Transcript THE WINDSCREEN CHANGE

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“Why We Need to be ^Proactive”
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David F King
Deputy Chief Inspector of Air Accidents
• Air Accidents Investigation Branch
• United Kingdom
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Measuring Safety Culture
a Maintenance Human Factors Perspective
• 26th April 2004
BAC 1-11
BAC 1-11
Airbus A320
Boeing 737
Boeing 737
COMMON FEATURES
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Night shift - Circadian lows - Much Maintenance at night.
Supervisors tackling long, hands-on involved tasks.
Interruptions.
Failure to use the Maintenance Manual - IPC
Confusing -misleading difficult manuals
Shift handovers - poor briefing - no detailed stage sheets
Time pressures
Staff shortages
Limited preplanning paperwork, equipment, spares
Determination to cope with all challenges.
Boeing 757 Nosewheel Axle failure
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Birmingham to Malaga - uneventful landing.
Exit via rapid taxiway - 20kts vibration.
Aircraft stopped - passengers evacuated via steps.
Inspection - right nose wheel canted over Outer Bearing disintegrated.
Boeing 757 Nosewheel Axle failure
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1725hrs
Operator informed - Duty Engineer
Right nosewheel bearing collapsed.
Telecon Commander
OK towed slowly - consequential damage? Axle change anyway!
Telecon contract maintenance company
Two engineers to go to Malaga no can do!
Boeing 757 Nosewheel Axle failure
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Another co aircraft due take-off for Tangier 1800hrs
Held for divertion malaga with wheels and change kit.
Certifying engineer (LAE) rings in - to check shifts!
Aircraft full of passengers - is he available?
Feeling tired been Flying microlight - Agrees to go.
1730hrs Told he is going.
Duty Engineer copies extracts from AMM
Torque loading for wheel change
NOT ‘Time Limits/Maintenance Checks - mandatory
borescope inspection after bearing failure!
Boeing 757 Nosewheel Axle failure
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1815hrs LAE arrives at Airport
Asks for mechanic to go with him - Only one seat on aircraft!
1825hrs Aircraft departs for Malaga
No opportunity for LAE to check AMM not one on aircraft.
Only authorised procedure for nosewheel axle repair by replacement.
1830hrs Duty Eng told aircraft jacked
Wheel was off & axle was ‘not too bad’.
1900hrs Avionics Eng takes over as Duty Eng.
2115hrs LAE arrived in Malaga
Boeing 757 Nosewheel Axle failure
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2115hrs LAE in Malaga - asked about length of delay?
Damaged wheel already loaded - unaccessible.
Saw bush and axle nut damaged - elected to re-use.
Identified axle damage
Between bearing lands - 11/2” long 1/16” deep.
Could see no ‘bluing’ or overheat on outside of axle.
Decided aircraft OK return Birmingham after blending
Informed Duty Eng at Manchester.
Duty Eng concerned no repair limits in Manual.
Contacted Boeing 24 hr desk - go to AMM/provide sketch?
Boeing 757 Nosewheel Axle failure
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LAE used torch in attempt to see inside axle
Could not see 7” as Borescope inspection required.
Missed evidence of overheating.
Blended damage
Using half round file and emery paper.
Did not raise ADD but regarded as temporary repair
no drawings or blend limits to work to - no blending allowed.
During inspection distracted
Tangier aircraft having refuelling problem - gave advice.
During blending distracted
Refuelling problem again - went to assist.
Boeing 757 Nosewheel Axle failure
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LAE replaced right wheel without problem
Changed left hand wheel.
2215hrs (1 hour after arrival Malaga)
Contacted Duty Eng
brief description of damage
Aircraft satisfactory for service
Axle change should be planned when schedule allowed.
2259hrs Aircraft Took off.
0121hrs Aircraft landed at Birmingham
Slowed to 12kt when axle failed.
Discolouration 400C
Region ‘dressed’ since mechanical damage - before fracture.
Fracture initiation in dressed region
COMMON FEATURES
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Night shift - Circadian lows - Much Maintenance at night.
Supervisors tackling long, hands-on involved tasks.
Interruptions.
Failure to use the Maintenance Manual - IPC
Confusing -misleading difficult manuals
Shift handovers - poor briefing - no detailed stage sheets
Time pressures
Staff shortages
Limited preplanning paperwork, equipment, spares
Determination to cope with all challenges.
That’s All Folks
WINDSCREEN CHANGE
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Short staffing - Night shift of 7 down by 2.
Shift Manager does job himself, alone.
A/C remote - took Manager away from his other duties.
Time pressures - AM shift short - aircraft to be washed.
Task between 0300-0500 hrs - time of Circadian lows.
Manager was on his 1st night work for 5 weeks.
MM only used to confirm Job ‘straight forward’.
IPC was not used - IPC was misleading.
The safety raiser used provided poor access.
WINDSCREEN CHANGE - SHIFT MANAGER
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assumed bolts fitted OK - incorrect bolts 4 years before.
chose bolts by matching - stores below min stock level.
ignored advice of storeman on bolt size.
bolts from open AGS Carousel - faded labels - dark corner.
did not use his reading glasses at any time.
increased torque from 15 lb in to 20 lb in.
didn’t notice excessive countersink or next window
different.
• didn’t recognise different torque for corner fairing.
• rationalised use of different bolts next night doing same job
FLAP CHANGE
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LAE and team were new to the task.
LAE authorised but A320 rarely seen - 3rd party work.
Planning was a job card - 'change flap' + some tooling.
Maintenance Manual in AMTOSS format.
Tooling deficient or incorrect - no collars for spoilers.
LAE requested experienced help - none available.
Other tasks during delays - changes in tasking.
Task worked in early hours - time of Circadian lows.
Tried task without disabling spoilers - couldn't do.
Spoilers disabled no collars/flags - deviation from MM.
FLAP CHANGE
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Shift hand over verbal, paperwork incomplete misunderstanding over spoilers.
Spoilers were pushed down during flap rigging.
Familiarity with Boeing aircraft where spoilers auto reset.
Flaps functioned - spoilers not - a deviation from the MM.
Duplicates were lead by day shift engineer.
Failure to follow Maintenance Manual.
During flight crew Walk round nothing amiss.
Pre-flight check, 3 seconds mismatch control/surface
position required to generate warning.
Engineers demonstrated a willingness to work around
problems without reference to design authority - including
deviations from Maintenance Manual.
BORESCOPE INSPECTION
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Inspections not in accordance with Task Cards or MM:HP rotor drive covers not refitted.
Ground idle engine tests not conducted.
Tech Log wrongly signed completed as in MM
Work originally planned for Line, transferred to base.
Line and Base staff shortages - three Base supervisors.
Minimal preplanned paperwork - Line Maintenance.
To keep authorisation Base Controller did inspections.
A/C remote - took Controller away from other duties.
BORESCOPE INSPECTION
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Line Engineer gave verbal handover to Base Controller.
Inadequate reference to Maintenance Manual.
Use of an unapproved reference source - school notes.
Poor lighting.
Many interruptions.
Early hours of morning - Circadian lows.
9 previous occurrences.
Borescope Inspections routinely non procedural.
Quality Assurance system had not identified deviations.
Regulator’s monitoring had not corrected lapses.
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Although many ingredients are demonstrated to have
come together to create these incidents, what if some
are there all the time?
The Heinrich Ratio
1
Fatal Accidents
Accidents
10
30
600
Tye/Pearson
Bird
Reportable Incidents
Incidents