Human Factor in Maintenance Case Studies QANTAS Engineering

Darren CookManager Quality & Safety Maintenance Operations

& Part 145QANTAS Engineering

IATA

Maintenance Symposium

Miami September 2015

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A330 NLG Shock Absorber

Just another shock strut service – right?

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A330 NLG Shock Absorber

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A330 NLG Shock Absorber

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A330 NLG Shock Absorber

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A330 NLG Shock Absorber - History

• Complex & Error prone task

• Not done very often

• A lot of equipment required

• Maintenance Manual complexity

• The job took many hours to complete

• Rework often required

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Investigation Results

Complex Task Complex design Task Knowledge

Maintenance Data Complexity Equipment difficult to fit Task

Difficult access New Task (often) Different from similar tasks

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Complex Procedure

Hydraulic replenishment of the NLG is made up of 12 key steps

1. Decrease P2 (HP) nitrogen pressure to zero2. Decrease P1 (LP) nitrogen pressure to zero3. Fill P1 (LP) pressure chamber with hydraulic fluid4. Pressurise P2 (HP) chamber with nitrogen to the correct pressure5. Fully compress sliding tube into the main fitting6. Refill P1 pressure chamber with hydraulic fluid to fully extend the

sliding tube7. Repeat steps 5 and 6 until hydraulic fluid is free from air bubbles8. Compress the sliding tube into the main fitting to set dimension “H”9. Pressurise P1 (LP) chamber with nitrogen to correct pressure10.Lower the aircraft off jacks11.Do a Pressure / Extension check of the NLG shock absorber12.Adjust the nitrogen in the NLG shock absorber

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Human Factors intervention

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Human Factors Intervention

• Embed the training for this task into the actual task

• When the task was called out the technicians would attend 30 minute training course on the task

• Task briefing then conducted prior to commencing the task

• This process has actually shortened the time it takes to complete this task

• No errors since the introduction of this intervention

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Circuit Breaker Errors

2013 – steady increase in circuit breaker related events

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Circuit Breaker Errors

• Aircraft departing with C/Bs tripped (some with warning flags still installed)

• Incomplete MEL application/reversal with C/Bs left set or incorrect C/B tripped

• Incorrect C/Bs tripped for maintenance

• Issues not limited to aircraft type

• Issues not limited to locations or shift types

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Circuit Breaker Error Investigation

Many Human Factors and Human performance factors involved• Complacency

• Distraction

• Time pressure

• Point of dispatch pressures

• System knowledge

• Manpower planning

• Communication

• Handover

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Circuit Breaker Error Investigation

Task related factors determined

• Inconsistent procedures across aircraft fleet types

• No defined procedure/requirements when C/Bs were tripped for maintenance

• Some individual and group behaviours

• Flight Crew CB checks not effective

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Circuit Breaker Error Solutions

• Realistic, Single, & Concise procedure for technicians to follow

• Simple & consistent procedure for checking C/Bs at the conclusion of all maintenance

• Training provided by experienced technicians

• Changes properly change managed

• Flight Crew C/B training

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Circuit Breaker Error Solutions

• Place C/B lock out tags where the technicians trip and lock out C/Bs

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Circuit Breaker Error Solutions

Separate Boeing and Airbus procedures

Airbus – computer monitored (A330 & A380)

Boeing – not monitored (B737, B767, & B747)

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Circuit Breaker Error Solution Results

• 90% drop in flown CB related incidents after 1 year

• Good acceptance by technicians

• Technician feedback provided further improvements

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Circuit Breaker Error Solution Results

• Damage to Airbus C/Bs caused by new tags. Different tags introduced for Airbus

• Multiple tag lock out introduced in Base Maintenance

Base Maint Multi Tag lock out Softer lockout collar for Airbus

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Conclusion