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Difference between revisions of "B734, vicinity East Midlands UK, 1989"

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[[File:GOBME ASC.jpg|thumb|none|500px|The wreckage of the aircraft showing the proximity to the runway (reproduced from the Official Report)]]
 
[[File:GOBME ASC.jpg|thumb|none|500px|The wreckage of the aircraft showing the proximity to the runway (reproduced from the Official Report)]]
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In the final stages of flight the aircraft was found to have demolished fencing and a motorway lighting column and a detached landing gear assembly had struck and deformed a motorway crash barrier.
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Witnesses on the ground who had observed the aircraft shortly before the crash reported having seen definite evidence of fire in the left engine with the intake appearing to be on fire and flames being emitted intermittently from the jet pipe in unison with ''“thumping noises”''. Others reported hearing ''“metallic rattling”'' and seeing flaming debris falling from the aircraft.
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It was found that after the aircraft had crashed, a Company Engineer who had been positioning on the flight had entered the flight deck and switched off the main battery switch and the standby power switch, later returning to switch off the engine start/ignition switches and fuel booster pumps. The engine start levers (fuel valves) were subsequently found in the cut-off position by investigators but it could not be established who had moved them to that position or when this had occurred.
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Following the impact the majority of the survivors were unable to evacuate the aircraft because of the extent of their injuries and/or because they were trapped or due seat failure or the effects of debris falling from overhead. ''“Only 14 of the passengers were able to make a significant contribution to effecting their own escape”'' and both pilots and one of the two forward-stationed cabin crew were trapped.
  
  

Revision as of 07:13, 20 December 2013

Summary
On 8 January 1989, a British Midland Airways Boeing 737-400, suffered a loss of control followed by terrain impact in the vicinity of East Midlands Airport, UK, on final approach, after an earlier engine malfunction had been followed by the shut down of the wrong engine.
Event Details
When January 1989
Actual or Potential
Event Type
Airworthiness, Fire Smoke and Fumes, Human Factors, Loss of Control
Day/Night Night
Flight Conditions IMC
Flight Details
Aircraft BOEING 737-400
Operator British Midland
Domicile United Kingdom
Type of Flight Public Transport (Passenger)
Origin London Heathrow Airport
Intended Destination Belfast/George Best Belfast City Airport
Actual Destination East Midlands Airport
Flight Phase Manoeuvring
MNV
Location - Airport
Airport vicinity East Midlands Airport
FIRE
Tag(s) Fire-Power Plant origin
HF
Tag(s) Ineffective Monitoring,
Procedural non compliance,
Inappropriate crew response (technical fault)
CS
Tag(s) Cabin air contamination
AW
System(s) Rotors,
Engine Fuel and Control
Safety Net Mitigations
Malfunction of Relevant Safety Net No
GPWS Available but ineffective
Stall Protection Available but ineffective
Outcome
Damage or injury Yes
Aircraft damage Hull loss
Non-aircraft damage Yes
Injuries Most or all occupants
Fatalities Many occupants ()
Causal Factor Group(s)
Group(s) Aircraft Operation,
Aircraft Technical
Safety Recommendation(s)
Group(s) Aircraft Operation,
Aircraft Airworthiness
Investigation Type
Type Independent


Description

On 8 January 1989, a Boeing 737-400 being operated by British Midland Airways on a scheduled passenger flight from London Heathrow to Belfast Aldergrove experienced a malfunction in an engine and the engine believed to be at fault was shut down. It was decided to make an en route diversion to East Midlands, but when thrust was increased on the engine believed to be serviceable on final approach, it failed and a fire warning was annunciated. Loss of control was followed soon afterwards by terrain impact in the vicinity of East Midlands which led to the destruction of the aircraft. There was no post crash fire but 39 of the passengers died as a result of the impact and a further 82 of the 126 occupants sustained serious injuries which in 8 cases led to their subsequent death.

Investigation

An Investigation was carried out by the Aircraft Accident Investigation Branch (UK) (AAIB). Data from the 25 hour Flight Data Recorder (FDR) and the 30 minute Cockpit Voice Recorder (CVR) were successfully recovered and the absence of any post crash fire in the fuselage permitted an unusually comprehensive and valuable examination of the wreckage.

A Special Bulletin S2/89 was issued on 20 March1989 to summarise factual information then available and to list the 7 Safety Recommendations which had been made to the UK CAA up to and including 23 February 1989.

It was established that as the aircraft was climbing through FL283 with the First Officer as PF, a series of compressor stalls had occurred in the No 1 engine. These resulted in airframe shuddering, ingress of smoke and fumes to the flight deck and fluctuation of the corresponding engine indications.

The aircraft commander had almost immediately disengaged the AP and “although no words were said, it was apparent to the First Officer that the Commander had taken control of the aircraft”. The crew responded rapidly and instinctively by disconnecting the A/T and reducing thrust on the No. 2 engine without any apparent assessment of the appropriate or otherwise available actions and without noting the indications on flight deck engine instrumentation.

ATC were advised of an emergency involving an engine malfunction and possible fire. The aircraft commander had immediately begun communications with Company Operations on the second radio whilst the First Officer was following a critical Quick Reference Handbook (QRH) procedure during which confirmation was required at various points. Shortly after the No 2 engine had been shut down some 5nm away from East Midlands, where the Company Head Office and engineering base was located, the Commander had agreed to a request from Company Operations to divert there and ATC had been advised accordingly.

Once the A/T was disconnected and the No 2 engine was being shut down, the No 1 engine vibration level slowly began to reduce from the maximum level achieved during the compressor stalls. Since the thrust now required was relatively low in order to accomplish a descent before turning back towards East Midlands, the No.1 engine appeared to be functioning normally, albeit at a slightly lower N1 speed than before. This had the effect of reducing the shuddering apparent on the flight deck which helped to convince the aircraft commander that the No. 2 engine had been correctly identified as the source of the symptoms previously evident. With the APU started and shutdown of the No. 2 engine complete, the smoke and fumes which had been present in the flight deck since the onset of the engine malfunction symptoms also disappeared. The Vibration Indicator for the No 1 engine continued to reduce as thrust was reduced until it reached and remained at 2 units, still a little above normal. Despite an indication of a higher than normal fuel flow, it was concluded by the crew that the No 1 engine was running normally.

Even with the minimum track miles required to achieve descent, a landing at East Midlands was still about 20 minutes flying time from the point where engine shutdown had occurred but crew workload nevertheless remained high. The First Officer attempted to re-programme the FMS for the diversion airport and, some 7.5 minutes after the initial problem, the Commander attempted to review the initial engine symptoms, but this process was interrupted by ATC instructions and not completed thereafter.

With the No. 2 engine shut down, the Commander advised the Flight Service Manager (FSM, the senior cabin crew member) of the intended diversion and instructed them to secure the cabin. In response to a closed question from the Commander, the FSM confirmed that there had been smoke in the cabin. About a minute after this, the FSM called to say the “passengers are very very panicky” and the Commander then made a PA stating that the right (i.e. the No. 2) engine had been shut down due to a malfunction and that the aircraft would be diverting to East Midlands and landing in abut 10 minutes time. Three of the cabin crew who had seen signs of fire on the left engine later stated that they had not heard the Commander's reference to the right engine in this PA but “many of the passengers who saw fire from the No 1 engine heard and were puzzled by the Commander's reference to the right engine, but none brought the discrepancy to the attention of the cabin crew, even though several were aware of continuing vibration”.

Fifteen minutes after the engine problem had occurred and descending through 3000 feet Altimeter Pressure Settings just under five minutes prior to ground impact, the Commander had increased thrust on the engine in use (No. 1) as the aircraft was establishing on the Instrument Landing System (ILS) LOC for runway 27. This action was followed immediately by the vibration indication for the engine again rising to its maximum 5-unit reading, but this was not noticed by either pilot.

Then, just under a minute before ground impact, with the aircraft at 900 feet agl and 2.4 nm from the runway with the landing gear down and 15° flap selected, there was an abrupt loss of thrust from the No. 1 engine and a concurrent engine fire warning. The commander had immediately instructed the First Officer to attempt to restart the No. 2 engine but the attempt was not successful. It became clear that it would not be possible to reach the runway and ten seconds before impact, the Commander broadcast “Prepare for Crash Landing” on the PA.

As the airspeed fell below 125 knots, the stick shaker activated and continued to do so until the aircraft struck level ground in a nose high attitude just to the east of the M1 motorway, which at this point was in a cutting below the general level of the terrain and running perpendicular to the extended runway centreline. The aircraft then passed through some trees before a second and major impact 70 metres to the west and 10 metres below the first one on the opposite (i.e. western/northbound) carriageway of the motorway on the lower part of its western embankment. It then slid up this embankment, through more trees breaking into three main sections and coming to a final stop approximately 900 metres from the threshold of runway 27 some 50 metres to the north of the extended runway centreline (see the illustration below). There was no significant post crash fire and what remained of the No. 1 engine fire was quickly extinguished by the emergency services.

The wreckage of the aircraft showing the proximity to the runway (reproduced from the Official Report)

In the final stages of flight the aircraft was found to have demolished fencing and a motorway lighting column and a detached landing gear assembly had struck and deformed a motorway crash barrier.

Witnesses on the ground who had observed the aircraft shortly before the crash reported having seen definite evidence of fire in the left engine with the intake appearing to be on fire and flames being emitted intermittently from the jet pipe in unison with “thumping noises”. Others reported hearing “metallic rattling” and seeing flaming debris falling from the aircraft.

It was found that after the aircraft had crashed, a Company Engineer who had been positioning on the flight had entered the flight deck and switched off the main battery switch and the standby power switch, later returning to switch off the engine start/ignition switches and fuel booster pumps. The engine start levers (fuel valves) were subsequently found in the cut-off position by investigators but it could not be established who had moved them to that position or when this had occurred.

Following the impact the majority of the survivors were unable to evacuate the aircraft because of the extent of their injuries and/or because they were trapped or due seat failure or the effects of debris falling from overhead. “Only 14 of the passengers were able to make a significant contribution to effecting their own escape” and both pilots and one of the two forward-stationed cabin crew were trapped.


Synopsis

This is an extract from the official report into the accident published by the Air Accident Investigation Branch (AAIB) UK:

The aircraft “[…] left Heathrow Airport for Belfast at 1952 hrs with 8 crew and 118 passengers […] onboard. As the aircraft was climbing through 28,300 feet the outer panel of one blade in the fan of the No 1 (left) engine detached. This gave rise to a series of compressor stalls in the No 1 engine, which resulted in airframe shuddering, ingress of smoke and fumes to the flight deck and fluctuations of the No 1 engine parameters. Believing that the No 2 engine had suffered damage, the crew throttled that engine back and subsequently shut it down. The shuddering caused by the surging of the No 1 engine ceased as soon as the No 2 engine was throttled back, which persuaded the crew that they had dealt correctly with the emergency. They then shut down the No 2 engine. The No l engine operated apparently normally after the initial period of severe vibration and during the subsequent descent.

The crew initiated a diversion to East Midlands Airport and received radar direction from air traffic control to position the aircraft for an instrument approach to land on runway 27.

The approach continued normally, although with a high level of vibration from the No 1 engine, until an abrupt reduction of power, followed by a fire warning, occurred on this engine at a point 2.4 nm from the runway.

[…]The commander called immediately for the first officer to relight (ie restart) the other [No .2] engine and the first officer attempted to comply. The commander then raised the nose of the aircraft in an effort to reach the runway.

[…]The last airspeed recorded on the FDR was 115 kts212.98 km/h
59.11 m/s
. No power became available from the No 2 engine before the aircraft struck the ground”.

The Cause of the accident was given as:

“The cause of the accident was that the operating crew shut down the No.2 engine after a fan blade had fractured in the No.1 engine. This engine subsequently suffered major thrust loss due to secondary fan damage as power was increased during the final approach to land.”

The Report identifies the following contributory factors to the incorrect response of the flight crew:

  • The combination of heavy engine vibration, noise, shuddering and an associated smell of fire were outside their training and experience.
  • They reacted to the initial engine problem prematurely and in a way that was contrary to their training.
  • They did not assimilate the indications on the engine instrument display before they throttled back the No. 2 engine.
  • As the No 2 engine was throttled back, the noise and shuddering associated with the surging of the No 1 engine ceased, persuading them that they had correctly identified the defective engine.
  • They were not informed of the flames which had emanated from the No.1 engine and which had been observed by many on board, including 3 cabin attendants in the aft cabin.

The Report's recommendations, beginning on page 118, also address institutional, manufacturers and organisational issues (see Further Reading).

Related Articles

Further Reading

For further information see the full accident report and appendices published by AAIB.