This document sums up all the important information concerning Human Performance and Limitations. Human Performance and Limitations is one of the fourteen subjects that a student pilot needs to pass in order to continue the ATPL-training program. It is written by myself and can therefore contain fa...
ATPL THEORY
Human Performance and Limitations - Complete Summary
,Table of Contents
Safety Models 3
The shell model 3
Safety culture 3
The atmosphere 4
Atmosphere 4
The gas laws 4
The Human Body 5
Breathing 5
Lung capacity 5
Gas transfer 5
Blood pressure 6
Hypoxia 6
Decompression sickness 7
G-forces 8
Ozone (O3) 8
Human senses 8
The eye 9
The ear 11
Nervous and endocrine systems 12
Central nervous system 12
Body temperature control 13
Spatial disorientation and illusions 13
Illusions 13
Constant angle collisions 14
Spatial orientation 15
Spatial disorientation 15
Motion sickness 16
Vertigo 16
Vibrations 16
Health problems in aviation 16
Problems influencing a pilot 16
Other diseases 20
Tropical and epidemic diseases 20
Resting 22
Sleep 22
Information processing 24
Vigilance 24
Perception 25
Memory, learning and acquiring skills 26
Learning 27
Human error 29
James Reason’s model 29
Strategies for coping with human error 30
Flight deck ergonomics 32
Decision making 33
Situational awareness 33
2
,Safety Models
70% of all the accidents are attributed to human errors. Many accidents are not caused by a
single factor only.
Human error can also be made by engineers/managers etc. on the ground. It’s not always the
pilot his fault.
Before training, the number of faults made by a human is 1:100. So, 1 fault in every 100 actions.
After training, this ratio can be brought back to 1:1000.
The shell model
The shell model is a model that lets liveware (people), relate to other
‘categories’:
- Software. Someone reading a manual/ checklist.
- Hardware. Using switches/ controls in a plane.
- Environment. Weather conditions.
- Liveware (other people). ATC communications.
Safety culture
There are at least two ways of treating a safety culture:
- What the organisation thinks (attitude of employees towards safety).
- What the organisation does (procedures/ protection etc.).
ICAO tries to set up international safety standards, since there are big differences between
countries. To do so, they publish Standard and Recommended Practices (SARP’s).
This leads to an open culture: people report incidents freely to improve flight safety and learn from
previous accidents and incidents.
Swiss Cheese Model: sometimes, even with many safety barriers, an accident happens because
all borders are passed.
Dr. Reason thinks that a safety culture consists out of 5 elements:
- An informed culture. Organisation collects and analyses relevant data, and actively
disseminates safety information.
- A reporting culture. Cultivating an atmosphere where people have the confidence to
report safety concerns without fear of blame.
- A learning culture. Organisation is able to learn from its mistakes and make changes.
- A just culture. Unsafe acts will not be punished if the error was unintentional.
- A flexible culture. Organisation and the people in it are capable of adapting effectively to
changing demands.
SMS stands for a Safety Management System.
TEM stands for a Threat and Error Management. Difference:
- Threats: events/ errors that occur beyond the influence of an operational person.
- Error: action/ inaction by an operational person that leads to deviations from the
organisational/ operational intentions and expectations.
3
,The atmosphere
Atmosphere
The atmospheric conditions are always compared to standards. This standard is called ISA, which
stands for International Standard Atmosphere. There are different standards at different heights:
The gas laws
There are multiple laws that describe how the volume, pressure and temperature of a gas can
change.
Boyle’s law
!"#$%& ∗ ()&**$)& = ,"-*./-.
As pressure increases, volume decreases.
Charles’ law
!"#$%& ∝ .&%(&)/.$)&
As temperature increases, volume increases, if pressure remains constant.
Dalton’s law
Sum of the partial pressures gives the total pressure. So: 21% oxygen is responsible for 21% of
the total pressure.
Fick’s law
Gas diffuses from high to low concentration areas.
Henry’s law
States that the amount of gas dissolved in a liquid is proportional to the pressure of that gas over
the liquid.
General gas law
This law relates to both Boyle’s and Charles’ laws.
23 ∗ !3 25 ∗ !5
=
43 45
4
, The Human Body
Breathing
Breathing: inhaling and exhaling to transfer O to the blood
2
and CO to the air. When exhaling, the
2
intercostal muscles relax. Breathing can be
referred to as external respiration.
Alveoli: One cell-layer thick: here the O <->CO process
2 2
takes place. Gas transfer.
Lung capacity
- Total capacity of 6000mL.
- Tidal volume of 500mL.
- Residual volume of 1000mL.
- Vital capacity of 5000mL.
Vital capacity is the difference between the capacity of the
lungs after maximum inhalation, and the capacity remaining
after maximum exhalation.
Residual volume is the volume remaining after maximum
exhalation.
Inspiratory capacity is made up of the resting tidal volume (air going in and out of the lungs
during normal respiration) and the inspiratory reserve volume (extra air being inhaled when
working out, when the body requires more oxygen).
Expiratory reserve volume is the volume of air in the lungs when the body is at rest, and normal
expiration has occurred. This comprises of the expiratory reserve volume and the residual
volume.
Gas transfer
Haemoglobin is used to transfer O , via red blood cells, through the body. CO dissolves in the blood
2 2
plasma.
The rate of breathing depends on both O and CO concentrations. CO is more significant. Rising
2 2 2
CO -concentration therefore means that it leads to a higher breathing rate, to restore the optimum
2
ratio between CO and O .
2 2
CO is a toxic gas. The body ‘thinks’ you’re breathing in O2, but actually gets tricked by the similar
looking CO-gas. When facing during flight:
- Put on oxygen masks.
- Switch off cabin heating.
- Open fresh air vents.
- Avoid smoking.
- Maybe land ASAP.
5
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