuel flow above flight idle.
 * 4) Certification requirements, with which the aircraft and engine fuel systems had to comply, did not take account of this phenomenon as the risk was unrecognised at that time.

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 (MLG) 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. It was recommended that Boeing redesign the landing gear attachment to reduce the likelihood of fuel loss in similar circumstances.

Similar incidents


On 26 November 2008, Delta Air Lines Flight 18 from Shanghai to Atlanta experienced an "uncommanded rollback" of one engine while in cruise at 39,000 feet. The crew followed manual recovery procedures and the flight continued without incident. The U.S. 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. The NTSB Safety Recommendation report 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 oil-fuel flow heat exchangers. Originally, it was thought that other aircraft were not affected by the problem. However, in March 2009, another similar incident happened with an Airbus A330 powered by a Trent series 700 engine.

The enquiries resulted in a stronger recommendation from Boeing in February 2009 to avoid icing in fuel lines in extremely cold conditions.

On 11 March 2009, the National Transportation Safety Board issued urgent safety recommendation SB-09-11 calling for the redesign of the fuel/oil heat exchangers 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 have already started on redesigning the component, with an in-service date of March 2010 at the latest. All affected engines will be fitted with the redesigned component within six months of its certification. In May 2010, the Airworthiness Directive was extended to cover the Trent 500 and 700 series engines as well.

Lawsuit
In November 2009, it was announced that 10 passengers were to sue Boeing for the incident. They have lodged a lawsuit with the Circuit Court of Cook County in Illinois, in the United States. It is reported that each of the ten plaintiffs could receive up to US$1,000,000 (£595,433 at the time) compensation. Boeing is reportedly trying to have the case heard at the High Court in London. The lawsuit alleges 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".

Dramatization
The story of the disaster was featured on the tenth season of Canadian National Geographic Channel show Mayday (known as Air Emergency in the US, Mayday in Ireland and Canada, and Air Crash Investigation in the UK and the rest of world). The episode is entitled "The Heathrow Enigma".