ALT EASA PART 145 HUMAN FACTORS Continuation Training.

HUMAN FACTORS

CONTINUATION TRAINING

Module 2 of 4

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CONTENTS:
4 Human performance & limitations

4.1. Vision

4.2. Hearing

4.3. Information-processing

4.4. Attention and perception

4.5. Situational awareness

4.6. Memory

4.7. Claustrophobia and physical access

4.8. Motivation

4.9. Fitness/Health

4.10. Stress

4.11. Workload management

4.12. Fatigue

4.13. Alcohol, medication, drugs

4.14. Physical work

4.15. Repetitive tasks/complacency

5. Environment

5.1. Peer pressure

5.2. Stressors

5.3. Time pressure and deadlines

5.4. Workload

5.5. Shift Work

5.6. Noise and fumes

5.7. Illumination

5.8. Climate and temperature

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5.9. Motion and vibration

5.10. Complex systems

5.11. Hazards in the workplace

5.12. Lack of manpower

5.13. Distractions and interruptions

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4. Human performance & limitations

4.1 Vision

The human eye is a sense organ that reacts to light and allows vision. Rod and cone cells in
the retina allow conscious light perception and vision including colour differentiation and the
perception of depth.

It is the limitations of human vision that make

it susceptible to illusions, particularly at night,
in poor light or in conditions with few external
visual cues.

The greater the object’s size, ambient

illumination, contrast, viewing time and
atmospheric clarity, the better its visibility.

During the day, objects can be identified at a

great distance with good detail resolution. At
night, the identification range of dim objects is
limited, with poor detail resolution.

During daylight, one can best see an object looking directly at it, but at night a scanning procedure to
permit off-centre viewing is more effective.

The eye’s adaptation to darkness is another important aspect of night vision. An exposure to bright light
after dark adaptation will temporarily impair retinal sensitivity.

Excessive ambient illumination, especially from light reflected off the canopy, surfaces inside the
aircraft, clouds, water, snow, or desert terrain can produce glare that may cause uncomfortable
squinting, eye tearing, temporary blindness and reduced visual acuity.

Refractive eye disorders include as myopia (near-sightedness — impaired focusing of distant objects),
hyperopia (farsightedness — impaired focusing of near objects), astigmatism (impaired focusing of
objects in different meridians), or presbyopia (age-related impaired focusing of near objects).

Self-imposed stresses such as self-medication, alcohol consumption (including hangover effects),

tobacco use (including withdrawal), hypoglycaemia and sleep deprivation/fatigue can seriously impair
vision.

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4.2 Hearing

Hearing is the ability to perceive sound by detecting vibrations through an organ such as the ear.
Hearing is performed primarily by the auditory system: vibrations are detected by the ear and
transduced into nerve impulses that are perceived by the brain (primarily in the temporal lobe).

Aging and chronic exposure to loud noises both contribute

to hearing loss. Other factors, such as excessive earwax, can
temporarily reduce how well your ears conduct sounds.

Noise can have a negative effect on performance when multiple

tasks are being performed at once,

Noise can mask speech when its magnitude is near that of the
speech.

After prolonged exposure to increased noise levels, a person may

experience a temporary threshold shift where signals must be “louder” than normal to be heard by
the individual. This state is usually temporary but can sometimes be permanent.

Exposure to noise may induce pathological effects, mainly cardio-vascular disease. This is due to the
creation of high levels of adrenaline that narrow blood vessel diameter and the resultant increase in
blood pressure.
People should wear hearing protection if the noise or sound level at the workplace exceeds 85 decibels
dBA. Hearing protection reduces the noise exposure level and the risk of hearing loss.

4.3 Information processing

Working in aviation requires engineering staff to take in information from a multitude of sources, assess
this information, prioritise it, and use it to make decisions and take actions. This complete process from
sensing information (whether it is aural, visual, or mental) through to taking action is referred to as
information processing.

Information processing capabilities vary from person to person, day to day, place to place and task to
task. It is particularly affected by age, health, stress, different environments, workplace cultures,
experience levels, interpersonal relationships, distractions, and, by its own limitations.

Knowing how our information processing capabilities can be limited is important in designing and
delegating tasks to ensure that the information processing requirements fall within the capabilities of
employees and colleagues (i.e. within their memory, attention and decision-making capabilities) such
that the following are minimised:

• Failure to see information.

• Misunderstanding information
• Handling the information incorrectly
• Forgetting the information.
• Reacting inappropriately

Perhaps more importantly, we should understand our own limitations, especially during periods of high
workload and/or when illusions may go unnoticed.

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4.4 Attention and perception

Attention is a necessary function if we are to focus on the things that matter at the right time. Various
theories exist which explain the mechanism that permits multi-tasking, and the degree to which we can
or cannot multi-task. One determinant of whether we can multi-task or not is the capacity we have for
dividing attention between stimuli. For the most intricate, or unfamiliar, tasks we usually require full
attention, and this will result in us being unable to perceive anything else that is occurring. In the
workplace this may also occur when we are fully occupied in dealing with many different inputs e.g.an
unfamiliar task in poor weather at night, we can fail to fit a component at the appropriate point. This is
why some aircraft warning systems utilise visual and aural alarms (Master Caution) to break the pilots
focus and grab his/her attention.

Perception is the process of converting sensory information into something that makes sense – i.e.,
creating an internal mental model of the outside world. Because we are unable to “collect” 100% of
external data our internal model will be incomplete. However, based on our previous experiences, we
are often able to make sense of the little data we receive and create a realistic model based on our
expectations. Much like the fact that we can easily recognise someone’s face from a badly pixilated
picture; if it’s someone we know, then our brain literally fills in the gaps and joins the dots. It is this
mechanism that helps us to divide attention and sometimes multi-task.

However, the same mechanism can lead us to “misperceive” the world – the more we rely on past
experiences the more our expectations will distort our perception. For example, a pilot who regularly
flies along snow-covered valleys in Norway will have a mental model of fir trees being 150ft tall. If he
enters a valley which is full of newly planted trees, he may fly much closer to the ground than intended
as he has misperceived the scale of the outside world. Hence the importance of cross-checking our
perceptions with other data; in this example – the radio altimeter.

Another source of misperception concerns how juxtaposed objects within an environmental setting can
influence each other to create a visual illusion.

In the illustration although we can measure each

horizontal line and recognise that they are the
same length, it is impossible to shake off the
perception that they are different.

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4.5 Situational awareness

Our situational awareness is built upon our perception of the world that relies on information attained
through our senses. The information available to us includes instruments, primary flight displays, vision,
communication, vibrations, noises, and smells, and more. It also includes our mental model of our
“plan” of how things are expected to occur, and our prediction of what others’ plans are, and how they
may progress. At any given moment, in three-dimensions, the accuracy of our situational awareness
depends on how accurate our perception is compared to reality. It is possible to be highly accurate,
especially in simple and familiar situations. However, our predictions for the future will be, overall, less
accurate, as will our perception in complex and busy environments. We may have a good idea of what
will happen when we ourselves make changes, corrections, and decisions, and this will be based on our
experience; however, it is less easy to judge what others will do. Therefore, maintaining situational
awareness is a continuous process requiring mental effort and it will become vulnerable during periods
of high workload where our information processing capacity is exceeded. And, usually, it is these high
workload situations when we need to ensure that our situational awareness is as accurate as possible.

4.6 Memory

Working Memory is the aspect of our memory that we use all the time when conducting any task. It
holds small amounts of data for a very short time, which is to be used immediately. Therefore, we can
read-back an numerical sequence and maintain these numbers long enough to enter them into the
appropriate systems. Mental repetition may be required to achieve the task, but once completed the
information is lost within 30 seconds and replaced with the next set of data we need e.g., setting-up the
display for a instrument system.

Typically, the capacity of our working memory is 7 digits +/-2. We can extend this by “chunking” digits
together into meaningful blocks such as a long telephone number with 12 digits (e.g., 44 123 747 7769)
can be chunked as shown into just 4 memorable blocks.

Similarly, the more times data is accessed in our long-term memory, then the more likely we are to be
able to recall it when needed. This fact gives support to the method of training called “over learning”,
where we repeat a procedure or task many more times than is necessary just to perform to a
satisfactory level.

Just because we have meaning and facts stored in our memory does not necessarily mean we can
always recall them, when required. Rarely used data can become inaccessible unless we happen to be
reminded by some context. As for all memory, the more we access and recall certain memories, then
the easier they will be to access and recall again in the future.

Action slips are unintentional behaviours that are the result of absent-mindedness, or a failure to pay
attention. They typically occur when doing an automatic and familiar task. An example would be
forgetting to stop at the supermarket on your drive home from work.

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4.7. Claustrophobia and physical access

There are many circumstances where people may experience various levels of physical or
psychological discomfort when in an enclosed or small space, which is generally considered to be
quite normal. When this discomfort becomes extreme, it is known as claustrophobia.

Claustrophobia can be defined as abnormal fear of being in an enclosed space.

It is quite possible that susceptibility to claustrophobia is not apparent at the start of employment.
It may come about for the first time because of an incident when working within a confined space,
e.g., panic if unable to extricate oneself from a fuel tank.

Although not peculiar to aircraft maintenance, working in restricted space and at heights is a
feature of this trade. Problems associated with physical access are not uncommon.

Maintenance engineers often wok in very small spaces, cramped conditions, elevated locations and
in uncomfortable climatic or environmental conditions.

Engineers should work in a team and assist one another if necessary, making allowance for the fact
people come in all shapes and sizes.

4.8. Motivation

Motivation can be thought of as a basic human drive that arouses, directs, and sustains all human
behaviour.
Motivated behaviour could be described as goal directed and purposeful.

Within the maintenance environment mechanics and certifying staff are expected to perform their
tasks diligently within their expertise. It is largely the specific motivation of the mechanics and
certifying staff which will ultimately determine what they will actually do in any given situation.

Therefore, we can say the following:

Motivation reflects the difference between what someone can do and what they will do.

Attributes of a Motivated Person:

· High performance with the ability to deliver positive results consistently
· Has energy, enthusiasm, and determination to succeed
· Displays a willingness to accept responsibility
· Has a willingness to accommodate change

Enthused with good intentions a mechanic may be motivated to complete a difficult task without
having the required competence for which they are not qualified. Clearly this is a good thing!

Motivation can be influenced by many factors and all the following are indicators of De-Motivation:
· Displays an Indifference to the job
· Has a reduced regard for safety whilst working
· High absenteeism
· Shares an exaggerated concern regarding difficulties encountered while working
· Typically involved in disputes and grievances
· Presents a distanced lack of co-operation in dealing with problems or difficulties
· Displays an unjustified resistance to change

Job Security provides a positive motivating effect just as a lack of Job Security can be demotivating.

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4.9. Fitness/Health

Certifying staff and technicians often undertake work which is physically demanding as well as being
called on to work in multiple environments include cold and heat, wind, and rain.

Fitness and health can have a significant effect upon job performance (both physical and cognitive). Day
to day fitness can be reduced through illness (physical or mental) or injury.

Not only does your employer need to look after your health but each worker is also responsible for their
own well-being as well as to take care of anyone who is working under their control.

The responsibility falls upon the individual to determine whether they are well enough to work on a
particular day.

Many conditions can impact on the health and fitness of an individual, such as:
▪ Minor physical ailments (such as colds, flu, etc.)
▪ Serious physical illness (such as cancer, heart conditions, etc.)
▪ Mental illness (such as depression, anxiety, etc.) –
▪ Small injuries, for example, a sprained wrist
▪ Serious injury for example broken limbs
▪ Age-related deterioration including hearing loss, visual defects, obesity, heart problems, etc.

Toxin Driven Health Issues

▪ Effects-driven by toxins and other foreign substances (such as carbon monoxide poisoning, alcohol,
illicit drugs, etc.)

Maintaining Fitness and Health

▪ Eating regular meals with a well-balanced diet
▪ Regular exercise
▪ Stop or reduce smoking
▪ Reduced or no alcohol intake

Look after yourself.

▪ Sleep well - Getting a solid amount of sleep every
night has been linked to higher productivity and higher
levels of mental activity. Sleep is important.
▪ Try to reduce your sugar and caffeine intake.
▪ Exercise.
▪ Water - Not drinking enough water can lead to
mental and physical fatigue.

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4.10. Stress

Stress is an inescapable part of life for all of us. From a human viewpoint, stress results
from the imposition of any demand or set of demands which require us to react, adapt or behave in a
particular manner to cope with or satisfy them. Up to a point, such demands are stimulating and useful,
but if the demands are beyond our personal capacity to deal with them, the resulting stress is a
problem.

Causes and Symptoms

Stress is usually something experienced due to the presence of some form of stressor,
which might be a one-off stimulus (such as a challenging problem or a punch on the
nose), or an on-going factor (such as an extremely hot
hangar or a painful divorce).
From these, we get acute stress (typically intense but
of short duration) and chronic stress (frequent
recurrence or of long duration) respectively.

Different stressors affect different people to varying

extents. Stressors may be:

• Physical - heat, cold, noise, vibration, presence of

something damaging to health (e.g., carbon monoxide)
• Psychological - emotional upset (e.g., due to
bereavements,
domestic problems, etc.), worries about real or imagined problems (e.g., due to financial problems, ill
health, etc.)
• Reactive - events occurring in everyday life (e.g., working under time pressure, encountering
unexpected situations, etc.)

A stress problem can manifest itself by signs of irritability, forgetfulness, sickness absence, mistakes, or
alcohol or drug abuse. Management have a duty to identify individuals who may be suffering from
stress and to minimize workplace stresses.
Individual cases can be helped by sympathetic and skilful counselling which allows a return to effective
work and licensed duties.

In brief, the possible signs of stress can include:

• Physiological symptoms - sweating, dryness of the mouth, etc.
• Health effects - nausea, headaches, sleep problems, diarrhoea, ulcers, etc.
• Behavioural symptoms - restlessness, shaking, nervous laughter, taking longer to do tasks,
changes to appetite, excessive drinking, etc.
• Cognitive effects - poor concentration, indecision, forgetfulness, etc.
• Subjective effects - anxiety, irritability, depression, moodiness, aggression, etc.

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4.11. Workload management

Humans have limited capability for processing information (such as from displays, alarms, and
documentation) holding items in memory, making decisions, and performing tasks. Excess workload can
result in human performance issues such as slower task performance and errors such as slips, lapses, or
mistakes. It should also be noted that low workload can also lead to human performance issues such as
boredom, loss of situation awareness and reduced alertness.

Workload issues may be more relevant in times of downsizing or temporarily during peaks (such as
incidents or turnarounds).

Workload is related to competence (e.g. some tasks can require less processing in experienced
personnel), working hours/patterns (e.g. underload in nightshift control room operators), organisational
change (where tasks or roles are changed) and staffing levels. Workload may be
higher in some industries/roles where there is an inadequate supply of skilled
staff. A high (or perceived high) workload not only adversely affects safety, but
also negatively affects job satisfaction and, as a result, contributes to high
turnover and staff shortages.

• Performance can be affected by workload being too high - or too low.

• Workload can ‘drift’ over time as new activities are added gradually.
• Consider the whole team, and whether tasks can be redistributed between
team members or shifts.
• Assess the balance of workload across a shift - can the timing of activities be redistributed to
spread workload?
• Workload should be reconsidered during unusual activities, such as start-up activities.
• Experienced operators may be able to utilise strategies for handling high task demands;
whereas inexperienced staff may be less able to cope (think about when you were learning to
drive).
• Perform a task analysis to understand exactly what staff are required to do, when, and what
information they need to perform these tasks. Involve the workforce in these analyses.
• Task analysis should consider both physical and mental workload.
• Consider not just the number of personnel, but how they are being utilised.
• Set clear roles and responsibilities, ensuing that staff are clear on their priorities. This will help
to ensure that even when workload is high, staff are able to focus on key activities.
• Some tasks may be re-allocated from humans to machines/computers, or vice-versa.

4.12 Fatigue

Fatigue refers to the issues that arise from excessive working time or poorly designed shift patterns. It is
generally considered to be a decline in mental and/or physical performance that results from prolonged
exertion, sleep loss and/or disruption of the internal clock.

Fatigue results in slower reactions, reduced ability to process information, memory lapses, absent-
mindedness, decreased awareness, lack of attention, underestimation of risk, reduced coordination etc.
Fatigue can lead to errors and accidents, ill-health and injury, and reduced productivity. It is often a root
cause of major accidents.

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Key principles in fatigue

1. Fatigue needs to be managed, like any other hazard.

2. It is important not to underestimate the risks of fatigue. For example,
the incidence of accidents and injuries has been found to be higher on
night shifts, after a succession of shifts, when shifts are long and when
there are inadequate breaks.
3. The legal duty is on employers to manage risks from fatigue, irrespective of any individual’s
willingness to work extra hours or preference for certain shift patterns for social reasons.
4. Employees should be consulted on working hours and shift patterns. However, some employees
may prefer certain shift patterns that are unhealthy and likely to cause fatigue.
5. Sets limits on working hours, overtime, and shift-swapping, and which guards against fatigue.
6. Problems with overtime and shift-swapping may indicate inadequate resource allocation
and staffing levels.
7. There is no single optimal shift system that suits everyone.
8. There are several key risk factors in shift schedule design, which must be considered when
assessing and managing shift work. These are the workload, the work activity, shift timing and
duration, direction of rotation and the number and length of breaks during and between shifts.
Other features of the workplace environment such as the physical environment, management
issues and employee welfare can also contribute to the risks associated with shift work.
9. Sleep disturbances can lead to a ‘sleep debt’ and fatigue. Night workers are particularly at risk
of fatigue because their day sleep is often lighter, shorter and more easily disturbed because of
daytime noise and a natural reluctance to sleep during daylight.

4.13 Alcohol, medication, drugs

When alcohol is consumed, it is very rapidly absorbed into the blood and tissues
of the body, but the process of detoxification is quite slow. The impairing effects of
alcohol are apparent quite soon after ingestion, but it takes about 3 hours for the
effects of 1 ounce of alcohol to wear off. Nothing, inclusive of sleep, coffee, or
exercise, will speed up this process or minimise the effects of the alcohol.

Prescription and over-the-counter drugs can impair judgment and affect coordination.
Some cold tablets and cough mixtures previously sold over the-counter are now only available with a
prescription. But just because a drug is available without a doctor’s prescription does not mean it’s safe
to take in an aviation environment.

All illegal drugs are unsafe for aviation activities.

The side effects of common drugs such as cold tablets, cough mixtures, antihistamines, appetite
suppressors and laxatives include drowsiness, confusion, blurred vision, and dizziness.

Always seek advice from a doctor or pharmacist before taking more than one drug at a time, as drugs
can interfere with each other, or worsen any side effects.

Antibiotics and antidepressants can have a pronounced effect on judgment, thinking and coordination.

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4.14 Physical Work

Ergonomics is a science concerned with the ‘fit’ between people and

their work. It puts people first, taking account of their capabilities and
limitations. Ergonomics aims to make sure that tasks, equipment,
information, and the environment fit each worker.

Manual handling

These problems may lead to physical injuries, such as low back pain or
injury to the
arms, hands, or fingers. They may also contribute to the risk of slips, trips, and falls.

• The load is too heavy and/or bulky, placing unreasonable demands on the
• person.
• The load must be lifted from the floor and/or above the shoulders.
• The job involves frequent repetitive lifting.
• The job requires awkward postures, such as bending or twisting.
• The load cannot be gripped properly.
• The job is performed on uneven, wet, or sloping floor surfaces.
• The job is performed under time pressures and doesn’t include enough rest
• breaks.

4.15 Repetitive tasks/complacency

A repetitive task is a task which is performed several times during a shift (a Transit Check or checking
lifejackets). What happens physiologically is that as a person becomes complacent his alertness
decreases along with his performance.

Repetitive tasks are essential tasks which require a low level

of mental acuity. Such tasks can quickly become tedious and
therefore induce a low level of arousal within the worker.

To put it another way, the task is boring!

However boring does not mean that the task is not

important - in some cases even it is critical, in others - less
so.

You need to be able to focus and need the self-discipline to be able to control your activities, it’s a good
idea to take regular breaks.

Monitor yourself and colleagues and if you do notice that you are losing focus stop and reassess your
situation.

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5 Environment

5.1. Peer pressure

Peer pressure is the direct influence on people by peers, or the effect on an individual who gets
encouraged to follow their peers by changing their attitudes, values, or behaviours to conform to those
of the influencing group or individual. This can result in either a positive or negative effect, or both.

We all develop personal standards, and all these elements have a bearing on our personal standards.
So, taking into account how we consider ourselves and others, and how we behave and act in front of
others, together with our individual experiences, forms the backbone which influences our personal
standards.

It is usual for less experienced employees to emulate or adopt the behaviours of the more senior and
experienced people.

When delivered in a good way it is possible to share the positive qualities of professionalism and
responsibility.

5.2. Stressors
A stressor is anything that causes the release of stress hormones. There are two broad categories of
stressors: Physiological (or physical) stressors and Psychological Stressors.

Physiological (or physical) stressors

These are stressors that put strain on our body (i.e.: very cold/hot
temperatures, injury, chronic illness, or pain).

Psychological Stressors
These are events, situations, individuals, comments, or anything we interpret as negative or threatening
(i.e.: not being able to find a babysitter for your sick child when you cannot take time off work).

5.3. Time pressure and deadlines

Consider that there are essentially two types of pressure: actual pressure and
self-imposed pressure.

Actual pressure is real pressure, applied directly or indirectly, for the task to be completed in a given
time. On the other hand, individuals or teams may feel self-imposed pressure to complete a task within
a given time, even when the time available may be unrealistic or the task may not be achievable with
the allocated resources and time frame.

The definition of self-imposed is something that you require or expect of yourself, rather than
something required by another, so our way of dealing with self-imposed time pressure is somewhat
different to how we can deal with external time pressure for example for commercial reasons.

As with stress, it is generally thought that some time pressure is stimulating and may improve task
performance. However, it is almost certainly true that excessive time pressure (either actual or
perceived, external source or self-imposed), is likely to mean that due care and attention when carrying
out tasks diminishes, and more errors will be made.

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Dealing with pressure:

• Allocate appropriate time for all maintenance tasks.
• Prioritise
• Ask for help.
• Communicate the reason for any problem.
• Do not deviate from procedures or take short cuts because of time pressure.
• Do what you can and if you cannot do the job safely in the time available, complete the work
that you can do, safely and professionally.

5.4. Workload

Workload is the amount of work an individual must do.

An individual aircraft maintenance engineer can usually identify what

work he must do quite easily. It is more difficult to assess how that work
translates into workload.

As the workload of the engineer may vary, he may experience periods of

overload and underload. This is a particular feature of some areas of the industry such as line
maintenance.

Overload occurs at very high levels of workload. Performance deteriorates when workload becomes too
high, and we are forced to shed tasks and focus on key information. Errors may also increase. Overload
can occur for a wide range of reasons, and it may happen suddenly or gradually. It can be difficult to
determine how work translates into workload, both for the individual concerned, and for those
allocating tasks.

Underload occurs at low levels of workload. It can be just as problematic to a engineer as overload, as it
too causes a deterioration in performance and an increase in errors such as missed information.
Underload can result from a task an engineer finds boring, very easy, or too few tasks. The nature of
aircraft maintenance means that available work fluctuates, depending on time of day, maintenance
schedules, and so forth. Hence, unless stimulating housekeeping tasks can be found, underload can be
difficult to avoid at times.

5.5. Shift Work

Shift work is work that takes place on a schedule outside the traditional 9 am – 5 pm day. It can involve
evening or night shifts, early morning shifts, and rotating shifts. Many industries rely heavily on shift
work, and millions of people work in jobs that require shift schedules.

People vary in how they cope with shift work depending

on their health, fitness, age, lifestyle, and domestic
responsibilities– some adapt well, others do not. Whilst
we cannot change our inbuilt characteristics, it is
possible to alter our behaviour or make lifestyle changes
that may makeshift work more tolerable.

Driving to and from work can be risky, particularly after

a long shift, a night shift or before an early start.

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Most adults need 7-8 hours of sleep a day although this may decrease with age. If you cannot do this,
try to rest, as this is still beneficial. Recording sleep patterns and problems using a diary may help to
explain fatigue and tiredness. It can also be used to help find the most suitable strategies and conditions
for a better quality of sleep.

Sleep loss and fatigue are some of the most significant problems for shift workers. It is important to try
and maintain your normal level of sleep and rest. Daytime sleep is usually lighter, shorter and of poorer
quality than night time sleep. It is more frequently disturbed because of warmer temperatures and
daytime noise. To promote sleeping, try to follow a similar routine to the one you follow before a
normal night’s sleep.

It is very important to consider the timing and quality of your meals. Digestive problems are common in
shift workers due to disruption of the body clock and poor diet. Plan your meals to help you stay alert at
work and to relax/sleep when you need to rest.

Shift workers often turn to stimulants such as coffee or cigarettes to keep them awake and sedatives
such as alcohol or sleeping pills to help them sleep. Avoid such aids as they only have short-term effects
on alertness as tolerance to their effects develops. Persistent use may also increase the risk of
dependence.

An unhealthy lifestyle combined with shift work may increase the likelihood of sleep disorders and sleep
loss or exacerbate existing sleep problems. A good diet, regular meals and exercise can improve sleep
quality, health and well-being.

On some shifts, such as nights and very early mornings you may find it difficult to remain alert and this
can affect your performance. It may also increase the risk of errors, injury and accidents.

• take moderate exercise before starting work which may increase your alertness during the shift.
• keep the light bright.
• take regular short breaks during the shift if possible.
• get up and walk around during breaks.
• plan to do more stimulating work at the times you feel most drowsy.
• keep in contact co-workers as this may help both you and they stay alert.

5.6. Noise and fumes

Noise is essentially unwanted sound not only is it unpleasant, but it carries the potential for personal
harm.
Working on Aircraft can incur significant exposure to Noise – It is not unusual
for this to exceed 85 db –90 db.
The louder the sound, the shorter the amount of time it takes for Noise-
Induced Hearing Loss (NIHL) to happen.

Hearing protection should always be carried and used when remaining in such an environment. Noise
can also impair communication.
Fumes can cause serious problems for anyone due to the potential for inhalation.
Confined space may exacerbate the situation and require additional controls and procedures and, in
some cases, for example, fuel tanks the use of breathing apparatus.

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Aircraft maintenance typically involves working with a variety of Fluids and Chemicals including greases
– oils, hydraulic fluid, paints, and cleaning chemicals. (When heated the potential for an increased
presence of fumes with added danger)
Some fumes have no smell but can be very dangerous – consider the effect of nitrogen in a confined
space. Whenever possible, steps should be taken to remove or minimize fumes.
Procedures should be understood to facilitate evacuation in the event of excessive fumes.
Apart from issues present due to the toxicity of fumes which can have serious health implications it is
important always to increase ventilation and duly inform supervisors/managers immediately.

5.7. Illumination
At its simplest, different levels of lighting are required for different types of
work – close, accurate work such as soldering a control panel will require
higher light levels than walking down a corridor. However, when considering
lighting, several different factors need to be considered such as colour,
contrast, glare and so on.

Lighting an environment is often a complex task principally considered during the design stage of the
building (by architects and interior designers). However, lighting should be designed for the tasks that
individuals are carrying out within that environment.

In general, the more detailed the task, the greater the light requirement. Directional sources of light can
bounce off reflective surfaces such as display screens and cause glare.

All sources of light have a particular colour. Some of these, such as sodium, can make coloured text and
diagrams difficult to read.

Sudden contrasts in light levels e.g. coming out of a well-lit area into a dark area or vice versa can be a
problem because it takes the eye several seconds to adapt to new lighting conditions. Changes in
lighting levels should be made gradually where possible.

5.8. Climate and temperature

The six factors affecting thermal comfort are both environmental and personal. These factors may be
independent of each other, but together contribute to an employee’s thermal comfort.

Environmental factors:
• Air temperature
• Radiant temperature (heat that radiates from a warm object)
• Air velocity
• Humidity
Personal factors:
• Clothing Insulation
• Metabolic heat (The more physical work we do, the more heat we
produce)

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5.9. Motion and vibration

Vibration is mechanical movement that oscillates about a fixed point, creating a
waveform which transmits energy. Vibration needs a physical structure through
which it can travel, e.g., through a vehicle, machine, tool, or person. In the real
world it is likely that a person will be simultaneously exposed to different frequency
vibrations.

Most people experience some form of whole-body vibration nearly every day of their lives, where a
surface they are seated on vibrates, either by the road surface or the machine itself, it transmits it
through the seat surface, through the body to the head. As vibration can occur in any direction,
sometimes making vibration a complex issue. Therefore, there are daily exposure limit values.

For hand transmitted vibration usually caused by power tools or other hand-held tools. Measurements
are based on the middle knuckle. Once again there are daily exposure limits to follow. Prolonged
exposure can lead to Hand-Arm Vibration Syndromes (HAVS)

Symptoms and effects of HAVS can be serious, disabling and can include:

• Tingling, numbness in fingers, resulting in an inability to do fine work or everyday tasks.

• Loss of strength in the hands.
• The fingers going white (blanching) and becoming red and painful on recovery.

Employers and employees need to:

• Consider working methods, organisation of work-rest periods, job rotation.

• Consider Improving the work layout and environment.
• Provide information and training on vibration related health risks and controls to employees
at risk.
• Limit the duration of exposure.
• Provide PPE to reduce exposure e.g., gloves.

5.10. Complex systems

All large modern aircraft can be described as complex systems. Within these aircraft, there are a myriad
of separate systems, many of which themselves may be considered complex.

The purpose, composition and function of a simple system is

usually easily understood by an aircraft maintenance engineer. In
other words, the system is transparent to them. Fault finding and
diagnosis should be relatively simple with such systems
(although appropriate manuals, etc. should always be referred to
where necessary).

With a complex system, it should still be clear to an aircraft

maintenance engineer what the system's purpose is. However, its composition and function may be
harder to conceptualise - it is opaque.

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To maintain such complex systems, it is likely that the engineer will need to have carried out some form
of system-specific training which will furnish them with an understanding of how it works and what it is
made up of. It is important that the engineer understands enough about the overall functioning of a
large, complex aircraft, but not so much that they are overwhelmed by its complexity. Thus, system-
specific training must achieve the correct balance between detailed system knowledge and
troubleshooting skills.

With complex systems within aircraft, written procedures and reference material become an even more
important source of guidance than with simple systems. They may describe comprehensively the
method of performing maintenance tasks, such as inspections, adjustments, and tests. They may
describe the relationship of one system to other systems and often, most importantly, provide cautions
or bring attention to specific areas or components. It is important to follow the procedures to the letter
since deviations from procedures may have implication on other parts of the system of which the
technician may be unaware.

Many engineers are qualified on several types and variants of aircraft. This will usually mean that they
have less opportunity to become familiar with one type, making it even more important that they stick
to the prescribed procedures and refer to the reference manual wherever necessary.

5.11. Hazards in the workplace

Hazards in the workplace tend to be a health and safety issue, relating to the protection
of individuals at work. All workplaces have hazards and aircraft maintenance engineering
is no exception.

There are many potential hazards in aircraft maintenance, and it is impossible to list them all here.
However, a thorough health and safety appraisal will reveal the hazards.

Physical hazards may include:

• Very bright lights (e.g., from welding)
• Very loud sounds (sudden or continuous)
• Confined or enclosed areas
• Working at significant heights
• Noxious substances (liquids, fumes, etc.)
• Excessive temperature (i.e., too cold or too hot)
• Moving equipment, moving vehicles and vibration

In the UK the Health and Safety Executive (HSE) have responsibility for overseeing safety in the
workplace. The various national Health and Safety At-Work Laws places a responsibility on employers to
produce a written statement of general policy with respect to the Health and Safety at Work of its
employees. The employer is also obliged to bring to the notice of all its employees this policy together
with the Organization and arrangements in force for carrying out that policy.

5.12. Lack of manpower

The link between manpower and company projects is simple:

Manpower is proportional to productivity. The more people
are available to work, the faster projects can be completed or
the more projects a company can take on. Conversely, a lack
of adequate manpower prevents businesses from completing
tasks. The lack of productivity translates into a reduction in
revenue and profit, which in some cases means the business can't stay operational.

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Safety
When a company employs enough workers, workers generally do not need to work a high number of
overtime hours. The assigned workload is more appropriate because there are more people to handle
tasks. As a result, workers usually are less stressed and more rested and alert. Similarly, when enough
workers are on the clock, there are more people to check adherence to safety regulations and policies,
and workers can seek assistance for physically challenging work. A good level of manpower thus helps
prevent problems such as burnout and injury. Lawsuits and workers' compensation claims may be
reduced as a result.

When the level of manpower in a company is adequate, the business has more options in how it
operates. It has some flexibility in terms of which employees cover shifts; it is easier to get people to fill
in. The company also has a greater pool of workers with which to construct strong teams and is more
likely to have employees with the skills, knowledge, and abilities to tackle current company problems.
Additionally, the company has more employees who can give their own ideas and perspectives. It
therefore may have an easier time remaining innovative and competitive.

5.13. Distractions and interruptions

Distraction could be anything that

draws a person’s attention away from
the task on which they are employed.
Some distractions in the workplace
are unavoidable, such as loud noises,
requests for assistance or advice, and
day-to-day safety problems that
require immediate solving. Other
distractions can be avoided, or
delayed until more appropriate times,
such as messages from home, management decisions concerning non-immediate work (e.g., shift
patterns, leave entitlement, meeting dates, administrative tasks etc), and social conversations.

Psychologists say that distraction is the number one cause of forgetting things: hence the need to avoid
becoming distracted and to avoid distracting others. Humans tend to think ahead. Thus, when returning
to a task, following a distraction, we tend to think we are further ahead than we actually are.

To reduce errors from distraction it is best to complete a task before responding. If the task cannot be
completed without hurrying, then we can prominently mark (or “lock off”) the incomplete work as a
reminder to ourselves and anyone else who may complete the work. When returning to work, after
being distracted, it is a good idea to commence at least three steps back, so that we re-trace some steps
before picking up the task again. If necessary, having someone else double-check our work using a
checklist may be appropriate and useful.

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Dealing with Distraction

Distraction is a Human Factor, and that means no one is immune to it. Hence, everyone must take active
measures to overcome the problems that distraction may cause. When it comes to dealing with the
problem of distraction, we can tackle it with a 2-pronged approach – Mitigation and Prevention. The
first prong is mitigation. This involves employing measures to correct the situation such that it does not
lead to further complications. The second is to prevent distraction from occurring in the first place.

Mitigation

There are various methods to mitigate the effects of distraction. An example is the '3-steps-back’
approach. Technician A is tasked to service a mobile generator, and part of his task involves securing
conductive cables to the generator set. As he is tightening a bolt in place, Technician A is momentarily
distracted by a vehicle cruising by.

Complications can arise as result of his attention being drawn away from his work. Technician A can
momentarily forget that he is in the midst of fully tightening the particular bolt in place, and hence fails
to complete his required task. To mitigate the situation, Technician A should refer to his checklist or
Standard Operating Procedure (SOP), to retrace 3 steps prior to the one in which he was interrupted. In
so doing, he ensures that the 3 prior steps have been completed, before continuing to complete the
task.

Prevention

It is often said that prevention is better than a cure. If one should think about it, ‘curing’ distraction is an
impossible task. It is, however, more feasible to prevent it instead. Let us consider some means in which
distraction can be prevented.

• Always finish the job or completely unfasten the connection. Mark the uncompleted
work. Never leave a fastener or connector partly installed.
• Lock wire where possible or use torque seal. Double inspect by another or self
• When you return to the job always go back three steps. Use a detailed check sheet.

END

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