Kegworth air disaster
| File:Kegworth Air Crash Scene.jpg The scene of the disaster, with the runway that G-OBME failed to reach at the top of the picture | |
| Occurrence | |
|---|---|
| Date | January 8, 1989 |
| Summary | Engine fan blade failure, Pilot error |
| Site | Kegworth, Leicestershire, UK 52°49′55″N 1°17′57.5″W / 52.83194°N 1.299306°W |
| Aircraft type | Boeing 737-4Y0 |
| Operator | British Midland |
| Registration | G-OBMEdisaster[1] |
| Flight origin | London Heathrow Airport |
| Destination | Belfast International Airport |
| Passengers | 118 |
| Crew | 8 |
| Fatalities | 47 |
| Injuries | 79 |
| Survivors | 79 |
The Kegworth Air Disaster occurred on 8 January, 1989, when British Midland Flight 92, a Boeing 737-400, crashed onto the embankment of the M1 motorway near Kegworth, Leicestershire, UK. The aircraft was attempting to conduct an emergency landing at East Midlands Airport. 47 people died and 74 people, including seven members of the flight crew, sustained serious injuries.
History
The aircraft was a British Midland 737-400, tail number G-OBME, on a scheduled flight from London Heathrow Airport to Belfast, Northern Ireland, having already flown from Heathrow to Belfast and back that day. After taking off from Heathrow at 7:52pm, Flight 092 was climbing through 28,300 feet to reach its cruising altitude of 35,000 feet when one of the fan blades on the left engine suddenly ruptured. 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 an aroma of burning entered the plane. Several passengers sitting near the rear of the plane noticed smoke and sparks coming from the left engine.
The flight was diverted to nearby East Midlands Airport at the suggestion of British Midland Airways Operations.
After the initial blade fracture, Captain Kevin Hunt had disengaged the plane's autopilot. When Hunt asked First Officer David McClelland which engine was malfunctioning, McClelland replied: 'It's the le... it's the right one'. In previous versions of the 737, the air conditioning ran through the right hand engine, but on the 737-400 it ran through both. The pilots had been used to the older version of the aircraft and did not realise that this aircraft (which had only been flown by British Midland for 520 hours over a two-month period) was different. When they smelled the smoke they assumed it was coming from the right engine; this led them to shut down the working right engine instead of the malfunctioning left engine. (They had no way of visually checking the engines from the cockpit, and the cabin crew did not inform them that smoke and flames had been seen from the left engine.)
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 simply a coincidence. When the autothrottle was disengaged to shut down the right engine, the fuel flow to the left engine was reduced and the excess fuel which had been igniting in the jet exhaust disappeared; therefore, the ongoing damage was reduced, the smoke smell ceased, and the vibration reduced, although it would still have been visible on cockpit instruments.
During the final approach to the East Midlands Airport, more fuel was pumped into the damaged engine to maintain speed, which caused it to cease operating entirely and burst into flames. The flight crew attempted to restart the right engine by windmilling, using the air flowing through the engine to rotate the turbine blades and start the engine, but the aircraft was by now flying too slowly for this. The captain managed to keep the now-gliding aircraft airborne long enough to avoid a crash landing in the village of Kegworth by pointing the nose up and stretching the glide, but just before crossing the M1 motorway, the tail hit the ground and the aircraft bounced back into the air and over the motorway, crashing on the opposite embankment and breaking into three sections.
Casualties
Forty-seven of the 118 passengers (126 people on board including flight staff) died (39 at the scene, 8 later). All eight of the flight crew survived the accident. Of the 79 survivors, 5 had minor injuries and 74 were seriously injured. No one on the motorway was hurt (and no vehicles were damaged), although one driver who was the first person to help at the scene did subsequently receive damages for post-traumatic stress disorder.
Causes
Shutting down the wrong engine
The Captain, Kevin Hunt, believed the right engine was malfunctioning due to the smell of smoke because in previous Boeing 737 variants bleed air for the air conditioning system was taken from the right engine. However, starting with the Boeing 737-400 variant, Boeing 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 the pilots were aware that the left engine was malfunctioning.
It was a coincidence that the smell of smoke disappeared when the autothrottle was disengaged and the right engine shut down. In the event of a malfunction pilots are trained to check all meters and review all decisions, and Captain Kevin Hunt proceeded to do so. Whilst he was conducting the review, he was interrupted by a transmission from East Midlands Airport informing him he could descend further to 12000ft 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. The dial on the vibration meter was no bigger than a 20 pence piece 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.
Engine malfunction
Analysis of the engine from the crash determined that the fan blades (LP Stage 1 compressor) of the uprated CFM56 engine used on the 737-400 were subject to abnormal amounts of vibration when operating at high power settings above 25,000 ft. 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 all 99 Boeing 737-400s (since G-OBME had crashed) 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, however the damaged engine was unable to burn all the additional fuel, with much of it igniting in the exhaust flow, thus creating a large trail of flame behind the engine.
Aftermath
Evaluation of the injuries sustained led to considerable improvements in aircraft safety and emergency instructions for passengers. The official report into the disaster made 31 safety recommendations.
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 were seriously injured in the crash, and were later dismissed following the criticisms of their actions in the AAIB report[2].
Media
Flight 92 was featured in an episode of Seconds From Disaster.
See also
References
- ^ "G-INFO Database". Civil Aviation Authority.
- ^ Disaster in the Air, Andrew Brookes, 1992, ISBN 071102037X, p135
- 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")
- Jack Ramsay, SAS, The Soldiers Story: Pan Books, 1997, ISBN 0-330-34750-0.