18 Years Today...

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18 Years Today...

Postby EGNX » Mon Jan 08, 2007 11:48 am

On the 8th of January 1989, Flight 92, a brand new Boeing 737-400 operated by British Midland Airlines, departed Heathrow destined for Belfast. During the climb to 35,000 feet one of the fan blades on the left engine suddenly ruptured, and the aircraft diverted to East Midlands Airport. After the initial blade fracture the Captain asked the First Officer which engine was malfunctioning, he replied: 'It's the le... it's the right one'. They had no way of visually checking the engines from the cockpit, but because the pilots had been used to an older version of the aircraft, they did not realize that the aircraft was different. In the old version, the air conditioning ran through the right hand engine, but on the new model it ran through both. 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. This was all caused because of a slight upgrade that the pilots were unaware of. After shutting down the only functioning engine the smell of smoke stopped and the pilots believed that they had solved the problem.

During the approach to East Midlands the pilots opened the throttle on the left engine to try and maintain speed. The excess fuel being pumped to the malfuntioning engine caused it to burst into flames and cease working completely. The Captain now realising the situation tried to restart the right engine by windmilling. The aircraft was now gliding, and only a few miles from the runway at East Midlands, the Captain kept the 737 airborne long enough to avoid a crash landing in the village of Kegworth by stretching the glide, but by now the aircraft was travelling dangerously slow and with a very high angle of attack. At 20:26 the aircraft hit tail first into a field before bouncing and coming to rest upon the embankment of the M1.

47 of the 128 people on board died, miracuously no one on the motorway was killed.Image
ImageThe aircraft came to rest 900m short of the runway

ImageImage


From Wikipedia:
Engine malfunction
It was discovered after analysis of the engine from the crash 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 as such, the engine was only ever tested in the laboratory. Upon this discovery all 737-400s (around 100 at the time) were grounded and the engines modified. Since the crash it has also become mandatory to carry out test at representative conditions for all turbofan engines, whether they are a brand new design or a major redesign.

This unnoticed vibration created excessive metal fatigue in the turbine blades and on G-OBME this caused one of the fan blades to break off and cause damage throughout the engine. 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.


Click here for a video of the aftermath of the accident
Last edited by EGNX on Mon Jan 08, 2007 12:05 pm, edited 1 time in total.
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Re: 17 Years Today...

Postby VVM » Mon Jan 08, 2007 12:02 pm

what makes this accident even more tragic imo is that they were so close to being 'safely' on the ground.
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Re: 17 Years Today...

Postby EGNX » Mon Jan 08, 2007 12:04 pm

Edit to Post: 18 Years today, not 17 :P
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Re: 17 Years Today...

Postby C » Mon Jan 08, 2007 12:13 pm

Basically, when the initial problem happened, with no (known) abnormal gauge indications (we'll come back to that later), the Captain decided to bring each throttle back in turn to diagnose the problematic engine. When they brough the right hand throttle back, the vibration stopped. This lead them to believe that the right hand engine had the problem (what actually was happening was the engine control system trying to equalize the thrust, hence the left engine fuel supply reduced, temporarily halting the vibration). The engine instruments still appeared apparently normal. They continued the approach. Passengers in the cabin were told by the captain that they'd had an right hand engine problem, and that the engine had been shut down. No passengers queried with any of the cabin staff whether the Captain was aware of the large number of sparks being seen from the left engine.

To cut a long story short, it failed, and one 737-400 glider was left a mile short of the runway.

Factors: The 737-400 was a new aircraft. There were no simulators in Europe, and the airline did not send them to the USA, and pilots converted from the -300 using groundschool notes. This is partly why they were unaware of two small, poorly designed vibration gauges. These were the only clue the pilots had that the left engine was the faulty on. Howeverm it had no coloured arcs on its scale, and it would have relied on the pilots knowing what the excessive would be. Trivial. They didn't really know it was there.

Cabin crew and passengers not questioning the flight deck crew when they clearly announced they had shut down the right hand engine (the one with sparks coming out).

ATC interference - at one stage the CVR recorded the captain saying something along the lines of "lets double double check we've got this right", only to be distracted by ATC, and then subsequently not telling them to shut up whilst they (literally) sorted their lives out...

Finally the engine manufacturer. For the -400 they wanted 5% or so more thrust. CFM (?) decided this could be done by uprating the same engine, without new major part, and most catastrophically no air testing. Then under the increased stress it was a fan blade on the aircraft that gave way.

The Captain and Co-Pilot had their careers ruined. The Captain was retired IIRC, and the Co-Pilot lost his license. Admittedly they made mistakes, but ultimately there were some very, very serious deficiencies in training, design of both the aircraft, and worde, the cost cutting in the engine manufacture.

Very sad indeed....

...but on more thing. Remember the Manchester 737 disaster in 1985, where 55 or so people were killed in a ground fire? After that the AAIB reccommended that a CCTV camera be mounted (in the fin) to give the crew an immediate external view of a problem (in the Manchester case they would not have bothered taxying off the runway and shutting down etc, and in this case the Captain would have seen the left hand engine abnormalities). It wasn't implemented after Manchester or Kegworth. Think of another one it may have change the outcome of. Paris? I bet if the Concorde Captain had see the state of his left wing on take off, he would have kept the aircraft on the ground at all costs.
Last edited by C on Mon Jan 08, 2007 12:18 pm, edited 1 time in total.
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