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The Heathrow Enigma : Why British Airways Flight 38 Crashed Shortly Before Landing

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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. On 17 January 2008, the Boeing 777-200ER aircraft operating the flight crashed just short of the runway while landing at Heathrow. There were no fatalities. Of the 152 people on board, 47 sustained injuries, one serious. It was the first time in the aircraft type’s history that a Boeing 777 was declared a hull loss and subsequently written-off.

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. The AAIB then identified the rare problem as specific to Rolls-Royce engine FOHEs and Rolls-Royce developed a modification to its FOHE; the European Aviation Safety Agency (EASA) mandated all affected aircraft to be fitted with the modification before 1 January 2011.

ACCIDENT

British Airways Flight 38 (IATA code “BA 38”) is a scheduled passenger flight from Beijing Capital International Airport (PEK) in China to London Heathrow Airport (LHR) in the United Kingdom, a ,100-kilometre (4,400 nmi; 5,000 mi) trip. The aircraft involved in the accident was a 150-tonne Boeing 777-236ER, registration G-YMMM (manufacturer’s serial number 30314, line number 342), powered by two Rolls-Royce Trent 895-17 engines. The aircraft first flew on 18 May 2001 and was delivered to British Airways on 31 May 2001. It had a seating capacity for 233 passengers. 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.

Flight 38 departed from Beijing at 02:09 Greenwich Mean Time (GMT). It flew over Mongolia, Siberia and Scandinavia, at an altitude which varied between 34,800 and 40,000 ft (FL348–400, between 10,600 and 12,200 m), and in temperatures between −65 °C (−85 °F) and −74 °C (−101 °F). 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 there was any danger of the fuel freezing. This did not prove necessary, as the fuel temperature never dropped below −34 °C (−29 °F), still well above its freezing point.

Although the fuel itself did not freeze, small quantities of water in the fuel did. Ice adhered to the inside of the fuel lines, probably where they ran 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 symptoms of the fuel flow restriction were noticed by the flight crew at a height of 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 (200 km/h) 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 to decrease the drag on the aircraft and stretch the glide.

At 12:42, the 777 passed just above traffic on the A30 and the airport’s Southern Perimeter road and landed on the grass approximately 270 metres (890 ft) short of runway 27L. The captain declared an emergency to air traffic control a few seconds before landing. The decision to raise the flaps allowed the plane to miss the ILS beacon within the airport perimeter avoiding more substantial damage.

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 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. One passenger received serious injuries (concussion and a broken leg), and four crew members and eight passengers received minor injuries.

PROBABLE CAUSE

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:

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.

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’.

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.

Certification requirements, with which the aircraft and engine fuel systems had to comply, did not take account of this phenomenon as the risk was unrecognized at that time.

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