more“Why We Need to be ^Proactive”
• David F King
• Deputy Chief Inspector of Air Accidents
• Air Accidents Investigation Branch
• United Kingdom
• Measuring Safety Culture
• a Maintenance Human Factors Perspective
• 26th April 2004
BAC 1-11
BAC 1-11
Airbus A320
Boeing 737
Boeing 737
COMMON FEATURESCOMMON FEATURESCOMMON FEATURESCOMMON FEATURES
• 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 failureBoeing 757 Nosewheel Axle failure
• 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 failureBoeing 757 Nosewheel Axle failure
• 1725hrs Operator informed - Duty EngineerRight 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 failureBoeing 757 Nosewheel Axle failure
• Another co aircraft due take-off for Tangier 1800hrsHeld 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 failureBoeing 757 Nosewheel Axle failure
• 1815hrs LAE arrives at AirportAsks for mechanic to go with him - Only one seat on aircraft!
• 1825hrs Aircraft departs for MalagaNo opportunity for LAE to check AMM not one on aircraft.
Only authorised procedure for nosewheel axle -
repair by replacement.
• 1830hrs Duty Eng told aircraft jackedWheel was off & axle was ‘not too bad’.
• 1900hrs Avionics Eng takes over as Duty Eng.
• 2115hrs LAE arrived in Malaga
Boeing 757 Nosewheel Axle failureBoeing 757 Nosewheel Axle failure
• 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 damageBetween bearing lands - 11/2” long 1/16” deep.
Could see no ‘bluing’ or overheat on outside of axle.
• Decided aircraft OK return Birmingham after blendingInformed 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 failureBoeing 757 Nosewheel Axle failure
• LAE used torch in attempt to see inside axleCould not see 7” as Borescope inspection required.
Missed evidence of overheating.
• Blended damageUsing half round file and emery paper.
• Did not raise ADD but regarded as temporary repairno 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 failureBoeing 757 Nosewheel Axle failure
• 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 BirminghamSlowed to 12kt when axle failed.
Region ‘dressed’ since mechanical damage - before fracture.
Discolouration 400C
Fracture initiation in dressed region
COMMON FEATURESCOMMON FEATURESCOMMON FEATURESCOMMON FEATURES
• 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 CHANGEWINDSCREEN CHANGE
• 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.
• 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
WINDSCREEN CHANGE - SHIFT MANAGERWINDSCREEN CHANGE - SHIFT MANAGER
FLAP CHANGEFLAP CHANGE
• 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.
• 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.
FLAP CHANGEFLAP CHANGE
BORESCOPE INSPECTIONBORESCOPE INSPECTION
• 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.
• 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.
BORESCOPE INSPECTIONBORESCOPE INSPECTION
• Although many ingredients are demonstrated to have come together to create these incidents, what if some are there all the time?
Fatal Accidents
Accidents
Reportable Incidents
Incidents
1
10
30
600
The Heinrich Ratio
Tye/PearsonBird