AVIATION ACCIDENTS AND INCIDENTS ROSS APTED

Scene of the disaster – wreckage on M1 motorway near Kegworth

KEGWORTH AIR DISASTER

WHAT HAPPENED

On 8th January 1989 British midland flight 92 crashed while undertaking an emergency landing.

Crashed site : M1 embankment near the village of Kegworth.

The Boeing 737 -400 aircraft was severely damaged 79 of the of the 126 people aboard the plane survived.

An investigation was carried out by the Air Accidents Investigation Branch (AAIB). (Air Accidents Investigation Branch, 1989)

AAIB INVESTIGATION

Events of the crash

1. During the ascent of the aircraft to its cruising altitude of 35,000 feet metal fatigue occurred on the fan blades in the left engine.

Due to the engine design not being able to withstand vibrations caused by operation above 25, 000 feet and a high power setting.

Boeing 737–400 Engine

AAIB INVESTIGATION

2. Fan blade broke off causing decrease in power and increase in vibrations. This caused the left engine to produced a jet of flames.

3. Smoke flooded into the cabin. Captain shut down the engine on the right.

4. Smell of smoke and vibrations reduced.

5. Crew diverted to Midlands Airport. Left engine completely failed during the descent of the emergency landing

AAIB INVESTIGATION

Causes of the Crash

The flight crew shut down the right engine(which was functioning correctly – could have sustained aircraft)

In response to the left engine being damaged(blade fracture.)

The left engine then completely failed due to increases stress during approach to land.

The wrong engine was shut down.

Primary cause: Human error

Secondary cause: technical failure

CONTRIBUTING FACTORS

Inadequate knowledge of the aircraft

Flight crew observed smoke in the cabin.

Believed they could not trust the Vibration sensors. Was true of the old Boeing 737 but not the new 737-400.

Indicates the state of the engines.

Fell back on general knowledge of aircraft which was wrong. Thought that bleed air(pressure and heating) was taken from the right engine.

In fact the air conditioning systems utilized both engines in the new model.

BOEING 737 (OLD)

Key - bleed air via air

conditioning

Right engine

BOEING 737-400 (NEW)

Key - bleed air via air

conditioning

Right engine Left engine

CONTRIBUTING FACTORS In adequate training

The combination of violent engine vibrations and the smell of smoke while climbing to covered attitude was not covered in training.

Two separate protocols existed for each event but not in conjunction.

No simulation training for engine failure of this kind, or what to do if the situations fall out of bounds of standard procedures.

Differences in the Boeing 737 and 737-400 were not adequately taught.

WHY THE MISTAKE WAS NOT FOUND

By chance the the smoke dissipated and the vibrations reduced – this was actually due to standard procedure reducing fuel flow to both the engines.

Pilots did not communicate with the cabin crew who had visual confirmation of which engine was damaged.

Immediate division to Midlands airport create a high cabin workload this resulted in incorrect review procedure after the right engine was shut down.

Right engine was shut down

In adequate training

Left engine failed

Insufficient knowledge of aircraft

Crash

Improper design testing

ACADEMIC LITERATUREOn a Wing and a Prayer? Exploring the Human Components of Technological Failure (Smith, 2000)

Key points

Exploring the role of human error in complex technical systems.

Case study Kegworth

Thesis – Import to not only focus on individual but social and managerial framework in which the exist.

Conclusion – With fly – by –wire system on the rise it is ever more import to look at the organization as a whole and not just focus on individual aspects.

Qantas A330-303 - the type of aircraft that the incident occurred on

QANTAS FLIGHT 72

WHAT HAPPENED

On the 7th October 2008 Qantas Flight 72 made an emergency landing due to in flight accident.

A series of in uncommand pitch down maneuvers were initiated resulting in crew and passenger injury.

An investigation was carried out by The Australian Transport Safety Bureau (ATSB). (Australian Transport Safety Bureau )

ATSB INVESTIGATION

Events of the accident

1. At cruising altitude one of the Air Data Inertial Reference Unit stated to providing incorrect values know as spikes to flight systems.

Air Data Inertial Reference Unit(ADIRU) –provides air data such as air speed, altitude and angle of attack the pilots flight instruments.

2. The autopilot disconnect an warning were triggered.

3. Aircraft rapidly pitched down unprompted. Due to the flight control primary computer the angle of attack spike.

ATSB INVESTIGATION

4. Sudden forces cause severe injuries to the aircrafts occupants.

5. A second pitch down occurred moments later.

6. Pilots switch to manual operation a sent a Mayday distress.

7. Flight was diverted to Learmonth, Western Australia

ATSB INVESTIGATION

Cause of the accident

flight control primary computer

Is a “full-authority” flight control system. Get its flight data from the ADIRU’s. 3 ADIRU for error resistance and redundancy.

If all 3 ADIRU are consistent the and average of ADIRU1 and ADIRU2 is used.

If ADIRU1 or ADIRU2 are not consistent then a memorized value is used for 1.2s.

Fault occurred when there was multiple spikes 1.2s apart.

ATSB INVESTIGATION

ADIRU data-spike

ADIRU entered a failure mode in which it was sending invalid data to flight system but marking it as being valid.

No warning that the unit had failed was trigged.

Hardware bug – the CPU module of the unit would inexpiably combined the parameter for value with the label for another parameter.

AIRBUS VS BOEING

Airbus philosophy - safety will be reduced by removing human error

= giving the computer more control.

Boeing philosophy - safety will be reduced by removing the complexities between the interactions of humans and technology.

= give pilot unlimited control but make it easier to interact with the computer.

Boeing 747- the type of aircraft that the incident occurred on

AAIB BULLETIN- INCIDENT

SERIOUS INCIDENT

Serious incident involving a Boeing 757-21B found in the June 2012 bulletin. (Air Accidents Investigation Branch, 2012)

AAIB Bulletin – A monthly notice of accidents and serous incident.

What happened:

The Aircraft lost power to its left AC electrical bus, causing the failure many flight instruments.

BACKGROUND1. Mid-flight the “L AC BUS OFF” and “L GEN OFF” warning

lights triggered indicating a power failure.

2. Multiple flight instruments failed.

3. Commander carried out the drill for power loss in the left generator.

4. Bus reset and power temporally restored

5. Power went off again this time accompanied with thin smoke on flight deck.

6. MAYDAY was sent and aircraft was diverted to nearest airport.

Only effect on passengers was that they had to catch a new flight.

AAIB INVESTIGATION

Found that be a corroded crimp terminal at the D1114J connector which is part of the left power generation system.

Procedure

Split into previous and post incident maintenance actions

Still focuses on crew actions

Standardized format for bulletins – focus on primary sources of information little root cause analysis.

Broken D1114j connector

REFERENCES

Air Accidents Investigation Branch. (2012). June 2012 Bulletin. Aldershot: Air Accidents Investigation Branch.

Air Accidents Investigation Branch. (1989). Report on the Accident to Boeing 737-400 G-OBME near Kegworth, Leicesterhire on 8 Janury 1989. Aldershot: Air Accidents Investigation Branch.

Australian Transport Safety Bureau. (2008). In-flight upset 154 km west of Learmonth, WA 7 October 2008 VH-QPA Airbus A330-303. Canberra: Australian Transport Safety Bureau.

Smith, D. (2000). On a wing and a prayer? Exploring the human components of technological failure. Syst. Res. , 543–559.