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EMSG Conference 10 October 2007AAIB Farnborough

RISK IN THE MAINTENANCE

ENVIRONMENT

ROYAL AERONAUTICAL SOCIETY

ENGINEERING MAINTENANCE STANDING GROUP

CONFERENCE

AAIB FARNBOROUGH, 10 OCTOBER 2007

Alan P Simmons M.Sc., C.Eng., M.R.Ae.S.

Principal Inspector of Air Accidents,Air Accidents Investigation Branch, United Kingdom


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PRESENTATION OVERVIEW

SAFETY SYSTEMS AND HUMAN PERFORMANCE

MAINTENANCE ERROR AND BUSINESS RISK

REMEDIAL MEASURES


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IN MAINTENANCE

Our safety systems have evolved:

Checking/inspecting: Quality Control

Controlling the production process: QC, TQM

Managing safety: MEMS, SMS


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SAFETY

MANAGEMENTSYSTEMS


IN MAINTENANCE


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LIMITATIONS OF HUMAN PERFORMANCE

Perception and Cognitive limitations

Optical and Auditory limitations

Tunnelling and focusing


IN MAINTENANCE

Man errs as long as he strives.

Goethe


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ERROR TYPE MAINTENANCE EXPERT

DATA ASSESSMENT

Skip a step 0.15 0.001

Skip a task 0.026 0.001Ignore a warning/caution 0.042 0.013

Intentionally deviate 0.042 0.32

Improperly remove/replace 0.033 0.02

Improperly repair 0.089 0.0023

Incomplete installation 0.089 0.01

Improperly adjust 0.09 0.1Allow/cause debris to enter 0.17 0.01


IN MAINTENANCE

Source Ostrom et al, INEEL


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PROCEDURES MITIGATE RISK OF HUMAN ERROR

Clear documentation

Parts kitsChecklists

Inspections

Function checks

Even pre-flight checks


IN MAINTENANCE


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WHY PROCEDURAL ERRORS UNDERMINE SAFETY:

Clear documentation is useless if not used

Parts control cannot work if uncontrolled stocks are held

Independent Inspections must be truly independent

Function checks must be carried out


IN MAINTENANCE


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Can your maintenance staff actually perform the

required inspections?


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Do you have uncontrolled small parts?


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Do your engineers improvise?


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Are your engineers under pressure to avoid

ground runs at night?


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Do your engineers sign off task cards sight unseen?


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Is the Approved Data correct and is there a viable

procedure to amend errors?


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Most maintenance error events investigated by AAIB

are INCIDENTS not ACCIDENTS

Maintenance related incidents form a largerproportion of total maintenance related events

investigated by AAIB than accidents

Incidents are less spectacular but very expensive



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Procedural deviations are at the root of many maintenance

related events

Maintenance error arising from non-procedural practices

incurs a dual risk to the business:

1 The risk of exposure to loss (loss of safety,earnings)

2 The risk of fines, litigation, denied insurance claims


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THE COSTS OF A MAINTENANCE EVENT

Rework/re-instatement costs

Additional hangar time costs

Repair costs for consequential damageMaintenance re-scheduling and knock-on delays

Operational schedule related costs

Compensation costs

Cost of hiring a replacement aircraftBusiness costs

obtaining and retaining market share



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EMSG Conference 10 October 2007

AAIB Farnborough

Recent examples from AAIB investigations into actual

incidents:

A technician assembled propeller de-icer boots withoutthe required sealant materials, which were difficult to

obtain. The boot detached causing injury and damage.

A mechanic assembled a helicopter rotor head without

the required shims, because the job was urgent. Thehelicopter suffered severe vibration and blade cracking.

After major maintenance, an engineer stamped up a

number of job cards to close all remaining open panels,

but not all the panels were open at the time. One of the

closed panels was not properly closed and latched. The

panel came off and penetrated the cabin.


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AAIB Farnborough

How can we reduce the risk of maintenance error?By promoting:

A culture which rewards procedural compliance

and discourages violations

Error-tolerant systems

Reporting systems which work and are used

An analytical approach to risk



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AAIB Farnborough

In 1994 AAIB stated: The Civil Aviation Authority shouldformally remind engineers of their responsibility to ensure

that all work is carried out using the correct tooling and

procedures, and that they are not at liberty to deviate

from the Maintenance Manual but must use all availablechannels to consult with a design authority where

problems arise; if full compliance cannot be achieved the

engineer is not empowered to certify the work.

[Airbus A320, G-KMAM AAIB Report 2/95, Safety

Recommendation 94-41]

This is still the only way forward.



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AAIB Farnborough

THANK YOU FOR YOUR ATTENTION

10oct07 simmons

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