1 Human Factors 1

8/3/2019 1 Human Factors 1

http://slidepdf.com/reader/full/1-human-factors-1 1/81



AUTHORITY

It is IMPORTANTto note that the information in this book is for

study /training purposes only.

out a ....-'"'''.,.,.,

refer to the

s handbook.

""''Wr'Wo,l.''-4 also follow the.....n the UK)and laid

s, recording, report W1t~.lg,

NOTE

It is policy to review our study material in the light of changing technology

and syllabus requirements. This means that books are re-written and/ or

updated on a regular basis.

-~p -140 Narbeth Drive

Aylesbury

Bucks

HP201QA UK

Tel: (+ 44) 01296433871

Fax: (+ 44) 01296330697

Email: W.Aw.info@licencebypostcom

Website: www.Iiccnccbypo st.corn

mailto:W.Aw.info@licencebypostcom

mailto:W.Aw.info@licencebypostcom



LBP

Additional material due to feedback from students taking the CAAexamination

March 2002.

Human Factors

Drink and Sleep

Alcoholbefore bedtime tends to cause early waking and the wrong kind of sleep-

ie, reduced REM.

Consumption of excessive caffeine will cause lack of sleep and disturb the

circadian rhythm.

a,"rinr1u u•...,..,"'·o height. BMI "'''\·'lILa')i:)

weighs 75kg

and a B....,:,:.....". __

hypertension

the joints), CU~I~::}"'V

\..lJt.:·,,,,, aabetes is also

At temperatures of 60°F/ 15°Chand and finger dexterity begin to decrease. At

55°F/ 12°C dexterity is reduced by half.

Hyperthermia - exceptionally high body temperature (about 41°C and above).

Hypothermia - reduction of body temperature below the normal range.

Hearing

The most common form of hearing lose is age related and the second most

communis-noise related - which is-associated with-damage to the inner ear..

auditory nerve or auditory nerve pathways to the brain. Tinnitus (a ringing or

hissing sound in the ear) is caused by broken or damaged hearing receptors.

Age related hearing lose starts at about the age of 20 and affects men more than

women.

(1)



The frequency of sound is measured in Hz (Hertz -cycles per second) and relates

to the pitch of the sound. The intensity of the sound is measured in decibels (Db).

The human ear can hear frequencies between 20Hz (lower than the lowest note on

a piano) to 20,000Hz (higher than the highest note from a piccolo).

Normal conversation is between 500 to 3,000Hz.

In general hearing protection should be worn by people exposed to prolonged

periods of noise in excess of about 85dB (in some countries this is a regulation).

Exposure to noise levels for long periods of 90Bb can cause temporary hearing

lose. Discomfort can occur with brief exposure periods for noise levels of 120dB.

Pain for levels of 130dB and eardrum rupture at 140dB.

Active •••.0 se Red~..•..tion (ANR)he:>

the 10 ret frequil1,bes and work I .__.,measure. e .... lpient noise. c.,1t;~a;ru~IS5~(~Y.LtI]

noiserfrequency:bf the ambien • tes an an signal of the

same amplitude which is sent to a tiny speaker in the ear-cup. When the

generated signal combines with the ambient signal they cancel each other out and

the result is silence. Battery powered.

Noise protectors for the ears may be PASSIVEor ACTIVE.Passive attenuation is

: ~ r s l ~ .. ~ ~ ~ t E ~ : ~ ! ~ : E e l 1 l i r : t : d s ~ : d o r h e a dprovidp ise reduction of 40dB, again aene:n

variabl§ set out for ear plugs.

larlQi,P'l()reexpensive) at

each ear to

WARNING.Wearing ear defenders can be dangerous as a person will not hear

sounds than can warn of danger - an approaching vehicle, a warning bell, a

warning shout, running machinery etc.

-

Aroutine test for noise is the ability to hear an average conversational voice in aquiet room at a distance of 6ft (2m). Failing this test would require an proper

hearing test (audiogram).

Sleeping Pills

Taken by prescription or otherwise - may be herbal or otherwise. Will tend to

induce sleep or drowsiness, slow up response times and should not be taken to

relieve stress - there are special pills for this. If stress is a problem consult a

doctor.

( )



Miscellaneous

(ACAAquestion of extremely doubtful usefulness). In February 1995 after work

had been carried out on both engines of a 737 a serious in-flight incident

occurred. The cause was poor maintenance practice !ll! lack of rule basedknowledge !!!!

An engineer who develops his/her own way of doing things is almost certainly not

doing the job properly.

Motivation is concerned with reward (cash, praise etc) to increase performance

and reduce errors.

The

(ACAA l l . i ' < · A : < 'C'T1r'"

artificial :

depend

The overall ideal behaviour of a good engineer is to be both goal and person

directed.

The best method of checking long term memory is to use checklists.

Peer Pressure

This is the feeling a person gets to try to perform well to meet the actual or

perceived expectations of others in the same group (the peer group) - work

colleague~~_

Sight

In short sightedness (myopia) the eyeball is too long and the image falls in front of

the retina. This can be corrected by wearing glasses which have concave lenses.

(3 )

-~.

~-



CONTENTS

Human performance 1

Accidents 2

The human body 5Vision 5

Hearing 9

Noise 10

Touch 12

Smell 12

The lungs 13

r7fhe"cittlmosphere

sure

thing

circulation system

The

Mental workload

Fitness/health

Sleep

Fatigue

Stress

Peer pressure

Harassment

Drink and drugsPhobias

Fitness for work

PAGE

The working environment

Heating

Lighting

Colour rendition

Air quality

Vibration

Noise

The work place

ClothingBody pO~lft:t'7'J'"'"~

Body

Working alf:U:p~,U

Repetitive

RSI

InspectionVisual .

plex sys LC;lU;:f::t~:!ICl;:'.I\.;:'

26

27

29

33

34

36

36

39

41

42

PAGE

47

47

48

49

50

50

51

52

5253

55

57

59

61

62

64

66



HOW TO TACKLE THESE BOOKS (1 & 2)

Human Factors is split into 2 books. The split is arbitrary, with both bookstogether covering module 9 of the JAR66 syllabus. The books are written to the

category B level, with the following areas studied to a lesser extent for the

category Aperson:

* Accidents - Murphy's Law.

The bodily functions.

Human error.

Hazards in the workplace.

*

*

*

All other sections should be studied to the same level as the category B person.

ro~tl,mlent"nd the "dome

sical part and the

adeup

*, . . . .*

*

**

*

*

*

*

to describe

.ty for ,,-.I\.(1JI"'lUH ...

19t1tiU~eror exampl

t is madi:';' p of the physical

social psycho 9 ' .cal environment

Something about the Human Factors element in the cause of

accidents.

The rudiments of how the body works - in particular: the brain;

the eyes and the ears.

Howhuman factors affect performance - the physical condition

and the mental condition.

About self-certification for work.The physical parameters that make up the ideal work

environment.

The social parameters that go to make up a good working

envirorrrnent.v:

About communication and dissemination of information to ALL

involved with aircraft operations.

Howdifferent tasks affect performance, and related hazards.

Something about "errors" and how to avoid them.

Some of the material in this book you should find fairly straight forward -

much of the work related information for example. Other parts will need a littlemore effort (egthe human body and the brain) and may require more than one

read through for the information to "SInk in)':E:~-=~.~.



HUMAN PERFORMANCE

Human Factors or Human Performance is concerned with the relationship of a

person (the worker) with that person's surroundings. Its study, called

ergonomics (biotechnology in the US) is concerned with safety and improved

output in the workplace.

The "person" is made up of the physical part (the body) and the mental part

(the psychological make-up), and the "surroundings" for the purpose of this

book is split up into the domestic or non-work environment, and the work

environment.

Our main concern is the relationship between the person and his/her work

environment, but the physical condition and mental attitude of a person does

not depend on this alone, but is affected by hereditary factors, historical

factors and the non-work environment.

lUl~~~~!e hereditary lal;LO~7fl~~

Rlfj~\~rtr1:ti"N1Ub~proved,nd we

trafficin discipline with the obje

professional relationship with others and a better interaction with their work

environment.

The person - physi

The "domestic"

The work

~. . . ')

•. . . . 0 0

INPUTS PERSON

Fig. 1 INTERFACE OF "MAN" AND ENVIRONMENT

1 -



Ifwe know more about how the body works; it's thought processes; it's inputs

and outputs; and the conditions required to help it perform better then we

should be able to carry out our job better. We should also know about the

organisation of the workplace and the management structure designed around

the human performances element.

ACCIDENTS

Murphy's Law

If anything can go wrong then it will go wrong. If there is a task that can be

performed incorrectly then someone will do it incorrectly. In an ideal world the

designer of the aircraft/ systems should make most tasks "Murphy proof' (the

hydraulic quick release connections are all different sizes, for example, so they

cannot be fitted the wrong way round). This type of solution is not always

possible - so we have to be forever aware that a task can often be performedwrongly. . . . . . . " I

1 . . . . : . " .

~.> .

If the \ e ' i gineer is aware of this, of the danger~:.Q;l.H"

carry ••••••••.to minimise these po then accidents

g to think that accideh ..~p,

to think that that

titude, with

rated to safe .....~ ...·.,

!.:.:.:.:.:/

Accidents can occur because of one error or may be the resurt of several quite

unrelated errors.

In the latter case people/organisations may have contributed to the accident -./

many years prior to it actually happening. The object of the exercise where all

the work is recorded and signed for on an aircraft means that at any time

records can show who has been involved - from the production of the raw

metal, to the designer, to the draftsman, to the manufacturer, to themaintenance engineer.

The whole history of the aircraft and it's components can be traced back to the

smallest rivet. In this way if-anything-goes wrong thenreeords will show the

history and, hopefully, where the error lies. This is not to say we need this

process for punishment purposes, but to find out what went wrong with a view

to learning and putting procedures into place that will help prevent the same

thing happening again.



Single Cause Accident

Almost non-existent - a man walking into a lamp post is a good example -

possibly. He might have been stressed-out due to domestic troubles, pressure

of work or a number of other, seemingly, unrelated events. So it might not be a

single cause accident.

Most accidents are the result of a chain of single events occurring in aparticular sequence, with many of the single events occurring many times

before. Statistical surveys have shown that for every major accident as many as

600 precursor single events have occurred - but not all together, or in the right

sequence to cause an accident.

Multi-cause accident - example 1

to engine ~~:1~~~g~t? Wereduties? What to the lad

as the family hurry? Did he

trating? W mentally alert

",,,, , , ,· , ' ,.:s:'thu training/ tui

So this one accident brings out several points. Some or all could have been a

contributory factor in the accident. In is not within the scope of this book to

analyse the accident any further but you can see that many things could have

been wrong from management procedures to just one person's actions.

Multi-cause accident - example 2

A large transport coming into land. The pilot selects another fuel tank, theengines fail, the aircraft crashes with all those on-board killed as well as loss of

life in the houses into which it crashed.

The chain of events:

1. The fuel NRV(NonReturn Valve)was designed in such a way that

it could be fitted in the fuel supply pipe either way.

Amaintenance engineer fitted it the wrong way round (Murphy's

Law), even though an arrow indicated the direction of fuel flow.

2.

-3 -



3. He failed to test the system after valve replacement.

4. The pilot selected the (new) tank on approach - against the rules.

5. Fuel was not available from that tank due to the incorrect

positioning of the valve and the engines failed.

6. There was no height and no time to correct the mistake and the

aircraft crashed into a residential area.

Some analysis of the events

1. The design was at fault in not designing the valve as Murphy Proof,

but was it the designer or the design organisation? Did they have a

policy of Murphy Proofing? If the valve had been designed so that it

could ONLYbe fitted the correct way round then there would not

have been an accident.

The maintenance engineer was at fault because he failed to check

the flow direction arrow on the body of the valve and, cardinal sin

of all, failed to carry out a functional check afterwards. Was hepoorly trained? Was he in a hurry? Was his mind on other things?

Did the pilot for'tg.¢i" ..ot notice he wa /.' in then tanks being used? ' ' V Y ' ' s his d on ot.her

Each ~v nt in this chain, by it ••

accidt~, but get each event inl~'"~~~~~:)'U

M U l t i l l use ac

~ ~ : t c l 1 k r l q ~ fi~~~e incide il~e~~~~":::'l"f~':+,t,;;~erCialt:r~~~~

the WIndscreen when it blew ~~~~:-;::: saved by the of the

crew who held onto him.

2.

The windscreen was fitted by a maintenance engineer using the wrong

bolts! screws. They where such that they did not engage with the threads of thev-->'

anchor nuts correctly. When the aircraft pressurised at altitude the windscreen

blew out and the rush or air sucked the pilot out --at least most of his body

was out when he was held onto by his legs. Only the quick thinking of his crew

saved his life.

The windscreen was a replacement on the ramp. Time was short. The aircraft

had to be turned round. There were other aircraft to be turned round also, and

schedules andtake-cff slots to be met: The shift was not-up to full strength.

This was an unscheduled defect with no spare capacity to fix it. The pressure

was on.

Should planning have ensured that shifts were up to strength? Or should there

have been a back-up aircraft (expensive) so the defect could have been rectified

later when there was less pressure on time. Should there have been a back-Up

rectification team?



Were the procedures in the AMMspecific enough, and available? Was all the

correct equipment available - tools, access ladders etc?

Was education at fault? Is it possible that someone might think that the

aerodynamic force on the windscreen is high enough to overcome the cabin

pressure? (Thewindscreen is fitted from the outside).

There are many other questions to be asked about the accident, which the full

enquiry that ensued went into - and recommendations made.

Conclusion

It has been established that Human Factors is the most frequent causalfactorin air accidents.

better idea of how a p

to understand at leastssom

ility to

*

*

** c : • • • . • • • .• . . . . .

Also covered will be the function of the brain and the "back-up systems" such

as the heart, breathing and the circulation system.

Most important to learn are the sight, hearing and brain functions with the

other subjects discussed to a lower level.

Each subject will be covered on a descriptive basis with comments associated

with its relationship to theworkplace and some likely consequences of that

particular function not working properly.

VISION

Of the five senses this is the one that is more useful to man than any other.

Most of the brains information comes from visual images. We are more aroused

to anger or passion by the visual inputs than by, say, feel or smell.

The basic structure of the eye is shown in the next drawing.



The eye acts very similar to a camera in that light is taken in through the

cornea and lens. The lens is attached to the cornea by small muscles which

helps change the shape of the lens to focus the beam into a sharp image onto

the retina (the image being upside-down). Receptors on the retina generate

nerve impulses which are sent to the visual centre (iconic memory) of the brain

via the optic nerve.

The iris will control the amount of light entering the eye by altering the size of

the hole in the middle. It can change shape very quickly - changing the

luminance level by up to 5 times.

The light can also be adjusted by a change in the chemistry of the retina - but

this can take up to 30 minutes depending on the changed conditions.

Luminance level changes up to 150,000 times can be catered for.

IRIS

OPTIC NERVE

/

MUSCLES

• . • • • . ! ' f ! f T CHANGE

f · · · · y . t : f f S SHAPE

}<>:L . ,I

LENS

CORNEA

Fig.

This means that when the eye experiences a change in light intensity the iris

can react quickly to cope with 'reasonable' changes. But if the change is, say,-

from normal daylight to the dark room of an NDTx-ray investigation room then

the eye (retina) will take time to adjust to the new conditions. You might have

noticed that when changing from light conditions to very dark conditions - it

takes time to get used to the dark.

When the light intensity is low the eye can only see in monochrome (black and

white). So where colours are involved - certain NDT techniques and colour

coding of electronic components for example; are involved, reasonable light

levels and good light rendition conditions should prevail (see later chapters).

6



When we read (this print for example) the image is projected into the centre of

the retina where the acuity (acuteness of vision) is at its highest. This centre is

called the Fovea where there is the largest number of cones (Cones are light

receptors and are essential for good acuity). The surrounding part of the retina

has poor acuity but is more sensitive to movement, flashing lights etc. In our

more primitive state we would catch the movement of something in the jungle

in our peripheral vision although we could not actually "see" what it was - we

would be alerted to any danger.

Dangers to the eye include foreign objects, fluids and certain light sources.

When carrying out any task that might involve flying debris - grinding, milling,

wire cutting, drilling, dealing with hazardous fluids etc, then protective goggles

(to BS specifications) are to be worn.

Ultra violet (uv) light - from the sun and other sources (NDT)- is harmful, as is

also blue light.

to the retina are

UQ.uU;;~Fl'o;;'::::'IIV the blood vessels in

cause damage t~:tl:.... :. . ~ f.11ffii~~),~ uv light .....A.·,u s c"6..Pte safety glasses (to B when using

.........~"~!'5 these spectrums ( example). It is

sunglasses when t sunlight.

with

Long sightedness is caused by the distortion of the eyeball which shortens the

distance between the lens and the fovea. This means that the focussed image

falls behind the retina. This will cause blurred vision when looking at relatively

close objects unless the combined refractive power of lens and cornea can

focus the image correctly.

Short sightedness is caused by the lengthening of the distance between the

lens and retina with the result that the image focuses in-front of the retina -unless the eye can correct for this (as above). Distant objects will be out of

focus whilst near objects will be clear.

,~Dlasses / contact lensescan correct for both theabove.-

Good sight is important but if a person's vision is less than perfect then

glasses, contact lenses, imaging enhancing equipment such as magnifying

glasses etc, good lighting and job matching can assist considerably in

satisfactory task completion.



SHORTENED EYE

LONG SIGHTEDNESS

IMAGE BEHIND RETINA

NORMAL EYE

IMAGE FORMED ON

FOVEA PART OF RETINA

C 3 " 0 0 2 4 ~ ' > , _ LENGTH ENE D EYI5(RTIfmIill37--It~~-=~f.l SHORT SIGHTEDN

\""ljVIr\,U~ FORMED IN

OF RETINA

Fig.2a

our b~dness (where d,,''t'IPr',=,(

rare,l.lJ. pri~d the ~erson .•...

not ~qtgreanY' colour Identl1!!.·.~•.~lID.~1:satisfactorily.

The most usual form of colour blindness is Daltonism (red blindness) - in

which the person has difficulty it distinguishing between reds and greens.

Again job matching is called for and the person should not work in any

situation where colour identification is required. Medical opinion should be

sort with eye tests to establish the exact extent of the condition. The engineer

should contact management and inform them of the condition.

Colour blindness is usually hereditary but may occur due to retinal disease.

It goes without saying that the eyes are the most important tool in the

engineer's arsenal of non-destructive testingtechniques - look after them.':



HEARING

The hearing system is made up of:

* The outer ear - from the ear flap to close-to the eardrum.

The middle ear - from the eardrum (tympanic membrane) to the

cochlea.

The inner ear - includes the cochlea and auditory nerve.

*

*

Noise is modelled as sound waves whose amplitude defines "loudness", and

frequency defines "pitch".

The sound wave travels down the canal in the outer ear and strikes the

eardrum.

The eardrum will vibrate at a corresponding amplitude and frequency and

,.... transmit this movement to 3 small bones in the middle ear. (Interestingly

~ ~ ~ ~ i : r ~ ~ c ~ ~ ~ a m m e r . p]. This m o v e itted t o) 1

.';:.

Fig. 3 ANATOMY OF THE EAR

Vibrations of the fluid in the cochlea will trigger nerve impulses which pass to

the brain via the auditory nerve. The brain "hears" the sound.

To allow the air pressure to equalise across the ear drum the inner ear is

connected to atmosphere via the eustachian tube which leads to the throat and

nose. There is a small flap valve in the end of the eustacian tube, which allows

air OUT-of the middle eaflWlien-IncfeasiI1g altitude inan aircraft - increasing

cabin altitude, decreasing pressure - for example).

When descending (decreasing cabin altitude - increasing pressure) this valve

can shut and stop air going INTOthe middle ear. This can cause lack of

pressure equalisation across the ear-drum causing distortion and pain.

Swallowing or yawning may assist the air to pass the valve.



Part of the inner ear structure is the semicircular canals. These canals are

connected to 2 balance chambers and filled with fluid.

Movement of the head will cause the fluid in the canals to push against sense

receptors, which send signals to the brain - to assist in balance.

Also pendulum like sensors in the chambers note any movement and send

balance signals to the brain.

Also other signals are sent to the brain such as vision signals to "compute"

balance.

The auditory nerves are connected to the brain in such a way that the direction

of the sound can be ascertained by the listener.

Damage to the ears can be caused by poking things into them. Don't, it could

cause the ear-drum to become punctured. Apunctured or burst ear-drum is

CalcM.tWI!panic ==»: . it is .very painful ult inhenR . ss, bleedmg and Inhe ear).

v .

i 'V"·

It is# the smallest thing

to the ear due to pres~Y~,&.ij~~_ge..trauma. (Otic = ear.

medi

Dam. to th~ar due to s u. ~..

be te ~ard is called , . . -< I'- " " "" J . .. .. .. .

. . . . . 1

Any \ V a X Infl1ei

ear that might cause u.~.,vu~

be removed by a medically qualified person.

Noise can also damage the ears. The result of Noise Induced Hearing Loss

(NIHL)may be temporary at first, but continued exposure to excessive noise

will cause permanent damage and hearing loss.

Noise

Noise is measured in dB (decibel). It is one tenth of a bel and is a ratio of a

nominal "sound" to the sound level in question (named after Alexander Graham

Bell).As-at6ugh guide to sbUhdlevels:

30dB

50dB

120dB

Noise in a library.

Noise in an office.

Close proximity to a large jet aircraft during an engine run.

()



Sound levels above 90dB can cause hearing damage - and the longer the

exposure the greater the damage, eg the same damage can occur from the

following:

90dB for 8 hours

103dB for 30 minutes

116dB for 1 minute

NOTE.The dB scale is a logarithmic scale (it is non-linear). This means that an

increase of 3dB will in fact double the noise level.

From what has been said it is important to protect the ears from excessive

noise such as:

* Operating noisy machinery - "windy" drills for example.

When involved with ground running jet engines.

When close to noisy engines - combustion engines, running

aircraft on the ramp etc.

*

*

problem use ppr~{~L~~l¢l~ders. Remem

" ' ' ' '' ' . '' ' ' • .• ' - '' I ' i' ' '' ' ';~ they can cut-out nv."",~" t warn you of Uq,l,lJr.';_'A

out an engine hear a

u"",.uu.'.V""",,,V be visually more <:lnT'~F.'" going on

defenders.

Ifyou are going to be in the flight when cabin pressure testing then you

should be medically cleared in relation to ear damage such as a perforated ear

drum and you should not have a head cold/flu that might block the eustacian

tube/sinuses.

Age

Hearing ability, like most bodily functions such as sight, tends to g(!tworsewith age. Interestingly, the frequency of sound that the human ear is most

sensitive too is about that of a woman's scream. As we get older it is the higher

frequencies that we lose the ability to hear first.

Hearing is a valuable tool to the engineer. Tuning a radio would be difficult

without it, and the sound of a failed bearing in a rotating assembly gives an

immediate aural indication that something is wrong.



TOUCH

The sensation of touch, to any part of the body, will send a signal to the brain

to tell us if that surface is hot, cold, vibrating, smooth, rough, sharp, wet, dry

etc.

The hands can check (carefully) if the heater of a Pitot static probe is working.

The hands can feel, where there might not be visual indication, if a seat

cushion is wet.

This sense of touch or feel also lets the brain know if injury has occurred. Prick

your finger on a pin and you will soon be 'told' about it.

Touch sensors (nerve endings) are distributed allover the body but are

concentrated in the hands - more particularly in the finger and thumb ends.

lq),i+~~~Ql t some oils

- as as fuels. Fire is usu first -

beca •••...f we

r:it by feel t be too

~~~ti 'h~W~~~h:~~l:I-" .............~~.

between in ·lVl uals - sensiti

qJ<,-\l<u.tiono another.

dr1~()Jth'eln,nd different

A "smell" is no more than molecules floating in the air. They are breathed in

through the nose and are caught by mucus on fine alfactory hairs situated

high up in the roof of the nasal cavity.

The molecules dissolve in the mucus and stimulate the hairs to send signals to

the brain. We smell!

Colds and flu can affect these sensors so that the sense of smell is reduced.

All the above functions - smelling, feeling, seeing etc, have to be supported by a

system their-gels oxygen out of theair anrtpump it aroundthe body to be used--

throughout the body in the process of metabolism. This system is the lungs

and the circulation system.

- 12 -



THE LUNGS

Before we look at how they work we should know something about the

atmosphere. This should be revision for most of you as a knowledge of the

atmosphere is required for such things as Pitot static instruments, engine

running and cabin pressurisation.

The Atmosphere

This is an envelope of air that surrounds the earth. It is made up of gases and

is defined by its temperature, pressure and density. Because these parameters

vary so much from place to place around the world; and from day to day at any

one place an ICAOstandard atmosphere has been established.

As far as human factors for engineers is concerned we are more interested in

pressure, temperature and composition at sea level - or close to sea level. ForPilot~?i1'fme interest altitudes.

(-::.:,

QUESt. N:Can you state what how

they change with alWi"~~u",

Composition: 21%

ratios change little

:::: gas ~duces.

' : ; f e r e , i r 2 : ! ~ C ; ~L . i _ _ _ _ j _ J I J 2 r r E 8 0 9

The body needs oxygen for all it's functions so it is fortunate that there is some

at all altitudes.

H EIG HT IN F EE T

S EA L EV E L

ZERO 10 PSI

PRESSURE 1013.2 MB

Fig. 4 GRAPH OF PRESSURE AGAINST ALTITUDE

- 13 -



Temperature. For ideal working conditions the temperature should be

appropriate to the work in hand. Physical work in non windy conditions is

comfortable at temperatures down to freezing point whilst sedentary work at a

desk would require temperatures at around 20°C. Appropriate clothing,

heating/ air conditioning should cope with the temperature parameter. In

extremely cold conditions outside exposure times should be kept short.

Pressure. This is where the lungs corne in. At sea level there is plenty of it - at

altitudes there is not.

The pressure in the atmosphere causes a partial pressure to occur across the

tissues of the lungs. This means that oxygen diffuses across the lung

membrane into the blood stream. It is then transported to all parts of the body

for the various metabolic processes. This is all fine at sea level where there is

plenty of pressure. At altitude it does not work so well.

AIR

TRACHEA

Fig. 5 THE LUNGS (ONE LUNG SHOWN)

At high altitude the partial pressure across the tissues of the lungs is reduced ..._J

(due to the lack of atmospheric pressure) and less oxygen diffuses into the

blood. This can cause hypoxia (insufficient oxygen getting to the body tissues).

Hypoxia causes reduced mental capability, and if severe enough can causeunconsciousness and can be fatal. At high altitudes death can occur in a few

minutes with sudden cabin de-compression - unless something is done

quickly.

QUESTION:What can be done if sudden decompression takes place at altitude?

(5 mins)

ANSWER: 1. The pilot em cause the aircraft to descend quickly.

2. Emergency oxygen can be used.



For normal operations we can get round the hypoxia problem by providing

oxygen when flying at altitude andj or by pressurising the aircraft.

Providing continuous oxygen for passengers on civil aircraft is not practical,

and even then would only work up to an aircraft altitude of about 34,000 feet.

So pressurisation is the answer.

BLOODHIGH

INCOz

If R

IaLOODHIGH

INOz

/)

ai . t, t are pret l l ~ a i r r i i < t altitude is Some are

pressurised to higher cabin altitudes (less actual pressure acting on the body

and lungs) with a continuous oxygen supply.

Breathing

The action of the muscles on the chest wall and the lungs diaphragm causes

an INbreath. Relaxing the muscles allows the air to be pushed OUT.

The air that is breathed in is high in oxygen. Transportation of oxygen into the

blood stream and transportation out of the blood stream of carbon dioxide

means that the air leaving the lungs is high in carbon dioxide and low in

oxygen.

Breathing rate is automatically controlled by the brain. When oxygen levels

drop in the blood stream then breathing rate is increased.

1 ,-"

1:;)



THE CIRCULATIONSYSTEM

The heart pumps de-oxygenated blood from the body to the lungs and also

pumps oxygenated blood from the lungs to the body. It is an automatic

function that is controlled by the brain.

With exercise the heart rate is increased to provide more oxygenated blood to

the body to allow for the increased metabolic rate.

LUNGS

1tHEART

RIGHT SIDE LEFT SIDE

- 1

Fig. 7 THE CIRCULATION SYSTEM

Decompression Sickness

If the atmospheric pressure on the body is reduced too quickly then thenitrogen in the blood comes out of solution (forms gas bubbles).

These gas bubbles get into joints and can be painful - they can get into the

brain andean be fatal.. -~--

This condition is commonly called 'The Bends' (back pain experienced by

divers). It's medical name is aeroembolism.

Fortunately decompression sickness is rare but it can be a problem if the body

has been pressurised shortly before a flight.

- 16 ..



If this happens the body can experience a pressure change from say, 22psi

absolute (as when inside the pressure hull of an aircraft during a ground

pressurisation check) to l lpsi absolute at 6,000 feet (as when flying as a

passenger) - a pressure change of l lpsi. It is the change in pressure that

causes the problem.

The body can get "pressurised" in several ways:

* Divers use pressurised air when diving.

Engineers get "pressurised" when in the aircraft during a ground

pressurisation check.

People can get "pressurised" in a baric chamber (pressurised

chamber). Used for medical and testing purposes.

*

*

It is MOST IMPORTANThat you do not fly for 24 hours after being

"pressurised". Even if you fly in a pressurised aircraft the 6000 feet cabin

altitude can cause decompression sickness.

---_



THE BRAIN

This part of the book deals with the functions of the brain. It is the body's

computer to which all the senses send information, and it is in charge of all the

bodily functions - both automatic and those actions under our control.

THE BRAIN

MEMORY

PROCESSOR

FUNCTIONS

OUTPUTS

AUTOMATIC FUNCTIONS

BREATHING

HEART RATE

TEMPERATURE

BAlANCE

ETC

NON AUTOMATIC FUNCTIONS

RUNNING

TAlKING

EATING

MANUAl SKILLS

ETC

INPUTS

EYES· VISUAl

EARS·SOUNDS

BAlANCE

MOUTH • TASTE

NOSE· SMELL

~DS·FEEL

ETC

Eyes - vision

Ears - sound and

Nose - smell

J . L l ~ s -t~~~~h y;

The Ibrainalsoteceives signCUli;;..a4Xl~~8:·n·····er, 02 levels

others.

Large areas of the brain are devoted to memory, and the brain controls the

automatic functions such as heart rate, breathing rate etc. It is also in control

of motor functions - those functions we can control at will - blowing your nose,

eating a sandwich, forming a rivet, playing a piano etc.

Memory

This can be divided up into Long Term Memory, Working Memory and Motor

Memory..Long Term Memory can be.further divided into Semantic Memoryand

Episodic Memory.

Semantic Memory. This includes the knowledge of the things we have to do.

The understanding of words, phrases, numbers etc. We know the meaning of

things from this memory area.

_ 18 -



This memory - once stored successfully is never lost. Ifwe are unable to

remember anything in this part of the memory then it is because we cannot

retrieve it (recall). It is there but we can't find it. Can be very frustrating.

Episodic Memory. This part of the memory system deals with "episodes".

Specific events are stored here. Aday at the sea-side, jacking an aircraft etc.

It is interesting to note that this part of the memory is not static. The actual

event can be changed in the mind. This means that when asked to recall an

incident, any two people will often give conflicting reports. This can be very

difficult for accident investigators when collecting eye witness evidence.

An important note here. Ifyou are witness to an accident/incident getting

photographs (ifpossible) and writing it down immediately is more valuable than

the best memory in the world interrogated some time later.

SEMANTIC

M E M O R Y

EPISODIC

M E M O R Y

PERMANENT.

W O R D S

N UM BE RS E TC

SPECIFIC

E V E N T S

Fig. 9 MEMORY

Working or Short Term Memory. This area of the brain allows the storage of

information for short periods. If nothing is done to try to remember something

more permanently then, 10 to 20 secondslater, the information is lost.

Looking up the index in a book to find a page number for a particular subject

would use this part of the memory. Once the page is found and the information

on that page is studied the page number is forgotten.

- 19 -



Unless actively rehearsed information in working memory is lost in about 20

seconds.

This memory is strictly limited in size. The number of items that can be

retained can be increased by "clustering" or "chunking". For example the

numbers "0" and "1" and "8" and "1" can be remembered better by puttingtogether in one cluster - 0181. 0181 is remembered as one cluster as opposed

to 0, 1, 8 and 1 being remembered as 4 clusters.

Motor Memory. This is associated with skills. Motor in this sense means the

movement of hands, feet, legs etc. Skills with hands are often known as motor

skills.

When performing a new task a great deal of control processing of information

will be required by the brain. But after practise the task can be carried out

automatically.

Stage 1. Cognitive

action using the cen

though t has to

of the brain.

Stage 2. Associative

become integrated ~1(;k;teS~{(:l~'a

a task

is so well

With a little practise each separate element of the driving process is learnt but

we have to be careful when moving from the 1st element to the 2nd etc. -;»

When well rehearsed, we can get into a car and ma.ke very little conscious

thought of how to drive. We can concentrate our central processing powers on

the road conditions etc. Having a detailed conversation about technicalsubjects is easy with only a monitoring function of the brain lift to check the

process of driving.

-Motor memory can produce errors. Making-a-cup of tea and pouring the hot

water into the milk jug for example.

Sensory Store. Made up of separate memories for each sensory system where

information is stored for a very short time. Examples include - Iconic Memory

where information from the eyes is stored for between 0.5 and 1 sec, and

Echoic Memory where information from the eyes is stored for between 2 and 8

seconds.

_ .-=-="""='~-~~



Information Processing

Information is got to the brain via the senses - eyes, ears etc. This stimuli is

held in the sensory store for a short time. The information is then sent to the

attentional mechanism of the brain.

From the attentional mechanism the information is sent to the perception area.

Here the information is actually perceived. It is perceived in the form of shapes,

colours, sounds etc, which we recognise as a particular message, pattern etc.

STIMUli

(FEEl.

SIGHT.

SOUND

eTC)

CENTRAL

P ER c: ep 1 'I l~ • •il~~ PROCESSOR(DECISION

MAKER )

Fig. 10

Once the information has been perceived it is sent to the central processor.

Here decisions are made on what to do - or what not to do. Information is sent

to, and/or received from short term and long term memory to help in the

decision making process, and an action is finally decided upon.

Motor memory gets involved for those skills where little active decision making

is required. It gets data from the attentional mechanisms which is monitored

by the central processor.: "

-21 -



In general the following process applies:

STIMULI (SOUNDS, SIGHTS ETC)

u

RECEPTORS

u

SENORY STORES

Separate store for each of the senses. Short term - 1 second for sight -

8 seconds for sound. Allows information to be stored until we have

processing capacity to deal with it - eg, the chiming of a church or wall

clock. We may not actually "hear" the first or second chime, but once we

are aware of the chimes we can count them using the first chimes storedin the sensory short term store.

< 1

· · · · · · L f J1r ! ·....oiv·e~the conversion into m(~ijp,.itf1~

. slllitp'esetc. It is a co Involving concepts iitthin~lmc,rv

Much of the information that is sensed is held in the sensory stores We

perceive, or become aware, of what we are hearing, seeing, smelling etc.

What we perceive is often conditioned on what we EXPECT to perceive.

In other words the information is taken in and compared to information

held in memory. If the information taken in is not complete we may

"complete it" from information in the memory. Listening to a pilot talking

over the RT for example - It is often the case that we do not understand

what he or the other person is saying (codes - interference etc). But bothparties know what to expect in the conversation so only hearing parts

of it is not a problem.

u

CENTRAL DECISION MAKING

Once information has been perceived a decision has to be made what to

do with it.



It may require immediate action - turning off a flight-deck warning when

carrying out tests - the warning might be left running; the information

stored in working memory; and the engineer works out what to do about

the reasons for the warning.

During the reasoning process the central processor will use stored

information from long term and short term memory. Itwill also sendinformation to these centres.

Also during this process a decision is made to store the information

in short term memory or actively learn it and store it in long term memory.

u

ACTION

The action, when it comes, will produce feed-back. The audible click of a

switch when a light is switched ON - the visual image also. The noise,

the feel, the sight of forming a rivet with a riveting gun. The visual image(in the mirror) of putting a tie on.

This feed-back ( TlU,".·.M nua''nt/;~l''help to complete

allowing us to ""T"T"P,'n", " part of)that is not M.h-..t~t

LU.•q;:;:"""V....text it is information

..rtormed. It is calledand ..I"'. , . . t-·r.-~:Oh,

* The feel of a switch when it operates correctly.

* The sound of the switch when it operates correctly.

* The visual feed-back when the light comes on.

Steering a car is a good example. The wheel is turned to start to go round a

bend. The image to the eye (and possibly sideways accelerations to the ears)

shows how the car is positioned on the .roadat the start of the bend. This feed-back information is sent to the brain so as to initiate responses to correct for

any oversteer or understeer. This process will happen continuously as the car

proceedsround the bend.

With some driving techniques you can actually see the steering wheel being

corrected back and forth over a limited range as the car proceeds around the

bend. (Formula 1 racing cars showing steering techniques with a cockpit

mounted television camera for example).

- 23 -



The response time - the time between the receipt of the information by the

senses and initiation of an action - can vary considerably.

Response Time

In very general terms response time and accuracy are inversely proportional to

each other. In other words the faster the response the less accurate it is likely

to be. If you slipped from a ladder at height your response would be immediate

and you would grab at anything, whether it broke your nails, cut your fingers

or broke the item you grabbed at. Ifyou had warning the ladder was about to

slip and there was something to grab onto, then the action of doing the

grabbing would be more accurate and hopefully no damage to fingers, finger

nails etc.

Ifarousal levels are high eg, frightened of heights and working at the top of a

ladder then response times are shorter, but less accurate.

AU~QrY~timu1i (a shout "Loi*,oW~i.Sl'Rore likely to a

visual.a imuli - and hence the to be in error.

warn means "get out of my for example).

Ifwe

some

For e re(I:~':::lloVa'ing forOTR'if!OT'I:f. If, when the r",t"t:::t\!:>rn

:rel:t-t:t~:;l1'IDstikely

was expected.

Another example of incorrect response is the testing of a Pitot static probe

heater. It is switched on and tested carefully with the fingers. If it is switched

on we expect it to be very hot - if in fact it is not working and we are about totest it we 'tap' our fingers quickly on the probe, withdrawing them immediately

expecting it to be hot (an incorrect response to a cold object), but it is the

response to the stimuli we EXPECTED.

The 2 examples above show a marked difference in the outcome of the

response to an expected stimuli. The first one is inherently unsafe, whilst the

second is inherently safe.

In general the older we get the slower the response times.



Factors affecting attention

Stress. This will usually increase a person's arousal and affect the perception

process. With high stress levels, sampling rate is increased but to a narrower

range of stimuli. This means that in a stressed condition a person is likely to

miss something that is important because the attention is reduced to a limitednumber of channels.

Mental Workload. This may be increased by:

* Stress levels of the operator

Task complexity

Time constraints

Available skills for the task

Mental attitude (subjective state of operator)

*

*

**

Mental workload is considered to be the relationship between the imposed

demands of a task and the of channel capaci those

de "di\. ,..I

l ,...

GOOD

P 7 ! R M A H C E

~ d~.~.. . lPOOR

LO W WORK lOAD HIGH

Fig. 12 GRAPH OF WORKLOAD AGAINST PERFORMANCE

The graph shows the relationship between workload and performance. If the

workload is too heavy then stress levels increase and performance suffers.

If the workload is too low then concentration is reduced, boredom can set in

and we can lose interest. The channels are not monitored as they should be

and mistakes-and accidents can happefLSe-there is a happy medium to be

achieved.

Overload may come in two forms - qualitative - where the task is complex and

too difficult to perform, and - quantitative - where the tasks are simple enough

but there are too many of them.

~'nn"""""

. 26 -



FITNESS/HEALTH

There is nothing like "good clean living" to improve ones performance with any

task. This includes:

*Awell balanced diet

Regular exercise

Regular medical and dental check-ups

Regular personal hygiene

Not too much alcohol

No drugs - unless prescribed by a doctor or purchased from a

pharmacy

Good personal habits

*

**

*

*

*

There is evidence that a workforce with an increased fitness level perform

better and are less prone to work related symptoms.

Aw'-iH~~ess programme for(t=!Grt~~;;:cult ckground might me~[lF"ftt'''RQ!1?{:'OSS]

ar East countries for schemes are

any western co to be resis

tation. This resis from middle-and

ent, trade unions/ as individuals.

and

The two areas overlap and one is

HEAlTH &

SAFETY AT

WORK

Fig. T3u

--SAFETY AT WORKlPERSON:AL FITNESS-

Personal Health

Here we are looking at the mind and body. There are many things we can do in

our everyday routine to improve the health of both.

- 27 -



Avoiding hazardous situations is always a good idea - but in general the

following are all good pointers to a healthier you.

Diet. Awell balanced diet with regular meals to include plenty of ordinary

drinking water - and vegetables, fruit, fish - and where meats are concerned -

the white meats are to be preferred - chicken etc. A regular pattern of eatingmay be difficult if shift working is involved.

Whether shift working or not, if a meal is to be taken before bedtime then it

should be high in carbohydrates and on waking the ideal "breakfast" should be

high in protein (bacon and eggs etc).

Carbohydrates help in the promotion of sound sleep as they have the

chemicals which the brain needs during the sleep process.

Foods high in carbohydrates include bread, rice, potatoes, pasta and cereals. It

is generally considered that the diet should be higher in carbohydrates at the

exp~se;{ high protein

Foods, '..gh in protein include and milk.

1 • .• • •

Sleep •..••...ere is no substitute lW······i!II,,+G

- V i ry evening andg s used to. Irregular sf ck an~Arerformance

the" ....•••.•••y at ~?rk" section of. ,.- ' . - ,

ExeJise.isJoes not have of exercise

daily (without strain) where IS caused to beat faster is good.

Swimming, a brisk walk, are good examples of a daily exercise routine. ~:mes

for exercise will depend on your daily time-table, but the books all say that first

thing in the morning, after waking is the best time. Ifyou feel you might have a

medical problem in relation to exercise then see your doctor before

upsets the

be dealt with in

commencing a programme.

Toiletry habits. If possible should be on a regular daily basis.

Personal Hygiene and Care. Twice or thrice cleaning of the teeth daily. Adaily

(or more often) body wash. These help to improve ones self esteem and a

shower or soak in a bath can help reduce stress levels. More on stress later.

Avoid exposure to the sun= wear+rats, long sleeves; and use sun-block.

Personal Habits. Monogamous and or safe sex - only drugs prescribed by a

doctor, or available over the counter at a pharmacy (and then only as

prescribed on the label) - no smoking (difficult for some) - alcohol taken in

moderation.

28



Smoking. Known to be a major contribution to early medical problems and is a

contributory cause to lung cancer, heart disease and bronchitis.

High Blood Pressure. Called hypertension. Causes include kidney ailments,

hardening of the arteries, defects in the circulation system, obesity and others.

In most cases there no one specific single cause. Ifboth parents suffer from the

complaint then there is a higher risk. Strokes and heart disease are more

common in people with hypertension.

Relaxation. Good for the mind and the body. Always a good idea to set aside a

daily /weekly period for some form ofhobby / sport/relaxation event. Even

changing from doing a routine task to doing another task can help. This helps

relieve stress and can revitalise the system.

SLEEP

Ir+~"+, aily rhythm un... 8 hours in every

t to be

STAGE DETAILS APPROXTIME

(MIN)

1 Sleep starts here.

Slow rolling eye movement (SRMsleep).

Deepening stage of sleep.

Increasing depth of sleep. Slowwave sleep.

Deeper stage of sleep. Slowwave sleep.

Rapid eye movement sleep (REMsleep).

10

2

3

4

5

15

15

40

10

NOTES

* The above table is a generalisation more accurately showing the first

group of the 5 stages. Subsequent repeats of the 5 stages being different.

- - - - : : ? 2 -=~~



* Stage 1may only be repeated say 3 times during the night with a waking

period - beginning and end, and somewhere in the middle. Hence some

people wake up during the night - once or twice.

* Stage 2 sleep periods tend to get longer as the night progresses so that it

eventually makes up about 50% of the complete sleep cycle.

* Stages 3 & 4 are often called SlowWave sleep and most of it tending to

occur early in the night (from say 23.00 to 02.00hrs), with little or non

after that time.

* Stage 5 sleep is usually called REM sleep.

* REM sleep periods get longer as the night progresses (up to 60 minutes

long) and tend to de-synchronise with the other stages of sleep.

Th~.: ..•.d..cannot store "sleep" 14 hours sleep (if '111~sSible) one _,da ....•. ot last for 2 days (as·$;. UU:(.ff i f;(Ze!~ needs 7 hours 1 e body

has tp) ave a regular sleep is called

the "if adian rhythm".

t resting to note that th":~~~~!;l'tc:!rn

: e same each day if an 1¢~te1"rifdit:l)ple::; ple).

be

clock

Without external time cues the circadian cycle will slip by about 1 hour to 25

hours. This is sometimes called the Free Running circadian rhythm.

The sleep/wake cycle and the body temperature cycle run together. The body

temperature is at it's lowest about 5am (where it is usually the most difficult to

stay awake, if one as been up all night), and it is at its highest about mid

afternoon.

The body temperature has a circadian range of about 1.4°F (O.S°C)

It isInteresting to note that this temperature rhythm of the body is un-affected

even if sleep is not taken during this period.



ABOUT 90 MIN . .. . . . . . .

. . . . . . . . . . . .

15MIN J 15MIN. . . . . _ . . . . . . 40 MIN. . . . . . . . . . . . . .

.. . 10MIN . .0 MIN

STAGE 1 STAGE 2 STAGE 3 STAGE 4 STAGE 5

~ SLOW WAVE SLEEP--I

DEEPER STAGES OF SLEEP

SLOW ROLLING

EYE MOVEMENT

(S SLEEP

RAPID EYE

MOVEMENT

SLEEP

Fig. 14

wake system can be

"charging the

VI:~~~;~~.u5 hours the "batte

period

r-...·."...rr'"

and the body

36.9 98.4

DEGREESC DEGREE S F

36.5 97.7

2400 0600 1200 1800 2400

TIME OF DAY

Fig. 15 CIRCADIAN RHYTHM OF BODY TEMPERATURE



SLEEP+16

'CREDrr+12

+8

IN HOURS +4

- 4

SLEEP - 8

'DEFICIT'

IN HOURS

WORKING

NORMAL DAILY PATIERN LATE FRIDAY

NIGHT

SLEEPING

DWAKING

Fig. 16 GRAPH OF SLEEP CREDIT/DEFICIT

!1--1

t t t ' S to the facttas ediately afte well as they \,...UtI~~~~i

for some time. (Most of us would recognise this symptom).

imple terms 1 hours s

ime - although not

her less. Shift

it the system

8 hours per

eed less.

need

De synchronisation

If the work pattern/physical surroundings are synchronised with the circadian

rhythm (see graph above) then all is well, but difficulties arise when they are

out-of-phase - for example, the desire to sleep at 4am when one has been

working all day and been asked to work into the night.

Regular shift working may not help either. For people on regular night shifts,

for examplevsome may be able to re-synchroriise but others may stay de-

synchronised indefinitely. If this isaproblem then management should be

informed and shift patterns changed (jobmatching).

If the shift pattern is rotated (changed) regularly then the situation is usually

made worse. A "rotated" shift pattern may be phase delayed or phase

advanced.

- 32 --

___EF=~=



MAX IMUM

CIRCAD~

FUNCTION

MINIMUM

2400 0400 0800 1200 1600 2000 2400 0400

T IM E OF Oil Y

Fig. 17 GRAPH OF ADVANCE & PHASE DELAY

Phase advanced means, for example, that after a break of a day or two on

"days" (8am to Spm) the shift is moved forward to "earlies" {saymidnight to

8am ,·.·.·.·, ,.,

patterns uUf)"1'~:~:'.I'

fewer days..911PIe.r~~t'lIOd of seven

FATIGUE

Fatigue in the medical sense is not easy to measure. It is associated with sleep

depravation and lack of rest periods.

Those measurements that have been undertaken have relied on checking the

number of errors made per unit time when carrying out a particular task. The

tests have shown that the number of errors have increased the longer thatperson performs the task. This is called Fatigue.

___atigue is increased by:

*

Working during what should be sleep periods

Working longer hours

Working rotating shifts

Increased complexity of task

Poor environmental factors

*

*

**

- 33 -



STRESS

It is difficult to find a good definition for stress as a medical term. In

engineering terms it is the external forces acting as an object which set up

internal stresses. This is a good analogy to the stress that people feel to the

"pressures" that life puts on them.

Stress is very difficult to measure and those that have tried have related it to

individual performance - with too high stress levels producing a poorer

performance.

Generally high stress is considered to be the external events in a person's life

acting in such a way as to reduce that person's performance.

Some stress is an essential part of the human condition but if it gets too high

then performance is affected and sometimes illness may result. High stress

levels can be treated by:

Changing the

* Therapy.

* Medication.

are us

* Physical condition.

* The environment.

* The task in hand.

* The organisation.

This list may be expanded to include:

* Injury:--

* Mental problems.

* Fatigue.

* Environment (heat, cold etc).



* Time pressures.

* Work load.

* Personality conflicts (at work or in the home).

* Personal problems - family - money - health worries -lose of a loved

one - moving house - divorce - pregnancy - pre-menstrual tension

(PMT)etc.

* Diet.

* Drink (alcohol).

* Drugs.

* Peer pressure.

d",Uj.1"'\! important

person compared to

, whilst may got~E±2j~Jm~cts of the ev_e:mill~~~ by the ~$,t¢ln)lo~:ical

up of the person and the level quantity of the stressors that person has

experienced already.

n..,.·..ili...,hhas physical pro

hearing, or sight H'''''''~t.J....

GU..II9Q\.q exist. Like all the ..,.,.,_,.,_,=

In other words an event may be stressful because of the person's perceived

ability to cope with the perceived event. It may not be as bad as s x e ] she

imagines and he Ishe may be able to cope with it very well.

If a person is tired or suffering from fatigue the "event" will have a greater

impact.

If the person has a high work-load with limited time availability then this is an

additional pressure.

Not "getting on" with ones boss, feeling isolated from the rest of the team-

these are all personality conflicts which detract from a stress free envoiroment.

The physical environment (heat, cold, noise, air quality, lighting, physical

comfort etc) - all add to the background stress levels.

3



Working out-side in cold weather conditions, for example, will increase the

stress level (sometimes called 'cold stress'). More about environment later.

The domestic environment also has its stresses. The natural concern that one

may have for family, friends, housing, money problems, health worries. These

may all be sources of stress.

Travel to and from work, if it is arduous or lengthly can increase stress on its

own account but may also increase fatigue - which does not help.

Apoor diet, too much alcoholic drink and misuse of drugs reduce a persons

ability to perform correctly and may increase stress levels.

Peer pressure (making sure you don't let the team down) can be a significant

problem in terms of stress. It may mean a person is trying to perform at a level

at which he or she is not happy with. This increased work load will cause

stress which will be compounded if any failure occurs in that personsperforl 1 1 c m ce. -/

~~~~~,~aa~~~t~~ ~~f~~:tlarlw=!~errlen

ent, whether sexual, rp;·,~~~}~91

e are lucky (and sh

aircraft maintenance management ..p . : " " ' > . : t -' L . . . . . . . .

~ ? t 1 · . . . ~ _ " ' " i , , _ b . . . , . , ~ e. . .l ; ; ; ; ~ ~ _ : COP~

: ~ ~ l i to n ; : s ~ ~ ~ : ; e b e

,.: I

men ione 0 e person giving nce. said openly, in pnvate and in a nice

manner the person, in all probability, will stop.

If he/she does not stop then the person should be told that management will

be informed. When management is informed it should take steps to rectify the -I

situation. This can be done by:

* Having an informal talk with each party to investigate the exact

circumstances.

* Organising work patterns so that the two persons involved are

on separate shifts etc.

* Informing the offender that legal proceedings could ensue.

* Giving a formal written warning.

- 36-



Ways of Reducing Stress

This can be divided into 2 areas of responsibilty:

* The employer

* The employee

More will be said later about the work environment that is the responsibily of

the employer, so here we will concentrate on the employee.

Good personal habits help. These have already been discussed - good diet,

regular adequate sleep, and also regular exercise. It has been shown that

regular exercise can increase tolerance to stress.

,r

,.- Stress Reduction Techniques

Your doctor might recommend:

* Health and fitness programme

* Relaxation classes

* Counselling

* Medication

Health and fitness has already been discussed.

Relaxation classes are carried out at health centres and the techniques learnt

can be practised at home.

Counselling might be with professional counsellors trained in stress

management. It may be carried out over a period of many months or years.

- 37



Some firms may have their own stress management councillors who can be

seen during the working day.

Counselling can help reduce stress levels by pointing out to the person what

stressors to look out for and how to cope with them when they happen.

Counselling can also advise on any life style changes that will help.

High stress levels can cause physical symptoms and may show as one or more

of the following:

* Nausea

* Indigestion

* Diarrhoea

Asthma

* Headaches

*Ne~roses

* Allergies

* Colds and flu

The doctor can prescribe medication treatment for these symptoms and may

also prescribe other medication, such as tranquillisers.

Religious practice may also be of help. It does give very considerable support

to people, particularly after a major event such as bereavement.

"""""""

- 38



DRINKANDDRUGS

By " drink" of course we mean alcohol and by drugs we mean those that are

available through the pharmacy and other, mostly illegal, substances that can

be inhaled, injected, or taken by mouth to produce an affect on the body.

Alcohol

Beer, wines and spirits if taken in moderation in a social (non-work/non-

driving) environment are acceptable. Indeed they might be beneficial. They act

as relaxants and can aid in the relief of stress. Beer may also be prescribed

(rare) for some stomach disorders.

In the workplace and when driving, alcohol is not acceptable. It impairs

judgement and reduces reaction times. The person feels carefree and loses"-

,... some inhibitions. Not a good state to be in when working an aircraft - wheredepend on the kills and u . ' " " . .. .J.\...CU.JLy.t..'~=""""'"

andn1h'.'TPI'Y\O ....~,".,.. lost.

eneets to wear-off terms it hour for each====~unit of alcohol consumed to leave the body, ( V 2 a pint of beer [I/4 litre}is equal 1

unit of alcohol).

So if a person has 4 or 5 pints (2 or 3 litres) of beer in an evening it is more

than likely the body will not be free of the alcohol by start ofwork the following

morning. In that case it is the responsibility of the engineer NOTto report for

work - or at least NOTto work on aircraft or certify any work carried out on

aircraft.

Alcoholism

Generally defined as whenexcessivedrinking repeatedly damages a person's "

physical, mental or social life.

In the early stages most alcoholics do not present a picture of physical or

mental decay. Most hold responsible jobs and one apparently "sober citizens" .



As the problem develops, however, loss of control of the habit sets in. The

pattern of drinking becomes more destructive with a continuing deterioration

in the physical, mental, and social parameters.

Danger signs are in the early stages include:

* Drinking alone

* Desperation for the first drink

* Increasing the intake to feel good

* Loss ofmemory of the "night before" events.

* Morning shakes

Guilt feelings if criticised over the drinking

~./.? Adverse effe

LReco~i ion (by ones self, a fri

prom ....••..•.•..••.•.•..••..eatment. A frank operfriendss d work colleagues is ~mP.Qmt tHV

:'';'.: HFill22Z:~

Furt:.j help can come in the

supp .~

=rAlcoholics

Dru~>··f

*

centre and

Drugs may be taken for medical reasons and may be prescribed by a doctor or

purchased from a pharmacy. If they have adverse side effects then appropriate

warnings will be given on the label/literature which comes with the drugs.

Read the instructions carefully and take note of any warnings. If drowsiness or

inability to concentrate occurs do not drive or work on aircraft - or carry out

certification. It is possible that you can transfer to another job during the

period of medication.

If side effects are severe see your doctor.

Rememb-er t6-<Ttr'ial"anynew prescribed medicines several days prior to going

to work to check for side effects.

Illegal substances should not be taken at any time, let alone when at or before

going to work.



In some areas of the world, governments have made a statutory requirement

for employers to test employees for named substances such as:

* Maruana

* Cocaine

* PCPS

* Amphetamines

The testing to be carried out at a specific event such as:

* Prior to employment for a safety sensitive job

* When someone contributes to a serious accident at work.

-,.... In some work locations random drug testing is carried out.

, but these

Some conditions

Claustrophobia

"... A fear of closed-in spaces.

Ifwork is to carried out in a confined space such as a small enclosed structure,

or in a fuel tank then a person suffering from claustrophobia should not

undertake that task. Some-one else should do it.

Even then, if the area is confined with difficult axcess, a look out person

should be in attendance with continuous communication with the person

inside.

Provision should be made, prior to entry into the area, for quick evacuation in

the event of a fire-warning etc. Provision should also be made for adequate

lighting, ventilation, cooling, heating etc.

If extrication of the person inside could be difficult then a harness and rope

(leading to outside of the area) should be used.

1



All systems, of course, should be made safe, and if fumes might be a problem

then breathing apparatus will have to be used.

Acrophobia

A fear of heights.

Much of the work carried out on aircraft can be undertaken on or near ground

level, but on large aircraft some work has to go on as high as 30 or 40 feet (9m

to 12m) or more. For some people work at this height would be impossibe.

Those working at heights should not suffer unduly from acrophobia and should

take all necessary precautions to ensure there own safety and the safety of

others around (and beneath) them.

These precautions should include the use of:

Correct mainten

assembled and

ed,

* ': .

* SaIety barriers a

* Suitable warning notices.

Treatment of phobias is undertaken by counselling and may include the use of

virtual reality techniques.- -

FITNESSFORWORK

Whether a licensed engineer or not if you work on aircraft you should ensure

that you are mentally and physically fit enough to carry out your tasks in a

-"safe and competent manner.

Part of annex 1 to the ICAO(International Civil Aviation Organisation)

convention on international civil aviation relates to areas such as medical

fitness, drink and drugs, whilst working on aircraft.

- 42 -



In the UK the ANO(AirNavigation Order) and AWN(AirWorthiness Notice)47

specify your responsibilities in this area. The ANOarticle prohibits work on

aircraft if the engineer suspects that his/her condition (physical, mental, or

related to drink or drugs) makes him/her unfit to perform his/her duties

correctly.

So if you think you are unfit to work on aircraft - FOR ANYREASON- then

don't.

JAR66 also states that a person should not work on aircraft if their mental

condition renders them unfit to perform the task.

It goes without saying that if a person is unwell or suffering from the affects of

alcohol or drugs, then he / she is likely to let standards slip in terms of

engineering and inspection techniques. Decisions will be taken which will be

influenced by a person's condition both physical and mental. So the person

;"... should be physically and mentally fit and not influenced by drink or drugs.

formRcftA~r)onsibilityof each · · · ~ : ; ; ; ; n · ; · ; · · i · lt(fI:iQJl2fl;j~t

if he / she feels

;;;;;. should put into 1."'4...~'-' T\r''''''''''n

l1t::t~d~nt.

and air traffic

same legal

Professional medical certification is not necessary and many conditions are

obvious eg:

* Abroken limb

* Intoxication

* Drug abuse

Some unfit conditions may come-on gradually and may not be apparent to the

"Tridividual. Stress Telated conditionsusually fall into this category;

It is possible under these circumstances for others to notice the changes in an

individual's behaviour before the person himself/herself recognises it. His/her

family and friends might notice, and more importantly, so might his/her work

colleagues.

- 43 -



Any gradual changes in a persons behavioural pattern (dress, habits etc)

should be noted and the person concerned talked to about the changes.

Management should be informed so that appropriate support and counselling

action can be taken.

The following list (not exhaustive) gives an indication of 'fit for work'parameters - many of which have been covered in previous sections of this

book.

Fatigue

Caused by overtime working, shifts, long commuting journeys, moonlighting (a

second job), stress etc. All can cause fatigue and reduced performance.

Stress

I.: i.: .Str~s· 4 l i . • • • •QjJffel:eft$,.ways.ome str'esJs?1f~r:tpart e tc ving, but if it gets too verse mental

can 0 f : # r. See the section in

tial

Disa

Eyesight

A reasonable standard is required, with the use of glasses or contact lenses, if

necessary. Ifcolour blindness is a problem the person should work in a

situation where colour differentiation is not a requirement (job matching).

Companies should have procedures in place to address the problems of

eyesight requirements - particularly.related to 'colour' orientated work or fine

detail work.

Hearing

In general, a person should be able to hear a normal voice in a quiet room at a

distance of 6 feet (2m) from the person talking. Ifnecessary a hearing aid may

be worn.

44·



In the UK,under the Noise at Work Regulations 1989, companies are required

to monitor noise levels in areas of high ambient noise.

Drug and Alcohol Abuse

This is not acceptable in an aircraft maintenance environment. If found will

lead to licence j approval suspension.

Medication

Whether prescribed by a doctor or purchased from a pharmacy, three points

should be noted:

1. Is it really necessary to take the medication?

After taking the 111~~~,a

for work? If not, do

the blood up

when you areyour

Combining drink with drugs, sleeping tablets, andj or anti-histamines etc, can

form a lethal cocktail.

Anaesthetics

After an anaesthetic - general, local, or dental, a period of up to 48 hours must

elapse before going on duty. The actual time will vary depending on the person

and the amount and type of anaesthetic administered.

Sbtfre~edicines

Listed below are some of the drugs that are available on prescription or

available over the counter at a pharmacy (chemist). Their general affects are

given but in all cases expert medical advice should be sort prior to their use

and a pre-work trial carried out if in doubt.



Sleeping Tablets. They dull the senses, cause confusion and also slow reaction

times. Their effect may also still be apparent the following morning. Seek

medical advice before use and if you feel unfit for work in the morning don't go.

Tranquillisers. These depress the mental alerting system and have been a

contributory cause of accidents in the past. Do not work when taking them.

Antibiotics. These may affect work performance as well as the side effects of the

infection itself. Will almost certainly render an individual unfit for work.

Anti-histamine. Used to treat colds, hay fever, asthma, and allergic skin

conditions. In general, always seek medical advice and carry out a trial period

before reporting for duty. They tend to make the user feel drowsy.

'Pep Pills'. These may contain caffeine, Dexedrine, Benzedrine (an

amphetamine) etc, they are designed to 'wake you up', but may be habit

forming and can create dangerous over confidence. Should not be used prior

to or . work, you could but that's all..J

....a trade name cribed by

la~;~:¢(;~m(E.~S:" t . i . c : . ) i h . Itmay cauqo.""·:Q.J;J~~,,·t.:Y:'::4~~Cl.UCl.'-'U.e,nd rmance .

...used whilst at wo applies to other drugs in this category.

Herbal Remedies. Just because they are herbal does not mean that they do not

have side-effects. Ask about possible side-effects from the chemist and carry

out a pre-work trial. See your doctor if necessary.

" " " " " " " "



THE WORKING ENVIRONMENT

This includes:

* Heating.

* Lighting.

* Ventilation.

* Fumes Dust etc.

* Vibration.

* Noise.

"" All the above will have an influence on how well a person performs a task ands levels.

H

temperature to carry Q:Pf]:;j~

relative humidity, the

task in

-chill

.._ .......". the

comrortame workingtfn~~'~:':"!1'.:··'·hould be.

90

RELATIVE

HUMIDITY

(%)

OEGC19 2fr-

AMBIENT TEMPERATURE

Fig. 18 "COMFORT" GRAPH OF TEMPERATURE AGAINST HUMIDITYThe above data assumes light work with a light breeze velocity

of 50 feeUmin (0.2m/sec) and no direct sunlight.

4'-'- 1-



For work on aircraft temperatures should range between 18°C to 26°C

although temperatures outside this range can be coped with depending on

clothing, actual physical effort being used, age etc.

Relative humidity levels should be in the range 20% to 85%.

When working outside, temperatures are less easy to control. In cold weather,

good thermal clothing and portable heaters help reduce cold-stress. When the

wind blows the wind-chill factor will make it feel colder than the thermometer

would indicate.

In hot climates (heat-stress), particularly with high relative humidities, light

clothing, with protection from the sun (long sleeves, sun hat, sunblock etc) all

help to make it more comfortable and safer. Portable air-conditioning

equipment can make the working environment significantly more comfortable.

It is generally considered that cold-stress has more effect on the body thanhea -.. ..s, though thought ted to the physiolo tion more

thaft.-.~l'f'<hysical. Hurrying job because of example -

altho . wearing heavy clo means that motor

uld be more difficult.

e= » must be

>*<a.jility Lighting

'* 'T~~k Lighting =~~=~

Facility lighting covers ordinary hangers/workshops fixed lighting systems,

windows etc. This light should be even throughout a work area. Task lighting

is specialist lighting - fixed - adjustable - portable used to give a better

illumination for the specific task.

Light emission is measured in candela (SI system). The amount of light sticking

a surface is measured in lux or lumens and is called illumination. The lightbeing reflected from a surface is called luminance.

As an example the amounts of light needed, an exit sign is about 50 lux, area

lighting should be 750 lux min, burupto 1500 preferred; and for fine bench

work up to 5000 lux units of light would be required.

The light source should be positioned so it does not shine into the eyes - called

direct glare (light source from behind the person is best), and does not produce

glare from any reflective surfaces - called indirect or reflective glare - difficult

on polished/reflective surfaces.



LIGHT <,SOURCE \~

\0 CANDELAUNITS (light emitted)

LUXUNITS

(striking the surface) IUMINANCE

(reflected light)

SURFACE

Fig. 19 LIGHT

Ageneral rule of of thumb is if you can't see correctly, get the right light at the

correct angle so that you can. Also for an older workforce the light levels

should be increased by up to 50%.

~~~~~~ti~on~. The colour ~~"""""~ depends on the

"~"'''+''5 on it. In fact, the ~om~ is that which is

absorbed all the "'G1.li~~LJlef.

IOIl':mJloa..u~~".:". rendition. Rednatural light. IfIfift'W~(

Incandescent bulb

Fluorescent tubes

Mercury vapour lamps

Average

Poor

Poor

Average

Good

Note. When working with rotating machinery (lathes etc) in an area lit by

fluorescent tubes, it is important to have multi tube light fittings so as to avoid

the danger of the stroboscopic effect of a single fluorescent tube interacting

with the rotating part. Under some conditions it C e r n make a rotating part look

as if it is stationary - very dangerous.

In general natural light is preferred to artificial light. Ithas better colour

"rendition, provtdesa less directionaHightwith-less shadows=does not require

support (holding a torch with one hand for example) and does not use

electricity .

- 49 -



Air Quality

This is becoming a greater issue in the work place and also as an

imvironmental problem in our towns and cities.

In most hangers/workshops the quaility of the air is generally good - provided

there is ventilation (and most hangers can be drafty places anyway). It is when

something special is being carried out such as paint spraying, grit blasting etc

that air quailty can suffer.

When carrying out any of the followingoperations special precautions must be

taken in terms of air extraction/breathing apparatus:

* Paint removal - chemical or blasting.

* Paint spraying - or other application methods if fumes are

excessive.

Grit blasting.

* Sweeping hanger

Vibration

Many engineers will never suffer this as a problem because they do not work

for long periods with equipment that vibrates to any great extent. But those

that work for long periods of time with certain pneumatic equipment such as

rivetting guns can suffer from the effects of vibration.

Vibration of the whole body is generally less troublesome because of the

resonant frequencies of the various parts. For the hands, frequencies within

the range of 50T()15D~z~is1ikely tocause vibration problerns:-Theseproblems

include Vibration Induced White Finger (VWF)syndrome.

Methods of reducing vibration induced problems include:

* Reducing the exposure time of the operator.



* Manufacturing equipment so that frequencies are outside the

critical range.

* Reducing the amplitude of the vibration by increasing the weight

of the tool or reducing the force of the forcing function.

* Providing damping material between the object/tool and the

operative.

Noise

Noise may be a problem when using certain pneumatic equipment an when jet

engines are running.

In general, noise levels in hangers are in the range of 70 to 75 dB - which is

acceptable, but if they are higher than this and are sustained over long periodsthen. res must be the noise levels.

'O /

Noise

* Reducing resonant noise by damping and/ or stiffening

techniques.

" " " " " " " " " , , "



THE WORK PLACE

Tasks can range from the simple (checking that a light comes on) to the

complex (an auto pilot functional check for example).

The task in hand may require a standing, sitting, or some other position of thebody.

Itwill require body movements, eyes, head, legs, hands etc.

Itwill require the use of one or more of the senses - the eyes almost certainly,

but also maybe the sense of feel, smell, hearing etc.

Correct clothing should be worn with correct body posture for the task in hand.

Clothing

....hould be comfortarufL·':lm¥4l::u

Pockets should be 0 , " , , " * " " 1 ' * ,

ced in pockets that ~c.u"'..,",,'~

check should be

ost tasks,

o v . ~ " " ' ' ' ' , . . . .for essential nersen

uMitea-upor zipped-

'-4.... j ' . " ' ' ' ' ' sonal items

should

The

structures), nor cause sparks.

Specialist protective clothing/ glasses / reporators / footwear will be required:

* When dealing with heavy equipment movement (safety boots).

* Grinding, milling etc (safety glasses).

* Working in fuel tanks (wet suits/respirators).

* Working with chemicals/ detergents/toilet/ systems.

wet suits, goggles/respirators.



Body Posture

Standing. Standing on a firm level surface is best with feet slightly apart. If

"pushing" is required (such as filing)then lean in the direction of the push.

During the push place one foot in front of the other to maintain balance.

Standing at a bench. The bench should be strong enough to cope with the

loads that might be imposed on it and rigid enough to withstand any side-

loads.

The actual surface area of the bench will depend on the work in hand and,

ideally the height should be related to the "elbowheight" of the person using

the bench. For most manual tasks this height is 2in (Scm) lower than elbow

height. When filing using a bench vice the item being worked on should be at

elbow height.

For visual tasks at a bench the work should be between elbow height and lOin(2 elbow height.

~.,.~,--...--",are not adjustab

oenen is too high then woooenwhen moving away

If

on a

* Use a secure harness.

* Place safety notices below if tools and equipment could fall and injuresomeone.

* Try if possible, never to walk on wet/oily/frosted/snow covered

surfaces - they can be extremely slippery.

* Walk within designated walking zones. (Refer t()_tpeAMMand check

walking areas painted on the wings, tailplane etc.

* Always be aware of aircraft over balance eg, standing on the

-----tailplane ofa srrrall nose wheeled aircraft;

Standing in the aircraft. Beside the forgoing make sure there is sufficient head

room. If there are sharp parts of the structure/components near the head and

work is going to take some time then temporary padding may be used for

protection. Ensure its removal after job completion.

--~----



Standing at height outside an aircraft. The equipment (ladders, platforms etc)

will be dealt with under the heading "Working at Height" but the engineer

should work without stretching; wear a safety harness and (for platforms) have

guard rails in position.

Walking/Running. Unless it is absolutely essential (fire, emergency etc) thenrunning should be avoided in the workplace - there are too many hazards for a

person to run into to make this anything but an unsafe operation. When

walking always look out for body level obstructions - particularly important in

this area are ariels, drain masts etc when walking under/ducking under

fuselages and wings.

Sitting. If a person's job entails a lot of sitting then a comfortable correct

posture position is important. The chair base (on which the bottom sits) should

be padded and an inch (25mm) of so wider both sides of the bottom. It may

slope slightly forewards and have sufficient length to support the legs up to the

back of the knees. The height should be adjustable from 13in (33cm) to 21in(53cm.

c _ , : . . :

Ideallg: e back should be.. to the full width of

y be fitted depending !#;"t~~

ork - computer workstlA1~~i¥4di6B?

...•..•..•.g a~~.......:nch ther~ sh knee room [1

U. WltlJl:' bench height )].

::ve~~~~~l~;~:ack, area IS advisab~~.s i ~ ecare when getting upfrom these positions - make sure there is sufficient head room, roll over onto

the stomach and push the body up using the hands and arms.

When laying on the side - in aircraft for example then a cushion for the head

can reduce neck strain.

Difficult positions. Kneeling - use knee pads or other suitable padded material.

Only kneel down where the full length oLthe lower leg is supported. Lying,sitting, etc, in aircraft - use padding to make a comfortable area. Remove after

the work is finished.

REMEMBER

With any working position do not lay, sit, bend, kneel or stand without

movement for any length of time. Change ones position from time to time. If

you start to ache - go for a walk or a short break. Ifyou can take up a slightly

different position to do the task then do so.

-54.-



BodyMovements

This is concerned with some of the simpler actions/movements of the body.

Lifting. Always try to aviod strain. If something is too heavy to lift without

strain then get a friend to help you or use lifting equipment. If the item is too

bulky then again, get assistance, or use lifting equipment.

" - _ - .

a h e a v y ' 0and cause injury.

the legs

"~:~11'4E> to keep the

get someh_':~i!!ii~ ... is bent to lift

column

,.. When straightening up, keep the arms bent and the item as close to the body

as possible holding the item away from the body produces a moment which the

back muscles have to counteract - placing additional strain on the spinal

column.

Carrying. When carrying anything heavy keep it close to the body and restrict

the amount of time it is being held. Abattery for example, is a reasonably easy

item to lift - even though it is heavy. But if the lift continues for a period of

time, as when carrying, then strain can be caused to the back and back pain

can result+-This may not be- imrnediatelyapparent, but-may show up some_______~

time later - when in bed that night for example.

Reaching. Ideally whatever you are working on should be no more than the

forearms length away from the body torso. Never over-reach yourself on any

job, particularly at height, as this may cause overbalance with possible serious

consequences.

~55 -



DISTANCE (D)

FORCE (F)

THE GREATER THE DISTANCE

AN OBJECT IS HELD AWAY

FROM THE BODY THE GREII ,TER

THE MOMENT AND THE GREATER

THE STRAIN ON THE SPINE

MOMENT = F X D

etc.

(roll-over)

mle8i.1*ies to pushing.

If a wheeled vehicle is being moved ensure that is has a serviceable brake

system or some other means of stopping its movement. If it won't move with a

reasonable pushj pull get some help in the form of assistance or use

mechanical means. Whatever you do, do not strain.

Ifthe item you are pushing/pulling moved unexpectedly make sure you are in

no danger from roll-over or from over balance.

Hand movements. When drilling, riveting or using any tools the best position

for the wrist/hand is the fingers closed around a handle of 1to 1V 2 in diameter

(25 to 38-mm~with the thumb going in the opposite direction.The handle tobe

in at right angles to the forearm.

:_,b



Fig. 22 BEST HAND POSITION

Aword of caution when hand cranking an internal combustion engine.

Because of the possibility of it firing before top-dead-centre and causing aBac causing the to kick back . thumb

the handle b

* Height adjustable work platforms.

* Aircraft docking systems (forlarge aircraft during major servicing).

* Safety harnesses.

The design of the equipment is governed by local country regulations - in the

UK - the British Standards Institute (BSI)make sure the equipment you use is

designed to be safe for the operation it is to be used for, and comforts toregulations.

Most firmswilt have-in place a mainten-ance programme-fm--the-equipment with

a recording and identification system to ensure that it is serviceable and it has

suitable documentation to confirm it's services history (an attached wallet

containing a signed servicing recorder example).

- 57 -



Leaning ladders are not often used in the aircraft maintenance environment,

but when they are used they should be used on firm flat level ground using

non-slip feet. They should lean at the correct angle, and, if the work period is

going to be lengthy it should be secured at the top.

S T RUCTURE P ROTECTIO N

SLOPE OF LADDER A = 114B

A

>. » ding stepladders are

use i,$. ould be high enough

engin e =r: is

Whed U ing efght adjustable

be q t i 's e . I

L.:.~~~;;';

* Steady feet in position before raising - if fitted.

* Never overload the platform. Safe working load (SWL)will be

indicated on the side of the platform .

* Never over-balance the platform - load evenly distributed on top.

* Always ensure guard-rails are in position;

* When raising/lowering ensure personnel arid aircraft structures are

clear.

* Protect structure from platform damage using fender cushions

(rubber protective fenders).

* Keep gap between structure and platfrom as narrow as possible.

* Use safety locks when raised into position,

~ 58 -



The problems with docking systems are similar to those of working platforms,

They can be very extensive with several stories of platforms with steps (and

sometimes lifts) to each. With careful design/ careful positioning of the

aircraft/ docking system, they can provide a safe and convenient solution to the

problem ofworking at height.

Guard rails around work platforms should be almost waist height with a low-

level fine screen to prevent small objects, tools etc from falling off.

Safety harnesses should be worn by all personnel if working on a

platform/ladder outside the aircraft if 10 feet (3m) or more from ground level.

The harness should be of the BSI approved type and attached to the working

platform harness attachment. When working on a ladder it should be attached

to a strong part of the aircraft.

Of course if you suffer from acrophobia (fear of heights) then you should not

attempt to work more than a few feet from the ground - or at least above any19-G:~~~ feel

the best examples of rtt~~~¢]i;l;rsl<~s

pr'OQUCflUflnines - the motor .

job could be

and women

~<.A.'1~n,. to do and

Solutions like this are not always possible. Repetitive processes may initially

improve production but it has to be recognised that they have their drawbacks.

Repetitive tasks in the aircraft industry can include:

* Riveting

* Soldering

* Component testing - in bays

* Component dismantling/ reassembling

Tasks are normally classed as repetitive if the task duration is comparatively

short and task frequency is high. It is also related to how often the task is

performed.

If one put in 5 rivets, it could hardly be classed as a repetitive task with all the

problems associated with the term.

~- ¥=-- 59 -



Ifyou put rivets in day after day for months on end - then that is a repetitive

task.

'Larger' tasks may also become repetitive. For example, doing a tum-round

inspection on one particular aircraft several times a day - and doing that over

many months.

So the definition of 'repetitive' is a difficult one.

If a task does become repetitive then boredom will start to creep in, there is

reduced motivation and mistakes are likely to occur.

QUESTION:From what you have read about information processing can you

say how the brain is likely to cope with a repetitive process? (10

mins).

After the initial u~~~~

coupled with the'iieriti~~jtm.f~s

memories, the mo

occasional moni

term

It is in the interests of safety and productivity that once you realise that a task

has become repetitive, management is informed and you should be moved into

another job.

Ajob change is not always possible, or at least available straight away, so in

the mean time:

* Take regular short breaks - just a few minutes will help.

* Adjust ones position - if satl standing etc.

* Try and break the work pattern with a different task - if this is

possible.

* Check manuals etc, from time to time to confirm correct procedure.

- 60 -



Repetitive Strain Injury (RSl).This is the fastest growing category of industrial

injury. It is normally caused by repetitive tasks where the body (or part of)is

held in a slightly strained position. Changing position from time to time (if

possible) will help this, but in the long term the only solution is to

modify/ change the repetitive task that is causing it.

Ifyou are worried about RSI then seek medical advice.

"""""", , , ,"", ,"

r 10-,



INSPECTION

The process of inspection, whether we just use the eyes or specialist test

equipment, is the main process by which we ascertain the serviceability, or

otherwise of an aircraft/ aircraft equipment.

It relies mostly on the eyes, but may involve feel, smell and the sense of

hearing.

Of course, to get the best out of a person in terms of inspection, a good

physcial environment is required - heating - lighting - ventilation - low noise

levels - comfortable surroundings etc. We have dealt with the physical

environment; here we are going to deal with the organisation of the inspection

method.

Operator / Job Matching

: best performance oott)M~y§teln

to the job or vice

y be re-arranged to s

n process required th

':'~.operator was colour U~f~.~'!o.Ir~~::R

, r - or even the use of Pln:~rt'i'"l"¥iiUlf::::

e task in

the

test}

e use of

Operator Training

There is no substitute for it - plenty of it - good quality - well monitored with

standards moderated by external bodies (eg, in the UKCity &Guilds, BTEC

and external examination bodies such as the CAA).

Updating

Keeping up-to-date with modern techniques and changing technology. Courses

are put on by operators for managers, technicians, licensed engineers etc.

TheseenslXte that theworkforce is trained on-modem-development!n€w-

aircraft / new techniques.

Reading commercial aircraft periodicals; watching technical programmes on

the TV, and down-loading technical information from the net all help in the

process of 'keeping abreast of things'.

62



With to-days world of rapidly changing technology it can almost be a full time

job keeping up-to-date.

Subject Knowledge

We have all heard of the term 'if all else fails read the instructions'. There are

not many people dealing with technology that have not used this from time to

time. Of course it is WRONG. The CORRECTthing to do is read the 'book'

FIRST.With aircraft this is most important.

Read the safety notices. Read the AMM.Read the SRM. Read the IPC. Read the

job cards printed for the purpose. Make sure you know what you are doing

before you start the job.

ofg . m e n ; ; U · there (and w .'@t ; , e Z ~ i . 'a70~~te an Th~~ ,:;e a lot

licence. They perform their tasks well and are safe, good engineers - but in

to-day's modern world you have to prove to people that YOt:are good. Having a

'fist full' of qualifications is the most universal way of doing it. Having

qualifications does not guarantee you are good - it actually says you can pass

exams, which is not necessarily the same thing as being a good engineer.

Unfortunately (for those that can't "do exams") 'qualifications' are the only way

of gauging a person's ability to do the job.

For most ofus the 'licence' is the qualification to get. It has to~be said - the UK

licence is highly regarded world-wide, and it looks as if the JAR 66 licence will

follow suit.

Currency / experience

There is no substitute for experience. All the training/ qualifications in the

world cannot put an 'old head' on 'young shoulders'.

6? -



Ifan engineer maintains his/her currency he/she not only retains licences

held (without further examination) but also remains reasonably abreast of

current trends both in technology and maintenance procedures.

Visual inspection

The most important 'tool' the engineer has are his/her eyes. Almost all of the

work carried out on aircraft involves the visual sense, although some work

requires the use of other senses such as feel, smell and hearing.

Reasonably good eyesight is essential, aided by spectacles/contact lenses, if

necessary. Colour blindness may be a problem particularly if the job entails

colour identification of cables, flight deck indicator systems etc.

Colour may also be a problem caused by using the wrong type of light source(colour rendition). See the section in this book entitled "The Working

Environment" .Q . . '

blindness is a proble

hould work with tasks

by an eyesi

colour dep

\..u/:t::::C;I\.~sistanceh

the

See the

a centre line

H~"tfFt·'HTt"'4:l£ttyt source (na

about head heigh e observer.

Some instruments (electrical multi-meters and "AVOs"for example) have a

mirror behind the pointer, thus, when looking at the instrument, parallax error

can almost be illiminated, by moving the instrument so that pointer and mirror

image are super-imposed one upon the other.

Aids to visual inspection. The following additional aids may be used to assist inthe 'visual' inspection of a component:

* Magnifying glass.

* Mirrors.

* Remote viewing mirror and light source.

* Intrascopes.

* Fibre optics.

* Video cameras and colour CRT displays.

* Portable computer/optical displays.



With most engineering tasks the use of the eyes is concentrated on one object

such as the piece of locking wire we are trying to twist together; the corrosion

we are inspecting for; the crimp terminal we are placing in the crimping tool.

This means that eye movement is fairly static. Ifone sits at a computer for long

periods then this static fixed focus position can cause eye strain and a change

of eye activity is recommended.

Looking out of the window, or across the room will help. The most relaxing

colour to look at is green.

If, on the other hand, we are carrying out a task that requires several visual

parameters to be monitored all at the same time such as flight deck instrument

monitoring during engine start-up, then visual scanning such as small and

frequent eye movement will be involved.

", ,"", ,", ,"

- 65 -



COMPLEXSYSTEMS/TASKS

Many modem aircraft systems are such that anyone system may involve more

than one trade/licence category. Anyone system/component may be related

hydraulically, electrically, electronically or mechanically to many other

systems / sub-systems.

On modern aircraft the computer system (computers, data buses and related

interface units) connect almost all the aircraft systems together, one way or

other. A good example is the Air Data Computer.

The Digital Air Data Computer (DADe) takes (mainly) Pitot and static pressures

and converts them to digital signals where they are then put on the data bus

for other computers to use.

Air data can be used in so many systems, but 2 are taken as an example - the

pressurisation computer (controlling cabin pressurisation], will use some ofthis d<l~a'iiswill the FADEC .. ority Digital' computer) - .J

to hlJip···· the engines. ......

t ; ~ . ' · ·

When all separate trade area work is completed and serviceable it is important

that nothing is left out (particularly at trade boundary interfaces). The aircraft

as a whole should be serviceable. --/

To this and the following points should be studied.

* Duties & responsibilities of each engineer.

* Maintenance manuals.

* Task-cards {joh-~cards):::

* Recording.

* Sufficient inspections.

* Stage inspections / duplicate inspections.



* Supervisory checks.

* Liaison between trades.

Duties and Responsibilities of a Licensed Engineer

All national authorities specify these duties, and for the UK, the CAApublish

them in Airworthiness Notices. Notice number 3 specifies the certification

responsibilities in relation to the ANOand JAR 145.

It relates to type licences/authorisations issued under BCARs sect Land

JAR66.

It also relates to those type licensed engineers who perform work on aircraft

outside their licence responsibilities.

ca

Maintenance

Overhaul

Repair

It SOeOll1eShe various types of c~ltffii6i¥til

ponsibility of the ~"'.LJ_.""

A-

~~~olryB-

Category C - Engines -

Category D - Engines - Overhaul

Category A& C - Rotorcraft - Maintenance

*

*

*

* Category X - Instrument - Maintenance

* Category X- Electrical- Maintenance

* Category X- Autopilots - Maintenance

* Category X - Combined - Maintenance

*Category R- RadiQ- Maintenance

* JAR66 Category A - Line Maintenance

JAR66 Category B1 - Aeroplanes/Engines - Maintenance

-~-~B-l.1 - Aeroplanes Turbine ---~---

B1.2 - Aeroplanes Piston

B1.3 - Helicopters Turbine

B1.4 - Helicopters Piston

JAR66 Category B2 - Avionic systems - Maintenance

JAR66 Category C - Aircraft - Base Maintenance

*

**

67-

---_-~---------



The Notice specifies areas of trade responsibility together with exclusions

where work is NOTpermitted by certain licence/ authorization holders.

It will state, particularly in relation to JAR66 categories, areas normally

considered outside a specific trade into which responsibilities extend.

Manuals - Hard Copy or CD Form

These include:

* Maintenance Manuals (AMM)

* Wiring Manuals

* Illustrated Parts Catalogue (IPq

* Structure Repair Manuals (SRM)etc

The appropriate manual should always be studied before carrying out a task.

Even if the task is well should be made ual in case -:»

you~ig>:' have forgotten t since

the lalst time the task was

e

e work/procedure

onsib~li¥es as a

eed w~ work. . If theyto'9rought m to __""..",~... :---_...;::

Ifyo'::-':u~e~e""'-;-Fe=":';manuals incorrect any detail/procedure

that you have the correct manual, it is up-to-date and the effectivity is verified.

Check that you are working/looking at the correct aircraft - component -

location. If after this check you still feel the manual is incorrect then the

manufacturer should be contacted - either direct or through your company

publications office. Work should not proceed until clarification has been

obtained from the manufacturer.

ual against aining/duties

If they are all ible, then you

other, more L..WlUU.c;u, personnelvUJlU.&Oil"").v the task.

Work Cards/Job Cards

Many organisations produce work cards/job cards. The procedure is printed

on the cards withprcvlsion made for sigrrattrresatregular intervais,stage

inspections and duplicate inspections.

The information on the cards is similar to that in the manual and is specific to

the task in hand and is laid out in a, usually, more readable and logical

manner.



If the task is long and/or complex the job card can be written out in such a

way as to break it down into stages. If the cards are kept up to date with

signatures and dates etc recorded as and when each stage is completed then a

continuous record is maintained.

This continuous record is important, particularly in relation to shift working or

when handing over a part completed job to another engineer.

During the handover, a de-briefing should occur between the 'outgoing man'

and the 'incoming man'. The de-briefing should include:

* Checking the cards are signed and up-to-date.

Averbal explanation of the progress of the job to-date.

An indication of any possible problems that may arise.

A situation report.

Aprogress report on the spares situation.

Expected (bymanagement) completion date and time.sible exchange numbers for ua.~±t'~~

*

**

*

*

gIrleel'n.~\elllC1Le~l'eM · ' .

and improve ,".::-,_wo fitted to

an example of how electronics have come to the aid of the '-UI"'U~--~

/ duplicate in

~-\JL'''''''I ......t and signed for

. . . . . " ' : : q J . l ' ~ ~ )as part of the

Amore recent development is the belt warn notebook computer with a head-up

display worn on the head by the engineer whilst working. The Rockwell Trekker

is a good example of this type of technology.

COMPUTER UNIT

-HEAD STRAP

Fig. 24 THE TREKKER NOTEBOOK COMPUTER

- 69 -



The small computer is worn on the waist belt and the screen (liquid crystal

display) is fitted by a strap to the head of the engineer. Control of the computer

is by voice commands which leaves both hands free to get on with the work.

Contents of the AMMcan be voice commanded and the pages/pictures are

"floated" as a virtual image on the 1 inch square liquid crystal monocular head-up display.

The computer is strapped to the waist of the engineer and the monocular unit

(with mic) is place on the head - with a cable attaching to the waist unit.

This system allows both hands free to get on with the work and at the same

time reduces the time spent "information gathering". The man/woman can get

on with the job whilst at the same time reading about it. There is no

interruption between "information gathering" and "job execution" .

Lap[(PRnmputers

Thes~i' ke the PC, can be

Can ij¢ sed at the work locatiV ;

Bo~i~' as re<:ently (2001) u~4~~_~~oftware 1..Ia.\~n.Ollro..""i

~ ; ~ o ~ . p . , ; ;• .~ ¥ ~ n . l. . 9 " . s . C ~ E ~ ~ ~ ~ ~ ·ua:tla:LrCral tM~~~~~ ~C;U::U;~II;:'

othe;~ ufa9fPrers will

d • ••• • • • • • • . • . . • . • . .. • . • • • • • • •• •On-board Fault Computers

As systems on aircraft have become more sophisticated the need has arisen to

provide on-board fault finding/BIT equipment. These simplify line maintenance

by providing an on-board fault recording system/ and instant checks to verify

component operational serviceability.

The data generated is usually in 2 forms, operational data and maintenance

data.

Operational Data will give the flight crew real-time information on the system's

status. It will allow them to act accordingly either using an alternative system

or checking with technical grourid~staff (radio or com/sat) on possible in-flight

rectification procedures.

Maintenance Data. This is generated by each system's built in test equipment

(BITE)which is consolidated before down loading by maintenance staff to

prepare the necessary rectification, spares procurement etc

- 7 0 _ ; : 0 . .



In general there are 3 classes of failure:

1. Failures which have an operational impact on the current flight. These

may also have an impact on subsequent dispatch depending on the

minimum equipment list (MEL)and are always reported to the

maintenance staff. Datalinking (comsat and sometimes by radio) can

send this information ahead of the aircraft to allow maintenance to

prepare the necessary rectification procedures, spares location etc.

2. Failures with no immediate flight operational consequences. Details are

only made available to the flight crew by request on a status page.

Rectification of a class 2 failure will depend on existing deferred defects

and the MEL.

3. Minor failures with no operational significance for the current flight

which are not even displayed for the flight crew. They are available to the

maintenance staff on request but cause no dispatch restrictions

ures.

the on-

displays

a dialoi':" ith any system

etc. The norm:::';: ode also

flight deck in .••.•.•••...ions and theas ce m(~ssi~~~miLPfo1vides a powerfUl·tdO.in fault

rectification, as well as verbal flight crew reports and aircraft logbook entries.

" " " " " " " " " , , , , , , "

1 Human Factors 1

Documents

Transcript of 1 Human Factors 1