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