Unit and information source for users ofUnit and information source for users of





Unit 2: Human Factors and Behaviours
in Aviation





1 – Human Factors and Human Performance

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A report by Patrick Teper


Terms of Reference

This report is being written to
produce some introductory exemplar training materials on the role of human
factors, their features and limitations. The report will include: labelled
diagrams, table and use of case studies where appropriate that can be used as a
reference and information source for users of the training materials.




Information for this report has
been researched through the internet and referenced appropriately. This
information has then been combined with my own thoughts and common knowledge to
produce the report.



In the
aviation industry, Human Factors are human conditions, such as fatigue,
complacency, and stress that can cause problems due to human error. These
factors are highlighted by Dupont’s Dirty Dozen which was developed in 1993 by
Gordon Dupont for the Transportation Safety Board of Canada. (See Appendix A.) The
twelve factors are the most common causes of accidents in the air due to
carelessness. (Renee Dupont-Adam – 2015) Human Factors are important in the
aeronautical engineering workplace due to small problems leading to
catastrophic effects in aviation.  Human
factors help link people to the systems that they work in thus improving
performance and safety in aviation. It is important that employees are aware of
the importance of human factors as employees are a direct link between human
factors and accidents in aviation.

Disregarding the psychological
aspects of human factors can lead to catastrophic consequences. For example, in
July of 2013 a South Korean Boeing 777 headed for San Francisco crashed on
landing, killing three passengers and injuring approximately 200.
Investigations suggested that pilot fatigue was one of the contributing human
factors. Complacency could also be seen as a contributing factor due to two of
the fatalities being caused by passengers not wearing their seatbelts.

 The SHELL model is a model in human factors
that concentrates on how humans interact with software, hardware and the
environment they are in as well as other people within the business. The SHELL
model was first developed in 1972 by Elwyn Edwards and then sorted into a
‘building block’ style structure by Frank Hawkins in 1984. (Frank Hawkins –
1993) The SHELL model focuses on a perspective that humans are very rarely the
only reason an accident occurs. Utilising the SHELL model can help saves lives
and money within a business by making employees more aware of dangers within
the company.

Heightened awareness now means that
accidents are less likely to occur. So much so, that 2016 was recorded as the
second safest year in aviation history. Over previous decades numbers of fatal
air accidents has decreased, even though the number of flights occurring has
increased. Air accident rates were at their highest in the 1970s and have
decreased greatly since then. It was within the years of accidents decreasing
that human factors were introduced to aviation so this data shows that
awareness of human factors has increased. There are fewer overall accidents
these days, even though the number of flights per year is much higher.

The Human

The human eye is made up of many
parts that help us see and interpret images. When light first hits the eye it
is mostly focused by the cornea, a transparent structure found in the very
front of the eye. Light then passes through the pupil, an adjustable circular
opening of the iris. Light is then passed through the lens which continues to
focus the light. After passing through the lens the light travels through the
vitreous gel and hit the retina, a series of sensitive cells. When light hits
these sensitive cells it is converted into electrical signals and transmitted
to the brain through the optic nerve. The brain then translates the electrical
impulses into the image seen by the person. (Ker Than – 2016)


The Human Ear

Sound waves are created by
vibrations and travel through the air. These sound waves enter the ear canal
and travel down until they hit the eardrum, causing it to vibrate. This
vibration moves the three small bones: hammer, anvil and stirrup. This linkage
then knocks on the membrane window of the cochlea and causes fluid in the
cochlea to move. This then passes an electrical impulse to the auditory nerve
which passes a message onto the brain. The brain then translates the impulses
into sounds we hear. (Emmanuel Deruty – 2011)

Degraded eyesight and hearing can
result in poor human performance and behaviour. With poor sensory information,
the brain can be distracted or not receive information it should. Poor hearing
can lead to accidents by masking warning signals and affect concentration and
decision making, such as not hearing warning sirens on machinery or vehicles.
Poor eyesight can lead to instructions being read incorrectly or important
things being missed. Degraded senses can result in many of ‘Dupont’s Dirty
Dozen’ including Lack of Communication, Lack of Awareness and Fatigue. This can
result in accidents occurring.

Long term memory storage is created
in our brains by approximately one billion neurons called pyramidal cells.
These are only approximately 1 percent of the brains total neurons. It is
believed that memories form in the connections between neurons and across
neuron networks. Each neuron links to about one thousand other neurons. (Adam
Hadhazy – 2015) It is believed that humans won’t fill their long term memory so
therefore the human memory is not seen as limited.

Short term memory however is
limited. Short term memory tends to be between 15 and 30 seconds of memory and
has a capacity of about 7 items. The storage can be lost easily through
distractions as it is very fragile. Short term memory is usually acoustic with
visual information often being translated into sounds.(Saul McLeod – 2009) The
duration of short term memory was proposed by Atkinson and Shiffrin in 1968
along with the ‘Multistore model of memory’. The idea of short term memory
having a capacity of 7 items was developed by G Miller in 1956 and published in
a review as ‘The magical number seven’. Tests have shown that most adults are
able to store between 5 and 9 items in short term memory which averaged out at

Memory loss can occur due to poor
concentration and noticing things in the first place due to a poor attention
span. Memory loss can also be caused by head traumas and strokes, causing
sudden memory loss.(NHS – 2015)

Memory and attention can be affected
by many different factors some of which are also part of Dupont’s Dirty Dozen.
This can include sleep deprivation, depression, stress and nutritional


Working in demanding situations can
cause risks to airworthiness and personal safety. Working in demanding
situations can result in many of Dupont’s ‘Dirty Dozen’ such as stress,
pressure and fatigue. These factors can result in employees making mistakes or
forgetting to do things that can compromise the airworthiness of an aircraft or
the safety of other employees. With decreased performance come risks to pilots
and passengers of aircraft as well as people on the ground.



Appendix A

The dirty dozen are:

1.         Lack
of Communication

2.         Complacency

3.         Lack
of Knowledge

4.         Distraction

5.         Lack
of Teamwork

6.         Fatigue

7.         Lack
of Resources

8.         Pressure

9.         Lack
of Assertiveness

10.       Stress

11.       Lack
of Awareness

12.       Norms

(Renee Dupont-Adam – 2015)



Renee Dupont-Adam – ‘Let’s Talk Human Factors – Origin of Dirty Dozen’
– August 17th 2015


Frank Hawkins – Human Factors in flight – 1993 Ker Than – ‘How the Human Eye Works’ – May 5th
2016http://www.livescience.com/3919-human-eye-works.html National Eye Institute – Diagram of the Eye https://nei.nih.gov/health/eyediagramBBC Bitesize – Diagram of the Earhttps://www.bbc.co.uk/education/guides/z8d2mp3/revision/2Emmanuel Deruty – ‘How the Ear Works’ – March 2011https://www.soundonsound.com/sound-advice/how-ear-worksAdam Hadhazy – BBC Future – What’s the most we can
remember? – April 2nd 2015http://www.bbc.com/future/story/20150401-whats-the-most-we-can-remember NHS – Memory Loss (Amnesia) – January 12th 2015https://www.nhs.uk/conditions/memory-loss/https://ihf.co.uk/5-aviation-accidents-caused-by-hf/