On Jan 17th, a British Airways B777, BA038 crash landed at London Heathrow.
Power loss caused BA 777 crash landing at Heathrow
By David Learmount
All 136 passengers from a British Airways Boeing 777-200 were evacuated, three of them suffering minor injuries, when the aircraft was badly damaged by landing short of the runway at London Heathrow, according to a statement by the airline’s chief executive Willie Walsh.
From the limited information available within a few hours of the accident, the aircraft appears to have suffered engine power loss on the approach.
Inbound from Beijing, China, flight BA38 was on the approach to runway 27L at 12.43 local time, when there was a loss of power on both engines at some stage late in the approach. The reason for the power loss is not yet known, nor is it known whether power loss was total.
The crew managed to control the descent to a touchdown with wings level, on grass just over the perimeter fence at Heathrow, on the 27L extended centreline. The gear was down, flaps were set at about 20°, and the indications are that the crew had started the auxiliary power unit.
On touchdown the 777’s gear dug into the soft ground and separated. The aircraft came to rest at the threshold of runway 27L having made a short ground run of about 350m (1,150ft), probably because at touchdown the aircraft was close to its stalling speed.
When the main gear separated it caused considerable damage to the engines and the wings near the wing-root trailing edge.
The weather at Heathrow at the time was wind from 220° at 16kt (30km/h), broken cloud at 1,400ft (426m) and 2,000ft, temperature 11°C, dew point 9°C, with a warning that the wind might vary temporarily to 240° at 20kt, gusting to 32kt. The visibility was greater than 10km (6.2 miles).
Airport operator BAA says the aircraft (G-YMMM) made an emergency landing, but it is not clear whether that statement is a description of the crash landing or an affirmation that the crew had declared an emergency. BA is unable to say whether the crew had declared an emergency before touchdown.
Almost all the passengers who have commented since the accident say the approach felt normal and the crew did not provide any warnings, but the touchdown was hard and the evacuation was uneventful and took a short time. There was no fire. There were 136 passengers, three flightdeck crew and 13 cabin crew on board, the airline confirms.
Heathrow’s southern runway, 27L, was closed briefly, but it is now operation for take-offs only, and the northern runway is in operation.
The article states “From the limited information available within a few hours of the accident, the aircraft appears to have suffered engine power loss on the approach”. Someone speculated this problem was similar to that occurred to the QF2 flight on Jan 7th: water leaked in the electronics bay causing the failure of 4 generators and the need to land in Bangkok with the power provided by the batteries. The engines on the Qantas B744 were operating fine. In fact, as written in my previous post (http://cencio4.wordpress.com/2008/01/11/qantas-electric-failures/) an aircraft loosing the power of the generators can fly or land, as the QF2 happy ending shows. An engine power loss is obviously much different from an electric one, even if, theoretically, even without engine power, an aircraft fully established on the ILS could still be able to glide to the touchdown point. Nonetheless, minor thrust adjustments are always required to keep target speed even under good weather conditions. Consequently, an engine power loss occurring a few miles from touchdown is a very bad experience when you are flying a wide body.
Fuel contamination is also a possible cause of the engine power loss but there are at least two points that let me discard this theory:
1) A lot of flights, including other B777 with engines like those carried by G-YMMM, flew out of Beijing on the same day and no one experienced any engine problem.
2) In case of fuel contamination it is very unlikely that both engines loose power more or less at the same time. Same type of engine on the same aircraft have different performances, different consumption, etc. If fuel contamination had occurred at the departure airport, the engines would have had problem in different moments.
On the other hand, based on the pictures showing the engines, it looks like that one engine was still running and one wasn’t; this could also means that the failure didn’t affect both engines or that it didn’t affect them at the same time.
That said, the initial report of the Air Accidents Investigation Branch let me think to the FADEC (Full Authority Digital Engine Control) software as the root cause of the engine problem:
Accident to Boeing 777-236, G-YMMM at London Heathrow Airport on 17 January 2008 – Initial Report
Initial Report AAIB Ref: EW/C2008/01/01
Aircraft Type and Registration: Boeing 777-236, G-YMMM
No & Type of Engines: 2 Rolls-Royce RB211 Trent 895-17 turbofan engines
Year of Manufacture: 2001
Date & Time: 17 January 2008 at 1243 hrs
Location: Undershoot RWY 27L, London Heathrow Airport
Type of Flight: Commercial Air Transport (passenger)
Persons on Board: Crew – 16
Passengers – 136
Injuries: Crew – 4 (minor)
Passengers – 1 (serious)
Passengers – 8 (minor)
Nature of Damage: Substantial
Information Source: AAIB Field Investigation
Following an uneventful flight from Beijing, China, the aircraft was established on an ILS approach to Runway 27L at London Heathrow. Initially the approach progressed normally, with the Autopilot and Autothrottle engaged, until the aircraft was at a height of approximately 600 ft and 2 miles from touch down. The aircraft then descended rapidly and struck the ground, some 1,000 ft short of the paved runway surface, just inside the airfield boundary fence. The aircraft stopped on the very beginning of the paved surface of Runway 27L. During the short ground roll the right main landing gear separated from the wing and the left main landing gear was pushed up through the wing root. A significant amount of fuel leaked from the aircraft but there was no fire. An emergency evacuation via the slides was supervised by the cabin crew and all occupants left the aircraft, some receiving minor injuries.
The AAIB was notified of the accident within a few minutes and a team of Inspectors including engineers, pilots and a flight recorder specialist deployed to Heathrow. In accordance with the established international arrangements the National Transportation Safety Board (NTSB) of the USA, representing the State of Design and Manufacture of the aircraft, was informed of the event. The NTSB appointed an Accredited Representative to lead a team from the USA made up of investigators from the NTSB, the FAA and Boeing. A Boeing investigator already in the UK joined the investigation on the evening of the event, the remainder of the team arrived in the UK on Friday 18th January. Rolls-Royce, the engine manufacturer is also supporting the investigation, an investigator having joined the AAIB team.
Activity at the accident scene was coordinated with the Airport Fire and Rescue Service, the Police, the British Airports Authority and British Airways to ensure the recovery of all relevant evidence, to facilitate the removal of the aircraft and the reinstatement of airport operations.
The flight crew were interviewed on the evening of the event by an AAIB Operations Inspector and the Flight Data Recorder (FDR), Cockpit Voice Recorder (CVR) and Quick Access Recorder (QAR) were removed for replay. The CVR and FDR have been successfully downloaded at the AAIB laboratories at Farnborough and both records cover the critical final stages of the flight. The QAR was downloaded with the assistance of British Airways and the equipment manufacturer. All of the downloaded information is now the subject of detailed analysis.
Examination of the aircraft systems and engines is ongoing.
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.
The investigation is now focussed on more detailed analysis of the Flight Recorder information, collecting further recorded information from various system modules and examining the range of aircraft systems that could influence engine operation.
Another option could be an external Electromagnetic Impulse (EMI) impacting the engine controls. It is extremely unlikely though, since an EMI could interfere with unshielded equipment like comms and navigation while engine control are usually very well shielded.
An amateur video has been uploaded to youtube:
Looking at this video, it appears that the B777 is trying to keep the glideslope while speed is decreasing. The aircraft has in fact an unusual pitch attitude, probably induced by the autopilot that is raising the AOA (Angle Of Attack) to maintain the ILS to compensate insufficient thrust, under deteriorating speed conditions. Very dangerous attitude (especially) at 600ft that made the aircraft get less horizontal distance, thus touching short of the runway 27L.