This week has marked the thirtieth anniversary of the Kegworth air disaster, a plane crash on British soil caused by a long chain of mistakes.
At 7:52pm on Sunday 8th January 1989, British Midland Flight 092 – a new Boeing 737-400 – took off from London Heathrow Airport, heading for Belfast, with 118 passengers and 8 crew onboard. The flight proceeded normally until 8:05pm, whereupon there was a loud noise, the plane started vibrating violently, and the smell of smoke entered the cockpit, apparently coming from the cabin. Evidently, something was wrong with an engine – but the plane’s two engines could not be seen from the cockpit. Neither the captain, Kevin Hunt, nor the first officer, David McClelland, had logged many hours flying the new 737-400, so it was hard for them to determine from the updated instrument displays which engine was having problems. However, they knew that on other 737s, the air conditioning to the cabin flowed from the No 2 (right) engine, so the smoke would indicate that the No 2 engine was on fire. The first officer reported to the captain, “It’s the left…it’s the right one.” The pilots shut down the No 2 engine, and the vibrations stopped. With the plane now flying on one engine, they were given clearance to make an emergency landing at East Midlands Airport in Leicestershire.
The plane was on approach to the airport when, abruptly, the No 1 (left) engine failed altogether, leaving the plane unable to do anything but glide. Passing over the village of Kegworth, the pilots tried desperately to stay airborne long enough to reach the runway, which lay on the other side of the M1 motorway – but it was no good. At 8:24pm, the plane’s tail struck the ground and it bounced across the motorway, breaking apart on the far embankment, less than a kilometre from the runway. 39 passengers died at the scene, while another eight subsequently died in hospital; of the 79 survivors (which included all crew members), 74 were seriously injured. Nobody on the road was hurt.
Had both engines on this brand-new aircraft really failed independently of each other? Investigators soon discovered that in fact, a terrible error had been made: the No 2 engine had been perfectly fine. The plane crashed because the pilots had shut down their good engine, and were flying on the damaged one.
The entire accident had been caused by a combination of factors, which led to new recommendations to improve safety:
- The initial problem with the No 1 engine had been caused by a fan blade breaking off and damaging other parts of the engine. The break itself was due to metal fatigue; the fan blades of the 737-400’s engines vibrated excessively when spinning at full power and at high altitude. This had not been discovered during testing, as the engines were being upgraded rather than designed from scratch, and so were only tested in a laboratory, not in flight. Subsequently, redesigned engines must always be tested in flight.
- The pilots had had no simulator training with the 737-400’s instruments, and their lack of familiarity with the new plane led to them being mistaken about the air conditioning; on the 737-400, the air conditioning in the cabin was fed by both engines, not just the No 2. Simulator training for redesigned instrument systems was also made mandatory.
- The pilots thought they had made the right decision as the vibrations seemed to stop when the No 2 engine was shut down. In fact, this happened because they had disengaged the autothrottle, which had automatically increased the fuel flow to the struggling No 1 engine; the vibrations lessened because once the engine came under manual control, the fuel flow was reduced. However, as the plane approached the airport, the pilots increased throttle to control their descent, which caused the damaged engine to completely fail.
- Many people in the cabin noticed flames coming out of the left engine, but did not communicate this to the pilots, trusting their judgement even after the captain announced that they had shut down the right engine. Communication between pilots and cabin crew was subsequently improved as part of crew training.
- More research was done into the brace position and seat integrity after studying the survivors’ injuries from the impact.
Captain Hunt and First Officer McClelland were both dismissed by British Midland following the accident, though McClelland later received a settlement after suing for unfair dismissal.