Kegworth air disaster
This article needs additional citations for verification. (October 2010) (Learn how and when to remove this template message)
The scene of the disaster, with the runway that G-OBME failed to reach at the top of the picture.
|Date||8 January 1989|
|Summary||Wrong engine shutdown after fan fracture due to design flaw|
|Site||Near East Midlands Airport, Kegworth, Leicestershire, England |
|Aircraft type||Boeing 737-4Y0|
|Flight origin||London Heathrow Airport|
|Destination||Belfast International Airport|
|Survivors||79 (71 passengers and all 8 crew) (initially 87)|
The Kegworth air disaster occurred when British Midland Flight 92, a Boeing 737-400, crashed onto the motorway embankment between the M1 motorway and A453 road near Kegworth, Leicestershire, England, while attempting to make an emergency landing at East Midlands Airport on 8 January 1989.
The aircraft was on a scheduled flight from London Heathrow Airport to Belfast International Airport when a fan-blade broke in the left engine, disrupting the air conditioning and filling the cabin with smoke. The pilots believed this indicated a fault in the right engine, since earlier models of the 737 ventilated the cabin from the right, and they were unaware that the -400 used a different system. The pilots mistakenly shut down the functioning engine. They selected full thrust from the malfunctioning one and this increased its fuel supply, causing it to catch fire. Of the 126 people aboard, 47 died and 74 sustained serious injuries.
The inquiry attributed the blade fracture to metal fatigue, caused by heavy vibration in the newly upgraded engines, which had been tested only in the laboratory and not under representative flight conditions.
The aircraft was a British Midland-operated Boeing 737-4Y0,[note 1] registration G-OBME, on a scheduled flight from London Heathrow Airport to Belfast International Airport, Northern Ireland, having already flown from Heathrow to Belfast and back that day. The 737-400 was the newest design from Boeing, with the first unit entering service less than four months earlier, in September 1988. G-OBME itself had been in service for 85 days, since 15 October 1988, and had accumulated 521 airframe hours. The aircraft was powered by two CFM International CFM56 turbofan engines.:11–22
The flight was crewed by 43-year-old Captain Kevin Hunt and 39-year-old First Officer David McClelland. Captain Hunt was a veteran British Midland pilot who had been with the airline since 1966 and had approximately 13,200 hours of flying experience. First Officer McClelland joined British Midland in 1988 and had accrued roughly 3,300 total flight hours. Between them, the pilots had close to 1,000 hours in the Boeing 737 cockpit,[note 2] only 76 of which were logged in Boeing 737-400 series aircraft.[note 3]:8–9
After taking off from Heathrow at 19:52,[note 4] Flight BD 092 was climbing through 28,300 feet to reach its cruising altitude of 35,000 feet when a blade detached from the fan of the port (left) engine. While the pilots did not know the source of the problem, a pounding noise was suddenly heard, accompanied by severe vibrations. In addition, smoke poured into the cabin through the ventilation system and passengers became aware of the smell of burning.:1 Several passengers sitting near the rear of the plane noticed smoke and sparks coming from the left engine.
After the initial blade fracture, Captain Kevin Hunt had disengaged the plane's autopilot.:3 When Hunt asked First Officer David McClelland which engine was malfunctioning, McClelland replied: "It's the left.... It's the right one".:3 In previous versions of the 737, the left air conditioning pack, fed with compressor bleed air from the left (number 1) engine, supplied air to the flight deck, while the right air conditioning pack, fed from the right (number 2) engine, supplied air to the passenger cabin. On the 737-400 this division of air is blurred; the left pack feeds the flight deck but also feeds the aft passenger cabin, while the right feeds the forward passenger cabin. The pilots had been used to the older version of the aircraft and did not realise that this aircraft (which had been flown by British Midland for only 520 hours over a two-month period) was different. The captain later claimed that his perception of smoke as coming forward from the passenger cabin led them to assume the fault was in the right engine.:98 The pilots throttled back the working right engine instead of the malfunctioning left engine.:98 They had no way of visually checking the engines from the cockpit, and the cabin crew — who did not hear the captain refer to the right hand engine in his cabin address — did not inform them that smoke and flames had been seen from the left engine.:5
When the pilots shut down the right engine, they could no longer smell the smoke, which led them to believe that they had correctly dealt with the problem. As it turned out, this was a coincidence: when the autothrottle was disengaged prior to shutting down the right engine, the fuel flow to both engines was reduced, and the excess fuel which had been igniting in the left engine exhaust disappeared; therefore, the ongoing damage was reduced, the smell of smoke ceased, and the vibration reduced, although it would still have been visible on cockpit instruments.:99
During the final approach to the East Midlands Airport, the pilots selected increased thrust from the operating, damaged engine. This led to an engine fire that caused the engine to cease operating entirely. The ground proximity warning system (GPWS) activated, sounding several "glideslope" warnings. The pilots attempted to restart the right engine by windmilling, but the aircraft was by now flying at 185 km/h (115 mph), too slow for a restart. At 20:24:33, captain Hunt broadcast to the passengers via the aircraft's public address system: "Prepare for crash landing," instructing passengers to take the brace position. The stick shaker then activated. Just before crossing the M1 motorway at 20:24:43, the tail and main landing gear struck the ground and the aircraft bounced back into the air and over the motorway, knocking down trees and a lamp post before crashing on the far embankment approximately 475 metres (519 yd) short of the active runway's paved surface and approximately 630 metres (689 yd) from its threshold. The aircraft broke into three sections.:7–8 This was adjacent to the motorway; remarkably, there were no vehicles travelling on that part of the M1 at the moment of the crash.
Of the 118 passengers on board, 39 were killed outright in the crash and eight died later of their injuries, for a total of 47 fatalities. All eight members of the crew survived the accident. Of the 79 survivors, 74 suffered serious injuries and five suffered minor injuries. In addition, five firefighters also suffered minor injuries during the rescue operation.:7 No-one on the motorway was injured, and all vehicles in the vicinity of the disaster were undamaged. The first person to arrive at the scene to render aid was a motorist, Graham Pearson. A former Royal Marine, he helped passengers for over three hours and subsequently received damages for post-traumatic stress disorder.
The investigation established that the fire warning lights were not cross-wired (left/right).:55
Shutting down of wrong engine
Captain Hunt believed the right engine was malfunctioning due to the smell of smoke in the cabin because in previous Boeing 737 variants bleed air for cabin air conditioning was taken from the right engine. Starting with the Boeing 737-400 variant, Boeing had redesigned the system to use bleed air from both engines. Several cabin staff and passengers noticed that the left engine had a stream of unburnt fuel igniting in the jet exhaust, but this information was not passed to the pilots because cabin staff assumed they were aware that the left engine was malfunctioning.:106
The smell of smoke disappeared when the autothrottle was disengaged and the right engine shut down due to reduction of fuel to the damaged left engine as it reverted to manual throttle.:99 In the event of a malfunction, pilots were trained to check all meters and review all decisions, and Captain Hunt proceeded to do so. Whilst he was conducting the review, however, he was interrupted by a transmission from East Midlands Airport informing him he could descend further to 12,000 feet (3,700 m) in preparation for the diverted landing. He did not resume the review after the transmission ended, and instead commenced descent. The vibration indicators were smaller than on the previous versions of the 737 in which the pilots had the majority of their experience.:69
The dials on the two vibration gauges (one for each engine) were small and the LED needle went around the outside of the dial as opposed to the inside of the dial as in the previous 737 series aircraft. The pilots had received no simulator training on the new model, as no simulator for the 737-400 existed in the UK at that time. At the time, vibration indicators were known for being unreliable:69–70 (and normally ignored by pilots), but unknown to the pilots, this was one of the first aircraft to have a very accurate vibration readout.
Analysis of the engine from the crash determined that the fan blades (LP Stage 1 compressor) of the uprated CFM International CFM56 engine used on the 737-400 were subject to abnormal amounts of vibration when operating at high power settings above 10,000 feet (3,000 m).:118–120 As it was an upgrade to an existing engine, in-flight testing was not mandatory, and the engine had only been tested in the laboratory. Upon this discovery the remaining 99 Boeing 737-400s then in service were grounded and the engines modified. Following the crash, it is now mandatory to test all newly designed and significantly redesigned turbofan engines under representative flight conditions.
This unnoticed vibration created excessive metal fatigue in the fan blades, and on G-OBME this caused one of the fan blades to break off. This damaged the engine terminally and also upset its delicate balance, causing a reduction in power and an increase in vibration. The autothrottle attempted to compensate for this by increasing the fuel flow to the engine. The damaged engine was unable to burn all the additional fuel, with much of it igniting in the exhaust flow, creating a large trail of flame behind the engine.
The official report into the disaster made 31 safety recommendations.:149–152
Evaluation of the injuries sustained led to considerable improvements in aircraft safety and emergency instructions for passengers. These were derived from a research programme funded by the CAA and carried out by teams from the University of Nottingham and Hawtal Whiting Structures (an engineering consultancy company). The study between medical staff and engineers used analytical "occupant kinematics" techniques to assess the effectiveness of the brace position. A new notice to operators revising the brace position was issued in October 1993.
The research into this accident led to the formation of the International Board for Research into Aircraft Crash Events (IBRACE) on 21 November 2016. IBRACE is a joint cooperation between experts in the field for the purpose of producing an internationally agreed, evidence-based set of impact bracing positions for passengers and (eventually) cabin crew members in a variety of seating configurations. These will be submitted to the International Civil Aviation Organization (ICAO) through its Cabin Safety Group (ICSG).
There is a memorial to "those who died, those who were injured and those who took part in the rescue operation", in the village cemetery in nearby Kegworth, together with a garden made using soil from the crash site.
Captain Hunt and First Officer McClelland, both seriously injured in the crash, were dismissed following the criticisms of their actions in the AAIB report. Hunt suffered injuries to his spine and legs in the crash. In April 1991 he told a BBC documentary: "We were the easy option—the cheap option if you wish. We made a mistake — we both made mistakes — but the question we would like answered is why we made those mistakes." BM later paid McClelland an out-of-court settlement for unfair dismissal. The accident led to the adoption of Crew Resource Management.[failed verification]
Graham Pearson, a passing motorist who assisted Kegworth survivors at the crash site for three hours, sued the airline for post-traumatic stress disorder and was awarded £57,000 in damages in 1998 (£101,000 today).
The crash was featured in a 1991 documentary of Taking Liberties named 'Fatal Error'
There was an ITV documentary in 1999 of the Kegworth crash.
Flight 092 was also featured in an episode of Seconds From Disaster, called "Motorway Plane Crash".
- List of accidents and incidents involving commercial aircraft
- TransAsia Airways Flight 235, another incident in which the pilot shut off the wrong engine
- The aircraft was a Boeing 737-400 model; Boeing assigns a unique customer code for each company that buys one of its aircraft, which is applied as a suffix to the model number at the time the aircraft is built. The code "Y0" was assigned to leasing company Guinness Peat Aviation, from whom British Midland leased the aircraft, hence "737-4Y0". British Midland never ordered an aircraft directly from Boeing and therefore never received their own unique customer code.
- Regardless of variant; Captain Hunt had 763 hours, and first officer McCelland had 192 hours.
- On the -400 variant only; captain Hunt had only 23 hours, and first officer McCelland had 53 hours.
- First officer McCelland was the pilot flying until the engine failure, after which captain Hunt took control:8–9
- Ranter, Harro. "ASN Aircraft accident Boeing 737-4Y0 G-OBME Kegworth". aviation-safety.net. Aviation Safety Network. Retrieved 12 July 2019.
- "G-INFO Database". Civil Aviation Authority.
- "Air Accidents Investigation Branch report 4/1990 Boeing 737-400, G-OBME". Air Accidents Investigation Branch. 8 January 1989. Retrieved 7 August 2015.
- "G-OBME British Midland Boeing 737-400". www.planespotters.net. Retrieved 31 March 2020.
- "British Midland Airways G-OBME (Boeing 737 - MSN 23867)". www.airfleets.net. Airfleets aviation. Retrieved 31 March 2020.
- Truslove, Ben (8 January 2014). "Kegworth air disaster: Plane crash survivors' stories". BBC News. BBC Online. Archived from the original on 8 January 2014. Retrieved 8 January 2014. - The content about the safety improvements is from the sidebar "The legacy of Kegworth"
- "Why did British Midland plane crash on the M1 near Kegworth?". ITV News. ITV. ITV Report. 8 January 2014. Retrieved 13 January 2017.
- "UK, Air crash hero wins damages". BBC News. BBC. 10 February 1998. Retrieved 16 May 2011.
- Scientific and Technical Aerospace Reports. NASA, Office of Scientific and Technical Information. 1993. p. 1423.
- "Kegworth Village – Kegworth Air Disaster 1989". Retrieved 8 January 2014.
- Brookes, Andrew (1994). Disaster in the air. p. 135. ISBN 0-7110-2037-X.
- This is Nottingham (8 January 2009), Kegworth: Sacked pilots claim they were 'scapegoats', Nottinghampost.com, retrieved 8 January 2014
- "No. 519981". The London Gazette (Supplement). 29 December 1989. p. 15.
- "Aircrash Confidential: Lethal Malfunctions Videos at". Yourdiscovery.com. 24 February 2011. Retrieved 16 May 2011.
- Macarthur Job, Air Disaster Volume 2: Aerospace Publications Pty Ltd, 1996, ISBN 1-875671-19-6, p. 173–185
- David Owen, Air Accident Investigation: Patrick Stephens Limited, 2001, ISBN 0-7509-4495-1. (The Kegworth air disaster is given a detailed mention in Chapter 9, "Pressing the Wrong Button")
- HW Structures, CAA Paper 90012 Occupant modelling in aircraft crash conditions: Civil Aviation Authority, 1990, ISBN 0-86039-445-X.
- Hawtal Whiting Technology Group, CAA Paper 95004 A study of aircraft passenger brace positions for impact: Civil Aviation Authority, 1995, ISBN 0-86039-620-7
- Trimble, E J (1990), Report No: 4/1990. Report on the accident to Boeing 737-400, G-OBME, near Kegworth, Leicestershire on 8 January 1989, Air Accidents Investigation Branch
- BBC 10th anniversary page about the crash
- BBC 'On This Day' page about the crash
- Pre-crash and crash pictures of the aircraft from Airliners.net
- Field, James (8 January 2019). "Op-Ed: Learning From The Kegworth Air Disaster, 30 Years On". Airways International.
- Accident description at the Aviation Safety Network