BASIC TRAINING FOR HKCAD HKAR-66 LICENCE CAT.

A & B
MODULE 9 HUMAN FACTORS
Syllabus Reference : HKAR-66 M9

CONTENTS

9.1 General
 Introduction to Human Factors
 Statistical Data

9.2 Human Performance and Limitations

 Human Performance
 Human Performance: Capabilities and Limitations
 Vision and Hearing
 Sensing and Perception
 Information Processing Memory

9.3 Social Psychology

 Social Psychology
 Basic Psychology

9.4 Factors Affecting Performance

 Fatigue and Sleep
 Stress, Arousal and Workload
 Alcohol and Drugs

9.5 Physical Environment

 Physical Environment

9.6 Tasks
 Tasks

9.7 Communication
 Communication

9.8 Human Error

 Introduction to Maintenance Errors
 Human Error Fundamentals
 Error Management

9.9 Hazards in the Workplace

 Hazards in the Workplace

9.10 Organizational Factors

 Organizational Factors

Reference: HKAR-66 Module 9

Revision date: 13 Oct 2009
HKAR-66 SECTION 4

MODULE 9. HUMAN FACTORS

Level
A B1/3 B2

9.1 General 1 2/2 2

The need to take human factors into account;

Incidents attributable to human factors / human
error;
‘Murphy’s’ law.

9.2 Human Performance and Limitations 1 2/2 2

Vision;
Hearing;
Information processing;
Attention and perception;
Memory;
Claustrophobia and physical access.

9.3 Social Psychology 1 1/1 1

Responsibility: individual and group;

Motivation and de-motivation;
Peer pressure;
‘Culture’ issues;
Team working;
Management, supervision and leadership.

9.4 Factors Affecting Performance 2 2/2 2

Fitness / health;
Stress: domestic and work related;
Time pressure and deadlines;

20 February 2009 4-App 1-34 ISSUE 2

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SECTION 4 HKAR-66

Level
A B1/3 B2

Workload: overload and underload;

Sleep and fatigue, shiftwork;
Alcohol, medication, drug abuse.

9.5 Physical Environment 1 1/1 1

Noise and fumes;

Illumination;
Climate and temperature;
Motion and vibration;
Working environment.

9.6 Tasks 1 1/1 1

Physical work;
Repetitive tasks;
Visual inspection;
Complex systems.

9.7 Communication 2 2/2 2

Within and between teams;

Work logging and recording;
Keeping up to date, currency;
Dissemination of information.

9.8 Human Error 1 2/2 2

Error models and theories;

Types of error in maintenance tasks;
Implications of errors (i.e. accidents);

ISSUE 2 4-APP 1-35 20 February 2009

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HKAR-66 SECTION 4

Level
A B1/3 B2

Avoiding and managing errors.

9.9 Hazards in the Workplace 1 2/2 2

Recognising and avoiding hazards;

Dealing with emergencies.

20 February 2009 4-App 1-36 ISSUE 2

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Human Factors

Objective:
After Completing this training, you should be able to visualize the effect of human
factors on maintenance system and make your own judgement & appropriate
action to avoid maintenance errors.

Definition:
Human factors is the interaction between
• People and Machines
• People and People
• People and Procedures
• People and Environment
Anything within the maintenance system that prevents the engineer from
completing the task as required.

What are human factors:

Skills, tasks, training, work schedules, equipment, aviation stressors that
influence performance.
The goal is to optimize the match between individuals, the working environment
and the demands of their work. The application of this research data should
enhance performance, efficiency and aviation safety.

History of Human Factors (HF):

Began in the Second World War in response to the ‘people problems’ faced by
military aviation.
Several disciplines involved at outset:
- Aviation medicine (high altitudes, g-forces)
- Industrial psychology (people at work)

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 - Basic psychology (how the mind works)
- Basic physiology (how the body works)
- Ergonomics (human performance)
- Anthropometry (the body's dimensions)

The spread of Human Factors:

After W.W.2, HF expanded to cover a wide range of potentially hazardous
activities, including:
– Nuclear power plants
– Chemical process plants
– Oil exploration & production
– Space flight, commercial aviation
– Railways & shipping
– Road transport, etc.
– Anesthesia & surgery

Human Factors cases:

 BAC 1-11 (6/90): Left windscreen blown out at 17,300 ft. Captain half
sucked out of aircraft. Window installed with wrong bolts.
 A320-212 (8/93): Undemanded roll to right on takeoff. Re-instatement and
functional check of the spoilers after flap fitment was not carried out.
 B747-251B (3/94) dropped and dragged its #1 engine on landing. Upper
link fuse pin fractured due to failure to secure fastenings of aft diagonal
brace fuse pin during major overhaul. (At least 5 similar incidents).
 B737-400 (2/95). Rapid engine oil loss. Emergency landing 13 min later.
Both HP rotor drive covers had not been replaced.
 B737-200 (7/95) Gear lever would not move up after takeoff. Bus
protection panel G7 found incorrectly fitted.
 A320 (5/96) Engine shut down due to low oil contents. Piece of old seal
found in oil filter clamp seating. Oil filters changed with no engine ground
runs specified on job card.

Common features:
 Errors by maintenance personnel.
 System failures: procedures, job cards, checks
 Organizational weaknesses: inexperience, bad housekeeping, stores, etc.
It is rare that just one person is wholly responsible for a maintenance lapse.

No one best way

No single "quick-fix” solution.
Requires careful coordination of several targeted measures:
 directed at individuals

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  directed at groups and teams
 directed at tasks and activities
 directed at situations and workplaces
 directed at the system as a whole

Human Factors’ goals:

 To promote working behavior that is safe, efficient and of high quality.
 To achieve all of these goals in ways that are closely integrated. HF is not
an 'add on'.
 HF is about making good people excellent, not about making not-so-good
people better.

Why Human Factor is needed:

The 1 accident per week scenario:

Worldwide accident rate is 3 per 1 million departures
1997 departures are estimated at 17 million
3 x 17 = 51 accidents per year

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Typical Scenarios:
Aloha B737 Space shuttle
Aloha B737 Space shuttle

CAL B747

Events speak louder than words:

Accidents happen in spite of the regulations, quality systems and house

procedures in place.

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Why Human Factor is needed:
Seeing human factors from another angle
 Could it happen to you?
 Could you have made that particular slip?
 Could you have made that particular lapse under those conditions?
 If you couldn't what makes you so special?
 If you could, what can you do about it?
These are the questions we have to address.……..

Aviation safety:
Human performance in maintenance and inspection:
The human element is the most flexible, adaptable and valuable part of the
aviation system. But it is also most vulnerable to influences.

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Current HF concerns:
 Human capabilities and limitations
 Interactions of people with their jobs and working environments
 Human contribution to incidents and accidents
 Influences of environment, equipment, procedures and system design on
human performance
 Organizational factors affecting safety and productivity

The human sciences:

The human sciences study the structure and nature of human beings, their
capabilities and limitations and their behaviours both singly and in groups.

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Industrial Engineering:
 Focus on the human at work
 Systematic analyses of work
 Design of work procedures
 Design of displays, knobs, and dials
 Manufacturing, office automation

Anthropometry:
 Measurements of human body dimensions
 Matches equipment and systems to human
characteristics

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Ergonomics:
 Studies on human physical actions, body co- ordination, task performance
 Matches equipment and systems to human characteristics
 Design for operation of systems and devices
 A more dynamic aspect

Cognitive Science:
 Focus on Human information processing
 Design of human computer interfaces
 Information presentation
 Mental Workload
 Human Errors

Major models used in aviation Human Factors:

 SHEL(L) model
 PEAR model
 'Swiss cheese' model
 Dirty Dozen

The SHEL Model:

 Software
 Hardware
 Environment
 Liveware
 (Liveware)

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Why Models?
 Mental vs. Physical
 Complex Systems
 Simplify
 Difficult to Picture
 Metaphors
 Realism

The SHEL Model:

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SHEL: The interfaces:

The SHEL model as modified by Hawkins:

S= Software (procedures)
H= Hardware (machine)
E= Environment (the situation in which the LHS must function)
L= Liveware (human)

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Liveware:
 Most critical and most flexible element
 Most vulnerable to influences that affect performance
 Edges not simple and straight (This means components of the system
must be carefully matched to humans)

L-H interface:
 Design of seats to match the human body
 Design of displays to match sensory and information processing
 Mismatch means potential hazards and safety problems

L-S interface:
 Checklist procedures
 Computer programs
 Noticeable in accident reports
 Difficult to observe and resolve

L-E interface:
 Flying suits
 Oxygen masks
 Past trend is to adapt the human to environment
 Present trend is to adapt the environment to humans

L-L interface:
 Communication
 Teamwork
 Leadership and personality interaction
 Culture, corporate climate and company operating procedures

Liveware: the human elements:

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Physical size & shape Body movements required for the workplace
Physical needs Food, water and oxygen
Input characteristics The sensory system (eyes, ears etc.)
Information processing Memory and attention
Output characteristics Physical movement or communication
Environmental Temperature, pressure, noise, time of day, darkness,
tolerances heights, enclosed spaces.

Liveware-liveware interface between people:

Management policy Culture issues

Company organization Norms and habits
Leadership Peer pressure
Crew cooperation Personality and attitude
Teamwork Motivation
Personal interactions Reward system

The Swiss cheese model:

Successive layers of defenses, barriers, & safeguards

Factors line up to cause an accident:

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  Accidents don’t just happen
 The hazard is well known but accidents occur
 Factors line up to cause an accident
 A chain of events that interferes with technical judgment

Murphy’s Law:
Edward Murphy was an engineer in the U.S. Armed Force in the 1950s. He
conducted a test using a test rig.
The technician responsible to install the instruments wrongly connected the
wirings, leading to erroneous results.
Therefore he concluded that:
 Anything will go wrong will go wrong
 And is follows that: If there are two or more ways to do something, and
one of those ways can result in a catastrophe, then someone will do it

To some people, once a sign is put out to warn others of the trap, incidents
should not occur. Murphy's Law says the opposite. Incidents will continue to
occur until the trap is totally removed. The price will be too heavy if we have to
learn a hard lesson this way.

Murphy's Law:
"That which can go wrong will go wrong."

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How useful are warning signs?

Applying Murphy's Law to system design:

Before any incident happens, always ask yourself these questions: (Safety net
advice: Think of what may happen.)
 How the equipment can be misused?
 How a line replaceable unit can be mis-installed?
 How a MM procedure can be mis-understood?

Review/Summary:
 HF problems now dominate the risks to aviation safety
 A basic knowledge of HF is an essential part of an aircraft maintainer's
expertise
 Aviation accidents have many causes arising from different levels of the
system
 Maintenance errors are frequent, costly and dangerous
 Murphy’s Law

Reference: HKAR-66 Module 9.1

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Statistics
Statistical Data:

Estimates of human error:

(as a per cent of all failures)

Jet transport 65-85
Air traffic control 90
Maritime vessels 80-85
Chemical industry 80-90
Nuclear plants (US)power 70
Road transportation 85

Causes and costs of air accidents:

The top four ranked by O/B fatalities:

 Controlled flight into terrain (2169)
 Maintenance and inspection (1481)
 Loss of control (1387)
 ATC and communication (1000)
(1982-91, data from Boeing)

Cost Factors Associated with Maintenance Errors:

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  Material
 Regular and overtime labor
 Repair to dock stands and hangar wall
 Loss of bay during extra repair duration
 Delayed or 3rd party maintenance for other A/C
 Operational complications due to A/C unavailability
 Investigation and re-mediation
 Estimated cost was $900,000

Cost Implications*:
 Annual airline revenue $12,000,000,000
 Revenue/day $33,000,000
 Estimated profit margin 5%
 Profit/day $1,650,000
 Total repair/associated costs $900,000
 Summary: Error consumed 1/2 day of total profit!
*Revenue data from 1994 ATA annual report

CAA Top Ten Safety Risk Issues:

 Crew & Human Factors
 Design Related
 Regulatory Oversight
 Company Management
 Failure to Maintain Safe Separation
 Freight, Ferry & Positioning Flights
 Occupant Survivability
 Incorrect/Inadequate Procedures
 Non JAA/FAA Operator Safety
 Failure to Adopt/Fit Best Available Technology

CAA No. 1 Safety Risk Issue:

 Crew and Human Factors
 Maintenance Human Factors
 Omission of Action/Inappropriate Action
 Flight Handling

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  Poor Professional Judgement/Airmanship
 Failure in Crew Resource Management
 Lack of Positional Awareness

Boeing?s top 7 Errors 276 Inflight shutdowns (1994):

 Incomplete installation (33%)
 Damage on installation (14.5%)
 Improper installation (11%)
 Equipment not installed or missing (11%)
 FOD (6.5%)
 Improper troubleshooting, inspection, test (6%)
 Equipment not activated or deactivated (4%)

Boeing study: 122 maintenance lapses in a major airline:

 Omissions 56%
 Incorrect installations 30%
 Wrong parts 8%
 Other 6%

Top Eight Maintenance Errors*:

 Incorrect installation of components
 The fitting of wrong parts
 Electrical wiring discrepancies (including cross- connection)
 Loose objects (tools etc...) left in the aircraft
 Inadequate lubrication
 Cowlings, access panels and fairings not secured
 Fuel/oil caps and refuel panels not secured
 Landing gear ground lockpins not removed before departure
*3 year study by UK CAA

How likely is maintenance error?

At the 14th Maintenance Human Factors conference in Vancouver in March 2000,
the NTSB announced that unlike the reported level of maintenance related
accidents, at about 12% of the total, the actual experience in the USA was:
In the last fifteen years FAR 121 operator had suffered 14 hull losses, 7 of which
were attributable to maintenance or engineering failures. That is 50% of the
total

What gets omitted:

 Fastenings left undone or incomplete 22%

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  items left locked or pins not removed 13%
 Fill/breather caps loose or missing 11%
 items left loose or disconnected 10%
 Items-spacer, washers, etc. missing 10%
 Tools, spare fastenings not removed 10%
 Lack of lubrication 7%
 Panels left off 3%
 Miscellaneous omissions 11%

Maintenance error types: Most common*

 Omissions (48% of total errors)
 System operated in unsafe condition (13%)
 Incorrect installation (11%)
 Towing events (8%)
 Fault not found (5%)
*Hobbs (1997) Bureau- of Air Safety Investigation Aus.

Areas of aircraft most likely to be affected by errors (in rank order):

Engine Fuselage
Flight controls Hydraulics
Thrust reversers Fuel
Wings Engine oil
Landing gear Doors
Galley Stabiliser

Consequences of errors:
 Potential hazard to another worker (40%)
 Actual contact with hazard (17%)
 Damage to aircraft (17%)
 Problem corrected (10%)
 Potential damage to aircraft (10%)
 A/C signed off with unrectified fault (10%)
 Delayed aircraft (3%)

Local error-producing factors (in order of impact):

 Inadequate tools and equipment
 Perceived pressure or haste
 Environment

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  Convenience
 Knowledge, skills & experience Communications
 Procedures

Ground Damage:

Ground Damage Incidents Hazard patterns:

 Aircraft parked at the hangar, gate or on tarmac (62.3%)
 Aircraft is being towed (37.7%)

GDIs: Contributing factors:

 Poor equipment (27%)
 Correct number or personnel not used(14%)
 Lack of awareness of risk/hazards (13%)
 Poor communication (11%)
 Inadequate space (11%)
 Problems with painted guidelines (8%)
 Pushback policies not enforced (6%)
 Personnel unaware of concurrent work (3%)

Reference: HKAR-66 Module 9.1

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Human Performance and Limitation

Human-Machine Systems
• System
• The SHEL Model
• The PEAR Model
• Human Capabilities
• Machine Capabilities
• Human Performance

The System View

A System is:
 A number of functional components
 Working together
 To achieve an objective.

System Components (Examples)

 Typical Engine Fuel System

 Fuel Pumps
 Fuel Control/ Metering Unit
 ECU
 Sensors
 Fuel Filters
 The Human Digestive System
 Mouth, Teeth & Saliva Gland
 Esophagus
 Stomach, duodenum
 Intestine, Colons

Component Relationship

 Connections
 Hydro-mechanical
 Electronic
 Functional Relationships
 Positive
 Negative

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  Neutral

System Response

 Obvious or Hidden
 Direct or Indirect
 Immediate or Delayed

Human-Machine System Components

 Humans
 Machines
 Practices, Procedures and Tools
 Physical Environment
 Organizational Environment

Reference: HKAR-66 Module 9.2.1

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Human Performance: Capabilities and Limitations

Human Capabilities
Human is better than machines in some way when doing some things.
 Flexible
 Able to deal with novelty
 Exercise Judgment
 Pattern Matching
 Physical Adaptability
 Compassion

Human Limitations
Human introduces certain weakness into systems.
 Physical Stresses
 Emotional Stresses
 Physical and Sensory Limits
 Errors
 Mental Calculations
 Vigilance
 Memory
 Laziness
 Greed

Machine Capabilities
Machine is better than human in some way when doing some things.
 No Emotional Stress
 Little Physical Stress
 Good at Complex Calculations
 Very fast and very slow, Stable
 Able to apply great physical force
 Uniformity

Humans & System Performance

Can humans affect system performance?
 Variation
 Errors

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  Defeat Safeguards
 Common-mode failure

Can systems affect the way people perform?

 Complexity
 Time Pressure
 Physical and Emotional Stress
 Communication
 Training

Human Performance
Three-stage model of performance

1. Sensing & Perception

Affected by: Poor lighting, Noise, etc.
2. Decision Making
Affected by: Fatigue, Time Stress, etc.
3. Output
Affected by: inadequate procedures, distraction, etc.

Reference: HKAR-66 Module 9.2.2

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Vision and Hearing

Sensing and Perception

Human Senses:
 See
 Hear
 Taste
 Smell
 Touch

Anatomy of the Human Eye:

Cornea
- Iris and Pupil
Iris is the aperture, pupil is the centre of the iris.
Amount of light can be adjusted by a factor of 5:1
- Lens and Ciliary’s muscle
Ciliary’s muscle surrounding the lens “squeezes” to change the shape of the
lens and therefore its focal length : accommodation.
- Cornea accounts for 70% ~ 80% of total focusing.

Retina
- Rods and Cones

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 Rods are good at detecting movement – peripheral vision,
Cones are for detecting color and fine details in good light.
3 types of cone cells for the 3 primary colors: green cones, blue cones, red
cones.
- Fovea
The centre area on the retina, rich in cones.
- Blind spot
The bundle of nerves going through the retina here. There are no optical cells
here.
- Beware of the Image falling on the blind spot during inspection.
- Fortunately, constant movement of eye (saccades),
prevents image falling on the blind spots in both eyes.

Range of human Visual Adaptation

Environment Factors Affecting Vision

- Light adapted
adapted to bright environment
- Dark adapted
adapted to dim environment better acuity if dark adapted,
7 min. for cones, 30 min. for rods, rods perform better in the dark.
- If you go from a bright environment to a dark environment,
look slightly to one side of the object. This allows the image to fall on the rod-
rich area of the retina.
- Older people need stronger illumination.

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The Human Eye

Image put on the blind spot:

1. Put your face/eyes at a distance of 10 to 15 cm from this page.
2. Then close your left eye, and focus your right eye on the cross.
3. Now the image of the dot falls on the blind spot.

Factors Affecting Clarity of Sight

- Physical imperfections;
- Influence of ingested or inhaled substances,
such as: drugs, medication, alcohol, nicotine;
- Environment;
- Objects being viewed:
Size & contours, contrast of the object with the surrounding,
Relative motion, distance & angle of the object from the viewer,
- Others: hypoxia, fatigue.

Physical Factors Affecting Clarity of Sight

- Myopia: longer-than-normal eyeball

(short sight) corrected by concave lens

- Hypermetropia: shorter-than-normal eyeball

(long sight) corrected by convex lens

- Presbyopia:
Unable to focus on near objects due to weakening of the ciliary’s muscle
associated with ageing.

- Astigmatism: irregularly shaped cornea

Visual Acuity & Age

Ability to see clearly decreases as one becomes older.

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Eye chart

Color Vision
What numbers can you see?

Physical Factors Affecting Clarity of Sight

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- Colour-defective Vision: 8% of men, 0.5% of women.
Usually red/green, or sometimes blue-yellow
Colour vision is essential for:
Wiring identification, recognizing symbols, indicating lights, warning lights &
signals in airfield and flight-deck.

- Other visual problems:

Cataracts: clouding of the lens due to ageing,
UV glaucoma: building up of pressure of the fluid in the eye, causing damage
to the optic nerve,
Migraine: severe headaches leading to distorted vision.

Environmental Factors Affecting Vision

- Airborne particles: dust, rain, mist

- Can make spectacles dirty, wet, scratched.
- Contact lenses, especially hard or gas- permeable types, dry out / irritation.
- Maximum contact lens wearing time less than ~ 8 to 12 hours

Vision -- Key Points of AN 47

- A reasonable standard of eyesight is required for an aircraft engineer.

- Glasses or contact lenses should be worn as prescribed.
- Frequent eyesight checks should be made.
- Colour discrimination should be considered dependant on the tasks required
to be performed.
- Organisations should have procedures to address eyesight testing etc....

Sensory limit - Vision

Seeing includes sensing and perception.
‧We have discussed on Sensing.
‧Perception: Interpretation by your own experience.
‧We’ll see perception later this chapter.

Hearing

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Anatomy of the Human Ear

- Outer ear: auditory canal, eardrum

- Middle ear: 3 small bones - the ossicles: malleus, incus, stapes hammer,
anvil, stirrup
2 muscles - protects from noise > 80 dB reduce by up to 20
dB for 15 min, by acoustic reflex.
No protection against sudden bang.
1 Eustachian tube - to the back of nose & mouth.
- Inner ear : Cochlea basilar membrane - ciliated cells with auditory nerve
3 semi-circular canals - the human accelerometers

- Typical audible frequency range 20 Hz to 20000 Hz

- Greatest sensitivity ~ 3000 Hz
- Presbycusis – hearing deterioration with age, from 30’s onwards,
High pitch sensitivity deteriorates first, worsens if affect by noise induced
hearing loss (NIHL).

Noise
- Ability to hear especially in the high frequency ranges decreases with age.
- Ability to hear is affected by the prevailing noise level.
-

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Airworthiness Notice 47 states:
“ The ability to hear an average conversational voice in a quiet room at a
distance of 2 metres (6 feet) from the examiner is recommended as a routine test.
Failure of this test would require an audiogram to be carried out to provide an
objective assessment. If necessary, a hearing aid may be worn but consideration
should be given to the practicalities of wearing the aid during routine tasks
demanded of the individual.”

- Noise is a fatiguing stimulus even at levels of less than 65 dBA.

- Generally accepted levels of 70-75 dBA.
- Concern when occasional levels of 110 dBA.
- Removing the source of noise is the preferred method of controlling noise.

- Noise level can be reduced by

‧up to 20 dB by ear plugs,
‧up to 40 dB by ear muffs.
- Intermittent & sudden noise are more disruptive

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- High frequency noise has more adverse effect than low frequency noise.

- Effect of noise related to intensity & exposure time

- Noise dose – combination of duration and intensity
- Equivalent amount for temporary hearing loss:
‧90 dB for 8 hours
‧103 dB for ½ hour
‧116 dB for appr 1 minute
- Noise dose over 8 hours TWA (time weighted average) Recommended max
TWA dose is only 90 dB.

Vision, Hearing and Physical Environment

- Effects of the working environment on vision and hearing will be discussed in
“Physical Environmental Factors”

Reference: HKAR-66 Module 9.2.3

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Sensing and Perception

Vision
- Sensory limit- vision
- Seeing is believing.
- How far is the statement true?

- Sensing and perception

- 1a. Sensing
- 1b. Perception
- Interpretation by your own experience

Perceptual Concepts
Example range of human visual adaptation

Contextual Perception

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Both the letter “I3” and the number “I3” are the same figure.
However, the context determines how you perceive them.
(Coren, et al, (1994), Sensation and Perception, Harcourt Brace College
Publishers)

2
How would you interpret “5,4, 2003.”
5th of April?
4th of May?

3
What do you see in the portrait?

- What do you see in the portrait on the right?

- IS the enclosed symbol the left eye or the left ear?
- IF you think it is the left eye, you will conclude it is an old woman.
- IF you think it is the left ear, you will conclude it is a young girl.

Seeing is Believing?

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Although you may see a rectangle (A) and a triangle (B), both, in fact, do not
exist.
Your mind is just filling in the blanks.
(Coren (1972), Psychological Review, 79, 359-367.)

Optical Illusions
Figures A-C all contain perfect squares.
Figure D is a perfect circle.
Figure E has completely straight, parallel lines.
Figure F, lines X and Y are equal lengths.

Reference: HKAR-66 Module 9.2.4

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Information Processing

Information Processing includes the following:

- Information processing
- Perception
- Attention
- Information storage and retrieval (memory)

Perception

- Visual perception
- Aural perception
- Cognitive perception; understanding
- Expectancy / Mind set

Attention

- Attention
- Distraction
- Selective attention
- Affected by stress and arousal
- Motivation

 Focused attention :
 To concentrate one’s attention to a single source and avoid
distraction.
 Divided attention :
 Common in most working situations,
 Doing more than one things at the same time (multi-tasking, time
sharing).
 Selective attention :
 Consciously attending to one source whilst still sampling other
sources in the background.
 e.g. “cocktail party” effect Benefit – automatic response Negative
side –distraction
 Sustained attention :
 The ability to maintain attention and remain alert over a long period,
often on one single task.
 e.g. inspection, radar monitor.

The Conscious Mind

38
- Limited capacity
- Can do clever things
- But slow and effortful
- Holds information for a few seconds
- Processes information sequentially
- Essential for new tasks

Memory

- Short-term memory
- Working memory
- Long-term memory
- Limitations of memory

 Short-term Memory
 Iconic memory for images, or other visual memories.
Echoic memory for sound, aural messages

Normal limitations
1. Lasts for 10-20 seconds, ultra short-term memory by
sensory stores can only last for 2 seconds,
it serves as a buffer
2. Can hold up to 5 to 9 (7+2) items at a time.
3. Limitation can be even low when motivation is low or
when attention is distracted.
4. For topics with more information contents,
use repetitions or other rehearsal mechanisms to improve
retention and information transfer.
5. Splitting into chunks can improve
e.g. phone numbers: in USA, Canada 1-206-765-4321, in
China 86-130-8765-4321
6. Human memory is fallible! Use temporary aides-memoires
is recommended for daily life.
Noting down temporarily can avoid forgetting or confusing
information.

 Long-term Memory
 Semantic memory :
Factual knowledge, e.g. concepts, rules, theories, language
 Episodic memory –
Specific events can be affected by personal view and
expectation and therefore may differ if collected from
different persons

(Semantic memory is more accurate and can last longer

39
 than episodic memory.)

 Vast collection of knowledge

 Unlimited and subconscious
 Rapid and effortless
 Does many things at once
 Handles routines, habits and everyday recurrences
 Motor programme –
Automatic performance from repeated practices,
see “skill-base behaviour”(Chapter 3)

The Two-process Theory of Memory

Risk assessment - Judgment and decision making

- Judgment is the selection of one of several options, based on risk
assessment.
- Good judgment is (generally) based on knowledge and experience.
- Decision making is the selection of one of several options.

40
Decision Making Procedure
 Identify / Define the problem
 Generate ideas
 Silent generation
 Presentation
 Discussion
 Prioritizing
 Implementation
 Feedback follow-up

Recognition failures
- The misidentification of objects, messages, signals, etc.
- The non-detection of problem states (inspection or monitoring failures).

Causes of misidentifications

- Similarity (in appearance, location, function, etc.) between right and

wrong objects.
- Indistinction: poor illumination and signal-to-noise ratios.
- Expectation: we tend to see what we want to see (confirmation bias).
- Habit: in well-practised and familiar tasks, perceptions become less
precise.

Memory failures

 Memory can fail at one or more of three information- processing stages:

 Input: Insufficient attention is given to the short- remembered

41
 material. Lost from short-term memory.
 Storage: Material decays or suffers interference in long-term
memory.
 Retrieval: Known material not recalled at the appropriate time.

Input failures
 Forgetting instructions, names, etc. Essentially a failure of attention at the
time of presentation.
 Forgetting past actions, where tools were left, etc. During routine actions,
mind is often on other things. Actions not attended to.
 place-losing (forget where you are in a sequence.)
 time-gap experience ('wake up' to find past actions a blank.)

Storage failures
 Forgetting the plan-a vague feeling that you should be doing something,
but can't recall what.
 “ What-am-I-doing-here??” experience -find yourself in front of open
drawer or cupboard, but can't recall what you came to get.
 Forgetting items in a plan- necessary steps omitted.

Retrieval failures
 Fail to recall something you know you know, Often a name, a word or a
fact.
 Frequently, the memory search is blocked by some other word or name
that you know to be wrong, but which keeps coming to mind.
 Tip-of-tongue states ended by further search, pop- ups (just comes to
mind later) or external prompts.

Attention failures
 Attention is a limited resource.
 Direct it to one thing and it is withdrawn from another (attention capture).
 When this happens, actions often proceed unintentionally along some
well-trodden pathway:strong habit intrusions.

A Typical Pattern

42
Summary
 The system view
 Strengths and weaknesses of humans and machines
 Systems affect performance
 Human perception
 Attention and Memory

Reference: HKAR-66 Module 9.2.5

43
Social Psychology

The Social Environment

Aircraft maintenance engineers work within a “system”. As indicated in the next page, there
are various factors within this system that impinge on the aircraft maintenance engineer,
ranging from his knowledge, skills and abilities (discussed in the previous chapter), the
environment in which he works (Chapter 5), to the culture of the organization for which he
works.

Even beyond the actual company he works for, the regulatory requirements laid down for his
trade clearly impact on his behavior. As will be seen in Chapter 8 on Human Error, all aspects
of this system may contribute towards errors that the engineer might make.

The Social Environment and the Maintenance System

Responsibility

Individual Responsibility

For licensed certifying engineers as per Airworthiness Notice number 3:

“The certifying engineer shall be responsible for ensuring that work is performed and
recorded in a satisfactory manner...”

44
For non-certifying technicians also have a responsibility in the maintenance process. JAR145
organisations must establish the competence of every person, whether directly involved in
hands-on maintenance or not.

An organisation can make provision on maintenance records or work sheets for the
mechanic(s) involved to sign for the work to provide the traceability to those who were
involved in the job.

The licensed certifying engineers are then responsible for any adjustment or functional test
and the required maintenance records are satisfied before making the legal certification.

Group or Team Responsibility

Advantages:
Work towards ensuring the group output is safe.

Disadvantages:
Diffusion of responsibility

“Everybody’s business is nobody’s business” – assuming that someone else will do it.

Group Responsibility vs. Individual Responsibility

Advantage of Individual Responsibility:

an engineer understands clearly that one or more tasks have been assigned to him and it is
his job to do them. It can also be a strong incentive to an engineer to do the work correctly
knowing that he will be the one held responsible if something goes wrong.

Disadvantage:

may overlook the importance of working together as a cohesive team or group to achieve
goals.

Responsibility

Diffusion of responsibility

“Everybody’s business is nobody’s business “.

Social psychological experiments:

A situation was contrived in which someone was apparently in distress, and noted who came
to help.

45
If a person was on their own, they were far more likely to help than if they were in a pair or
group. In the group situation, each person felt that it was not solely his responsibility to act
and assumed that someone else would do so.

Social loafing:

The tendency for some individuals to work less hard on a task when they believe others are
working on it.

They consider that their own efforts will be pooled with that of other group members and not
seen in isolation.

Responsibility is an important issue in aircraft maintenance engineering, and ought to be

addressed not only by licensing, regulations and procedures, but also by education and
training, attempting to engender a culture of shared, but not diffused, responsibility.

Group

Intergroup conflict in which situations evolve where a small group may act cohesively as a
team, but rivalries may arise between this team and others (e.g. between engineers and
planners, between shifts, between teams at different sites, etc.). This may have implications
in terms of responsibility, with teams failing to share responsibility between them. This is
particularly pertinent to change of responsibility at shift handovers, where members of the
outgoing shift may feel no ‘moral’ responsibility for waiting for the incoming shift members to
arrive and giving a verbal handover in support of the written information on the work cards or
task sheets, whereas they might feel such responsibility when handing over tasks to others
within their own shift.

Intergroup Conflict

Small group cohesion can be so strong that they form a unit and rivalries may arise between
this team and the others (e.g. between shifts, between departments)

If a company creates competition between groups or departments, this may create greater
rivalry mind between units and therefore friendly cooperation between units may be
jeopardized.

Group polarisation:
- The tendency for groups to make decisions those are more extreme than the individual
members’ initial positions.
- Can usually result in more cautious decisions.

Risky shift:
- In some other situations, a group may arrive at a course of action that is riskier than that
which any individual member might pursue.

46
Groupthink:
- The desire of the group to reach unanimous agreement overrides any individual impulse to
adopt proper, rational (and responsible) decisionmaking procedures. (Another example of
group polarisation)

Motivation & Demotivation

Maslow’s Hierarchy of Needs

Possibly one of the most well known theories which attempts to describe human motivation is
Maslow’s hierarchy of needs. Maslow considered that humans are driven by two different sets
of motivational forces;
• Those that ensure survival by satisfying the basic physical and psychological needs;
• Those that help us to realise our full potential in life known as self-actualisation needs
(fulfilling ambitions, etc.).
• The higher levels are more difficult to achieve.

Think about these cases:

• Can you focus on your studies/readings if you are hungry?
• Do people risk their lives in the name of adventures?

NOTE: Maslow’s hierarchy theory is hypothetical.

The Hawthorne effect

47
An interesting experiment on motivation was carried out in 1924 at the Hawthorne Works of
the Western Electric Company in Chicago. Here, the management altered various factors
such as rest periods, lighting levels, working hours, etc. and each time they did so,
performance improved, even when the apparent improvements were taken away!

This suggested that it was not the improvements themselves which were causing the
increased production rates, but rather the fact that the staff felt that management were taking
notice of them and were concerned for their welfare. This phenomenon is known as the
Hawthorne effect.

needs (fulfilling ambitions, etc.).

Highly motivated people tends to show:

• High performance and results being consistently achieved;

• The energy, enthusiasm and determination to succeed;
• Unstinting co-operation in overcoming problems;
• Willingness to accept responsibility;
• Willingness to accommodate change.

De-motivated people tend to show:

• Apathy and indifference to the job, including reduced regard for safety whilst working;
• A poor record of time keeping and high absenteeism;
• An exaggeration of the effects/difficulties encountered in problems, disputes and grievances;
• A lack of co-operation in dealing with problems or difficulties;
• Unjustified resistance to change.

Note: these behaviors can also be signs of stress.

People who are de-motivated lack motivation either intrinsically or through a failure of their
management to motivate the staffs who works for them.

IS FINANCIAL REWARD IS A MOTIVATOR?

There is a school of thought which suggests:

Lack of financial reward is a demotivator. Then is financial reward is a motivator?

The attraction of the extra pay offered to work a ‘ghoster’ can be a strong motivator for an
individual to ignore the dangers associate with working when tired.

The motivating effects of job security and the de-motivating impact of lack of job security is
also an area that causes much debate.

The ‘hire and fire’ attitude of some companies can, potentially, be a major influence upon
safety, with real or perceived pressure upon individuals affecting their performance and
actions.

48
“Reward to productivity”, “reward to delivery” policies:

• Ignoring hazards, quality

• “Hire and fire” policy in competitive environment:
• Impose pressure on engineers, leading to:
- “can do” attitude, nobody says no, nobody voices out tight schedules;
- Quality and standard compromised

These are actually NOT motivation in the true sense!

Maintenance engineers are motivated by a desire to ensure safety (Maslow’s ‘self esteem/self
respect’), rather than by a fear of being punished and losing their job (Maslow’s ‘security’).

The “can do” culture, which is evident in some areas of the industry, may be generated by the
expectancy that if individuals do not ‘deliver’, they will be punished (or even dismissed) and,
conversely, those who do ‘deliver’ (whether strictly by the book or not, finding ways around
lack of time, spares or equipment) are rewarded and promoted.

This is not motivation in the true sense but it has its roots in a complex series of pressures
and drives and is one of the major influences upon human performance and human error in
maintenance engineering.

Peer Pressure

Peer Pressure

Peer pressure is the actual or perceived pressure which an individual may feel, to conform to
what he believes that his peers or colleagues expect.
An individual may feel that there is pressure to cut corners in order to get an aircraft out by a
certain time, in the belief that this is what his colleagues would do under similar
circumstances.
There may be no actual pressure from management to cut corners, but subtle pressure from
peers, for instance: taking the form of comments such as “You don’t want to bother checking
the manual for that. You do it like this…” would constitute peer pressure.

Conformity

Conformity is the tendency to allow one’s opinions, attitudes, actions and even perceptions to
be affected by prevailing opinions, attitudes, actions and perceptions.

The degree, to which an individual’s view is likely to be affected by conformity or peer

pressure, depends on many factors, including:
• Culture (people from country A tend to conform more than those from country B);
• Gender (men tend to conform less than women);
• Self-esteem (persons with low self-esteem are likely to conform more);

49
• the individual’s familiarity with the subject matter (a person is more likely to conform to the
majority view if he feels that he knows less about the subject matter than they do);
• The expertise of the group members (if the individual respects the group or perceives them
to be very knowledgeable he will be more likely to conform to their views);
• The relationship between the individual and group members (conformity increases if the
individual knows the other members of the group, i.e. it is a group of peers).

Countering Peer Pressure and Conformity

• Conformity is closely linked with ‘culture’. It is highly relevant in the aircraft maintenance
environment where it can work for or against a safety culture, depending on the attitudes of
the existing staff and their influence over newcomers.
• It is important for an organization to engender a positive approach to safety throughout their
workforce, so that peer pressure and conformity perpetuates this. In this case, peer pressure
is clearly a good thing.
• Too often, however, it works in reverse, with safety standards gradually deteriorating as shift
members develop practices which might appear to them to be more efficient, but which erode
safety. These place pressure, although possibly unwittingly, upon new engineers joining the
shift, to do likewise.
• Conformity is closely linked with ‘culture’. It is highly relevant in the aircraft maintenance
environment where it can work for or against a safety culture, depending on the attitudes of
the existing staff and their influence over newcomers.
• It is important for an organization to engender a positive approach to safety throughout their
workforce, so that peer pressure and conformity perpetuates this. In this case, peer pressure
is clearly a good thing.
• Too often, however, it works in reverse, with safety standards gradually deteriorating as shift
members develop practices which might appear to them to be more efficient, but which erode
safety. These place pressure, although possibly unwittingly, upon new engineers joining the
shift, to do likewise.
• The influence of peer pressure and conformity on an individual’s views.
• Can be reduced considerably if the individual airs their views publicly from the outset.
• Asch’s experiments:
when asked, many participants said they agreed with the majority as they did not want to
appear different or to look foolish.

50
Basic Psychology

External & internal motivation

External: System rewards & punishments.

Internal: Do it because we want to.

What people want from work :

– To feel valued and competent
– To feel in control (to a degree)

External sticks and carrots far less effective than internal motivation.

Reward and punishment: Effects on behaviour

Personalities
• Overbearing
• Dominating
• Shy / Reluctant
• Impatient
• Negative
• Feuding

Personality and Attitudes

• Personality traits are innate and acquired during the early stages of life.
• Attitudes are learned and conditioned by changes of environment.
• An attitude is a predisposition to react in a certain way.
• Cause of accidents has been inadequate performance by people who have the
capacity to perform effectively and yet fail to do so.
• It is unrealistic to expect a change of personality through routine training.
• Personality problems should be taken care of during initial screening and selection
process.

Personality types

51
Groups dynamics

Leadership styles
•Good at job
•Good with people
•Good with job and people
•Good with neither

Groups and teams

• Most maintenance work is done in teams.
• The behaviour and attitudes of team members is governed by:
- personal goals, beliefs and needs
- group norms

52
- Rules of company
• Company rules and group norms do not always correspond.

Crew coordination

A team vs. a collection of skilled individuals

Cooperation Vs. Competition

53
Characteristics of a Successful Team
• Good communication skills
• Clear goals
• Good team leaders
• Well defined decision making procedures

Interpersonal Relationships
• Successful Teams:
– Function smoothly
– Good relationships
– Accomplish goals

• Unsuccessful Teams:
– Waste time
– Feud

Ground Rules Regarding Teamwork

• Conversational Courtesies
• Language / Humor
• Behavior
- Dealing with tension
- Dealing with various personalities

Stages of Team Growth

• Forming

54
• Storming
• Norming
• Performing

Summary
This module has covered a number of aspects of basic psychology:
– Effects of stress & fatigue
– Individual differences
– Reward & punishment
– Groups and leaders

55
Fatigue

Fatigue is the weariness that accrues from applying oneself to a task over a
period of time; Fatigue can be mental or physical; Fatigue results in both an
inability to continue a task (mental or physical) and a disinclination to perform a
task (motivation); Vulnerability to error is likely to be increased for tired people;
Sleep and fatigue are closely related. Fatigue normally dissipates during normal
rest and sleep; each person has a different ability to withstand fatigue which
diminishes with age.

The onset of fatigue is insidious and the symptoms are not always recognized.
Fatigue can be acute or chronic

Acute – intense physical or mental activity of short duration that is cured by

normal rest or sleep

Chronic – intense physical or mental activity over a long period of time that can
result in serious illness

When we are tired…

Performance level degradation learning new skills

• Talk yourself through
• Respond to signals
• Recognize key signals
• Economize effort (timing)
• Automatic performance

56
Performance level degradation handling complex systems
• Following work habits mechanically (norms)
• Inability to see complex relationships
• Lack of forward vision
• Linear thinking
• Reductionism

Symptoms of Fatigue
• Diminished perception (vision, hearing, etc.) and a general lack of awareness;
• Diminished motor skills and slow reactions;
• Problems with short-term memory;
• channeled concentration - fixation on a single possibly unimportant issue, to the
neglect of others and failing to maintain an overview;
• being easily distracted by unimportant matters;
• Poor judgment and decision making leading to increased mistakes;
• Abnormal moods - erratic changes in mood, depressed, periodically elated and
energetic;
• Diminished standards of own work.

57
But tired people DO NOT recognize these signs, they think that they are still
fit. So look for your partners, your colleagues for these signs, especially in
night shifts or when performing complex tasks.

Symptoms of Chronic Fatigue

Performance decrements can be gradual, first signs of chronic fatigue may be:
• Moodiness,
• Headaches,
• Finding that familiar tasks seem more complicated than usual.

It is always sensible to monitor ones performance, especially when working

additional hours.

Physiological fatigue
• Reflects the body’s need for restoration;
• Related to physical activity, health, consumption of alcohol and circadien rhythm;
• Can be satisfied by rest and sleep.

Subjective fatigue
• The individual’s perception of how sleepy he feels;
• Not only affected by actual sleep but also affected by other factors such as
motivation.

Circadian rhythm

Circadian rhythms
Circa = about Dies = day

58
Virtually all species have developed biological clocks with frequencies close to 24
hours
The human works on a predominantly 25 hour cycle
Many functions are affected by the circadian timing system– hormonal output
– Body core temperature
– Rest
– Activity
– Sleep & wakefulness (sleep/wake cycle)
– Thinking and reasoning (psychological and mental processes)

Do you think jet-lag only happens when traveling between different time zones?

Daily Cycle for Body Temperature

Desynchronized Circadian Rhythm

59
Fatigue: Time of day effects (roughly inverse of body temperature)

Sleep
Theories abound as to why we need sleep but it would seem to serve a restorative
function
– Mentally
– Physically

Stage 1: A transitional phase between waking and sleeping. Heart rate

slows down and muscles relax. Easy to wake up at this stage.
Stage 2: A deeper level of sleep, but it is still fairly easy to wake someone.
Stage 3: Sleep is even deeper, quite unresponsive to external stimuli and
therefore difficult to wake. Heart rate, blood pressure and body temperature
continue to drop.
Stage 4: The deepest stage of sleep, very difficult to wake up.

Stages 1 to 4: non-REM (NREM) sleep.

Stages 2 to 4: slow-wave sleep (appear to relate to body restoration)
Rebound effects: if a person is deprived of a stage (REM or NREM), in
subsequent sleep, s/he will make up the deficit in that particular type of sleep.
Cycles: Typically, the first REM sleep will occur about 90 minutes after the
onset of sleep. The cycle of stage 1 to 4 sleep and REM sleep repeats during the
night about every 90 minutes. Most deep sleep occurs earlier in the night and
REM sleep becomes greater as the night goes on.

Stages of Sleep & REM

60
REM Sleep (REM = Rapid Eye Movement): Brain activity similar to a person who
is awake, even more difficult to awaken than stage 4. Also known as paradoxical
sleep. Muscles become totally relaxed and eyes rapidly dart back and forth under
the eyelids.

It is thought that dreaming occurs during REM sleep.

REM sleep seems to aid the strengthening and organization of memories.

Sleep Deprivation
Physiological effects
– Ultimately it will kill you!

Effect on performance (sometime prior to death)

– Sleepiness (obviously)
– Visual and tactile misperceptions
– Mild disorientation
– Irritability and short tempered
– Lethargy
– Negative mood states
– Involuntary sleep (micro-sleep)
– Memory affected

Reduced Sleep
 Most people do not go without sleep for more than one night
 Most people at some time have less than a full night’s sleep
 Less than 5 hours sleep per night for most people will reduce performance
 5 hours sleep per night is about the minimum that most people can tolerate

61
– 5 hours may not be enough for shift workers due to effect of circadian rhythms
and poor sleep quality during the day resulting in a day-to- day build up of sleep
deprivation

Shift Work
Body rhythm disturbance
Circadian, the 24-hour disturbance, is related to the earth's rotation time.

Maintaining factors:
- Light and darkness
- Meal times
- Physical and social activities
- Sleep quality
- Sleep deprivation
- Sleep disorder
- Insomnia
- Working at the trough of the circadian cycle.
- Alertness and attention is affected.
- With extra effort, alertness and attention can be partly restored.

Problems with Shift Work

• The body is continually trying to cope with circadian desychronisation
(trying to sleep or work at an inappropriate circadian phase)
• Sleep quality is poor
• Sleep is disrupted
– sleeping during daylight
– Digestive system shuts down at night
– Urination need

People prefer to work shift patterns for reasons other than their well-being e.g.
– More time with the family
– Second job
– Minding the baby whilst the mother works
– Shift pay
– Travel time to work reduced (greater choice on where to live)

Complaints Associated With Shift Work

• Chronic Fatigue Syndrome (CFS)
• Sleep disruption and deprivation
• Depression
• Moodiness
• High divorce rate
• Gastrointestinal problems
• Immune system problems
• Alcohol and drug abuse
• High blood pressure and heart disease

62
• Increase in traffic accidents

The worse shift patterns

The worse shift schedules are those that result in:
- Shortened sleep
- Fragmented or disrupted sleep
- Working hours not synchronized with circadian rhythm

63
Stress, Arousal and Workload

Stress
The word stress comes from the Latin word stringer, ‘to stretch’; Stress is any demand or
set of demands requiring us to adapt in order to match them; The cause of the stress is
called a ‘stressor’; We generally consider stress as our perceived inability to cope with
the demands placed upon us. (Time pressure can be actual pressure imposed by
management or customers but can also be self-imposed perceived pressure)

Stress is a normal part of life; The fight-or-flight response was originally effective for
primitive humans facing starvation, exposure and attack… etc; Stressors prompt the
nervous system to initiate a stress response e.g.... increase heart rate, blood pressure,
perspiration, blood sugar levels, slowing of digestion system… etc; Modern humans are
rarely subject to the same threats as our primitive ancestors;

Stress can be:

• Acute (intense but of short duration)
• Chronic (frequent recurrence or of long duration)

Stressors can be:

• One-off (e.g. a challenging problem)
• On-going (e.g. a hot environment or an acrimonious divorce)

Stressors can also be categorised as:

• Physical - e.g. heat, noise, vibration, toxic gas, bad smell…etc;
• Psychological - e.g. emotional upset due to bereavements, domestic
worries, breaking a relation, divorce, financial problem…etc;
• Reactive - e.g. events in daily life such as working pressure,
unexpected situations…etc;

Identifying Stressed Individuals

Management has a duty to identify individuals who may be suffering from stress and to
minimise workplace stresses. Individual cases can be helped by sympathetic and skilful
counselling which allows a return to effective work and licensed duties.

Signs of Stress
• Physiological symptoms - such as sweating, dryness of the mouth, etc.;
• Health effects - such as sleep problems, headaches, nausea, eczema,
diarrhoea, ulcers, etc.;
• Behavioural symptoms - such as restlessness, irritability, shaking, nervous
laughter, taking longer over tasks, appetite changes, drug and alcohol abuse, etc.;
• Cognitive effects - such as poor concentration, indecision, forgetfulness,
mistakes, etc.;
• Subjective effects - such as anxiety, irritability, depression, moodiness,
aggression, etc.

Stress and stressors

64
The same stressor produces different responses in different individuals. Any resulting
damage should be attributed to the response rather than to the stressor itself.

Cognitive stressors
Refers to mental demands of the task itself

Work stressors
Anxiety; incentives; group pressures; time pressure & deadlines; medical and proficiency
checks

Environmental stressors
Temperature; humidity; noise; pressure; fumes; vibration and illumination.

Domestic stressors
Family separation; well- being of dependents

Types of stressors
•Physical: heat, noise, vibration, etc.
•Social: anxiety, incentives, group pressures.
•Drugs: alcohol, nicotine, medication, etc.
•Work: too much to do in too little time, boredom, fatigue, sleep deprivation.
•Body clock: shift changes, jet lag.
•Personal: domestic worries, aches and pains, feeling under the weather, etc.

Modern stressors
• Frustration
• Conflict
• Disruption of circadian rhythm
• Problems and worries
• Major life changes
• Every day hassles and annoyances
• Pressures, including work load, time pressure & deadlines

Work overload and under-load

• Overload
– Stressor
– Trade off accuracy for speed, therefore more likely to make errors

• Under-load
– Low level of arousal (alertness)
– Prone to complacency
– Errors due to inattentiveness

Work Related Stress

Stress can be felt when carrying out certain tasks that are particularly challenging or
difficult, can be increased by lack of guidance in the situation, or time pressures to

65
complete the task or job. Stress feeling is related to the perceived demand and the
perceived capability; this type of stress can be reduced by careful management, good
training, etc.

How we cope with overload

• Ignore selected inputs.
• Trade-off accuracy for speed.
• Postpone things until quieter times.
• Reduce level of discrimination
• Redistribute the work if possible
• Abandon the task altogether

Time pressure and workload

Consider the followings when setting deadlines and allocating tasks
• prioritizing tasks,
• The actual time available to carry out work, (taking breaks, shift hand-over and
preparation into account),
• The personnel available throughout the whole job (allowing a contingency for sick-
leave),
• The most appropriate utilization of staff (considering specialization, strength and
limitation of individuals),
• Availability of spare parts, tooling and equipment
• Time pressure has been implicated in many major accidents and incidents.
• Insufficient time can reduce awareness, vigilance, and increase error rates.
But…
• Tight deadlines are a feature of aircraft operation and maintenance,
• OTP - time pressure is inevitable in line maintenance.

Responding to stress
We generally respond to stress using one of two strategies
•Defense Strategy
– alleviate the pain (medicine, alcohol etc)
– reduce the anxiety (blame someone else or deny to yourself there is a problem etc)

•Coping Strategy
– addressing the source of the stress, not merely alleviating the symptoms
– Involve dealing with the source of the stress rather than just the symptoms
 Delegating workload
 Priotising tasks
 Sorting out the problem
– adjust to the perceived demands of the situation or change the situation
– Stresses are often self-induced
 Stress is often the individual’s response to the perceived demand and the
perceived capability

Coping with stress

66
Good stress management techniques include:
• Relaxation techniques;
• Careful regulation of sleep and diet;
• Physical exercise;
• Counseling - by a supportive friend or seeking professional counselors

Arousal
Arousal is the body's reaction to stresses, drives and motivation.
Sleep (low arousal) -- Panic (high arousal)
Too little or too much arousal causes poor performance.
Low arousal: focus on task-irrelevant cues.
High arousal: neglect task relevant cues, narrowing of attention, panic.

About arousal
• Stress is linked to arousal.
• Arousal refers to non- specific changes (e.g. hormonal and brain activities) in the body
to external stimulation.
• From a low level, an increase in arousal increases performance.
• There is a point beyond which any additional boost of arousal will adversely affect
performance.
• Hence we have the inverted-U Curve which is the same across different tasks.
• The exact shape and location of each curve varies according to task complexity.

Relating arousal and performance

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Alcohol and drugs

Small doses of alcohol affect performance roughly the same as boredom, eating, fatigue,
many prescribed drugs and various everyday risk factors. Alcohol in combination with
drugs can be highly dangerous, even lethal. CAD Airworthiness Notice 47 provides
guidance alcohol and drugs and everyone involved in aviation maintenance should be
aware of its contents.

Alcohol
• Depressant on the nervous system;
• Disturbs normal sleep patterns;
• Causes poor quality of sleep;
• Effects persist after it has disappeared from the blood (hangover);
• Alcohol consumption will impair performance on:
- Tasks,
- Memory,
- Decision making;
• Impairment lasts for at least 14 hours, and longer in the case of large doses.

Drugs
• Drugs may be legal in that they are routinely available from a chemist, or available by
prescription.
• Illegal drugs are definitely prohibited e.g. cannabis, amphetamines, ecstasy...
• Any drugs could have an effect on personal performance. Such effects can last longer
than 24 hours.

Any form of medication, whether prescribed by a doctor or purchased over the counter
and particularly if being taken for the first time, may have serious consequences in the
aviation maintenance environment.

The following three basic questions must be considered:

(a) Must I take medicines at all?
(b) Have I given this particular medication a personal trial for at least 24 hours before
going on duty, to ensure that it will not have adverse effects on my ability to work and
make sound decisions?
(c) Do I really feel fit for work?

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Medication
Sleeping tablets
- Dull the senses, cause mental confusion and slower reaction times. Duration of effect
variable from person to person and may be unduly prolonged. Seek expert medical
advice before using them;

Tranquilizers
- Lower your alertness, induce sleep; when taken in therapeutic doses, has an adverse
effect on performance for up to 36 hours after administration.

Anaesthetics
- Include local, general, dental and other anaesthetics. After use, a period of time
should elapse before returning to duty. This period will vary depending upon individual
circumstances, but may even extend up to 24 or 48 hours. Seek appropriate medical
advice.

Anti-depressants
- can depress the alerting system and have been a contributory cause of mistakes
leading to fatal accidents. Stop work when starting anti-depressants and only return
when it is clear that there are no untoward side effects. Seek medical advice before
returning to work.

Antibiotics and sulpha drugs

- Include penicillin, mycins, cyclines. Can have short term and/or delayed effects on
performance. But usually used in fairly severe infection, so the effects of the infection
may be more important.

Anti-histamine
- Used for allergies, asthma, hay fever, and in cold cures. May cause drowsiness, trial
period required.

Hypertension drugs
- All have some side effects and should not be administered before adequate
assessment of the need for treatment. Advise from prescribing practitioner on any side
effects to be considered.

Anti-malaria drugs
- Recommended doses do not usually have any adverse effects. Should be taken in
good time with the 3 questions in AN47 considered.

Oral Contraceptives
- in the standard dose, do not usually have adverse effects, regular supervision is
required.

Pseudo-ephedrine Hydrochloride
-(Sudafed) commonly used for nasal congestions, can cause anxiety, tremors, rapid
pulse and headaches, not a preparation to be taken when making engineering decisions
or performing licensed duties.

Pep pills

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- (e.g. caffeine, Dexedrine and Benzedrine) Potentially habit forming and can lead to
over-confidence, headaches, dizziness. Caffeine can be acceptable, but Dexedrine and
Benzedrine are NOT acceptable.

Caffeine
The good points
• Caffeine is contained in many food products naturally (tea, coffee) and in many cases
it is added e.g. soft drinks.
• In moderate doses can increase the ability to sustain vigilance, increased alertness
and gives a positive mood state.

The bad points

• Excessive consumption of caffeine can result in anxiety and disturbed sleep.
• Heavy takers can suffer headaches and negative mood states if caffeine is suddenly
stopped (cold turkey).

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Physical Environment Factors

Factors to be considered:
 Temperature
 Noise
 Lighting
 Fumes
 Phobias & Cramped conditions
 Time of day
 Changes affecting body clock
 Time pressure

Environmental factors – Temperature:

Human performance at various temperatures:
Temp(C) Performance Effect
32 Upper limit for performance
28 Maximum acceptable upper limit
25 Optimum with minimal clothing
21 Optimum for typical clothing and tasks
18 Optimum for winter clothing
15 Hand and finger dexterity begins to deteriorate
12 Hand dexterity reduced by 50%

Temperature: Adverse effects:

 Likelihood of poor performance depends on type of task
 For tasks involving reaction time, memory and speedy decisions, effects depend
upon both temperature and time of exposure
 For tasks requiring sustained attention and vigilance, effects depend on
temperature alone

Noise:
 Noise is a fatiguing stimulus even at levels of <65 dBA
 Generally accepted levels of 70-75dBA
 Concern when occasional levels of 110dBA
 Removing the source of noise is the preferred method of controlling noise
 Effect of noise is related to intensity & exposure time
 Noise dose – combination of duration and intensity,80 dB over 8 hours TWA
(time weighted average)
 e.g. 95 dB for 3.5 hrs, then 105 dB for 0.5 hr, then 85 dB for 4 hrs, then TWA =
93.5 dB
 Recommended max TWA dose is only 90 dB

Noise Induced Hearing Loss (NIHL) effect of noise intensity as well as duration. Damage
can be temporary or permanent.
Employer’s responsibility for workers working in high noise:
 80 dB (normal speech cannot be heard clearly at 2 metres)

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  access the risk, tell the employee & propose precautions
 provide ear protectors and explain their use
 90 dB (normal speech cannot be heard clearly at 1 metre)
 reduce exposure to noise in addition to hearing protector
 mark zones where noise > 90 dB level, and restrict entry.
TWA > 85 dB for 8 hrs is hazardous, exposure >115 dB must use protective device.

Noise Level:
The measurement of noise is the power transmitted but presented in logarithmic scale.
i.e. increasing the power level by 10 times is presented as 1 Bel or 10 decibels (10dB).

20 dB increase means 100 times increase.

30 dB increase means 1000 times increase.

Doubling the noise level (power level) is a 3dB increase.

Reducing the noise level by 50% is a 3dB attenuation.

Hearing loss due to noise:

Noise above 90 dB will cause damage. Dependent on both total noise energy and length

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of exposure
The following produce equivalent amounts of temporary hearing loss:
 90 dB for 8 hours
 103 dB for half an hour
 116 dB for a minute

Effects of Noise:
 annoying
 interference with communication
 masking warning signals or messages
 fatiguing, distraction, affect concentration, decision making
 impairing workers’ hearing

Noise and performance:

 Continuous broadband noise at around 100dB affects performance on tasks
involving vigilance and memory.
 Rythmic sound (music) can improve performance on some tasks, but noise
impairs performance.
 If people believe they have control over noise levels, adverse effects are reduced
 Sudden bang noise can cause distraction, shock
 Sudden noise impulse shock can make an individual sluggish for a period

Illumination:
 Frequently found problems
 Lighting conditions can vary dramatically
 Variety of lighting systems in use
 Average levels on upper and lateral external surfaces frequently sufficient
 Average levels elsewhere frequently inadequate

 Effects of poor illumination:

 Mis-identification, poor colour rendition, poor accuracy, longer time to
accomplish;
 Dim environment can make one drowsy.

 Effects of flashing or strobe lights:

 Discomfort, difficult to adapt;
 Mis-identification, poor accuracy, longer time to accomplish;
 Strobe light can even lead to series cramp or epilepsy.

 90% of inspections are visual inspections

 Daylight may be sufficiently bright but the eyes may be light-adapted, it takes 7 to
30 min. to adapt to a darker environment, e.g. under the shadow in strong
daylight, or entering into a dark compartment or a bay.
 Artificial lighting or task lighting may be required.
 Individual illumination requirements change with age - older people need brighter
illumination.

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  Glare (direct or reflected) interferes with the inspection task

Lighting for Inspection:

 Pre and post maintenance inspections (30 to 75 f-c)
 Maintenance (75 to 100 f-c)
 Ordinary inspection (50 f-c)
 Detailed inspection (100 to 200 f-c)
 Fine inspection (200 f-c)
Source: Illuminating Engineering Society

 Fluorescent light saves electric power

 Some specific problems
 Fluorescent light may create parallel fringes that affect visual inspections
 One needs to rotated to another orientation and inspect again
 Colourful background also interfere insp.
 Fluorescent penetrent inspection is a practical remedy

Fumes:
 Reduce visibility
 Discomfort due to bad smell
 Irritation to eyes, nose, throat, skin
 Allergy, nauseating, faint and other poisoning effect
 Many chemical vapours have explosive or corrosive nature
 Respirators should be worn
 Noxious fumes detected in the hangar may require evacuation

Motion and Vibration:

 Difficult to align, measure, aim at target
 One needs to balance, loses sense of security - causing distraction
 Prolonged motion may lead to motion sickness for some people
 Hman body absorbs most of the energy at 0.5 to 20 Hz
 Tools driven at 50 to 150 Hz can cause V.W.F. (Vibration- induced White Finger
Syndrome) - reduced local blood flow and pain.

Phobias:
 Claustrophobia
 Physical access
 Fear of heights (Acrophobia)

Claustrophobia:
 The fear of being isolated in an enclosed space
 the fuel tank access scenario

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  all safety precautions taken
 a two-man job
 communication protocol to be established (keep in touch to the person inside the
tank)

Environmental Factors – Access:

 Appropriate access must be given dependent on the task that is being performed
 People need to feel ‘comfortable’ when performing tasks

Poor access & cramped conditions:

 Rated as one of the major problem affecting quality and reliability
 Increases likelihood of error and reduces error detection
 Increases feelings of fatigue, irritation and discomfort--all possible distractors
 High probability of omissions due to desire to get out

Time of day: Body temperature:

 Body temperature fluctuates throughout the 24-hour cycle (circadian rhythm).
 Lowest point at around 0400hrs, highest at 1400 hours (difference around 0.5
degree C)
 Performance efficiency corresponds closely to temperature cycle
 Individual differences: morning and evening workers (temperature differences)

Time of day: Accidents:

 Many major accidents/incidents have occurred in the early hours of the morning:
o Three Mile Island
o Bhopal
o Chernobyl
o BAC 1 11, etc
 Emergencies in early hours of morning are less likely to be dealt
with effectively

Jet lag:
 On average, it takes approximately one day to recover from each time zone
travelled away from home. Complete after 8 days
 In general, recovery from east-west travel (phase delay in sleep/wake cycle) is
quicker than west-east (phase advance)
 Recovery faster for journey toward home than away from home

Adjusting to shift work changes:

 Steady shifts alter body rhythms, while rotating shifts do not. But rotating shifts
mean working at lowest point of efficiency cycle and highest point in fatigue cycle
 Adjustment faster with positive attitudes and willingness to change day-off
schedule

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Time pressure:
 Tight deadlines are a feature of aircraft maintenance
 Time pressure has been implicated in many major accidents and incidents
 Insufficient time can increase error rates by x 11, making it the second most
powerful error- producing factor (after insufficient knowledge)

Summary:
 Human performance is strongly influenced by workplace factors
 This module has looked at some of the more important factors for aircraft
engineers: temperature. noise, cramped conditions, time-of-day, body clock
changes, time pressure

Reference: HKAR-66 Module 9.5

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Tasks

Nature of tasks:

Physical work: Repetitive tasks:

 Human size and shape  Loss of interest
 Physical exertion  Complacency
 Ergonomics  Clues not noticed
 Teamwork  Lack of awareness

Visual inspection: Complex systems:

 Illumination level  Conscious mind
 Visual acuity  Good extent of information
 Information processing processing
 Judgment involved  Judgment involved
 Attention failures  Proactive application of experience

Repetitive Tasks:
 Frequent doers of the task may think that the task is easy > this leads to
complacency
 Repetitive task can be of low arousal, therefore prone to complacency
 People may assume they have done the task many times, even if they have not
perform the task for a time

Complex Systems:
 Wide variety of inputs
 Single output or many outputs / responses
 Simple systems are transparent
o easily understood
 complex systems are opaque
o composition & function more difficult to conceptualise
o require system-specific training

Characteristics of a complex system:

 Presence of relevant and irrelevant clues
 Multiple-person and multi-trade involvement
 Continuation work, sometimes at a delayed future time
 Continuation work Example:
 Cannibalization of parts from a spare engine
 Replacement of serviceable parts
 Functional and leak checks.

Maintenance Tasks of Complex Systems:

 Important to follow guidance material such as manufacturers’ instructions

77
  Long time tasks need hand-over
 Tasks may need engineers of different trades to work together
 However, engineers are multi-type-rated, but systems in different aircraft (and
their variants) may be very similar. (e.g. A330, A340, A340-600). Therefore:
 Less familiar to various a/c systems
 Confusing, Vulnerable to errors
 Reference to Manuals is extremely essential

Complex Systems:
 Many maintenance tasks require lots of working steps to be accomplished
 It involves a lot of people of different trades to work on the complex system
 Hence Documentation is very important
 Task Analysis with job cards divided into logical steps and sequence is essential
 Work has to be done in a logical & step by step way
 Work cards should be certified by all trades involved
 Duplicate inspection should be carried out as a safety net if necessary

Planning a Task:
 Poorly planned tasks usually invite problems
 Should consider the followings when planning:
 What exactly is the task?
 Are resources (such as personnel, equipment, documentation, guidance,
facilities) available?
 Do we have the skills and proficiency related to the task?
 Supervisors should ensure the resources are readily available.

Visual Inspection:
 Includes: Surveillance Inspection (SI), General Visual Inspection (GVI) and
Detailed Visual Inspection (DVI)
 Using the eye, alone or in conjunction with various aids, to examine
 Use judgement to evaluate the condition of components, structure or systems of
an aircraft
 Aids such as magnifiers, mirrors and borescopes can be used to enhance visual
capabilities
 Camera or video recorder are used for keeping records
 Good eyesight is of prime importance
 May be accompanied by using other senses (i.e. vision, plus touch, hearing,
smell, etc.)

Visual Inspection:
 Lighting condition is an important factor

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  Different inspection methods require different illumination level as per AC43-204
(Ref. chapter 5, this handout)
 Removal of parts and thorough cleaning required for most type of inspection
 Follow-on reinstallation is as important as inspection

Limitation of Visual Inspection:

 Very dependent on individual ability & attitude of the inspector : low arousal, lack
of motivation > fail to find a fault
 Adequate and appropriate training is essential
 Visual Acuity is also a factor
 Inspector must be aware and observe the work card requirement and expect
what he is required to see (e.g. hairy crack, 2-inch crack)
 Whenever in doubt, seek second opinion or use NDT methods to confirm findings

Keys to Reliable Inspection:

 Focus / concentration required
 Good understanding and knowledge of the inspected item
 Illumination level must be appropriate: bright enough and no glare, no flash
 Locate the area, component or system to be inspected
 Environment conducive to the visual inspection task
 Systematic visual search, moving eyes in a set pattern
 Short breaks between discrete insp. Tasks is better than pausing midway
through an inspection
 Expect to find a flaw during inspection

What are the eyesight requirements for an inspector? (AN 47, and Chapter 2 this hand-
out,)
What are the illumination requirements?
 general illumination for the hangar, and
 specific illumination for inspection ?
Use the SHEL model to establish a good visual inspection procedure

Human Performance maybe affected by:

 Physical Environmental factors
 Drugs, medicines and alcohol
 Emotions
 Physical fitness
 Fatigue and circadian rhythms
 Stresses
 Motivation
 Social Environmental factors

Physical Environmental Factors Affecting Human Perfornance:

Noise:
 Continuos noise
 Sudden bang noise
Lighting:

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  Dim illumination
 Glare
 Strong Flashing lights
Temperature
Humidity
Ambient pressure
Fumes:
 Reduce visibility
 Body responses
 Hazards
Motion and Vibration:
 Motion sickness
 VWF
Cramped condition:
 Claustrophobia, house keeping/tidiness
Height:
 Acrophobia

Reference: HKAR-66 Module 9.6

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Communication

• An active process and a two way process

• The sender encodes, the recipients decode
• Feedback = Response, acknowledgement reply of the recipients

Communication Process involves:

Transmission, Encoding, Decoding, Receiving and Feedback

Effects on Encoding
• Encoding may distort/change message
• Terminology used
• Personal training and experience
• Transmitter’s opinion of receiver
• Assumptions by the transmitter of the receiver’s skills

Other Encoding Effects

• Body Language
• Tone of voice
• Distraction
• Noise
• Environment

Feedback - Critical for Communication

• Types
– Verbal
– Non-verbal

• Feedback Flow two ways

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– Give Feedback
– Receive feedback

Communication
Aircraft maintenance engineers regularly communicate:
• Information;
• Ideas;
• Feelings;
• Attitudes and beliefs.

Verbal / spoken communication:

Sentences, phrases, a single word, a grunt

Written / textual:
Printed words, hand-written notes, fax, e-mails

Non-verbal:
- Graphic: diagrams, diagrams, photos, indications
- Symbolic: e.g. thumbs up, beckoning, nodding body language : facial
expressions, postures

Verbal & Written Communications all communicating parties:

– use the same channel,
– recognize and understand the language,
– are able to make sense of the meaning.

Message be appropriate to the context of the work place, preferably compatible to

the receivers’ expectation.

Similar understanding of technical knowledge, technical language, jargon, and

acronyms is expected.

If ambiguity exists, must clarify

– assumptions can be dangerous

Communication
Verbal
- Most frequently & commonly used within a team and between teams;
- Relies on transmission skills and interpretation;
- Obtain F/B to ensure message is heard & understood;
- Good communication skills help maintain group cohesion.

Non-Verbal
- Most frequently & commonly used between teams;
- Ensures traceability;
- Verbal backup preferred - briefing to ensure message is received & understood.

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- Usually used in shift handover to convey info on:
– tasks in progress,
– tasks completion,
– tasks to be carried out,

Example Written Communication

• Work Cards/Non-routine write ups
• Technical Orders
• Advisory Circulars
• Notes/Letters/Facsimiles/E-mails

Requirements of Good Written Communication

• Must convey the complete message
• Must be easy to understand
• Must relate accurately to the problem at hand
• Must be readable
• Should be free of any emotional or hidden messages

Achieving Good Written Communication

For the message to be correct
– Technically accurate
– Proper reference to the maintenance manual

For the message to be complete

– Provide enough information
– One action per step
– Proper sequence
– Be careful of errors of omission

For the message to be clear

– Say what you mean
– State the point
– Use short sentences
– Be careful of acronyms and abbreviations.

For the message to be concise

• Readability: Relevant factors are character style, type form, size, contrast
and spacing.
• Relevance: Giving more than enough information will only confuse the
reader or listener.
• Objective: Mention specific assumptions. Give data evidence.
• Using photograph diagrams, charts or tables replacing long descriptive text.

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Guidelines for Written Communication
• Write legibly
• Be concise
• Beware of assumptions
• Proofread

Communication
Communication before starting a task
– to find out what to do;

Communication during a task

– to discuss work in progress, ask colleagues questions, confirm actions or
intentions, or
– to ensure that others are informed of the maintenance state at any
particular time;

Communication at the end of a task

– to report its completion and highlight any problems.

Dissemination of Information

Currency:
the engineers must keep abreast of pertinent information
Provide appropriate training before working on a new aircraft type or variant.
Engineers are likely to keep up-to-date by:
• undertaking update courses;
• reading briefing material, memos and bulletins;
• studying maintenance manual amendments

Bulletin boards are not effective (binders are even worse)

- no follow up action to ensure the info is read and understood.

Assumptions can make communication go wrong;

Assumptions based on context and expectations;
Some tips to minimize poor communication:
- think about what you want to express;
- speak or write clearly;
- listen or read carefully;
- seek clarification wherever necessary.

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Introduction to Maintenance Errors

Aviation Accidents

Nuts & Bolt Example

Only One way to disassemble

40,000 ways to error in re-assembly!

So what is maintenance error?

According to Airworthiness Notice 71 paragraph 2.4 :
A maintenance error is considered to have occurred when the maintenance system
(including the human element) fails to perform in the manner expected in order to
achieve its safety objectives.

Estimates of human error

(as a per cent of all failures)
Jet transport 65-85
Air traffic control 90
Maritime vessels 80-85

85
Chemical industry 80-90
Nuclear power plants (US) 70
Road transportation 85

Causes and costs of air accidents

The top four ranked by O/B fatalities
Controlled flight into terrain (2169)
Maintenance and inspection (1481)
Loss of control (1387)
ATC and communication (1000)

(1982-91, data from Boeing)

Cost Factors Associated with Maintenance Errors

•Material
•Regular and overtime labor
•Repair to dock stands and hangar wall
•Loss of bay during extra repair duration
•Delayed or 3rd party maintenance for other A/C
•Operational complications due to A/C unavailability
•Investigation and re-mediation
•Estimated cost was $900,000

CAA Top Ten Safety Risk Issues

•Crew & Human Factors
•Design Related
•Regulatory Oversight
•Company Management
•Failure to Maintain Safe Separation
•Freight, Ferry & Positioning Flights
•Occupant Survivability
•Incorrect/Inadequate Procedures
•Non JAA/FAA Operator Safety
•Failure to Adopt/Fit Best Available Technology

CAA No. 1 Safety Risk Issue

Crew and Human Factors :
•Maintenance Human Factors
•Omission of Action/Inappropriate Action
•Flight Handling
•Poor Professional Judgement/Airmanship
•Failure in Crew Resource Management
•Lack of Positional Awareness

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UK Experience of Human Factors in Aircraft Maintenance
•BAC 1-11, June 1990
•A320, August 1993
•B737, February 1995

Review of the AAIB Reports for the BAC 1-11, A320 & B737
• All the errors occurred at night
• Supervisors doing long hands-on tasks
• Interruptions
• Failure to use approved data or company procedures
• Confusing manuals

Review of the AAIB Reports for the BAC 1-11, A320 & B737
•Shift or task handovers
•Time pressures
•Staff shortages
•Inadequate pre-planning, equipment, spares
•A can-do attitude

Human Error Experience

Error Defined
• Slip: Good plan, bad execution
• Mistake: Bad plan
•Error: An unsafe act unintentionally committed.

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•Violation: Intentional deviation from safe operating practices, procedures,
standards or rules.
•Active Failure: Action with immediate effects.
•Latent Failure: Caused by someone or something having a delayed effect.

Two types of Error

- Active Failure: Action with immediate effects.
- Latent Failure: Caused by someone or something having a delayed effect.
•Type 1 error: A sound item is incorrectly identified as faulty.
•Type 2 error: A defective item is incorrectly identified as a sound item.

Human Error
Three types of human error:
–Error of commission
•Performing a different act or behavior

–Error of omission
•Not performing an act or behavior - just didn’t do it

–Extraneous error
•Performing an additional action

Levels of consequences of human error

–Personal injury
–Little or no effect
–Physical damage to equipment
–Catastrophic event

More Error Classification

• The Consequences--What went wrong?
• Action Descriptions--How did it go wrong?
• Underlying Causes--Why did it go wrong?

(Reason approach, 1996)

Boeing’s top 7 Errors 276 Inflight shutdowns (1994)

•Incomplete installation (33%)
•Damage on installation (14.5%)
•Improper installation (11%)
•Equipment not installed or missing (11%)
•FOD (6.5%)
•Improper troubleshooting, inspection, test (6%)
•Equipment not activated or deactivated (4%)

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Boeing study: 122 maintenance lapses in a major airline
•Omissions 56%
•Incorrect installations 30%
•Wrong parts 8%
•Other 6%

Top Eight Maintenance Errors*

•Incorrect installation of components
•The fitting of wrong parts
•Electrical wiring discrepancies (including cross- connection)
•Loose objects (tools etc...) left in the aircraft
•Inadequate lubrication
•Cowlings, access panels and fairings not secured
•Fuel/oil caps and refuel panels not secured
•Landing gear ground lockpins not removed before departure

*3 year study by UK CAA

What gets omitted

Fastenings left undone or incomplete 22%
items left locked or pins not removed 13%
Fill/breather caps loose or missing 11%
items left loose or disconnected 10%
Items-spacer, washers, etc. missing 10%
Tools, spare fastenings not removed 10%
Lack of lubrication 7%
Panels left off 3%
Miscellaneous omissions 11%

Most common*
•Omissions (48% of total errors)
•System operated in unsafe condition (13%)
•Incorrect installation (11%)
•Towing events (8%)
•Fault not found (5%)

*Hobbs (1997) Bureau- of Air Safety Investigation Aus.

Areas of aircraft most likely to be affected by errors (in rank order)

Engine Fuselage
Flight controls Hydraulics
Thrust reversers Fuel
Wings Engine oil
Landing gear Doors
Galley Stabiliser

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Consequences of errors
•Potential hazard to another worker (40%)
•Actual contact with hazard (17%)
•Damage to aircraft (17%)
•Problem corrected (10%)
•Potential damage to aircraft (10%)
•A/c signed off with unrectified fault (10%)
•Delayed aircraft (3%)

How likely is maintenance error?

At the 14th Maintenance Human Factors conference in Vancouver in March 2000, the
NTSB announced that unlike the reported level of maintenance related accidents, at
about 12% of the total, the actual experience in the USA was: “In the last fifteen years
FAR 121 operator had suffered 14 hull losses, 7 of which were attributable to
maintenance or engineering failures”.

That is 50% of the total

Chain of Events
Multiple contributing causes that can lead to an accident.

Break the Chain of Events

Preventing any event could prevent the accident

If we can break the chain, the accident doesn’t happen

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Safety net
A safety net is a Regulation Policy, or Procedure which if applied, might prevent a link
from forming, or break an existing link

• Any mechanism that you put in place can help you break the chain.
• Stress- Mental, emotional or physical tension, strain, or distress.
• Stressors- What are they?

Safety nets- Handling stress

- Be aware of how stress can effect your work.
- Stop and look rationally at the problem.
- Determine a rational course of action and follow it. (Discuss it with someone)
- Take time off or at least have a short break.
- Ask fellow workers to monitor your work.
- Exercise your body.

Safety net Fatigue

- Be aware of the symptoms and look for them in yourself and others.
- Plan to avoid complex tasks at the bottom of your circadian rhythm.
- Sleep and exercise regularly.
- Ask others to check your work.

Dirty Dozen
•Lack of Communication
- A lack of clear direct statements and good, active listening skills.
•Complacency
- Self-satisfaction accompanied by a loss of awareness of the dangers.
•Lack of Knowledge
- Lack of experience or training in the task at hand.
•Distraction
- Draw one’s attention away, mental emotional confusion or disturbance.
•Lack of Teamwork
- Lack of working together to achieve a common goal
•Fatigue
- Weariness from labor or exertion, nervous exhaustion, temporary loss of power
to respond
•Lack of Resources

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 - Failure to use or acquire the appropriate tools, equipment, information and
procedures for the task at hand
•Pressure
- Pushing for something in spite of opposing odds, creating a sense of urgency
or haste
•Lack of Assertiveness
- A lack of positive communication of one’s ideas wants and needs.
•Stress
- Mental, emotional or physical tension, strain, or distress.
•Lack of Awareness
- Failure to be alert or vigilant in observing.
•Norms
- The commonly accepted practice of working routine jobs without the manual.

Norms

 A norm is a pattern or type of behaviour that is typical within a group of

people.
o e.g. routinely, nobody in the hanger performs an engine run after a
borescope
 Norms are very powerful as we have a strong desire to be accepted by the
group
 Non-conformance with established norms tends to lead to rejection by the
group (peer pressure to conform)

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  Norms can be good or bad (positive or negative)

Understanding Norms
Informal work practices or unwritten rules that are accepted by the group

Solution 1 is chosen because it has been chosen. When norms prevail, people will stop
thinking about whether the solution is best for the situation.

Example of Norms
• Performing a final walk-around before each flight.
• Working without using a maintenance manual.
• Asking a fellow AMT if s/he would check you work.
• Signing for work not done in order to get the aircraft out on time.
• Pushing the aircraft back without using a wing walker.
• Checking all nuts by hand after the job is done.
• Signing off on someone else work.
• Verbal handover.
• Running with scissors.

Positive and negative norms

Norms can be positive Norms can be negative (ineffective)

(effective)
Positive norms have an overall Negative norms are short cuts or
positive effect on the accepted practices which the group
organization. encourages or tolerates.
Example: Example:
Double checking your work Completing the job from memory.

Killer Norms

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Killer norms are those norms that may affect the safe operations.
Negative norms can become a killer norms when the group fails to see the danger in
the short cut or accepted practice.
Example: Deviating from manufacturers maintenance manuals.

Habits
A habit is a type or pattern of behaviour that is peculiar to that person.
–e.g. Keeping the access door open while performing tasks, fasteners left
undone...

Bad habits are difficult to detect during audits but should be detected by Supervisors.

Changing a Negative Norm or Habit is like ...

a spaceship leaving earth:

It takes a tremendous amount of energy at first, but gets progr

you leave the earth's (Norm's/Habit's) influence.

Local error-producing factors

(in order of impact)
 Inadequate tools and equipment
 Perceived pressure or haste
 Environment
 Convenience
 Knowledge, skills & experience - Communications
 Procedures

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Ground Damage

Ground Damage Incidents Hazard patterns

• Aircraft parked at the hangar, gate or on tarmac
(62.3%)
• Aircraft is being towed
(37.7%)

GDIs: Contributing factors

 Poor equipment (27%)
 Correct number or personnel not used (14%)
 Lack of awareness of risk/hazards (13%)
 Poor communication (11%)
 Inadequate space (11%)
 Problems with painted guidelines (8%)
 Pushback policies not enforced (6%)
 Personnel unaware of concurrent work (3%)

Conclusions
 Maintenance errors have unacceptable costs both in terms of lives and money.
 Maintenance is highly error-provoking activity, regardless of who is doing the job.
 The most common error type is leaving out necessary steps during installation.
 Can predict where errors might occur.

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Human Error Fundamentals

Human Errors (1) - Slips, Lapses, and Mistakes

The failure of planned actions to achieve their intended outcome. A
deviation between what was actually done and what should have been
done.

Two ways of not achieving your goal

•The plan may be OK, but the actions don't go as planned. These are called slips and
lapses.
•The actions may go as planned, but the plan is inadequate to achieve the desired goal.
These are called mistakes.

Errors and Performance

•Different tasks have different approaches
•Some tasks we do require very little thought, and others require a lot more

Classification of Errors
Models & Theories
•Design-Induced vs Operator-Induced errors
•Variable vs Constant
•Reversible vs Irreversible
•Omission, Commission and Extraneous
•Type 1 vs Type 2
•Slip, Lapses and Mistakes

Reason’s approach, 1996

•Causes, How, Consequences

More Error Classification

•Underlying Causes--Why did it go wrong?
•Action Descriptions--How did it go wrong?
•The Consequences--What went wrong?

(Reason approach, 1996)

Classification of Errors
Three types of human error:
–Error of commission
•Performing a different act or behavior
–Error of omission
•Not performing an act or behavior - just didn’t do it
–Extraneous error

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 •Performing an additional action

Design-Induced vs Operator-Induced errors:

Design-induced error
- A flaw in the original design of a machine/system leading to compromised
operational safety.
Operator-induced error
– Flawed procedures put in place by airlines, maintenance organisation or air
traffic control management leading to operational error.

Variable vs Constant
•Constant errors: predictable, can be controlled
•Variable errors: unpredictable, cannot be controlled
•info about the nature of the task, the working environment, the factors affecting
performance, and the nature of the individual >> higher chance to predict an error.
e.g. working at 3:00 am, poor illumination…etc.

Reversible vs Irreversible Errors

Well designed systems and procedures are such that errors made by maintenance
engineers be reversible and can be corrected.

Basic Error Types

Slips :
actions NOT carried out as intended or planned. e.g.
typing errors, Slips occur at the execution stage.

Lapses :
missed actions and omissions, i.e. failure to do
something due to memory lapses and/or attention.
e.g. forgetting to do something. Lapses occur at the
memory stage.•

Mistakes :
specific type of error brought about by a faulty
plan/intention, i.e. doing something believing it to be
correct when it was, in fact, wrong, e.g. due to wrong
judgement. Mistakes occur at the planning stage.

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Maintenance error types (classified by performance level)

Basic Error Types

•Skill-based behaviours:
–rely on stored routines or motor programmes that have been learned with
practice and may be executed without conscious thought.

•Rule-based behaviours:
–a routine or procedure has been learned,
–may comprise a set of discrete skills.

•Knowledge-based behaviours :

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 –no procedure has been established,
–require the individual to evaluate information, and then use his knowledge and
experience to formulate a plan for dealing with the situation

Skill Based Performance

•Driving a car or playing table tennis are examples of skill based performance
–Develops only with practice
–Little conscious effort
–Repetitive
–Allows us to do several things at once

•Errors at the skill based level are slips and lapses

•Slips and lapses are errors which result from some failure in the execution and/or
memory stage of an action sequence

Rule Based Performance

An example would be driving your car and a red light on the dashboard illuminated. Even
if you had never seen this light before, you know a red light means ‘Warning’ and you
should stop and investigate.
–Slower
–Sequential
–Can only think about one thing at a time
–Requires conscious effort

Errors at the rule based level are mistakes. i.e... the plan was defective.

Knowledge Based Performance

•An example would be if someone, who has never flown before, sits in a Business Class
seat and tries to operate the IFE. A very novel situation with no similar experiences to
draw upon.
–Not familiar with the situation
–Not sure how to deal with it
–Use all mental resources to solve the problem
–Trial and error / success

•Errors at the knowledge based level are mistakes. i.e... the plan was defective.

Slips & lapses: Three main types

•Recognition failures
•Memory failures
•Attention failures

Slips of action (attention failures)

•Strong habit intrusions

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•Omissions following interruptions
•Premature exits

A typical pattern

Strong habit intrusions

•Make tea instead of coffee. You are a tea drinker, but guest asks for coffee.
•Drive to work on Saturday morning when you meant to go to elsewhere.
•Intend to stop off to buy groceries on the way home, but drive straight past.

Environmental Capture
When an engineer carries out a certain task very frequently in a certain location, he may
inadvertently carry out the same task, in a similar environment, even if it is not required.

No conscious decision to operate the skill has been made.

e.g. A mechanic used to removing the HP rotor hand-crank cover and the
borescope plugs, may inadvertently remove the hand-crank cover when
preparing for a combustion chamber inspection, even though it is not required.
He has not made a conscious decision to operate the skill.

Reversion
- Performing the old procedure, although a new procedure has been effective.
- Can occur once a certain pattern of behaviour has been established, primarily because
it can be very difficult to abandon or unlearn it when it is no longer appropriate.

e.g. An engineer may accidentally carry out a procedure that he has used for years,
even though it has been recently revised. This is more likely to happen when people are
not concentrating or when they are in a stressful situation.

Omissions following interruptions

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•The failure to make the proper attention check on progress is caused by distraction:-
–Intend to collect manual, but on removing it from shelf other book fall down. You
put the books back to the shelf but depart without taking the maintenance manual
with you.
•Actions associated with the interruption can got unconsciously 'counted in' as part of the
intended sequence.

Premature exits
•Terminate job before all fastenings are attached, or oil/fluid replaced, or caps secured,
or all tools and foreign objects removed. Actual examples:-
•Nuts left finger tight and not torqued
–Centre P2 instrument panel slid out on takeoff.
–Pre-light check revealed that control column
–could not be moved backwards. 3 cm hole cutter found wedged between
balance weight and a/c structure.

General factors promoting wrong actions

•The performance of a routine, habitual task in familiar surroundings.
•Attention capture by preoccupation or distraction.
•Change, either in the plan of action or in the surroundings.

Slips versus mistakes

•Installation problems (omissions) are the largest class of quality lapses.
•While many of them are due to slips, this is not the whole story.
•Omissions can also occur because of mistakes: having the wrong idea about something,
or using the wrong procedure.
•Slips are hardly ever repeated, but mistakes are.

Summary
•This module looked at absent-minded slips and lapses:-
- recognition failures
- memory failures
- attention failures

•It is also introduced RB mistakes. The next module considers RB mistakes and
procedural violations.

Human Errors (2) - Mistakes and violations

Two main types of mistake
•These are related to the RB and KB levels of performance
•RB mistakes
•KB mistakes
•However, KB mistakes are very rare in aircraft maintenance (maybe 3-4% of all lapses),
so we focus on RB mistakes (judged by some to produce around 50% of all errors).

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Three common mistakes in aircraft maintenance
•Misapply a good rule
•Apply a bad rule
•Fail to apply a good rule (violation)

Misapplying good rules

•A ‘good rule or principle’ is one that has been useful in the past
•These good rules are the ‘rule of thumb’ principles that we use every day
•The problems occur when the rule or principle is wrongly applied

Examples of misapplied rules

•Aircraft pipe couplings are right hand threads.
•Applying this ‘normally good rule’ to an oxygen pipe could result in damage to the pipe.

Applying bad rules

•Most people pick up some 'bad rules' (bad habits) when learning a job.
•They are 'bad' because they can lead to something going wrong at a later time, even
though they might serve their immediate purpose on many occasions.
•Such 'bad rules' become established as part of the person 'toolbox'.

Violations
• Most stem from a genuine desire to do a good job. Seldom are they acts
of vandalism or sabotage.
• They represent a significant threat to safety as systems are designed
assuming people will follow the procedures

Violations are common in our everyday life.

We all break the rules e.g.
–Speeding
–Parking
–‘Do not walk on the grass’
–Using pirate or unauthorized software on our computers

How violations differ from errors

•Errors are unintended. Violations are deliberate (the act not the occasional bad
consequences).
•Violations are any deliberate deviations from the rules, procedures, instructions and
regulations
•Errors arise from information problems.
•Violations are shaped mainly by attitudes, beliefs, group norms and safety culture.
•Note: in the USA violations are more commonly called ‘circumventions’

What sorts of people tend to break the rules?

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•Males; research shows women tend to be far more compliant than men.
•Young people (check out your son’s car insurance premiums).
•‘Experts’

Mental ‘economics’ of violations

Source: J Reason

The violation 'balance sheet'

Perceived benefits Perceived costs

•Easier way of working •Accident to aircraft
•Saves time •Injury to self of others
•More exciting •Damage to assets
•Gets the job done •Costly to repair
•Shows skill •Sanctions / punishments
•Meets a deadline •Loss of job/ promotion
•Looks macho •Disapproval of friends

Benefits are immediate. Costs are remote from experience.

General factors in violations

•Violations have a tendency to become routine because they involve less time & effort.
•Time pressure and high workload increase the likelihood of all types of violations
occurring.
•People weigh up the perceived risks against the perceived benefits, unfortunately the
actual risks can be much higher.
•Organizational culture is an important factor. Most companies have safety as their
stated overriding goal. In reality production is often their first concern.
•If workers believe that the company want them to ‘bend the rules’ to get the aircraft
away, then ‘messages’ from management saying safety is first and follow the procedures
is seen as just covering their backsides
•If new procedures are added each time a bad event is encountered, after a period of

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time it becomes almost impossible to do the job by the book. Violations are therefore
inevitable.
•If managers and supervisors turn a ‘blind eye’ to violations, people will feel that their
actions are condoned.
•Violation + Error = an Accident

Violations at work
•Violations at work are highly susceptible to management influence.
•Most underlying causes of violations are either:
–created by management
–accepted by management
–condoned as normal working practice by management

Types of Violations:
•Routine Violations
•Situational Violations
•Optimising Violations
•Exceptional Violations

Violations:
1. Routine violations:
Things which have become ‘the normal way of doing something’ within the persons work
group. They can become routine for a number of reasons: Engineers may believe that
procedures may be over prescriptive and violate them to simplify a task (cutting corners),
to save time and effort. An example might be : > not changing ‘o’rings believing that the
old ones are OK to reuse.

2. Situational violations:
Occur due to the particular factors that exist at the time, such as time pressure, high
workload, unworkable procedures, inadequate tooling, poor working conditions. These
occur often when, in order to get the job done, engineers consider that a procedure
cannot be followed. An example is using alternative tooling to get the job done quicker
than if the proper tooling had been obtained.

3. Optimising violations:
Involves breaking the rules for ‘kicks’. These are often quite unrelated to the actual task.
The person just uses the opportunity to satisfy a personal need. Driving faster than
allowed to get to the aircraft or stores.

4. Exceptional violation:
Are typified by particular tasks or operating circumstances that make violations inevitable,
no matter how well intentioned the engineer might be.

Do we need procedures that cover everything?

•Not always!
•Detailed working instructions are not needed if the person is trained and competent.

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•Companies prefer to issue work instructions as it is cheaper than training and a
program of competence assessment.

Why do people not follow procedures?

•There is an assumption that people will follow the procedures laid down in the safety
management system.
•When this assumption is broken the whole basis of the safety system is put at risk.
•JAR 145, ergo safety, is based almost solely on an assumption that people will follow
the procedures.

Why do people not follow procedures?

Expectation that the rules will have to be broken to get the job done
Powerfulness, the feeling that one has the ability and experience to do the job without
slavishly following the procedures
Seeing the Opportunities that present themselves for short-cutting or to do things ‘better’
Inadequate Work Planning leading to working ‘on the fly’ and solving problems as they
arise

Reasons for not following procedures

•If followed to the letter, job wouldn't get done.
•People are not aware that procedure exists.
•People prefer to rely on own skills and experience.
•People assume they know what is in procedure.

Bad procedures
•Violations are only half the problem.
•The other half (or more) arises from bad procedures.
•In the nuclear power industry, 67% of all human performance problems have traced to
bad (incorrect, absent or unworkable) procedures.

Situational factors
•Time pressure
•High workload
•Unworkable procedures
•Inadequate equipment
•Bad working conditions
•Supervisors turn blind eye

From our extensive experience of maintenance error we know:

It is rare that one person is wholly responsible for a maintenance error So Why blame
someone?

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Addressing the blame issue - How
violations differ from errors
• Errors are unintended, violations are deliberate
• Violations are deliberate deviations from the rules, procedures,
instructions and regulations.
• Often we condone violation by our cultural norms.

General factors in violations

•Lapses are more often the product of error-provoking situations than error prone people
•The best people can (often do) make the worst mistakes

The way forward

Effective event investigation cannot be carried out unless the issue of blame is well
understood by the workforce and management
i.e. what behaviors will result in disciplinary action?
The first step is to establish a ‘just’ culture.
Not “no blame” or “blame”, but somewhere in the middle…
But where?

Once we’ve broken out of the blame cycle - we will be better able to
•Identify and correct error prone tasks
•Improve error producing work situations
•Identify and correct latent organizational conditions

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Maintenance Error Management

Error management
• Continuous process (should not be incident driven)
• Comprehensive package (no one fix; no magic bullet)
• A prime objective to remove gaps in the defense mechanism
• Components:
- HF training
- Team and coordination
- Workplace, tools, paper and computer
- Organization
- Safety culture - Informed culture - Just culture

What does it tell you?

The hard lesson is:

One person after another knocked on the structure.
Then, install a head bumper.

Error-reduction strategies
• Designed to intervene directly at the source of the error itself.
• Controls error by reducing it.
• Effective to deal with latent errors (organizational short-comings)
• Examples:
- Improving access to a part.
- Improving lighting.
- Providing better training

Error-capturing strategies
•Designed to capture an error before the aircraft departs.
•Controls error by capturing it and giving it a timely correction.
•Effective to deal with active errors (personal failures)

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•Examples:
- Post-task inspection
- Verification steps within a task
- Post-task functional and operational tests.

Error-tolerance strategies
•Designed to build in the ability of a system to accept error without catastrophic or
even serious consequences.
•Controls error by tolerating it and giving it multiple opportunities of detection.
•Effective to deal with both active and latent errors.
•Examples:
- Multiple hydraulic systems
- Multiple electrical systems
- Structural sampling inspection program

Example- Error reduction

•The hard lesson is:

The supply line was connected to the return fitting.
Then, stagger the hydraulic fitting on adjacent hydraulic lines. This prevents
mismatched assembly.

Example- Error reduction

•The wrong electrical plug was •Design and use different-size
connected to an electrical plugs and sockets.
socket. •This prevents cross- wiring.

•A lot of work was needed to •Relocate the access panels

access a component for very and equipment.
simple work every time. •This allows convenient
inspection and servicing.

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Error reduction
In a towing operation, the brake operator failed to operate brakes at emergency.
Damage was sustained. Then, Conduct an investigation. Find out the causes and
recommend corrective actions. Reinforce the rule to put qualified mechanics in
charge of brakes.

Error capture
•To learn the lesson, we must first suffer through the undesired event that serves
to teach us that lesson. Why not make a more proactive approach to agree with
the error principles?
The first basic human factor principle, Murphy's law. Then we should move on to
system integration.

Applying Murphy's Law to system design

Applying Murphy's Law to system design

Example- Use Murphy's Law

•Mission: install the plug into the socket (pay attention to the poles).

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Example- Use Murphy's Law

•Exclusion design: The design of a component or system makes it impossible to

commit an error.

•Preventive design: The design of the component or system makes it difficult, but
not impossible to commit a error.

•Fail-safe design: The design of the component or system reduces the

consequences of errors, without necessarily reducing the opportunity of error.

•The plug can only installed in one way. No reverse installation can be made.

•Instructions are located near the socket to guide the installation; no error follows
if the plug is installed as per instructions.

•System is equipped with additional device to ensure even the plug installation is
reversed, the system can still work.

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System integration

•The focus of the systems integration findings is information on how to integrate

humans into the various systems.
•The task analysis points to human/machine mismatches, work loading of the
human, and many other variables related to performance.

Examples- Use system integration

- The focus of the systems integration findings is information on how to integrate

humans into the various systems.
- The task analysis points to human/machine mismatches, work loading of the
human, and many other variables related to performance.
- Make control column movements agree with human instinctive nature.
- Reduce visual stress- design a dark cockpit.
- Design the crew seat to suit all sizes of pilots.
- Layout a system panel with flow bar lights and flow symbols.
- Have portable maintenance aid (PMA).
- Make it impossible to install a check valve in the reversed direction.
- Make it impossible to cross-connect electrical wires or control cables.
- Follow ATA conventions to write maintenance manual information.

In Dec 1972, a Lockheed crashed in the Everglades swamps near Miami. While
the crew was attempting to replace a faulty nose gear indictor light bulb, the
autopilot was inadvertently disconnected. The nose gear light fixture had not been
provided with a shadow divider between the two light bulbs. The second light bulb
failed when the aircraft was approaching Miami. The unlocked condition of the
nose gear was NOT properly indicated.

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Common features

- Several similar incidents in each case.

- Inexperience / unfamiliarity with task.
- Lack of compliance with manual.
- Night-time working / fatigue.
- Good people made bad errors. Inadequate regulatory /
management oversight. Poor communications / handovers. No one
person is wholly responsible.

Marx’s Law

“In any complex socio-technical systems, the rate of human error events can be
reduced by 50% every 3 years.”
• To start a program, the first 50% may take 5 years, with the first two of
which is setting up the system.
• If you can’t make 50%, it’s because your organization is not really trying.

EM: Basic principles

- Human error can be reduced up to a point, but it can't be eliminated altogether.

- Different error types have different mental origins, occur in different parts of the
system and require different methods of management.
- Safety-critical errors occur at all levels of the system, not just on the hangar floor.
- Measures that involve telling people to be more careful, e.g. warnings, have only

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very limited effectiveness.
- Lapses are more often the product of error provoking situations than error-prone
people.
- The best people can sometimes make the worst mistakes.

Maintenance Tasks

- Inspection, Repair, Overhaul, Modification, Replacement of Parts.

- Completed in accordance with the procedures, instructions and conditions
currently in force under the HAECO regulatory approval applicable to the
particular task.
- Proper documentation of all maintenance actions.

Good Maintenance Practices

• Safety Critical maintenance tasks (Airworthiness Notice 72);

• Shift handover procedures;
• Reuse of self locking fasteners;
• Cleanliness and foreign object/loose article inspections;
• Maintenance manual conformity and use of tooling;
• Preparation of task cards and stage sheets;
• Separate tasking of multiple systems on one aircraft;
• Retention of practical competency by managers/ supervisors;
• Control of blanks, rigging pins and ground lock pins.

Conclusion

• Human Error is Manageable

• The Science of Human Factors, and bit of Systems Engineering can help
• Not matter your position in your company, you can begin to change the
culture, you can make a difference
• Marx’s Law

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Hazards in the Workplaces
- Good examples of where and how a Liveware and Environment (L-E)
interface flaw can occur.
- Performance is impaired due to lack of health and personal safety provisions.
- More likely to commit errors:
Affecting the over-all safety of aircraft operation.
Effects of human error in maintenance are manifested far displaced in time
and location.

Potential Hazards in Aircraft Maintenance :

A thorough health and safety appraisal will reveal the hazards.

Physical hazards may include but not limited to:

‧ 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.
‧Chemical contacts
‧Poor ventilated areas e.g. Fuel tanks
‧Rotating assemblies or powered assemblies,
‧Radioactivity e.g. NDT inspection
‧Electric shocks,
‧Slippery and dark environment
‧Hot and noisy environment
‧Poor access and confined spaces

Hazards in the workplace tend to be a health and safety issue, relating to the
protection of individuals at work.
A maintenance organisation has a duty under health and safety legislation to:
‧ identify hazards in the workplace;
‧ remove them where possible;
‧ mitigate the risks to employees.

Chemical Hazards

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Organizations need to:

‧ Provide suitable training and/or instruction to meet any Health and Safety risks;
‧ Develop and introduce practices and procedures to reduce risks to Health and
Safety including the provision of special protective devices and personal
protective equipment;
‧ Provide for the welfare of employees;
‧ Discuss with and consult employee representatives on Health and Safety
matters.

Chemical Contacts

‧ Toxic materials in aircraft maintenance have become more prevalent :

Composite materials in aircraft structure or other hazardous substances,
such as tank sealants or structural bonding chemicals.
‧ Employees should be informed of and trained on the hazards associated
with handling toxic materials.
‧ Instructing staff in proper handling procedures for preparation, performing
the task and disposing chemical wastes.
‧ Provide staff with protective devices such as protective clothing, rubber
gloves and goggles.

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Biohazard

Radioactivity

‧ Radioactivity
X-rays and y-rays used for inspection are potentially hazardous.
‧ Employees should be informed of and trained on the hazards associated
with handling radioactive materials.
‧ Safety to self and others e.g. Cordoning while carrying out radiographic
inspections

Working Environment

Fumes

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- Irritating, toxic vapors
- Affects performance by affecting visibility and perception.
- Affects performance by paralyzing your brain activities.
Solutions
- Improve compartment Ventilation

Source of fumes

Aircraft materials Source of fumes

-------------------------------------------------------------------------------------------
‧Hydraulic fluid ‧Vapor in the cabin (air conditioning system)
‧Aviation fuel ‧Fuel vapor hazard
‧Sealants ‧Toxic vapor
‧Paints and primers ‧Toxic vapor
‧Mercury ‧Toxic vapor

Lighting

‧Glare and Dim illumination:

- Difficult to see hazards,
‧Flashing or flickering light
- e.g. Beacon lights
‧Exceptionally bright lights
- e.g. Welding

Noise

‧Continuous noise :
- Fatiguing effect,

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 - Reduce the audibility of warnings (noise/signal ratio),
- Affects performance by interfering with the detection and understanding
of task
- Related signals or speech
‧Sudden noise:
- Shocking effect that makes you sluggish.

Temperature

‧Temperature - excessive heat or the extreme cold

‧Excessive heat will cause performance decrement (How much? How long
does it take to occur?)
‧When exposed to cold, body temperatures below 35C are dangerous.
‧Consciousness becomes clouded at 34C.

Work platforms, including movable buckets (cherry-pickers)

‧ Platforms stand several tens of feet from the ground, a slip or fall from a
work platform can cause very serious injury.
‧ Makeshift work stands and carelessly positioned ladders on slippery
hangar floors :
create more hazards and should be avoided.
‧ Properly designed and used work support systems will, in the long run,
be cost-effective because of reduced errors and improved performance.
‧ Hazards and discomfort impair performance, safety, comfort improve
confidence, and thus performance.

Avoiding Hazards

‧Use approved respiratory apparatus in poorly ventilated area and establish

communication with outside staff;
‧Wear protective gloves, goggles, ear mufflers and helmets as required during
maintenance;
‧Extra cautions in handling rotating or moving assemblies;
‧Keep away from radioactive area;
‧Follow company safety procedures;
‧Use approved ….
‧Wear protective … as required during maintenance
‧Extra cautions …
‧Keep away from …
‧Follow company safety procedures
‧The most important things are: Awareness of Hazards, Safety-consciousness

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Warning signs should be displayed to attract the attention of all staff.
The signs should be
‧Visible,
‧Clearly identify the hazards,
‧Describe the danger,
‧Inform personnel what to do.
‧ Positive wordings are more effective: Use “STAY BEHIND THE YELLOW
LINE” instead of “DO NOT COME NEAR”

Dealing with Emergencies

‧ Establish internal emergency rescue team

‧ Ensure safety equipment, special apparatus, first aid kits are available
‧ Ensure emergency rescue procedure in place e.g. Evacuation procedures.
These procedures must be practiced from time to time.
‧ If dangerous conditions beyond control, call outside bodies for help

Reference: HKAR-66 Module 9.8

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Organizational Factors

 How Time-bombs' in the system combine to cause incidents and accidents

Latent conditions:
 Arise from decisions made by managers, manufacturers and regulators
 These are the ‘time bombs’ sitting in the system. In isolation they do not normally
cause accidents.

Latent Conditions + Active Failures = “ACCIDENT”

Active versus latent failures:

 Active failures: Errors and violations having an immediate impact
 Latent failures: Delayed action failures. May lay dormant for a long time, only
becoming apparent when they combine with active failures and a bad effect is felt

System failures
Procedures
Task cards
Inspection
Duplicate inspection
Supervision
Working to Approved data
Quality Assurance

Organisational weaknesses
Management culture
Inexperience
Planning
Financing
Budgeting
Communicating
Purchasing/Logistics
Training
Health & safety
Shift restoring
Pay & reward/Discipline
Production incentives, Goal setting
Policy making
Manning levels

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Recruitment & selection
Leadership style
Organisational-structure

The 'organizational accident':

Stages in the accident sequence:

 Cultural and organizational factors
 Local workplace factors
 Unsafe acts
 Failed defenses
 Events, incidents and accidents

Why would anyone start an airline or maintain aircraft and components?

To make money!

Safety vs. Profit:

 Few commercial organizations can survive a major accident
 In all safety dependent industries decisions are made that balance profit against
the risk of having an accident
 Using accidents as a measure of safety is too crude. If a company has never had
an accident does this mean it is safe?

What sort of company is the most safety conscious?

The one that just had an accident (or nearly did)

Company culture:
 Unwritten, shared values and beliefs that shape peoples behaviour in the

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 company:-
 Shared values - What we think is important (e.g. profitability overrides all
other considerations)
 Shared beliefs - How things work in this company (e.g. “we all know we
have to do it our way to get the aircraft out on time”)
 Behaviour - How we do things around here

What is Company Culture?

"The reflections of the values and style of the leader"

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How different cultures handle safety information:
Pathological:
 Don't want to know
 Message are shot
 Responsibility isshirked
 Failure is punished or cover up
 New ideas are actively crushed

Bureaucratic:
 May not find out
 Something heard
 Responsibility is Compartmentalised
 Failures lead to local repairs
 New ideas often present problems

Generative:
 Seek information
 Message trained
 Responsibility is shared
 Failure lead to far- reaching reforms
 New ideas are welcomed

Organizational processes:

Goal-setting Financing
Policy-making Budgeting
Organizing Communicating
Forecasting Designing
Planning Purchasing
Scheduling Monitoring, etc

Error-producing Factors in the workplace:

 Changes in plans, equipment and routines

 Poor signal/noise ratios
 Inadequate feedback from job or equipment
 Bad communications
 Inadequate work/rest schedules
 Time of day/night effects
 Poor mix of hands-on work and instructions

Violation-producing factors in the workplace:

 Violations are pardoned

 Compliance not rewarded

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  Macho culture
 Low morale
 Poor supervisory example
 Unsuitable procedures
 Bad working practices

Factors promoting both errors and violations:

 Shortage of time.
 Inadequate tools and equipment
 Mixture of inactivity & high workload
 Inadequate training / experience
 Poor access to job
 Poor supervisor / worker ratio
 Workforce told but not heard

Two kinds of defenses:

 Hard’ defenses: provided by fail-safe designs engineered safety features,

automatic warnings, mechanical barriers. etc.
 'Soft' defenses: provided by procedures, rules, regulations, training, licensing,
checking and signoffs, quality monitoring and auditing, etc.

HF accident scenario:

Summary:
 Accidents in complex systems arise from a combination of both active failures
and latent condition--organizational accidents
 People at 'sharp end' are more often the inheritors rather than the sole instigators
of an accident

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  Latent conditions are present NOW. They can be identified and corrected
BEFORE they combine to create a future, accident

Reference: HKAR-66 Module 9.10

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