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Human Performance

Human Performance and LimitationsMaintenance Briefing Notes

Maintenance Briefing Notes

Human Performance

Human Performance and Limitations

I

Introduction

With the traffic growth and increased demands upon aircraft utilization, the pressure ofmaintenance operations on-time performance tends to increase. Consequently, there isat present a growing need for an enhanced awareness of the importance of humanfactors issues in aircraft maintenance.

The safety and effectiveness of airline operations are also becoming more directlyrelated to the performance of the people who maintain, inspect and service the aircraft

fleets.

The diverse nature of operations within today's complex aerospace industry gives riseto dramatically different maintenance structures. With the dynamics of aviationmaintenance operations and the associated technician human factors there is a need tounderstand the varying effects imposed by the unique maintenance environment.

The objectives of this Maintenance Briefing Note are:

To provide the reader with an enhanced human factors awareness on aircraftmaintenance;

To show how human capabilities and limitations can influence task performance and

safety within the maintenance environment; and,

To guide the reader towards the related prevention strategies.

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Human PerformanceHuman Performance and Limitations


II

II.1

Case Studies

To enhance awareness of maintenance operations this Maintenance Briefing Noteincludes educational background coming with statistical data and case studies onreported maintenance events, highlighting what happened, why it happened and whatcan be done to avoid recurrence.

The source of case studies

Supplemental to the treatment of technical in-service reports by the Airbus Customer

Services Technical Support, a Maintenance Event Analysis Panel (MEAP) has been put inplace.

The role of the MEAP is to review all in-service events classified as significant related to

maintenance operations, and to conduct investigations in a broader perspective.In order to view the problem from different angles, a wide range of experts( representing domains such as human factors, flight safety, engineering, technicaldata, maintenance engineering, maintenance training and some others ) areparticipating to regular meetings.

Each significant maintenance event is investigated including considerations of potentialconsequences in a different context, related maintenance and troubleshootinginstructions, scheduled maintenance tasks, and the environmental circumstances underwhich the event happened.

Further to this analysis the MEAP has the authority to launch revisions to maintenancemanuals and tasks, ask for further investigations or propose technical changes if so

justified.

In each Maintenance Briefing Note we intend to share a real in-service event related tomaintenance activities, including the description of the event, possible reasons why itoccurred, and recommendations on how to avoid the re-occurrence.

The events investigated through the MEAP proceeding will be one source among others,for these case studies.

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III Statistical Data

Human failures are often recognized as being a contributor to incidents and accidents.Technical and maintenance faults took over from CFIT as the biggest cause of fatalairliner accidents. Some authorities consider that improper maintenance is nowcontributing to a greater proportion of accidents than it did in the past. This is because

we did a lot to reduce CFIT.

Graphic 1 summarizes all the above.

7 (21%)

5 (15%)

4 (12%)

11 (31%)

7 (21%)

Weather/icing Human Factors

Unknown Controlled Flight Into Terrain

Technical/Maintenance

Number Of Accidents

( Source: Flight International Airline Safety Review )

Graphic 1

Fatal Commercial Accidents Category / Main Causal Factor

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IV Learning more about Human Factors in Maintenance Environment

The interaction between three factors affects human performance at work: the job,the individual and the organization.

This means that, in a well-managed organization, taking the ideal situation:

The company will also select

Individuals matched to the needsof the job. (Fitting the human to the

job). They will have: the most

suitable physique (size, build andstrength), personality and

intelligence fitted to the job. They

will be fully competent by having theright skills, understanding,experience and training.

Management within theOrganization takes responsibility

for all aspects of work and work

design and encourages a goodsafety culture by showing

commitment and consulting theworkforce when making decisions.A learning organization will take

into account the latest thinking on

best practice in safety and willlearn from accidents and near

misses.

The Job is well designed to match

known strengths and limitations of

the person or team doing it. Thisincludes: work areas, the

environment, tools, materials,machinery, control and displaydevices, management and

communications systems and all

technical documentation forguidance and job control.

Figure 1

The ideal World

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IV.1

Factors influencing the behavior of people at work

However, the management has to understand the influencing factors affectingthe behavior of people at work. Following are the main reasons why people do notalways perform their work properly:

The Environment:

Weather inconvenience, extreme temperatures, high noise levels, inadequatelightning, insufficient environment protection;

Shift work: breaks across shifts, handover;

Task characteristics: new, complex, confusing, rarely performed, requires good

memory, monotonous, etc.; and,

Operational pressure: (time pressure, Customer pressure).

The Individual:

Physical fatigue, synchronization (time zone, date/night shifts), medical conditions,

hearing, sight;

Insufficiency of technical knowledge; and,

Communication skills, moral, attitude towards work and colleagues.

The Organization:

Procedures can be missing or are out of date;Unclear designed checklists;

Not enough tools, inappropriate equipment;

Aircraft design is not always good for maintainability; and,

Lack of spare parts and relevant material.

Errors are possible in all maintenance tasks some are more error-prone than others.Human errors are major cause of accidents and can occur in all jobs including

operations, maintenance, modification and management.

Does this mean that people have become more careless, forgetful, inattentive andreckless over this period? Probably not, but it does reflect two important and

widespread trends:

Aircraft components, along with most other items of equipment, have become bothmore sophisticated and more reliable over the past three decades; and

There is a growing appreciation that designers, manufacturers, corporate decisionmakers, and maintenance managers can make mistakes which, in turn, createthe conditions promoting errors on the hangar floor.

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Error is a normal component of human behavior. The trouble with an error in aviation

lies with the negative consequences it may generate in operational context. However,we can trap the negative consequences before they produce damage.

Organizations can manage human errors by implementing re-active and pro-activemeasures, and strategies.

V

V.1

Origins of Human Error

The origins of human errors are generally differentiated by whether the error wascaused by the individual involved in the incident, by design features of the equipmentor procedures used by the individual which compelled them to make the mistake.

This focuses on determining whether the source of the human error was due tothe technician, which are attributed to such factors as individual choice of inaccuratebehavior, poor judgment or decisions, or generated by circumstances such as incorrector inadequate policies/procedures, equipment, design, and tooling, working conditions,limitations or stressors.

Active failures versus latent failures

The main characteristic of maintenance errors is their lack of visibility. Maintenanceerrors can remain silent for very long time in the system before producing visibleeffects.

Active failures

Active failures are the result of unsafe acts (errors and violations) committed by thoseat the "sharp end" of the system. In the case ofactive failures, the negative outcome isalmost immediate.

Latent failures

Latent failures are created as the result of decisions, taken at the higher echelons of theorganization. Their damaging consequences can take a long time to reveal themselves,sometimes many years, only becoming evident when they combine with local triggeringfactors (e.g., errors, violations and local conditions) to breach

the system's defenses.

That is often the case for latent failures that cause or contribute to maintenance errors.

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V.2

Some local triggering factors that impact maintenance activities

The aircraft engineer is the central part of the aircraft maintenance system.It is therefore very useful to be aware of the factors which affect maintenance activities.

Knowledge, skills, experience:

Being unfamiliar with a failure report or aircraft type;

Lack of specific training or skills;

Inappropriate experience for a job; and,

Changes in aircraft type with no experience compared to past routines orexpectations, etc.

Familiarity/Routine job with:

The task;

Safety procedures;

Ground Support Equipment (GSE) and tools (availability, quality, location, deliveryand/or collection, identification, handling heavy or awkward items, etc.); and,

Paperwork (unavailability of relevant manuals or procedures, failures to completepaperwork correctly, etc.).

Morale:Personality conflicts;

Being unhappy with the work situation; and,

Inadequate incentives/motivations .

Support:

Difficulties with support from other areas; and,

People unavailable in other areas, insufficiency of manpower.

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Fatigue:

Problems with tiredness, unusually slow working;

Disturbed sleep patterns, particularly at the beginning of a shift; and,

The balance between work and rest.

Pressure / Time constraints:

High workload;

The workforce being spread too thinly over the jobs;

Many interruptions;

Too little time to perform the job; and,Pressure of flight schedule.

Shifts working:

Difficulties with shift patterns, time of day or night; and,

Communication at shift handover.

Environment:

Weather inconveniences;

High noise levels;

Inadequate lighting; and,

Insufficient environmental protection, etc.

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VI Prevention of Human Failures in Maintenance Activities

A series of Human Factor problems form an error chain. If any one of the links in thischain had been broken the incident may have been prevented. It might be done bybuilding in measures/defenses, which may not permit an error at one or more ofthe stages. A good example is J.Reasons Swiss Cheese Model, here below.

DefensesInadequate

Productive ActivitiesUnsafe Acts

Preconditions

Line ManagementDeficiencies

Decision MakersFallible decisions

Ma i n t e n a n c e -

r e l a t ed e v e n t

Figure 2

J.Reasons Swiss Cheese Model

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VI.1

VI.2

Situational Awareness or Knowing What Is Going Around You

Definition

Situational awareness is a synthesis of an accurate up-to-date mental model of onesenvironment and state. That means perceiving important elements (for example,feeling the cold as you walk outside on a winter morning), understanding their meaning(understanding there may be black ice on roads), and projecting this statusinto the future (appreciating that such conditions could cause the car to skid andconsequently adapting your driving speed).

The process of attention, perception and judgment should result in awareness ofcurrent situation.

The aircraft maintenance engineer must be aware of:

Who is working around the aircraft to avoid injuries;

The status of the system he/she is working on;

The relationship between the reported effect and the intended rectification;

The possible effect of this work on other systems; and,

Consequence of his/her own actions for the others.

In aircraft maintenance engineering, the entire team needs to have situationalawareness, not just of what they are individually doing, but of their colleaguesactivities as well.

Use of maintenance check list: what is involved in maintenanceenvironment

In order to manage maintenance well, you should be able to match the issues below.

The challenges for maintenance management:

Be fully aware of which maintenance work can lead to a major risk;

Put in place good defenses/protection to make sure these accidents are veryunlikely, including:

o Safety notices and devices;

o Quality controls (permits, procedures, checklists);

o Management controls (supervision and checking of tasks);

o Highly competent maintenance teams; and,

o Well-designed maintenance planning.

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VII

VII.1

VII.2

Base your maintenance program on major accident risk assessment;

Communicate well during shifts and between shifts;

Take special care of temporary or inexperienced maintenance technicians andcontractors;

Do walk around inspections of maintenance tasks in progress;

Look for early signs of problems (e.g. a large backlog of jobs; excessive repairtimes; adverse feedback from staff); and,

Investigate near misses and accidents while learning from failure.

Case study

Description of the event

An operator performed a scheduled slide deployment test on doors 1L, 2L, 3L, and 4L.

Two of the doors 1L and 4L didnt automatically open and required manual opening withsubsequent successful slide deployment. However, the operators engineeringdepartment noticed that pressure was still within the green band on boththe emergency actuators and the diaphragms were not punctured meaning thatthe actuators did not operate.

Upon further inspection it was found that the percussion mechanism on both of theactuators were not correctly positioned and locked.

Findings

When the arming lever is placed in the ARMED position the activation lever moves

under the release lever of the percussion mechanism on the actuator.

If the door is then opened in ARMED mode the door lifts and the activation leveroperates the release lever which in turn punctures the diaphragm in the reservoir tooperate the actuator.

Refer to Figure 2, on Page 12.

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Release Lever

Activation Lever

Figure 3

Door Emergency Actuation Mechanism

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Door 1L Emergency Actuator Percussion Mechanism Release Lever Position

Release lever was not placed in the correct fully extended position. A gap can be seen

under the knurled screw.

Incorrect wire locking. Instead,

should be locked to this point

here.

Door 4L Emergency Actuator Percussion Mechanism Release Lever Position

Release lever was not placed in the correct fully extended position. A gap can be seen

under the knurled screw.

Incorrect wire locking. Instead,

should be locked to this point

here.

Familiarity with MaintenanceManual procedures andillustrations

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VII.3

-

-

-

Recommendations

In order to reactivate the percussion mechanism, the following steps have to beaccomplished:

Push release lever to the fully extended position against the spring and hold it;

Tighten the knurled screw, fully engaged in the bore of the release lever; and,

Safety the knurled screw by wire locking to the lug provided on the release lever.

Release lever placed in the correct fully

extended position with the knurled screw

engaged and tightened

In order to avoid similar issues in the future, a caution has been included inthe relevant AMM tasks to highlight that if the release lever is not placed in the

correct position then the emergency actuator will not operate correctly when thedoor is operated in emergency mode.

Familiarization withprocedures andsupervision/checking ofperformed tasks

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Human Performance

Human Performance and LimitationsMaintenance Briefing Notes

It is very important to read Warnings and Cautions.

WARNING: calls to use of materials, processes, methods, procedures, or limits which

must be followed precisely to avoid injury to persons.

CAUTION: calls attention to methods and procedures which must be followed to avoiddamage to equipment.

VIII

Summary of Key Points

Since people design, build, operate, maintain, and manage potentially hazardous

technologies, it is hardly surprising that their decisions and actions contribute, in oneway or another, to unwanted events. However, mistakes made must be an occasion tolearn from error in order to prevent these undesired events.

Reminder of the main factors, leading to incite an error:The nature of the workplace;

The quality of tools and equipment;

Whether or not supervisors or managers turn a blind eye in order to get the jobdone;

The quality of the rules, regulations and procedures; and,

The organizations overall safety culture, or indeed its absence.

This Maintenance Briefing Note (MBN) is part of a set of Briefing Notes that provide an overview of the applicable standards,techniques, best practices, human factors, suggested company prevention strategies and personal lines-of-defense related to

major threats and hazards that may affect maintenance.

This MBN is intended to enhance the reader's safety awareness but it shall not supersede the applicable regulations and the

Airbus or airline's maintenance documentation; should any deviation appear between this MBN and the Airbus or airlinesmaintenance documentation, the latter shall prevail at all times.

In the interest of aviation safety, this MBN may be reproduced in whole or in part - in all media - or translated; any use ofthis MBN shall not modify its contents or alter an excerpt from its original context. Any commercial use is strictly excluded.All uses shall credit Airbus.

Airbus shall have no liability or responsibility for the use of this MBN, the correctness of the duplication, adaptation or

translation and for the updating and revision of any duplicated version.

Airbus Customer Services

Maintenance Engineering Services

1 Rond Point Maurice Bellonte - 31707 BLAGNAC CEDEX FRANCE

MBN Reference : MAINT HUM_PER SEQ 01 REV 01 NOV. 2006

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