A wise philosopher once observed that there is nothing new under the sun.
But he added, there are many old things that we do not yet know.
This observation is especially true in the context of aviation.
According to air accident statistics, 73% of all aircraft accidents
which are occurring at the beginning of the 21st century are caused by human error.
Yet looking back 60 years to the early days of the Second World War,
we read in an Air Ministry training manual for Royal Air Force pilots
that 75% of all accidents happen when taxiing, taking off or landing.
These are not difficult things for the experienced pilot to do.
The accidents happen when he allows attention and accuracy of performance to lapse.
Armed with this rather surprising and revealing statistic,
we can quickly deduce that a thorough understanding of our performance capabilities
and limitations as human beings might do much to serve the cause of flight safety.
In the very early days of aviation, many accidents were caused by equipment failure
or other factors beyond the control of the pilot.
But in the past 50 years or so, human error or failing has been the major cause of accidents,
most often attributable to flight crew but also to maintenance personnel and air traffic controllers.
Airframes have become more reliable.
Modern engines and associated equipment seldom fail.
And navigational equipment, both in the aircraft and on the ground,
has improved in leaps and bounds, giving a degree of accuracy undreamt of by the early pioneers of flying.
The improvement in the equipment available, allied with the advances in meteorological forecasting,
should have virtually eliminated aviation accidents, except for the most freak conditions.
But these accidents have not reduced at the rate one would expect from the advances of technology.
The factor that has not changed is human fallibility.
It is often seen in reports of aircraft accidents that the cause was pilot error.
A more correct reason would be human error.
Human error can occur at all stages of an aircraft's life or operation.
Designers may make small arithmetical slips which may not be picked up.
Servicing personnel can put the wrong fuel and lubricants into engines or fit components incorrectly.
Operations and loading staff can get the weights wrong.
But the major cause of accidents are errors committed by pilots.
This CBT course in Human Performance and Limitations has been designed to help you, the pilot,
to appreciate the limitations of the human being in the aviation environment.
Our bodies are designed to exist on the surface of the Earth in the lower atmosphere
and to be subject to an unchanging gravitational force.
When flying, your body is exposed to a new environment,
such as the rarefied air and low pressures of the higher altitudes, changes in pressure, shortage of oxygen,
variations in acceleration forces, sometimes referred to as g-forces.
It is true that most private pilots flying light aircraft in Europe operate at altitudes below 10,000 feet
and are not exposed to very high altitudes.
But your licence may entitle you to fly aircraft with operating ceilings much higher than 10,000 feet.
All pilots are, however, exposed to changes in pressure and variations in gravitational acceleration.
As a pilot, therefore, you will need to learn, amongst other things,
how to recognise the symptoms of oxygen deficiency and the effects of high g-forces,
or significant changes in temperature.
Furthermore, you will need to develop an appreciation of the psychological aspects of flying,
such as perceiving and processing information under high workloads, assessing data, making decisions,
and carrying out the necessary actions to ensure the safe progress of your flight in all conditions.
By following this course conscientiously, you will learn some of the ways in which mistakes occur
and be able to reduce your potential for error-making to a minimum.
We certainly hope that you will not have to face any real emergencies in your flying career,
but to be forewarned is to be forearmed. Knowledge brings confidence.
This CBT course is designed to increase your knowledge of yourself and your limitations,
and thereby greatly increase your chances of enjoying an accident-free flying career.
Men and women have been piloting powered aircraft for about 100 years, so there are a lot of teachers to
learn from.
Much of the old advice is still good, especially where light aircraft flying is concerned.
The manual of elementary flying training issued to World War II aircrew cadets emphasised to pupil pilots,
watch your own progress and practice the things you do badly.
After a flight, go over it in your mind and extract from it new lessons it most certainly has to
teach you.
Some things never change.
An often quoted saying in the flying world, which underpins the importance of the subject of human performance and limitations,
is that aviation in itself is not inherently dangerous, but to an even greater degree than the sea,
it is terribly unforgiving of any carelessness, incapacity or neglect.
Human performance and limitation considerations are relevant wherever and whenever the human being is involved in aviation.
Thus the subject plays a fundamental and vital role in promoting the efficiency and expediency of flight operations.
But above all else, knowledge of the subject promotes the cause of flight safety.
With a sound understanding of human performance and limitations, your appreciation of and performance in the following areas will be
enhanced.
Use of checklists and charts. Getting maximum benefit from training. Communications.
Another principal aim of human performance and limitations is to endow you with an outlook and approach to flying matters,
which, at the same time as achieving the aims already stated, will make you into a competent pilot.
Or it is the competent pilot who conducts himself within the aviation environment in such a way that the flying
operations in which he is involved take place safely and expeditiously and achieve the aim of the sortie.
When assessing the competency of a pilot, a number of qualities are sought.
The following qualities go towards making a safe, effective and competent pilot.
The competent pilot has a highly developed sensor responsibility, is a master of flying theory, possesses good piloting and aircraft
handling skills,
is motivated to maintain the highest standard of airmanship and piloting proficiency, is physically fit, reliable, of even temper,
is an effective member of the aircrew or ground crew team, remains calm in a crisis, has an eye for
detail, is able to assess risk and take the right decision based on that assessment,
can retain self-control and take effective decisions in high stress situations, is an effective manager of the aircraft's crew.
During your formal flying training, your flying will be carried out under the supervision or authorization of your flying instructor.
He will structure your training and deliver practical and often theoretical instruction.
He will also give you briefings before training sorties. After the sortie, he will carry out a debrief.
But after you qualify for your pilot's license, you will do much of your flying as pilot in command or
maybe share your flying with another qualified pilot.
The training process should, however, never cease. That is where self-training comes in.
Self-training is a process aimed at developing within yourself specific skills, knowledge or attitudes.
Though you should never hesitate to ask to fly with an instructor or to talk through with an instructor aspects
of piloting and aviation that concern or interest you,
it is of fundamental importance that you do not rely solely on formal training to maintain or further your aviation
expertise.
Every opportunity should be taken to increase your competency, knowledge and professionalism.
Set yourself an aim for every flight and always self-debrief after landing.
Read, research, discuss and discover as much as you can of this enormous and fascinating field of human activity.
As your competence and expertise increase, so will your self-confidence.
This in turn will arm you to tackle new aspects of flying with enthusiasm and conviction.
When compared with other forms of transport, aviation has the best safety record.
The risk of death per person per year in a car accident is 1 in 10,000 in the UK
and 1 in 4,000 in the USA.
The flying accident rate is approximately 1 per million airport movements, in other words, approximately 1 accident per million legs
flown.
But despite the many tremendous technical advances in aircraft and engine design, instrumentation and air traffic control capability,
and improvements in overall standards of safety that have been achieved in recent decades,
the complex relationship between man, the flying machine and the air in which both fly still causes accidents to happen.
As you can see from the chart, the fallibility of the human being is doubtless the single greatest cause of
flying accidents.
In aviation, perhaps more than in other fields of human endeavour, mankind remains as much a victim of himself as
of the elements around him.
Approximately 73% of all accidents are caused by human factors.
Historically, this figure has not changed since the 1950s.
Controlled flight into terrain, CFIT, remains the most common general form of accident.
The five most common specific causes of pilot-induced accidents in order of frequency are
loss of directional control, poor judgement, airspeed not maintained, poor pre-flight planning and pre-flight decision making, not maintaining
ground clearance.
The phases of flight most prone to accidents starting with the most common are
intermediate and final approach, landing, take-off, descent.
Since awareness and recognition of one's responsibilities is to be halfway towards being sure of carrying them out,
we will end this introduction to human performance and limitations by mentioning some of the most important responsibilities of the
pilot in command.
Our list is not exhaustive. Your flying instructor will give you further guidance.
Click on the continue button to reveal our list of the responsibilities of the pilot in command.
Thank you for watching.
The Earth's atmosphere is the envelope of air which surrounds our planet.
All aeroplane flights take place within the atmosphere as aircraft, by definition, rely on air to generate the lift which
keeps them airborne.
Their engines too, unless they are rockets, rely on air for the combustion process which is so essential to their
function.
Human beings live their lives in the lower reaches of the atmosphere where temperatures, pressures and oxygen supply are able
to support life.
Knowledge of our atmosphere is important to pilots because human pilots can operate at high altitudes only if the systems
of the aircraft they fly can reproduce the conditions of the lower atmosphere.
The two layers of the atmosphere in which all conventional aeroplane flights take place are the troposphere, closest to the
Earth, and the layer above it, the stratosphere.
For our purposes in human performance and limitations, the troposphere may be considered to stretch from the Earth's surface to
an altitude of about 36,000 feet.
The stratosphere reaches up to over 100,000 feet but it can be seen that all light aircraft flying takes
place in the troposphere.
The troposphere contains three quarters of the total atmosphere measured by weight of air and it is also that layer
of the atmosphere containing almost all the weather.
For our present purposes, the atmosphere may be considered as air consisting of the following gases.
We give their proportion by volume. Nitrogen makes up just over 78% of the air or atmosphere by volume.
Oxygen comprises almost 21% of the air. A mere 0.03% of the air is made up from
carbon dioxide.
The remaining 1% of the air consists of argon plus traces of other gases.
In that part of the atmosphere in which aeroplanes fly, the relative proportions of the constituent gases we have mentioned
remain constant.
As pilots concerned with our cabin environment and our well-being, we need to understand how pressure and temperature vary
with altitude.
The best way to do this is to consider what is known as the International Standard Atmosphere or ISA.
As you are aware, atmospheric conditions, for instance pressure, temperature and humidity, change from day to day.
Thus, in order to describe the atmosphere, scientists have created an idealised standard atmosphere or ISA which you see represented
graphically on your screen.
The atmospheric conditions depicted here may probably never be present on any given day, but they give us a yardstick
by which to measure atmospheric phenomena.
The most important factors to note for the subject of human performance and limitations are that pressure and density reduce
with increasing altitude throughout the atmosphere as a whole
and that temperature falls with increasing altitude throughout the troposphere while remaining almost the same at around –56.5°C throughout
the stratosphere.
Note especially how the sea level air pressure decreases with altitude.
Depending on local or national convention, the ISA value of sea level air pressure may be referred to variously as
1013.25 hPa, 1013.25 mbar, hPa being units of equal magnitude, 14.7 pounds per square inch, 29.92
inches of mercury or 760 mmHg.
At 8,000 feet the pressure is three quarters of its sea level value.
At 18,000 feet the pressure is half that at sea level.
By 36,000 feet the pressure has reduced to only a quarter of its sea level value.
One other relevant factor for human performance and limitations that you should note is that the ISA reduction of temperature
with height, the environmental lapse rate, is 1.98°C per 1,000 feet.
We have already learned that though atmospheric pressure decreases with altitude, the volumetric proportions of the constituent gases of the
atmosphere remain constant.
Oxygen for instance continues to make up about 21% of the air we breathe at 8,000 feet, even
though the air pressure at 8,000 feet is only three quarters of its value at sea level.
In order that we may understand how our breathing is affected by increasing altitude, it is important to note here
the physical fact that if air pressure decreases with altitude, the partial pressure of oxygen will also decrease with altitude.
For example, we know that ISA sea level pressure is 1,013.25 HPa or millibars.
This is equivalent to 760 mmHg because air pressure can support a column of mercury 760 mmHg at sea level.
Oxygen making up 21% of the air by volume consequently has a partial pressure of 160 mmHg at sea
level.
At 8,000 feet, total air pressure measured in millimeters of mercury is only 570 mm.
The partial pressure of oxygen at 8,000 feet is therefore 120 mmHg.
We now have sufficient knowledge of the atmosphere for our present purposes.
We have already seen that human beings live their lives in the lower reaches of the atmosphere.
Our bodies are used to the temperatures, pressures and supply of oxygen that prevail there.
In our normal existence, we are exposed to the normal gravitational force or acceleration which we sense through the weight
of our body.
Unless we have a very high powered job, our bodies do not have to function under conditions of abnormal stress
or very high workloads.
The judgments and decisions we take from minute to minute do not normally determine whether we live or die.
And if we are taking medically prescribed drugs or medicines, we can usually carry on as normal.
These conditions and assumptions which apply to our everyday life on the ground do not always hold true when we
are piloting an aircraft.
While steady cruising flight at low or medium altitudes imposes no unusual conditions or stresses on our bodies,
flight at high altitude, over 10,000 feet, and the practice of aerobatics, exposes the body to conditions and forces
not met on the ground.
Cockpit workload can be high, especially in an emergency or bad weather, or in critical phases of flight such as
landing or flying on instruments.
Pilots therefore need to learn how the human body reacts, both physiologically and psychologically, to the effects of stress, altitude,
and variations in g-forces etc.
The safe and efficient pilot therefore needs a good basic understanding of how the human body functions under normal conditions,
and under conditions it may be subject to, and stresses it may have to endure in flight.
In human performance and limitations, our study of the body will concentrate on the functioning of three of its principle
systems,
the nervous system, the respiratory system, and the circulatory system.
The nervous system is the most highly developed and delicate of all the body's systems.
It correlates and controls all the other systems of the body through a type of electrochemical communications network of nerve
fibers.
At the center of the nervous system is the brain, through which we control all purposeful bodily functions, including decision
making and speech,
and where we experience consciousness, vision, hearing, taste, smell, thought, and memory.
In human performance and limitations, our study of the nervous system will mainly be concerned with vision, hearing, balance, situational
awareness, decision making, and stress tolerance.
But first of all, it will be useful to consider briefly the nervous system's general architecture.
The nervous system is divided into three main parts.
The central nervous system consists of the brain and the spinal cord.
It is the brain which analyzes and interprets the sensory data fed into it from the rest of the nervous
system.
The peripheral nervous system connects the central nervous system to the various organs and muscles of the body through sensory
nerves and motor nerves.
The peripheral nervous system regulates all the purposeful and reflex actions carried out by the body's organs and muscles.
Sensory impulses traveling towards the brain have their beginnings in various peripheral structures such as the skin, muscles, joints, and
special organs like the eye and the ear.
The senses of sight and hearing are so important to pilots that they will be considered in dedicated lessons.
Other functions regulated by the autonomic nervous system are arterial pressure, gastrointestinal motions, urinary output, sweating, body temperature, and fight
or flight response or reaction to stress.
We shall return to the nervous system when we cover vision, hearing, balance, situational awareness, making decisions, and stress tolerance.
In order to function correctly, oxygen is required by all the cells and tissues of the body.
For example, brain cells will die if they are deprived of oxygen for as little as two minutes.
It is the respiratory system which, through the act of breathing, ensures the transference of oxygen from the atmosphere to
the cells and tissues and of carbon dioxide from the tissues back to the atmosphere.
Nitrogen is also absorbed by the body during respiration but plays no role in bodily processes. It does play an
important role, however, in the onset of decompression sickness.
External respiration is the absorption of oxygen from the air into the blood and the excretion of carbon dioxide from
the blood into the air. This takes place in the lungs.
Internal or tissue respiration refers to the transfer of oxygen from the blood to the tissues of the body.
At the same time as this occurs, the tissues give up carbon dioxide to the blood.
We can see then that the blood circulation system, which we shall be considering later, plays a vital role in
the respiratory process.
Normal breathing is a purely automatic process under the unconscious control of the nervous system, although for short periods the
rate and depth of respiration can be controlled at will.
The normal rate of respiration in adults is 14 to 18 breaths a minute.
The respiratory center is especially sensitive to the amount of carbon dioxide in the blood.
The level of carbon dioxide in the blood effectively regulates the rate and depth of breathing so that the concentration
of carbon dioxide in the blood remains constant.
We shall return to the subject of respiration in the lesson on effects of partial pressure, where, amongst other things,
we will learn about the effects of altitude, hypoxia, hyperventilation, and the effects of rapid decompression.
In order to function properly, indeed in order to live at all, the organs and tissues of our body must
receive an adequate supply of nourishment and oxygen and be able to expel the waste products which result from their
activities.
This vital process is carried out by the blood.
The blood circulation, or circulatory system, is the mechanism that maintains the constant circulation of blood throughout the body.
This mechanism consists of the heart and the various types of blood vessels.
The heart is located in the chest cavity.
It is about the size of a clenched fist.
And is the powerhouse, or pump, of the circulatory system.
A section through a human heart is shown on the screen.
The heart has four chambers, two ventricles, two auricles, or atria.
The auricles, or atria, act as receiving chambers for the pump.
And the ventricles are the distributors which propel the blood through the lungs and circulatory system.
The aorta is the main artery of the body and is the channel through which the blood leaves the left
ventricle.
Leading into and out of the heart are various blood vessels.
The arteries, which carry blood from the heart at high pressure, and the veins, which return blood to the heart
at low pressure.
In the diagram on the left, the arteries are coloured red and the veins are coloured blue.
As the heart itself is a muscle, it requires its own blood supply system which is provided by the coronary
arteries and veins.
A narrowing or blockage of the coronary arteries or veins is the cause of one of the major diseases which
may affect the heart.
Oxygen is obtained from the atmosphere and the blood picks up the oxygen from the lungs for transport around the
body.
Blood containing oxygen is pumped around the body from the left ventricle.
A system of one-way valves in the heart prevents blood going the wrong way.
The oxygenated blood passes through the aorta into the major arteries which divide into the smaller arteries before arriving at
the smallest vessels of the system, the capillaries.
The capillaries have very thin walls, only one cell thick, which allow the passage of oxygen from the blood into
the tissues by diffusion.
They also allow carbon dioxide and water vapour to diffuse in the reverse direction.
It is emphasised that this exchange can only take place at the capillaries.
Even the smallest arteries and veins have walls too thick to allow the exchange of gases.
Deoxygenated blood passes from the venous capillaries to veins which progressively increase in size and returns eventually to the right
atrium.
It then passes to the right ventricle which pumps the blood via the pulmonary artery to the lungs.
The carbon dioxide and water in the blood are released to the lungs and at the same time the blood
is reoxygenated.
The blood then returns to the heart via the pulmonary vein and left auricle.
It is then pumped back into the aorta by the left ventricle.
Each time the left ventricle contracts, it forces blood into the aorta causing a wave or expansion to spread over
the whole of the arterial system, gradually dying away as it reaches the capillaries.
This wave or expansion constitutes the pulse which can be felt in the superficial arteries of the body.
The normal rate of the pulse is the rate of the heartbeat.
A healthy adult at rest has a pulse rate of between 60 and 80 beats per minute.
This rate is increased by exercise, emotional disturbances and disease.
For instance, when the body experiences stress or fear, adrenaline is released into the bloodstream causing an immediate increase in
the pulse rate.
We have already learnt that the blood plays an essential role in the maintenance of life.
It carries oxygen and other nutrients to the body's tissues and organs and removes their waste products.
The body of an average adult contains about 6 litres or 10 pints of blood which constitutes about one twentieth
of total body weight.
Plasma, a yellowish fluid, is the liquid part of the blood in which float the blood cells or corpuscles.
The plasma delivers digested food products such as glucose and amino acids, dissolved proteins, various hormones and enzymes.
The plasma also contains salt.
You may have noticed that blood tastes slightly salty.
The blood cells are of three types.
Red blood cells which contain haemoglobin and carry oxygen to the cells and tissues of the body.
White blood cells whose main function is the defence against disease.
They produce antibodies to fight bacteria.
And platelets, the smallest of the blood cells, which assist in the blood clotting process.
Click on the button on the screen to reveal the principal functions of the blood.
The circulatory system can malfunction in two principal ways.
The main components of the system, the heart and the blood vessels, may develop a fault.
The blood may become unable to carry enough oxygen for the needs of the organs and tissues of the body.
Like all other organs and tissues, the heart muscles require oxygen to continue working.
This oxygen is carried to the heart by the coronary arteries.
If a narrowing of these vessels should occur, then insufficient blood may reach the heart muscle.
This lack of oxygen, particularly when the heart is beating faster due to exercise or stress,
may give rise to the symptoms of angina, with a pain in the chest and arms.
If the blood supply is cut off completely, then a portion of the heart muscle may die, that is, suffer
an infarct.
The heartbeat may become irregular or even fail completely, the sufferer experiencing heart attack.
Among the factors predisposing a human being to the risk of angina or heart attack,
and which may be mitigated by medical treatment or change of lifestyle are high blood pressure,
raised blood cholesterol, smoking and lack of exercise.
Other factors such as stress, obesity, alcohol and certain dietary considerations are less clearly understood.
Body organs and tissues may be deprived of the oxygen they need because of illness or disease.
For instance, the blood of a sufferer from anaemia contains insufficient haemoglobin or red blood cells
for reasons that go beyond the scope of this course.
A pilot suffering from hypoxia may quickly be unable to guarantee the safety of his aircraft and passengers.
Both his intellectual and sensory judgement will be impaired.
If serious oxygen deprivation continues, the pilot will become unconscious and die within minutes.
For instance, at 25,000 feet without a supply of supplementary oxygen, a pilot would become unconscious within 3 minutes.
Hypoxia will be dealt with in the lesson entitled The effects of partial pressure.
The dramatic and sudden incapacitation of a pilot during flight is extremely uncommon and very rarely the cause of an
accident.
Regular medical examinations minimise the risk of total incapacity due to heart disease, epilepsy and so on.
As the pilot grows older, the frequency of medical checks increases.
Electrocardiogram recordings are used more and more with advancing age in order to spot those at risk.
The red blood cells carry oxygen to the body's organs and tissues
and it is haemoglobin within the red cells which is the main vehicle of oxygen transportation.
However, haemoglobin has a much greater affinity for carbon monoxide than for oxygen
and when carbon monoxide is present in the air that the body breathes in,
the haemoglobin will transport that gas in preference to oxygen.
Carbon monoxide is harmful to the tissues and organs.
Now, exhaust gases from reciprocating engines can consist of as much as 9% carbon monoxide.
So gases from leaking exhausts which may enter an aircraft's cabin, especially through the heater,
and be breathed in by the pilot will expose the pilot to the dangers of carbon monoxide poisoning.
Carbon monoxide is odourless and colourless which adds significantly to its dangers.
Its effects are also cumulative, so the chances are that a pilot will not immediately recognise the danger he is
in.
For both these reasons, carbon monoxide detectors are fitted to the instrument panels of many light aircraft.
These detectors become discoloured if carbon monoxide is present in the cabin.
Click on the button to reveal some of the symptoms of carbon monoxide poisoning.
Headache
Dizziness
Nausea
Impaired vision
Lethargy or weakness
Impaired judgement
Personality change
Impaired memory
Flushed cheeks and cherry red lips
Convulsions
If a pilot suspects that he or his passengers are displaying the symptoms of carbon monoxide poisoning,
or if the carbon monoxide detector becomes discoloured, immediate action needs to be taken.
Click on the button to reveal a list of recommended actions.
Turn off cabin heating
Open cabin ventilators
Consider using oxygen if available
Land as soon as possible
Smoking tobacco produces carbon monoxide which links with the haemoglobin in the blood to deny oxygen carriage.
The circulatory system of a pilot smoking 20 cigarettes a day may have a reduction in oxygen carrying capacity,
which puts him at an equivalent altitude of 4,000 to 5,000 feet higher than that at which he
is actually flying.
So a pilot who is also a smoker may experience the symptoms of oxygen deprivation or hypoxia at a lower
altitude than a non-smoker.
He will also have increased susceptibility to carbon monoxide poisoning.
Click on the button to reveal other dangers of smoking.
Lung cancer
Breathing problems
Circulatory problems
Reduced tolerance to g-forces
Increased risk of heart attack
Degradation of night vision
Alcohol is not really a stimulant.
It acts primarily as a depressant on the nervous system, with some critical areas of the brain being especially vulnerable.
By depressing the highest centres of the brain, it lessens an individual's powers of self-control, self-consciousness and anxiety.
Alcohol is not digested in the human body.
It is absorbed directly from the stomach and intestines into the bloodstream.
From there it is carried to every portion of the body.
The liver is then responsible for eliminating the alcohol and does this by changing the alcohol into water and carbon
dioxide.
Drunkenness occurs when the individual drinks alcohol faster than the liver can dispose of it.
Taking half a pint of beer or a standard glass of wine or tot of spirits as being one unit
of alcohol,
we may assume that alcohol is only slowly broken down by the body and eliminated from the blood at a
rate of approximately one unit per hour,
though that rate may vary from individual to individual.
The consumption of one and a half pints of beer or three whiskies will result in a blood alcohol level
of about 45 to 50 mg per 100 ml
and so it will take up to four hours for the blood level to return to normal.
Consumption of alcohol above certain levels can cause permanent damage to the body.
The recommended maximum levels can be read from the screen.
Research has shown that blood alcohol concentrations of 40 mg per 100 ml, which is half the current legal driving
limit,
are associated with significant increases in errors committed by pilots.
Click on the button to reveal a list of other effects that the consumption of even small amounts of alcohol
may have on the body.
For more information, visit www.agilent.com
This classifies a maximum blood alcohol limit for pilots of 20 mg per 100 ml of blood.
British regulations advise that pilots should not fly for at least 8 hours after taking small amounts of alcohol
and proportionally longer if larger amounts are consumed.
They recommend that pilots abstain from alcohol for at least 24 hours before flying.
Mixing the consumption of alcohol and drugs is absolutely prohibited, as this can lead to disastrous and unpredictable consequences.
Blood pressure is the pressure which the blood exerts on the walls of the main arteries.
When an artery is cut, it can be seen that in addition to the continuous stream of blood flowing out
under high pressure from the end nearest the heart,
there are regular spurts of increased pressure corresponding with each heartbeat.
The permanent pressure, the lower of the two, is called diastolic pressure.
The increased pressure occurring with each beat of the heart is called the systolic pressure.
Blood pressure is measured in millimetres of mercury.
Blood pressure is expressed as two numbers, the systolic pressure being mentioned first,
followed by the diastolic pressure, for example 120 over 80.
120 over 80 is a normal blood pressure for a healthy young adult.
The maintenance of a normal systolic blood pressure is necessary to good health.
Low blood pressure can be symptomatic of heart failure or shock, but it is high blood pressure or hypertension rather
than low blood pressure which is a major cause of unfitness in pilots.
High blood pressure can cause blood vessels to burst, especially in the brain, causing a stroke.
JIA regulations stipulate that a pilot with a blood pressure of 160 over 95 is unfit.
High blood pressure is difficult to detect without specialist measuring equipment.
Possible causes of high blood pressure are shown on the screen.
Stress, smoking, poor diet, for example excess fat and or salt, obesity, lack of exercise, age and narrowing of the
arteries.
Like many people, pilots may wish to donate blood.
However, in order to prevent the very slight risk of post-transfusion faintness, it is recommended that after giving blood
pilots rest supine for up to 20 minutes and drink plenty of fluids.
It is important to note that pilots should not fly within 24 hours of giving blood or blood plasma.
This concludes the lesson on the human body.
We learnt from the lesson on the atmosphere that air pressure decreases with altitude from its typical sea level value
of 1013.2 HPa or 760 mmHg.
At 36,000 feet, air pressure measures less than 255 HPa or 190 mmHg, about a quarter of the sea
level value.
We have learnt too that whatever the altitude, the proportion of oxygen in the air always stays the same, that
is about 21% by volume.
As the total pressure of air decreases with altitude, the partial pressure of oxygen decreases too, from a sea level
value of 160 mm to only 40 mm at 36,000 feet.
Air density also decreases with increasing altitude.
So, as density is defined as mass per unit volume, a given volume of air, say the volume of a
human lung, will contain a smaller mass of oxygen than at sea level.
The human organism is designed to function normally in the lower atmosphere under sea level values for air pressure, air
density and temperature.
People who live for long periods at high altitudes, for example in mountainous areas, can adapt to low partial pressures
of oxygen by producing extra red blood cells.
But normal healthy human beings used to living near sea level will need supplementary oxygen to carry out sustained physical
activity at altitudes exceeding 10,000 to 12,000 feet.
The lower air density means that less oxygen will be taken into the lungs with each breath compared to sea
level, and the lower partial pressure of the oxygen will mean that even less oxygen will diffuse from the lungs
into the bloodstream.
Pilots will normally begin breathing supplementary oxygen from 10,000 feet above sea level.
As altitude increases still further, the supply of supplementary oxygen must similarly increase.
At about 34,000 feet, pilots require 100% oxygen.
Above 40,000 feet, oxygen must be supplied to the pilot through a pressure breathing system.
The term hypoxia is used to describe the condition whereby the body is not receiving enough oxygen to meet its
needs.
It follows from what we have learnt about the effects of increasing altitude on the human body that the occupants
of an aircraft flying at over 10,000 feet will suffer from hypoxia if no supplementary oxygen supply is available
or if the supplementary oxygen supply is faulty.
Whatever the reason, the onset of hypoxia will be quicker, and its effects will be more severe the higher the
altitude.
The severity of hypoxia will also increase with increasing length of time, during which the human body is deprived of
an adequate oxygen supply.
In any given situation, the effects of hypoxia are further increased the higher the level of physical or mental activity.
Extremes of temperature can also aggravate the effects of hypoxia.
If a passenger has consumed alcohol, that too may aggravate the symptoms.
It should be noted especially that a tobacco smoker is likely to experience the effects of hypoxia at a lower
altitude than a non-smoker, because smoking reduces the availability of haemoglobin to transport oxygen.
A regular smoker will start to suffer from hypoxia approximately 4,000 to 5,000 feet below that of a
non-smoker.
In order to guard against the onset of hypoxia, it is very important that the crew of an aircraft should
be on oxygen above 10,000 feet.
It is also of vital importance that pilots be able to recognize the symptoms of hypoxia and to know what
steps to take to prevent its aggravation, minimize its effects and to eliminate its causes.
The first symptom of lack of oxygen is likely to be personality change manifested through a lack of inhibitions or
euphoria.
Then the affected person will experience difficulty in carrying out mental tasks.
Impaired judgement will follow.
Click on the button marked Reveal to view these and other common symptoms of hypoxia.
You may reveal the list as many times as you like if you wish to test yourself on the symptoms
of hypoxia.
The importance of pilots being able to recognize hypoxia cannot be overstated.
Early identification of the symptoms of hypoxia will allow the pilots to carry out the appropriate drills in sufficient time
to avoid jeopardizing the well-being of the crew or the safety of the aircraft.
Generally speaking, the immediate actions to take if hypoxia is suspected are
Provide oxygen
Descend to a level where atmospheric oxygen is present in sufficient quantities to meet the body's needs or to minimum
safe altitude, whichever is the higher.
Finally, pilots must familiarize themselves with the appropriate oxygen drills for the aircraft they are flying before venturing above an
altitude at which hypoxia can occur, that is above 10,000 feet AMSL.
Some of the factors predisposing to hypoxia are unavoidable risks of flying.
Others can be reduced by good personal habits and forethought.
Some pointers are
When anticipating flying above 10,000 feet, ensure that a serviceable supplementary supply of oxygen is available and that the
correct method of use is known.
Ensure that passengers are correctly briefed.
Fly only if you are 100% fit and you are not taking any medication or drugs.
Ensure that cabin heaters are thoroughly checked and serviceable.
Though most private pilots flying light aircraft do not operate at very high altitudes, here for your information is a
table showing for various altitudes how long it would take for a pilot or passenger to become incapacitated if totally
deprived of supplementary oxygen.
This is known as the time of useful consciousness.
Hyperventilation may be simply defined as over-breathing, that is lung ventilation in excess of the body's needs or breathing
in excess of the ventilation required to remove carbon dioxide from the body.
Hyperventilation may well be caused by hypoxia, but hypoxia is far from the only cause.
It is important to realise that hyperventilation that is unrelated to hypoxia cannot be treated by breathing oxygen.
At low altitudes, the most common causes of hyperventilation are anxiety, motion sickness, shock, vibration, heat, high g-forces.
Making the most of your training is the best way of avoiding the onset of hyperventilation in yourself as a
pilot.
High standards of training and the cultivation of a deep understanding of flying theory breed confidence and decreases the chances
of a pilot getting into dangerous situations or of becoming over-anxious in emergency situations if they are encountered.
As a pilot yourself, make sure that you are aware of nervousness or anxiety in your passengers and know how
to reassure them.
An anxious passenger may even begin to hyperventilate while still on the ground, so make a point of ensuring that
your passengers are well briefed on every aspect of the flight they are about to undertake, thus helping remove any
reason for anxiety that they may have.
The following symptoms of hyperventilation have been identified.
Dizziness and a feeling of unreality.
Tingling, especially in the extremities and lips.
Visual disturbances such as blurred tunnelling and clouded vision.
Hot or cold sensations which may alternate in time and occur in various parts of the body.
Anxiety, which of course tends to create a vicious circle.
Loss of muscular coordination.
Increased heart rate.
Spasms in the muscles of the hands, fingers and feet just prior to unconsciousness.
Loss of consciousness.
In order to treat hyperventilation effectively, it is imperative that you establish that the condition is hyperventilation and not hypoxia.
In flight, it can be difficult to distinguish between the symptoms.
The only appropriate action for a pilot in command to take is to assume the worst and to carry out
the drills for hypoxia, as this is the condition requiring the more urgent treatment.
However, if you are flying below 10,000 feet, hypoxia is unlikely to be suffered by any passenger or crew
member and hyperventilation may be assumed.
The symptoms of hyperventilation can be alarming, so if you suspect that any occupant of your aircraft is suffering from
hyperventilation, an immediate action to take is to try and reassure the afflicted person and calm them down.
It is also worth giving them a simple task to fulfil that might take their mind off their anxiety.
Because one of the direct causes of hyperventilation is a reduction in the carbon dioxide level in the blood, the
condition may be alleviated by getting the sufferer to breathe into a paper bag.
You could use a standard sick bag which is carried in most cockpits.
The immediate effect of taking this action is to increase the blood's carbon dioxide level, causing the brain to reduce
the breathing rate.
In the following lesson sequences, we will refer frequently to the term decompression.
Decompression means the lowering or relief of pressure.
Light aircraft usually fly at altitudes below 10,000 feet above sea level.
Operating at these low altitudes, ambient atmospheric pressure and pressure variation with height are such that an aircraft's occupants do
not normally risk suffering from conditions related to decompression due to pressure changes alone.
However, at higher altitudes, and especially when operating above 18,000 feet, reduced atmospheric pressure can lead to problems associated
with decompression, notably decompression sickness.
For occupants of an unpressurised aircraft, the higher the altitude and the longer the exposure to high altitude, the more
likely decompression sickness becomes.
Decompression sickness may even occur as low as 18,000 feet if exposure is long enough.
However, the condition is unlikely to occur below 14,000 feet.
Airliners and other high performance aircraft possess cabin pressurisation systems which ensure that the effective altitude to which aircrew and
passengers are exposed is much lower than the altitude at which the aircraft is actually flying.
Ideally, the cabin should be maintained at sea level, but this is impractical because of aircraft weight and fuselage strength
limitations.
Typically, the pressurisation of a commercial airliner flying at 30,000 feet produces an internal cabin pressure equivalent to about
6,000 feet with a maximum of 8,000 feet.
The pressure differential across the aircraft's skin is normally designed not to exceed 8 to 9 pounds per square inch.
The rate of change of cabin pressure while climbing and descending is limited to 500 feet per minute in the
ascent and 300 feet per minute in the descent.
Without a cabin pressurisation system, pilots and passengers in high flying aircraft would be exposed to all the rigours of
high altitude, among which are hypoxia and decompression sickness.
Let's look a little closer at the reasons for decompression sickness.
The condition is associated with nitrogen, the gas which constitutes the major part of our atmosphere.
Under atmospheric conditions at the Earth's surface, nitrogen is dissolved in our blood but plays no part in the normal
bodily processes.
But if, due to a rapid reduction in ambient pressure, the nitrogen in our blood should come out of solution
as small bubbles, severe physiological problems may occur.
The occurrence may be likened to bubble formation in fizzy drinks when the top of the bottle is opened and
the pressure allowed to drop.
If this occurs in the human body and nitrogen bubbles are formed in the blood, the process leads directly to
decompression sickness.
The symptoms of decompression sickness in the various parts of the body are as follows.
Joints. Bubbles in the joints cause rheumatic-like pains called the bends.
In aviation, the shoulder, wrist, knee and ankles are most commonly affected.
Movement or rubbing the affected parts only aggravates the pain but descent usually resolves the problem.
Skin. Nitrogen bubbles released under the skin causes the creeps when the sufferer may imagine that ants are crawling over
or just under the skin.
Respiratory system. This is known as the chokes.
Nitrogen bubbles may get caught in the capillaries of the lungs, blocking the pulmonary blood flow.
This leads to serious shortness of breath accompanied by a burning, gnawing and sometimes piercing pain.
The brain. The bubbles affect the blood supply to the brain and the nervous system.
This effect is known as the staggers.
The sufferer will lose some mental functions and control of movement.
In extreme cases, chronic paralysis or even permanent mental disturbances may result.
Treatment of decompression sickness.
The treatment of decompression sickness involves returning the sufferer to a region of high pressure.
If the symptoms of decompression sickness appear in any passenger or crew member, the pilot should commence an immediate descent
to a level at which the symptoms are relieved.
The aircraft should land as soon as possible.
Meanwhile, the sufferer should be kept warm and rested and put onto a 100% oxygen supply.
Medical assistance must be sought on landing even if the patient appears to have recovered.
The ground radio station you are talking to can be advised that medical assistance is required.
As we have noted, occupants of light aircraft operating below 10,000 feet above sea level are most unlikely to
suffer from decompression sickness solely because of exposure to low atmospheric pressure.
However, decompression sickness at these low altitudes can occur in individuals who have been diving using compressed air breathing apparatus
shortly before flying.
Air breathed under pressure increases the amount of nitrogen in the body.
On subsequent ascent, this may come out of solution giving rise to decompression sickness.
The pressure exerted by a 30 feet column of seawater is the same as that exerted by the atmosphere at
sea level, that is 760 mmHg.
Therefore, a person at a depth of 30 feet is exposed to a pressure of two atmospheres, one atmosphere caused
by the air above the water and the other by the water itself.
If after ascending from a depth of 30 feet a diver were directly to get airborne in a light aircraft,
the chances of his suffering decompression sickness would be high.
The following rules should be strictly observed by divers who also fly.
Failure to adhere to these rules could result in the onset of decompression sickness at altitudes as low as 6
,000 feet.
Do not fly at all within 12 hours of swimming using compressed air.
Avoid flying for 24 hours if a depth of 30 feet has been exceeded.
This concludes the lesson on partial pressure.
The eye delivers to the brain more information about the outside world and at a much faster rate than any
other sensory organ.
For example, it has 1.2 million neurons leading from the retina to the brain while there are only about
50,000 neurons between the brain and the inner ear.
It is not surprising then that when flying under visual flight rules as most PPL holders do most of the
time, we rely overwhelmingly on our visual perception to fly safely and efficiently.
If as a VFR-only qualified pilot we find ourselves in marginal visual meteorological conditions, we can very quickly get
into trouble.
We will begin the lesson on vision by looking at the physiology of the eye.
The word physiology is a technical term meaning the science of the organic functions of animals and plants.
We all know that the eye is the organ of sight. In fact, it is the most sensitive of all
our sensory organs.
It is the organ which receives electromagnetic waves within the visual spectrum from the external world and passes them to
the brain for interpretation into an image.
The basic structure is similar to a simple camera with an aperture called the iris, a lens called by the
same name and a light sensitive film called the retina.
Let's have a closer look at the structure of the eye.
The cornea. Light enters the eye through the cornea, a clear window at the front of the eyeball.
The cornea acts as a fixed focusing device and is responsible for between 70% and 80% of the
total focusing ability of the eye.
The focusing is achieved by the shape of the cornea bending the incoming light rays, the iris and pupil.
The amount of light allowed to enter the eye is controlled by the iris, the coloured part of the eye,
which acts as a diaphragm.
It does this by controlling the size of the pupil, the hole in the centre of the iris.
The size of the pupil can change rapidly to cater for changing light levels.
The lens. After passing through the pupil, the light passes through a clear lens.
Its shape is changed by the muscles, ciliary muscles, surrounding it which affect the final focusing onto the fovea.
This change of shape is known as accommodation.
The effectiveness of accommodation can be affected by the ageing process or fatigue.
When a person is tired, accommodation is diminished resulting in blurred images.
The retina. The retina is a light sensitive screen lining the inside of the eyeball.
On this screen are light sensitive cells, cones and rods, which when light falls on them, generate a small electrical
charge which is passed to the brain by nerve fibres, neurons, which combine to form the optic nerve.
Cones are used for direct vision in good light and are colour sensitive, capable of distinguishing approximately 1000 different shades
of colour.
The rods can only detect black and white but are much more sensitive at lower light levels.
As light decreases, the sensing task is passed over from the cones to the rods.
This means that in poor light levels we see only in black or white or varying shades of grey.
Rods are responsible for our peripheral vision.
The fovea. The central part of the retina, the fovea, is composed only of cones.
Any object that needs to be examined in detail is automatically brought to focus on the fovea.
The rest of the retina fulfils the function of attracting our attention to movement and change.
Only at the fovea can vision be 20 20 or 6 over 6.
This is termed as central vision.
The blind spot is the point on the retina where the optic nerve enters the eyeball.
Here the retina has no covering of light detecting cells.
The image of any object falling at the blind spot will not be detected.
Each eye is equipped with muscles which enable the eyeballs to rotate in their sockets, thus enabling them to keep
track of a moving object.
To track an object successfully or to focus on an object, the eyes need to move in harmony with one
another.
This means that the brain must coordinate control of the muscles of the two eyes.
When focusing on distant objects, the axes of the eyes are parallel.
But when focusing on near objects at less than about 15 feet, the axes of the eyes will be turned
in slightly.
In a fatigued person, coordination sometimes fails and the result is that very differing images are transmitted from each eye.
Subsequently double vision occurs.
For pilots this is just one more reason why they should be aware of their fatigue limits.
Binocular vision means seeing with two eyes.
The term binocular is a combination of the prefix by from a Latin word meaning with two and the Latin
word oculus meaning eye.
A person able to see out of one eye only is said to have monocular vision.
Binocular vision is an important asset to a human being and especially to a pilot.
Each eye sees an object from two slightly different angles.
The brain, however, merges the two images into one and is thus able to perceive that the image has depth.
Thus, using our two eyes we achieve stereoscopic vision.
A monocular person has a much flatter two-dimensional view of the world.
A further advantage of binocular vision is that the blind spot of one eye is covered by the other eye.
That is, light making up the image of a small object will not normally fall on the blind spot of
both eyes at the same time.
Thus, with binocular vision all objects within the normal visual field remain visible at all times.
Visual acuity is a measure of central vision.
That is, the capacity of the eye to determine small detail undistorted at a given distance.
The sharpest visual acuity occurs when the retinal image is sharply focused on the fovea
so that the pilot needs to look exactly in the direction of the oncoming aircraft to detect it.
A person with 20-20 or 6 over 6 vision is said to have normal visual acuity.
The figures 20-40 or 6 over 12 mean that the observer can read at 20 feet what a normal
person can read at 40 feet
or at 6 metres what a normal person can read at 12 metres.
Normal visual acuity will allow pilots to detect objects clearly at safe distances.
It is thus essential for pilots to have normal visual acuity.
If a person's vision with the naked eye is impaired this will not normally prevent that person from becoming a
pilot
provided normal visual acuity can be achieved by wearing spectacles or contact lenses.
Whereas normal visual acuity is required to see objects clearly at a distance
good near vision is necessary for a pilot to read instruments and maps.
Being able to focus on close objects is a function of the eye's ability to accommodate.
Normal accommodation is possible when the ciliary muscles can change the shape of the lens to enable the eye to
focus in on close objects.
The power of accommodation usually diminishes in middle age but can easily be corrected by wearing reading glasses.
Pilots and drivers normally wear bifocal spectacles to allow them to see clearly at a distance and to read their
instruments and maps.
The sharpness of central vision, that is the image at the fovea, drops as light falls on the retina at
increasing angles from the fovea.
At as little as 5 degrees from the fovea visual acuity drops to 20 over 40, that is only half
as good as at the fovea.
At approximately 25 degrees acuity decreases to a tenth, 20 over 200.
You may view other factors which limit the sharpness of visual acuity by clicking on the button labelled Other limiting
factors.
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All rights reserved until dark adaptation takes place.
On the other hand, if the person remains in darkness for a long time, the eye becomes super sensitive to
light so that even the minutest amount of light can irritate the retina and dazzle the person concerned.
The eye adjusts more quickly to this second occurrence than to the first.
This is why it is especially important for pilots to allow sufficient time for dark adaptation to take place before
flying at night.
It takes time for our eyes to adapt to darkness.
Dark adaptation takes time, about 7 minutes for the cones and 30 minutes for the rods.
It is important to be aware that in dim light it is easier to focus on an object if you
look slightly away from it.
The fovea contains no rods, which you will recall are the receptors required for vision in very low brightness levels.
Thus the centre part of the eye is virtually blind in dim light.
It is therefore necessary to look away from the object so that the peripherally located rods can perform their sensing
task.
This is most noticeable when night flying.
You can demonstrate this to yourself by looking at dim stars on a clear night.
Though they may appear extremely faint with direct viewing, they will be more clearly discernible if you look slightly off
to one side.
The blind spot is the point on the retina where the optic nerve enters the eyeball.
Here the retina has no covering of light detecting cells.
The image of any object falling at the blind spot will not be detected.
This has great significance when considering the detection of objects which are on a constant bearing from the observer.
If the eye remains looking straight ahead, it is possible for a closing aircraft to remain in the blind spot
until a very short time before impact.
Here you see a representation of the problem.
An aircraft at significant range passes into the blind spot of the pilot who has his head still and eyes
fixed looking forwards.
If in the pilot's blind spot the aircraft changes heading so that it heads towards our aircraft maintaining a constant
bearing, it may not be seen by the pilot until shortly before collision.
To lessen the danger of collision, pilots are taught to carry out a systematic lookout at all times which involves
moving the head to look out to the left and right as well as overhead.
Safe visual scanning demands frequent eye movement with minimal time spent looking in any one direction.
An effective scanning method, especially in a low wing monoplane, is to look out to one side of the aircraft
to just behind the trailing edge of the wing and sweep your gaze forwards looking above and below the horizon.
Then repeat this action in the other direction before checking overhead.
While moving your head, move your eyes also so that you quarter the sky in whatever direction you are looking.
Of course if both eyes of the pilot are open as one hopes they are and unobscured, the blind spot
is not a problem as each eye is able to see the detail in the other eye's blind spot.
However, there is a very real possibility that an approaching aircraft on a constant bearing will not be seen since
it remains in the blind spot of one eye and an object or person within the cockpit is obscuring the
aircraft from the pilot's other eye.
In the absence of anything to focus on, that is when your visual field is empty, the natural focus point
of the eye is not at infinity as was long assumed, but on average at a distance of between one
and two metres in front of the eye, although there can be wide variations between individuals.
This is very significant for a pilot who may be searching for distant contacts when visual clues are weak, as
the eye will not be adjusted to detect them.
The condition is aggravated when there are other objects close to the empty field range, such as rain spots or
specks on the windscreen for example, as the eye will naturally be drawn to them.
This phenomenon can occur in cloudless skies at high altitudes, in total darkness, under a uniformly overcast sky or when
resting the eyes.
Pilots often subconsciously ask themselves the question of whether a speck on the canopy is indeed a speck or a
distant aircraft.
Pilots should minimise the risks associated with empty visual range by periodically and deliberately focusing on objects, both close and
at a distance, thus exercising the eyes.
Very high light levels occur at altitude where light may be reflected from cloud and where there is less scattering
of the light rays by the atmosphere.
Normal sunlight contains all the colours of the spectrum, but at high altitudes pilots are exposed to light that contains
more of the high energy blue and ultraviolet wavelengths than is experienced at sea level.
The higher energy blue light can cause cumulative damage to the retina over a long period.
Ultraviolet wavelengths can also cause damage mainly to the lens of the eye, but most are filtered out by the
cockpit windows.
Wearing appropriate sunglasses can provide further protection against high levels of light.
But make sure you avoid using cheap sunglasses as these can allow the light to be over-diffused across the
eye, thus causing perceptional problems in flight.
The use of Polaroid sunglasses should be avoided since problems can occur when used with laminated aircraft windscreens.
Light-sensitive lenses, photochromic, are also generally forbidden for use in flight due to the time taken for the lens
to clear when moving from a bright situation to one of low light.
This delay may significantly reduce visual acuity at a critical time.
Click on the reveal desirable characteristics button to see a list of desirable characteristics that sunglasses for pilots should possess.
The most common visual defects are caused by the distorted shape of the eyeball.
Other defects are due to irregularities in the cornea, the lens and the eyeball itself.
We will deal with the visual defects and where appropriate the correction of the defect one by one.
Myopia is more commonly known as short-sightedness.
The normal eye is practically spherical and when the lens and ciliary muscles are relaxed, the image of a distant
object will fall on the retina.
But in a myopic eye, the eyeball is longer than normal.
This causes the images from distant objects to fall in front of the retina.
Thus distant objects will be out of focus for a short-sighted person.
A concave lens will correct the situation by bending or refracting the light from distant objects outwards before it hits
the cornea.
Close-up vision may however still be satisfactory in the naked eye of a short-sighted person.
Normal distance vision for pilots may be very approximately assessed as the ability to read a car number plate at
40 metres.
For the UK driving test, the distance required is 23 metres.
In long-sightedness or in medical terms, hypermetropia, a shorter than normal eyeball results in images being formed behind the
retina.
This is especially so for near objects.
A person with hypermetropia can often see distant objects clearly by accommodating slightly.
However, he is unable to focus on close objects because the eye's powers of accommodation are insufficient for this purpose.
Thus a blurring of the vision will result when looking at close objects.
Hypermetropia is also known as long-sightedness because only objects at a distance can be seen clearly.
A convex lens will overcome hypermetropia by bending or refracting the light rays from a close object inwards before they
meet the cornea.
The ability of the lens to change its shape and accommodate adequately, thereby focusing the images of close objects on
the retina, depends on its elasticity.
Normally this elasticity is gradually lost with age.
After the age of 40-50, the lens is often unable to accommodate fully and a form of long-sightedness,
known as presbyopia, occurs.
The effects start with difficulty in reading small print and poor light.
The condition normally requires a minor correction with a weak convex lens.
Half lenses or look-over spectacles will suffice.
Pilots who are also myopic will require bifocal spectacles.
The surface of a healthy cornea is spheroidal in shape.
Astigmatism is usually caused by a misshapen or oblong cornea and objects will appear irregularly shaped.
Although astigmatism can be cured by the use of cylindrical lenses, modern surgical techniques can reshape the cornea with a
scalpel or more easily with laser techniques.
It is convenient to note at this point that pilots who wear corrective spectacles or contact lenses for whatever reason
must carry a spare pair of spectacles at all times when they are exercising the privileges of their license.
The choice of spectacles and contact lenses for flying is an extremely important one and should always be made after
consultation with your doctor and or optician.
Good color vision is essential for pilots because of the use of color associated with the following equipment and fittings.
Navigation lights of aircraft, runways and airfields, ground obstructions, cockpit displays and instruments, maps and charts, emergency flares, light signals.
Color blindness or more accurately color-defective vision is caused by a defect in the structure of the color-sensitive
cones in the retina, normally when a single color-sensitive group is missing.
Whereas total color blindness is extremely rare, many people suffer from this defect to a degree.
The most common form is red-green blindness.
These colors are seen in shades of yellow, brown or grey.
You may look at a few extracts from a color vision test by clicking on the reveal color test example
button on the screen.
The numbers you see or do not see in the color patterns will depend on the accuracy of your perception
of color.
Do not draw any conclusions from what you see. The doctor will advise you about your color perception.
Color-defective vision does not affect acuity and many people go through their lives with no knowledge that they suffer
from this imperfection.
Color blindness is rare in women, however they do act as carriers of this incurable and congenital flaw.
Light aircraft flown by the majority of PPL holders cruise at speeds in the range of 90 to 140 knots.
Faced with the extreme situation therefore of another light aircraft approaching head-on, a possible closing speed between two light
aircraft could be as high as 280 knots, that is the sum of the speeds of the individual aircraft.
If one of those aircraft is a jet, closing speeds may be much higher.
The problem this poses for the pilots of aircraft in such a collision course situation is to be able to
take avoiding action sufficiently rapidly to be able to prevent a collision.
That is, the reaction time of the pilots must be less than the time it would take for the aircraft
to close to impact.
The total reaction time for the pilot is a function of the time taken for all the separate recognition and
reaction processes to take place.
These processes may be summarized as visual input, brain reaction, perception of danger, evaluation, decision, response.
In perfect conditions all these processes take approximately one second to complete.
However, this time may be extended by factors such as workload, fatigue, poor atmospheric conditions, darkness, size and contrast of
object.
Angular approach. An aircraft for example approaching head-on will stimulate the retina less than an aircraft crossing the visual
field from left to right or from right to left.
In any event as a practical consideration it is extremely useful for a pilot to be able to estimate how
long it would take for aircraft on a collision course to close to impact.
The important factor is the closing speed, that is, for two aircraft on a head-on collision course, the sum
of their individual air speeds.
We can already appreciate that two light aircraft might be approaching collision at anything between 180 knots and 280 knots.
If one of those aircraft is a jet, closing speeds may be much higher.
Low-flying military fast jets may be doing 450 knots, so if the aircraft approaching you is a fast jet,
closing speeds may be in the order of 600 knots.
We will carry out a few calculations to illustrate this point.
They should help you appreciate how long you would have to react in order to avoid collision if you ever
found yourself in a similar situation.
Of course visual acuity matters here too because the further away either aircraft is detected by one or both of
the pilots, the more time there is for avoiding action to be taken.
The calculation we need to make is simple. Speed is measured in miles per hour, kilometres per hour, metres per
second, feet per minute and so on.
In every case what we have is distance over time. This is indeed the basic formula, speed equals distance over
time.
By simple mathematical transposition this can be otherwise expressed as time equals distance over speed.
All we have to do to calculate time is to divide distance by speed.
What we have to watch out for though is our use of units.
If we have a speed in miles per hour and a distance in miles, that is an aircraft travels 300
miles at 120 miles per hour, the formula will give us the time in hours, in this case two and
a half.
If we wanted the time in minutes we would have to multiply by 60.
If we wanted the time in seconds we would have to multiply by 60 times 60.
Furthermore in order for the formula to work the speed and distance have to be expressed in matching units.
In the example we have just looked at we were only able to get an answer in hours because the
speed was in miles per hour and the distance was in miles.
Had the speed given in knots or nautical miles per hour the distance would have to have been in nautical
miles for the formula to work.
Thus if you are given mixed units such as speed in miles per hour and distance in say kilometres, we
would either have to convert the speed into kilometres per hour or the distance into miles.
In general we may see from the table what the units of the answer will be given the combinations of
units for speed and distance.
Remember the first thing we do is to make sure we have matching units.
Remember to carry out any necessary conversion of units before you put figures into the formula.
Here are some worked examples.
Two light aircraft are on a head-on collision course with a closing speed of 200 knots.
Flight visibility is 4 kilometres.
What would be the time available to either pilot to take avoiding action if visual contact were made at maximum
visual range?
Step 1. We note that the closing speed is in knots, nautical miles per hour.
The distance at which visual contact is made is in kilometres, in this case 4 kilometres.
Step 2. We have to convert one of the units so that speed and distance units match.
Thus we either have to change speed into kilometres per hour or the distance into nautical miles.
We choose to convert kilometres into nautical miles.
We can do this using our flight navigation computer.
See the CD-ROM containing instruction on the CRP1.
4 kilometres equals 2.16 nautical miles.
Step 3. We now insert the figures into the formula time equals distance over speed equals 2.16 over 200.
This gives us 0.0108.
Remember that the answer is in hours.
To convert this answer we multiply by 60 to give minutes and by 60 again to give seconds.
The answer thus becomes 38.88 seconds which we can round up to 39 seconds.
Naturally the answer will be required in seconds.
Let's look at one more worked example.
With an in-flight visibility of 5 kilometres a light aircraft flying at 120 knots sees a fastjet at maximum
visual range.
The light aircraft pilot assumes that the fastjet is flying at 450 knots.
What time would be left to the pilot of either aircraft to take avoiding action?
Step 1. Calculate closing speed.
This would be 120 knots plus 450 knots making 570 knots or 570 nautical miles per hour.
Step 2. Convert the 5 kilometres in-flight visibility to nautical miles.
This gives us 2.7 nautical miles.
Step 3. Enter figures in the formula to calculate that the time available for reaction is 0.0047 hours or
just over 17 seconds.
Now do the following calculations for yourself.
Click on the answer buttons to reveal the answer.
With an in-flight visibility of 3 kilometres a light aircraft flying at 90 knots sees a fastjet at maximum
visual range.
The light aircraft pilot assumes that the fastjet is flying at 450 knots.
What time would be left to the pilot of either aircraft to take avoiding action?
Two light aircraft are on a head-on collision course with a closing speed of 280 knots.
Flight visibility is 5 kilometres.
What would be the time available to either pilot to take avoiding action if visual contact were made at maximum
visual range?
It is worth noting at this point that for the pilot of an aircraft on a head-on collision course
with a fast moving jet,
the image of the approaching jet will remain small increasing in size only slowly at first until just before impact
when the image would grow in size very rapidly.
This concludes the lesson on the eye.
The ear performs two quite separate functions.
Firstly it is used as a collector of sound waves in the air which the hearing mechanism then transmits through
nerve fibres to the auditory centre of the brain where sound is registered.
Secondly the ear acts as a balance organ and acceleration detector.
The overall construction of the ear is shown on the screen.
The auricle or pinna comprises the shell-like upper part of the ear and the lobe.
Its function is to collect sounds and conduct them to the auditory canal, meatus, and onto the eardrum.
The eardrum or tympanum separates the outer and middle ear.
Connected to the eardrum is a linkage of three small bones.
These are the ossicles.
They comprise the malleus, incus or anvil, and stapes or stirrup bone which transmit the vibrations across the middle ear
to the inner ear.
The middle ear is filled with air and the inner ear is filled with liquid.
The last of the bones, the stapes or stirrup bone, is attached to the oval window of the inner ear
where a diaphragm sets in motion the fluid, the cochlea.
The extent and frequency of vibration of tiny hair-like cells within this fluid are detected by the auditory nerve
which leads to the cortex of the brain where sound is perceived.
Highlighted here is the eustachian tube.
The eustachian tube vents to the mouth and nose allowing pressure in the middle ear to equalize across the eardrum
with outside or ambient pressure when climbing or descending in flight.
Pressure equalization through the eustachian tube can be hindered by inflammation, catarrh, a blocked nose or sinuses, or any infection
of the respiratory tract.
A blocked eustachian tube can cause severe ear pain or even lead to perforation of the eardrum.
Pilots must therefore ensure that neither they nor any passengers go flying if the eustachian tube is blocked and the
ears cannot be cleared.
While an aircraft is climbing, when outside or ambient pressure is decreasing, the higher pressure in the middle ear can
normally easily vent to the mouth via the eustachian tube, causing the pilot little problem.
During the descent, however, when ambient air pressure is increasing, then a small flap, which is not shown here, attached
to the end of the eustachian tube prevents such easy passage of air back up the eustachian tube to equalize
the pressure in the middle ear.
It is therefore then in the descent when pain is most likely to be experienced.
In extreme cases, rupture of the eardrum may occur. This condition is known as aortic barotrauma.
However, normal periodic swallowing movements mean that in a fit pilot the condition does not arise.
If you experience any problems with pressure equalization during a descent, swallow deliberately with the nostrils pinched closed, yawn or
blow down the nose again with the nostrils pinched closed.
Remember, never fly if your eustachian tube becomes swollen or blocked and you cannot clear your ears.
Sound is generated by waves or vibrations in the air. It has three main qualities.
Pitch, which depends on the frequency of the vibration. The greater the frequency, the higher the pitch or note produced.
Loudness or intensity, dependent on the amplitude of the vibrations.
Quality, which is a function of various aspects of vibrations, causing either harmonious musical sounds or else discord or noise.
The range of pitch or frequency of sounds that a fit young person can hear lies between 20 and 20
,000 Hz or cycles per second.
However, this detectable sound range also depends on loudness which is measured in decibels.
It is your ability to detect a range of sound frequencies of varying degrees of loudness which may be tested
during your medical examination.
Here is a table showing typical noise levels in decibels against a corresponding description of sounds that might produce such
degrees of loudness.
Any degradation in our ability to hear clearly is known as hearing impairment.
Hearing impairment can be caused by three main factors.
Isolated but very loud noises and prolonged exposure to excessively high levels of noise.
Damage to the hearing mechanism itself caused by a physical blow or otic barotrauma.
Advancing age. A build-up of wax.
Hearing impairment is broadly classified into three categories.
First of all, there is conductive deafness caused by a build-up of wax or damage to the sound conducting
system, the ossicles or the eardrum.
This may be caused by a blow to the ear or by otic barotrauma.
A second category of hearing impairment is noise-induced hearing loss.
Loud noises can damage the very sensitive membrane in the cochlea and the fine structures on this membrane.
The loss of hearing may at first be temporary but continued exposure to loud noise in excess of 90 decibels
may result in permanent loss of hearing.
An early symptom of noise-induced hearing loss is an inability to hear high-pitched notes as these notes are
normally detected by the finer cells which suffer the greatest damage.
There is evidence that overexposure to loud music at discos and the use of personal stereos can cause the early
onset of hearing impairment in young people.
Environmental noise pollution can be a significant factor in the prevalence of noise-induced hearing loss.
You should always make sure that you protect your hearing whenever environmental noise is excessive.
The most dangerous noise to the ear is noise of high frequency.
Finally, a person's hearing deteriorates with advancing age, especially the ability to detect high frequency sounds.
This is known as presbycusis.
As pilots we should always take great care to protect our hearing.
Hearing impairment can lead to the misinterpretation of RT transmissions which in turn may possibly cause a flight safety hazard.
And of course any significant deterioration in a pilot's hearing can lead to the loss of a pilot's license.
Growing older is unavoidable and accidents may strike even the most prudent amongst us.
But we may all plan to protect ourselves from noise-induced hearing loss or at least reduce it to a
minimum.
Always protect your ears if you know you are going to be exposed to excessive noise.
Headset style ear protectors give the best protection. Ear plugs can also be used.
In the cockpit, use the best quality headset you can afford to reduce background noise.
When visiting a large airport, avoid standing near a running jet engine if you have no ear protection.
As well as distinguishing sound, the ear also provides us with our sense of balance, helping us to orientate ourselves
spatially through mechanisms which detect accelerations both in a straight line and when turning.
Note that the term orientation refers to a human being's ability to maintain equilibrium and to interpret the body's position
in space.
In terms of maintaining spatial orientation, the balance sensors situated in the ear provide us with a secondary system only.
Always remember that the primary and most reliable sense of spatial orientation is eyesight.
However, it is extremely important for the pilot to understand the function of the ear's balance sensors so that he
can understand how spatial disorientation may occur in flight.
Let us take a closer look then at the balancing mechanism within our ears.
Within the ear, the semicircular canals and the otoliths together make up the vestibular apparatus which helps a human being
maintain spatial orientation.
The otoliths are located between the semicircular canals and the cochlea.
The otoliths detect acceleration in a straight line while the semicircular canals detect angular acceleration.
There are three semicircular canals orientated at right angles to one another.
The angular accelerations that each semicircular canal detects can be likened to pitch, roll and yaw in an aircraft.
We have already said that the word orientation refers to a human being's ability to maintain equilibrium and to interpret
the body's position in space.
Human beings maintain spatial orientation using a combination of three factors.
Their sense of vision, the ear's balancing mechanism and the body's ability to detect pressures through nerve receptors, often known
in the flying world as the seat of the pants sense.
The system of nerve receptors that give us this seat of the pants sense is known as the somatosensory system.
As pilots we must be very aware that information from our somatosensory system is very unreliable and deceptive.
In flight we must maintain spatial orientation using our most reliable sense, vision, either by looking outside the aircraft when
flying in visual meteorological conditions or relying on our flight instruments if no outside visual references are present.
We now know then that using our eyesight is the most reliable way of maintaining spatial orientation and that our
somatosensory sense is not reliable at all.
As pilots we must also be aware that even our ear's balancing mechanism, that is our vestibular apparatus, is not
sufficiently reliable for us to maintain spatial orientation using this sense alone.
We will now therefore look briefly at how the vestibular apparatus works and at the problems of balance and disorientation
that may arise in flight.
As we have noted, the otolithic organs detect linear accelerations and the three semicircular canals detect angular accelerations.
Note that they detect accelerations or changes in velocity only and not constant linear or angular velocity.
Therefore, in the absence of any visual signals, the ear's balance sensors alone will not differentiate between a state of
rest and flying at a constant speed nor will they differentiate between a steady balance turn or flying wings level.
Another way of saying this is that our balance organs can detect accelerations but cannot determine what position we are
in if no acceleration is present.
This is the principal point to learn and is the reason why pilots must always rely on their eyes and
or flight instruments.
Relying on our vestibular apparatus alone often leads to disorientation.
Let's examine the matter more closely.
Both otolithic organs and the semicircular canals send signals to our brain by means of impulses arising from the body
being subjected to accelerations.
To illustrate this, we will look at fluid accelerations in the semicircular canals.
The otoliths function according to a similar principle but without the involvement of fluid.
Remember, we will be dealing with principles only.
We give no neurobiological details of the operation of the vestibular apparatus.
The semicircular canals contain fluid which can flow freely through the canal.
Fluid flow occurs when the body or head is subject to angular acceleration.
The flow takes place in the opposite direction to the acceleration, the fluid lagging behind the displacement.
There is no fluid flow when the body is at rest or if linear and turning movement is taking place
at a steady speed.
When the fluid moves, sensory hairs contained within a gelatinous material will move with the fluid in the same direction.
Nerve cells within the hairs convert this movement into electric signals which are then conveyed to the brain.
This is how a human being perceives movement.
When the angular acceleration ceases, fluid flow also ceases and the sensory hairs are no longer displaced.
The brain therefore no longer detects any motion.
This no displacement situation will occur whether the body is upright and motionless,
upright and travelling at a steady speed,
or inclined at an angle in a steady turn at constant angular velocity.
In all these three situations, the vestibular apparatus will signal zero motion to the brain.
The brain therefore, when receiving information from the vestibular apparatus only,
is unable to sense whether the body is upright or in a steady turn.
Only information from the eyes and instruments can tell us this.
It is this basic principle which can cause problems of balance and disorientation for a pilot.
Let us now look at the various sensations that a pilot needs to understand to help him maintain his spatial
orientation.
In level flight, a pronounced acceleration in a straight line will cause the hair sensors in the otoliths to move
backwards.
This sends a signal to the brain indicating falsely that the head is tilting backwards,
giving the pilot the false impression that the nose of the aircraft is pitching up.
Conversely, a sharp linear deceleration gives the impression that the nose of the aircraft is pitching down.
These illusions are sometimes known as the somatogravic illusions.
The lenes is the name given to the sensation experienced when the vestibular apparatus of the ear
leads to a pilot making an incorrect assessment of attitude on entering, maintaining or exiting turns.
There are two common circumstances in which the lenes may be experienced.
The first of these is when from straight and level flight the pilot commences a very gentle roll to the
right,
so gentle that the movement of the liquid in the semicircular canals is not sufficiently pronounced to cause a detectable
bending of the hair cells.
Therefore, although entering a turn to the right, the ear's balance mechanism senses that no change has been made
and the pilot still believes himself to be flying straight and level.
Now, if the subsequent corrective roll to the left to regain level flight is made sharply,
this acceleration will be detected by the ear's balance mechanism.
So even though the aircraft is now in reality straight and level, the pilot feels that he has entered a
turn to the left.
In the second case, the pilot has for some time been carrying out a steady turn to the left.
Because the turn is steady and balanced, there is no movement of fluid in the semicircular canals and the hairs
have erected themselves.
This gives the pilot the erroneous feeling that he is straight and level.
As the pilot exits the turn by rolling to the right to regain straight and level flight,
the fluid moves and the hairs give a false impression of entering a turn to the right when in fact
the wings are level.
In both the above cases, the pilot will be subjected to two conflicting signals.
His visual sense will tell him one thing, whereas his vestibular apparatus will tell him another.
This mismatch between vestibular and visual sensory inputs is the primary cause of spatial disorientation and indeed of motion sickness.
As pilots, remember to respect at all times the cardinal rule that if you suspect you are suffering from disorientation,
you must concentrate on and believe the aircraft's instruments.
The rule for maintaining spatial orientation is, if in visual meteorological conditions, look out at the horizon.
If in instrument meteorological conditions, believe your instruments.
Motion sickness arises when a human being is exposed to real or apparent motion of an unfamiliar kind.
It is caused by a mismatch between the visual and vestibular signals.
The symptoms of motion sickness are, nausea, hyperventilation, vomiting, pallor, cold sweating, headache, depression.
Pilots who suffer from chronic motion sickness should consult their doctor.
Occasional motion sickness may be relieved in one of the following ways.
Keeping the head upright and still, if possible using the eyes to orientate oneself.
Opening the cockpit ventilators to increase the flow of fresh air.
Using smooth and coordinated control movements and avoiding manoeuvres which generate pronounced positive or negative g-forces.
Military pilots and airline pilots have to pass regular and stringent medical examinations in order to train for and pursue
their careers.
Candidates for professional pilot training may fail the initial medical selection because of quite minor defects of vision, respiration, cardiovascular
system and so on.
Thankfully, those wishing to fly as private pilots are not subject to the same severe medical regulations as their professional
colleagues.
Nevertheless, a medical examination does have to be passed and perhaps more importantly, private pilots, whether under training or qualified,
must be capable of positively assessing their own fitness to fly before every single flight.
We learned in lesson 1 of Human Performance and Limitations that when flying, our bodies are exposed to a potentially
more hostile environment than on the ground.
At high altitudes, the amount of oxygen in the air we breathe will be smaller than at sea level and
the air pressure lower.
Certain aircraft manoeuvres will increase the gravitational acceleration to which our body is subjected.
Furthermore, in certain flight conditions, workloads will be high and demands on our decision making ability may be severe.
You'll readily appreciate, therefore, that in order to operate competently and safely in such conditions, a high level of general
fitness is required.
Consequently, as a pilot, you must be fit, stay fit and be able accurately to assess your day to day
state of health in order to make responsible decisions on whether or not you're fit to carry out each flight
that you undertake.
Remember also that you have a responsibility not only towards yourself but also towards your passengers, other users of your
airspace and to the general public living and working beneath your flight path.
To begin at the beginning, all applicants for a pilot's licence must be declared medically fit by an appropriate medical
authority.
First of all, let's look at the case for the JAA or JAR FCL private pilot's licence.
As the holder of a JAR FCL PPL, you may fly aircraft for which you have a type or class
rating in any JAA member state of which, in February 2003, there were 36.
Consequently, medical regulations are rather formal.
An applicant for a JAR FCL PPL must hold a valid JAR FCL Class 1 or Class 2 medical certificate.
In the United Kingdom, the medical examination must be undertaken by a CAA authorized medical examiner.
Full details of the medical requirements for the JAR FCL PPL can be found on the United Kingdom Civil Aviation
Authority's website.
In February 2003, the Earl was as shown on the screen.
This Earl may change, so if it doesn't lead you to the information required, go to the CAA's homepage or
contact the CAA's Flight Crew Licensing Department by telephone or mail.
The aim of the United Kingdom National Private Pilot's Licence or NPPL is to devolve the regulation of some recreational
flying to air sports organisations.
The licence itself is easier to obtain and easier to maintain than the standard JAR PPL.
Full details can be found on the NPPL website shown on the screen.
As far as the medical examination is concerned, instead of having to undergo a specific aviation medical examination conducted by
a CAA authorized medical examiner, a declaration of medical fitness may be made by the pilot himself.
The individual pilot's declaration then has to be validated by a doctor, normally a general practitioner, who has access to
the pilot's medical records.
A blank declaration of medical fitness form is shown on the screen.
Full details of the United Kingdom NPPL medical regulations are available on the United Kingdom CAA website.
Once you've been declared medically fit to fly, you'll wish to maintain the level of fitness required of a safe
and competent pilot.
Certainly, if you wish to make the most of your flying and to extend your pilot's skills and qualifications, maintaining
a high level of personal fitness is essential.
For the purpose of this lesson, the term personal fitness will cover exercise and weight, nutrition and food hygiene, alcohol,
drugs and self-medication, and personal hygiene.
For a person who does not suffer from any medical disorder, the main considerations for keeping fit and well are
to follow a healthy diet, exercise regularly, maintain a high standard of personal hygiene, and refrain from excess in terms
of alcohol consumption and stressful activity.
All these considerations may be lumped together under the term lifestyle.
To remain fit and well, a pilot must maintain positive control of his lifestyle.
A good indication that a person is following a healthy lifestyle is that his body mass index should lie within
prescribed limits.
A person's body mass index, or BMI, is simply a measure of a person's weight in relation to his height.
The BMI is obtained by dividing his weight in kilograms by the square of his height in meters.
The BMI is expressed as a coefficient, that is, a number without units.
For men, a normal BMI lies between 20 and 25. A normal BMI for a woman is from 19 to
24.
A BMI above or below these values indicates that a person is overweight or underweight respectively.
For example, a man who is 1.8 meters tall and weighs 85 kilograms has a BMI of 26.23,
indicating that he is overweight.
A BMI of over 30 for a man or over 29 for a woman is an indication of obesity.
As most of us are aware, being overweight or obese is a common health problem in modern Western society.
Keeping an eye on your body mass index is one way of monitoring whether you are of a healthy weight.
If you're not, then you may wish to consult a medical practitioner about the best way of controlling your weight.
Of course, obvious solutions are to eat a healthy diet and to exercise.
However, be aware that pilots should not try to lose weight by taking appetite suppressants unless under the direct supervision
of an aviation medical specialist.
Being badly overweight increases a pilot's susceptibility to the following conditions.
Heart attack
Hypertension
Hypoxia at lower altitudes than normal
General circulation problems
Gout
Osteoarthritis
Diabetes
The inability to tolerate G-forces
Problems with joints and limbs
Decompression sickness
Heavy sweating
Chest infections
Varicose veins
Of course, all the above conditions adversely affect the quality of a person's normal day-to-day life, too.
Exercise should be a feature of everyone's life who is serious about keeping fit.
Exercise promotes both mental and physical fitness and a sense of well-being.
Those who take regular exercise can cope with fatigue much better and their resistance to stress is improved.
Pilots are required to sit for long periods and regular exercise is of particular importance.
Pilots should seek professional advice on exercise regimes to suit their own circumstances.
A balanced diet
A balanced diet is the foundation of good health.
A high carbohydrate fibre and low fat diet can reduce the risk of coronary heart disease, strokes, diabetes and certain
forms of cancer.
Sources of carbohydrates include grains, vegetables, nuts, potatoes and fruits.
This type of food should make up more than 50% of the calories consumed.
The rest should come from lean meats and poultry, fish and low fat dairy products.
Many nutritionists advise never to miss breakfast and regard breakfast as the most important meal of the day.
Medical authorities state that breakfast should supply about 25% of the daily calorie intake.
Certainly a good breakfast is a must before spending a day at the airfield and remember never fly on an
empty stomach.
Vitamins are organic food substances found only in living things.
With few exceptions the body cannot manufacture or synthesise vitamins.
They must be supplied in the diet or in dietary supplements.
Vitamins are essential to the normal functioning of our bodies.
They help regulate metabolism, help convert fat and carbohydrates into energy and assist in forming bone and tissue.
It's beyond the scope of this course to teach the main benefit to be derived from the different kinds of
vitamin.
It's sufficient here to note that we can get the vitamins we need by eating a balanced diet.
The major sources of vitamins are shown on the screen.
Minerals are also very important because our bodies need them to grow, develop and be healthy.
Minerals are essential to many vital body processes from building strong bones to transmitting nerve impulses.
The three principal minerals which are critical to the body's functions are calcium, phosphorus and iron.
Calcium is the most abundant mineral in the body.
It helps with the building and maintaining of bones and teeth.
Its sources are milk, milk products, dark green leafy vegetables and shellfish.
Phosphorus, the second most abundant mineral, performs more functions than any other mineral and plays a part in nearly every
chemical reaction in the body.
Its sources are grains, cheese and milk, nuts, meats, poultry, fish, dried peas and beans and egg yolks.
Iron is necessary for the manufacture of haemoglobin.
Its sources are meats, beans, green leafy vegetables, grain products, nuts and shellfish.
Contaminated foodstuffs can cause stomach upsets and more severe conditions related to food poisoning.
The major sources of food contamination are from unhygienic, that is unclean, food preparation and environments,
undercooked or rancid meats, unwashed salads, fruit and vegetables or washing food with contaminated water, seafood and locally made ice
cream and mayonnaise.
The commonest cause of in-flight incapacitation resulting from food poisoning or drinking contaminated water is acute gastroenteritis.
The onset of the disorder is usually abrupt and violent. Symptoms include nausea, vomiting, abdominal pain, loss of appetite and
diarrhoea which can cause a rapid loss of fluids.
Gastroenteritis is a debilitating condition.
Pilots suffering from gastroenteritis are not fit to fly, even though they may be taking medicine which is relieving the
symptoms.
A high standard of personal hygiene must be practiced if the body is to remain healthy and free from infection.
Some of the elementary precautions are listed on the screen.
A fit or seizure is usually referred to as epilepsy.
This is not a specific disease, but a set of signs or symptoms in response to a disturbance of the
electrical activity in the brain.
Fits are often described as major or minor, although the distinction is not always clear.
In a major fit the sufferer may experience convulsions or uncontrolled movements.
In a minor fit there may only be a short period of absence or loss of attention.
Many patients with epilepsy will have an abnormal EEG tracing with characteristic signs.
An EEG may be used in the initial medical assessment of pilots or applied to pilots who may have had
a disturbance of consciousness.
Any fit, major or minor, is associated with an unpredictable loss of consciousness and is therefore an absolute bar to
the holding of a flying licence.
A faint is the more common cause of a loss of consciousness in adults.
The causes are many, shock, loss of blood, lack of food or fluid or other physiological stresses.
The basic reason is a sudden reduction of the blood supply to the brain, commonly caused by
standing up quickly after a prolonged sitting, especially when hot or dehydrated,
a sudden shock,
loss of blood after an accident.
This form of attack has no sinister significance as far as future flying is concerned, so long as the cause
is clearly understood.
Stroboscopic Effect
In helicopter operations it's been found that a limited number of people are affected by the stroboscopic effect of sunlight
reaching the observer through the rotor blades.
Problems are normally caused by flash frequencies between 5 and 20 Hz, that is between 5 and 20 cycles or
rotations per second.
This can lead to feelings of nausea, giddiness and in extreme cases can cause an epileptic type fit.
If a member of the crew or a passenger shows symptoms of the stroboscopic effect, the recommended preventative actions are
turn the aircraft out of sun,
move the person affected to a seat in the shade,
make the individual close his or her eyes,
the wearing of sunglasses may also help reduce the effects.
It's important to be aware that the in-flight environment may increase the severity of symptoms which may be minor
while on the ground.
Even minor ailments, such as a slight cold or a stomach upset, can cause a deterioration of piloting performance.
Consequently, if a pilot is feeling at all unwell, the decision whether or not to fly requires very careful consideration.
If there is any doubt whatsoever in a pilot's mind about his fitness to fly, he should stay on the
ground.
At this point you should have another look at the lesson on the ear and remind yourself of the dangers
of flying when you cannot clear your ears due to blocked sinuses.
You'll find this topic under the key terms Eustachian tube or Otic barotrauma.
Whatever the primary purpose for which drugs or medication are intended, for example to relieve the symptoms of an illness,
it's generally true to say that most drugs and medicines have unwanted side effects.
Individuals will also vary in the way that the drugs and medication affect them.
For these reasons it's absolutely essential that pilots do not fly as part of the operating crew of an aircraft
when taking drugs or medication,
unless they've been cleared to do so by an aviation medicine specialist.
Self-medication is particularly dangerous.
A pilot who takes charge of an aircraft while on self-prescribed medication not only runs the risk of suffering
side effects,
but also faces the hazards associated with the underlying illness in the in-flight environment which, as we've already stated,
can make the symptoms of any illness much more debilitating than they might be on the ground.
The possible dangers of side effects may not be obvious, particularly when a mixture of drugs is contained in an
apparently innocuous compound
on sale to the general public in the local chemist.
Nor will precautionary advice contained on the packaging take into account the special problems associated with flying.
Click on the list of common ailments on the screen to reveal some examples of groups of drugs and some
of their side effects highlighting the more dangerous agents.
The list is by no means complete, but gives an indication of the hazards involved.
Particularly dangerous is the mixing of drugs and medicines.
If two are taken at the same time, it may render both more potent or cause side effects not experienced
with each individual medicine.
.
Caffeine, a central nervous system stimulant, has a long history as a stimulant.
Yet it is one of the drugs which receives relatively little attention.
It is, however, the most widely used drug in the world.
Because of their lifestyle, pilots especially tend to have a comparatively high intake of caffeine and so must be aware
of the dangers.
Its effects on the body, both physiological and psychological, make it a drug which can be abused and lead to
addiction.
Caffeine is present in coffee, tea, cocoa, chocolate and many fizzy soft drinks such as cola.
Caffeine pills are also available and are sold as an aid to keeping awake and alert.
It is also found in medications for dieting and the treatment of colds, allergies and migraines.
An average coffee drinker consumes three and a half cups per day containing 360 to 440 milligrams of caffeine.
You should be aware that a consumption of six to eight cups of normal strength tea or coffee a day
could lead to dependence and that as little as 200 milligrams of caffeine may reduce performance.
One hundred cups of coffee, ten grams of caffeine, consumed over a short period would probably prove fatal.
Excessive intakes of caffeine over a period can lead to ulcers and other digestive disorders, increased risk of cardiac arrest,
hypertension, personality disorders, chronic muscle tension, insomnia, disorientation, hyperactivity, especially in children.
The recommended maximum caffeine intake per day is approximately 250 to 300 milligrams, corresponding to two to three cups of
coffee.
If you undergo a local or general anaesthetic, a minimum period of time should elapse before piloting an aircraft.
The period will vary considerably from individual to individual, but a pilot should not fly for at least 12 hours
after a local anaesthetic and for 48 hours following a general anaesthetic.
The more potent forms of analgesics, that is painkillers, may produce a significant deterioration in human performance.
If such analgesics are required, the pain for which they are being taken generally indicates a condition which means it's
safer not to fly.
The lesson on the human body teaches you about the nature of alcohol, its effects on the body, and the
dangers of combining alcohol consumption with flying.
We return briefly to the subject here in the context of your living a healthy lifestyle.
Alcohol is not digested in the human body. It's absorbed directly from the stomach and intestines into the bloodstream.
From there it's carried to every portion of the body.
The liver is then responsible for eliminating the alcohol, and does this by changing the alcohol into water and carbon
dioxide.
Drunkenness occurs when the individual drinks alcohol faster than the liver can dispose of it.
Alcohol is removed from the blood at a rate of approximately 15 milligrams per 100 milliliters per hour.
The consumption of one and a half pints of beer or three whiskeys will result in a blood alcohol level
of about 45 to 50 milligrams per 100 milliliters, and so it will take up to four hours for the
blood level to return to normal.
Contrary to popular belief, a person cannot speed up the rate at which alcohol leaves the body.
Black coffee and fresh air do not help.
Eating during drinking will only slow up the rate at which alcohol is absorbed into the blood, not the amount
of alcohol which is absorbed.
Once in the bloodstream, alcohol acts primarily as a depressant on the nervous system and slows down your reactions.
Some critical areas of the brain, such as the decision-making area, are especially vulnerable.
Any consumption above the following levels can cause permanent damage to the body.
For men, five units daily or 21 units per week.
For women, three units daily or 14 units per week.
People who consume in excess of these amounts may develop a dependency for alcohol and become an alcoholic.
The World Health Organization definition of an alcoholic is
A person whose excessive use of alcohol repeatedly damages his physical, mental or social life.
One final word, just to remind you that even small amounts of alcohol will degrade your performance as the pilot
of an airplane or the driver of a car.
It's a criminal offence to drive a car or pilot an airplane while under the influence of alcohol.
Though joint aviation regulations specify a maximum blood alcohol limit for pilots of 20 milligrams per 100 millilitres of blood,
the only way to be sure of being safe and responsible is to refrain totally from drinking alcohol when you're
piloting an aircraft.
The United Kingdom Civil Aviation Authority strongly advise that pilots should not fly for at least eight hours after taking
small amounts of alcohol,
and proportionally longer if larger amounts are consumed.
The CAA goes on to say that it would be prudent for a pilot to abstain from alcohol for at
least 24 hours before flying.
Tiredness and fatigue, though related concepts, differ in their long-term physical effects on the body.
Ordinary tiredness results from normal physical and or mental exertion over a normal waking period, say 14 hours.
If a person is tired in this way, a good night's sleep is the only requirement for that person to
be fit the following morning to continue with physical activity,
whether that be flying or any other kind of work.
The only consideration required to deal with normal tiredness is to ensure that periods of activity and periods of restful
sleep
comply with a normal pattern for a person's age and physical condition.
Fatigue, however, is a very deep tiredness due to the cumulative effects of a stressful lifestyle and or living and
working environment.
Whereas normal tiredness is instantly recognizable by the sufferer and the remedy obvious, the effects of fatigue can be insidious.
They can creep up slowly on the sufferer.
Moreover, the sufferer may for a number of reasons be unwilling to recognize or admit that he is suffering from
fatigue.
The important fact for pilots to be aware of is that both tiredness and fatigue can kill them and their
passengers.
There are differences, however. Pilots may be naturally unwilling to fly when they're normally tired,
but a pilot suffering from cumulative fatigue may not realize his condition or be unwilling to admit it.
Fatigue, then, is a highly dangerous condition for a pilot.
So, as pilots, we must be conscious of the symptoms of fatigue and be prepared to both recognize them and
admit to them.
Fatigue can be caused by the following circumstances.
Long-term ill health, either physical or mental.
Regular sleep deprivation, for whatever reason.
High levels of stress and or anxiety over a prolonged period.
A disturbed body cycle, for example jet lag, changing work shift patterns.
Long-term difficulties in personal or work-based relationships.
A stressful living and or working environment, for example high levels of noise or unreasonable physical or mental demands.
Symptoms of fatigue may be diminished awareness.
An appearance of tiredness.
Diminished coordination.
Memory lapses.
A propensity to make frequent mistakes in speech and actions.
Rapid changes of mood.
If you become aware that you have developed symptoms of fatigue, don't fly again until you have consulted a doctor.
If you are a professional pilot, the doctor should be an authorized aviation medical specialist.
As a minimum immediate self-help program, you might also try the following.
Accept the fact that you may be fatigued.
Make sure that you get regular undisturbed sleep.
Avoid alcohol and caffeine.
Eat a balanced diet of appropriate quantities of food.
Try to take the stress out of your life.
Always, however, consult a doctor.
As we've already mentioned, flying can expose the human body to conditions for which it is not naturally suited.
We've covered, for instance, extremes of pressure in some detail.
Here we'll look at the increase and decrease in gravitational force or, more accurately, gravitational acceleration to which the body
may be exposed in flight.
Under normal conditions on the ground, the body is subject to 1g, that is, normal gravitational acceleration of 32 feet
per second squared or 9.81 metres per second squared directed towards the centre of the Earth.
The reaction of the surface on which we are standing or resting gives us the sensation we call weight.
You'll be experiencing a 1g acceleration as you sit at your computer studying this course.
You'll also experience 1g in straighter level flight.
But if you carry out a level turn, at 60 degrees of bank, you'll be subjected to an acceleration of
2g acting vertically through your seat, if your turn is perfectly executed, that is.
As your body mass is constant, your weight will also increase by a factor of 2.
This is called the load factor.
In a 60 degree level turn, the whole structure of the aircraft is subject to a load factor of 2.
In a 70 degree level turn, should your aircraft engine be powerful enough to perform this manoeuvre, the load factor
increases to 3.
In aerobatics you may experience accelerations and load factors of this order.
In fact, a typical light aircraft cleared for aerobatics would be stressed to withstand positive load factors of up to
6.
Let's now look at the effect of increased accelerations or increased g or load factors on the body.
During increased g manoeuvres, the pilot's head becomes heavy.
Mobility is impaired and the body's internal organs can be displaced slightly.
Blood will also be drawn towards the lower parts of the body as the heart's ability to pump blood into
the brain is overcome by the increased load factor.
As g increases, the pilot's peripheral vision becomes impaired, giving the impression of tunnel vision.
This gives the pilot the impression of his world turning grey and the expression grey out is used to describe
this condition.
If g is further increased, the pilot's sense of vision may cease to operate and he is said to black
out.
If a blackout endures long enough, it's easy to imagine that the pilot may lose both consciousness and control of
his aircraft with possible catastrophic consequences.
The adverse effects of moderately increased g can sometimes be delayed or relieved by tensing the thigh and stomach muscles.
The quickest way to relieve blackout or greyout is to ease off the backward pressure on the control column.
Speak to your flying instructor about subsequent actions as they apply to your aircraft.
Under normal circumstances, a private pilot without aerobatic training should never find himself subject to accelerations of more than 1
.41 g.
This is the acceleration experienced in a level turn at 45 degrees angle of bank and in normal flying, angles
of bank greater than this are unnecessary.
It's important, however, to understand the circumstances which can give rise to higher values of g and the effects that
the associated higher loadings can have on the body.
Be aware also that anything which can have a harmful effect on the human body will reduce the body's tolerance
to accelerations in excess of 1 g.
Among factors adversely affecting g tolerance are alcohol, smoking, fatigue, excessive heat, obesity and any level of illness.
Whereas most pilots can learn to tolerate moderate increases in positive g, many find even the smallest exposure to negative
g to be unpleasant.
You may already have experienced negative g if you've ridden on a roller coaster or driven at speed over a
humpback bridge.
During flight negative g is experienced if, after pulling out of a steep dive, the control column is instinctively and
firmly moved forward,
because the pilot feels that he has his nose too high in an attitude that may lead to a stall.
You will almost certainly have this phenomenon demonstrated to you during your training and will be taught the difference between
this manoeuvre and standard stall recovery.
From the point of view of physical sensation you should know that negative g manoeuvres increase the flow of blood
to the head.
Blood pressure in the head increases, the face becomes very flushed, often painfully so, and the eyes begin to bulge.
In extreme cases blood vessels are likely to burst.
The combined effect of these symptoms causes what is described as red out.
Ultimately consciousness may be lost with the obvious attendant dangers.
Immediate relief from the symptoms may be obtained if the pilot ceases to push forward on the stick, selects a
normal flying attitude and waits for normal flight conditions to re-establish themselves.
As always be sure to consult your instructor's advice on piloting issues.
The word toxic derives from Latin and Greek words meaning poisonous.
The operation and engineering support of aircraft involve the use of many substances that are in themselves toxic or produce
toxic fumes, either spontaneously or when burned.
Even mild toxic effects can degrade a pilot's performance and lead to an accident.
Prolonged exposure to toxic influences can damage a person's general health.
It is therefore of crucial importance that pilots recognise the dangers posed by toxic substances so that they may act
accordingly in their presence.
One of the greatest toxic dangers is the exposure to carbon monoxide fumes in flight.
This subject is covered fully in the lesson on the human body elsewhere on this disc.
Click on the headings on the screen to uncover an explanation of other toxic hazards.
Anyone who has been exposed to any toxic hazard should seek medical assistance as soon as possible.
.
Finally, pilots must be aware that they must not carry certain defined items onboard their aircraft.
Such items are referred to as dangerous cargo because of the possibility that their discharge, spillage or breakage may endanger
the aircraft and or crew in flight or on the ground.
Among items classified as dangerous cargo are compressed gas containers, toxic substances, acids and other corrosive liquids, radioactive materials, firearms
etc.
On completion of your training, as the holder of a private pilot's licence, you'll be able to carry passengers with
you when you fly.
Taking friends and family into the air is one of the privileges and pleasures of holding a pilot's licence.
The privilege however also carries with it an enormous responsibility, that of the pilot for the care, comfort and safety
of his passengers.
This responsibility begins from the pre-flight briefing of passengers and lasts until the passengers have safely disembarked from the
aircraft and have left the operating area of the airfield.
We'll look at passenger care for each of the following phases of the flight.
Pre-flight briefing
Approaching the aircraft, embarking and strapping in
In-flight
Emergencies
Disembarkation
The best way to give your passengers confidence in your ability to take them safely into the air and to
bring them safely to earth again is to deliver your briefing in a confident and reassuring manner.
The CAA publish a free comprehensive guide to care of passengers on their website at the earl shown on the
screen.
Pre-flight briefing
The law requires that the commander of an aircraft gives a pre-flight briefing to all passengers being carried in
a United Kingdom registered aircraft.
During the pre-flight briefing, passengers should be given brief information about the nature of the flight, whether it is
to be a local sightseeing flight or a route flight.
For any passengers who have never flown before, it's useful to say a word or two about the sensations of
flight and to put them at their ease and to mention the pressure changes associated with climbing and descending and
how the ears may be cleared.
Please refer to the lesson on the ear to refresh your knowledge of this.
If the day of the flight is one where significant weather conditions prevail, make mention of them.
If cloud is extensive, or if turbulence is present, it will reassure passengers to be told about them before they
get airborne.
It's customary for information on any standard emergency procedures to be given during the pre-flight briefing.
We'll cover the contents of this briefing under a separate heading.
If parachutes are to be worn, now is the time to brief your passenger or passengers on how to put
on the parachute, how to exit the aircraft, how to deploy the parachute and how to steer it and land.
The brief on exiting should be repeated prior to take-off. In most light aircraft, parachutes will not be worn.
It's always worthwhile mentioning that airfields can be cold and windy places and that warm clothing should always be available.
It can always be removed before boarding the aircraft.
Emphasise that no loose articles are to be carried and, for example, that coins should be put in closed pockets
and pens safely stowed.
At this stage the pilot must make a final check that the weight of his passengers, his own weight and
any other payload such as luggage, parachutes, Maywests or other emergency equipment do not exceed all up-weight and centre
-of-gravity limits, either in total or for individual seats.
Refer to the lesson on mass and balance for full details of this essential consideration.
Finally, while you're still in the crew room, you should ask if any of your passengers have any questions to
ask you.
Brief your passengers thoroughly on how they are to cross aprons or other manoeuvring areas and taxiways and how they
are to approach the aircraft.
Check whether high visibility jackets need to be worn at your airfield.
Ideally the aircraft should be approached obliquely from behind.
If there are several passengers they should keep in one group so that you can supervise them efficiently.
In approaching the aircraft the passengers must be worn to stay well clear of the propeller arc.
The engine must be shut down during passenger embarkation.
Ensure your passengers are comfortably seated and correctly strapped in.
Refer to your aircraft's handbook for details on strapping in.
Passengers must be fully briefed on how to do up, adjust and release straps and harnesses.
Ensure that passengers understand how to adjust and lock their seats.
The passenger who sits in the front or the right hand seat will need to be briefed not to permit
any part of his body or equipment to interfere with your operation of the aircraft controls.
The operation of doors, windows and direct vision panels and ventilation ports must be fully explained.
It's the pilot's responsibility to check that all doors are closed and locked.
Check that headsets are properly fitted and adjusted and that operation of the intercom is understood.
You may wish to explain that chat should be kept to a minimum because of your need to speak on
the radio and to concentrate on the safe conduct of the flight.
You should though encourage your passengers to point out to you when you're not transmitting or receiving anything of concern
to them or to ask any questions that they wish about the flight.
It's useful to take advantage of the extra pair or pairs of eyes and to ask for help in maintaining
a good lookout for other aircraft or for significant ground features.
Before you first make contact with air traffic control, remind passengers about action to take in the event of a
forced landing and the use of any emergency equipment.
Finally, if parachutes are worn, say in a two-seater, the procedure for abandoning the aircraft should be gone through
again.
If your pre-flight briefing and embarkation procedures have been effective, there should be no need for any formal briefings
or procedures during the flight itself.
Do, however, reassure passengers if anything unusual should occur, such as flying through turbulent air.
Be sure to point out interesting and relevant features in the air and on the ground.
Also, keep passengers updated about the progress of the flight.
If you're flying a route, they should be told about position and estimated time of arrival at the destination.
Whether en route or during a local flight, it is a good idea to advise passengers who fly infrequently that
you're about to execute a turn or initiate a climb or descent.
They will not then be surprised by an unexpected manoeuvre.
An emergency can occur in the air or on the ground. However, in the air during an emergency, events happen
quickly and the pilot's concentration is fully occupied with dealing with immediate safety of the aircraft and passengers.
Therefore, instructions to passengers on how they should react to an emergency must be given on the ground, in the
aircraft where possible.
Here we'll deal only with what emergency situations might arise and the general aspects of emergency briefings.
As a pilot, you must familiarise yourself with the emergency procedures and equipment pertaining to your aircraft and with the
specific emergency equipment made available to your passengers.
A forced landing is any emergency landing on a surface other than an airfield runway.
A forced landing may be necessary following an engine failure.
Fortunately, such occurrences are rare. As in everything in flying though, you must be prepared for the worst.
The aim of the forced landing briefing is designed to prevent passengers being injured through striking any objects within the
aircraft and to enable them to vacate the aircraft quickly and safely.
If a forced landing over land is inevitable, you must warn your passengers of the occurrence and order them to
check that their harnesses are tight and locked.
Before touching down, doors must be unlocked but not opened. Headsets should be removed and put aside just before touchdown.
Again, just before touching down, passengers must adopt the braced positions shown on the screen.
The passengers must know the most efficient evacuation order and how to unlock seat and back support restraints.
When flying over water in a single-engined aircraft, lifejackets must be worn. It's not sufficient merely to have lifejackets
available for donning.
In a twin-engined aircraft, passengers need to be instructed in the location of lifejackets and how to put them
on.
Passengers must be briefed on how to inflate their lifejackets and how to use any ancillary items such as whistles,
radio beacons and lights.
It is of vital importance to stress that no passenger must inflate his lifejacket until he is outside the aircraft
following ditching.
If a life raft or dinghy is carried, make sure that someone is made responsible for deploying it on ditching.
Procedures for inflating and boarding life rafts must be followed exactly.
As a pilot, it's your responsibility to get yourself instructed on the details pertaining to the equipment you carry and
to brief passengers before flying.
As already mentioned, a passenger must be briefed on donning the parachute, exiting the aircraft, deploying the chute, steering it
and landing before embarking.
This briefing is specialised and, except for the landing, dependent on the type of parachute worn and aircraft type.
Once again, as a pilot, it's your responsibility to get yourself thoroughly briefed on the parachutes you're using and bailing
out procedures for your particular aircraft.
Then you must brief your passenger.
Usually parachutes are worn only in two-seat aerobatic aircraft.
First Aid
Although there is no test in first aid for private pilots in Britain, a pilot who does not possess rudimentary
knowledge of first aid may be considered as unable to fulfil his duty of care to passengers he carries in
his aircraft or accompanies onto the airfield.
This CBT course does not aim to teach you first aid.
You should enrol on and complete a course in first aid run by a recognised and competent organisation such as
the St John Ambulance Brigade or the Red Cross.
A knowledge of first aid skills will be essential if, for instance, persons in your care injure themselves on the
airfield or sustain injuries following a forced landing.
You can save life or minimise the consequence of an injury if you know what to do between the time
of injury and the arrival of qualified medical help.
So get yourself trained in first aid.
In principle, at the scene of an accident, your priorities should be
Do nothing to aggravate the situation or further injure a casualty.
Do, however, remove a casualty from immediate further danger.
Summon the specialist help by the quickest possible means and ensure that emergency services know how to reach you.
For instance, position someone at the airfield entrance and know how to summon the emergency service at your home airfield.
Administer first aid. Remember the mnemonic ABC.
A is for airways. Clear the obstructed airways.
B is for breathing. Ensure that the injured person is breathing again. Consider artificial respiration.
And C is for circulation. Stop any bleeding.
Finally, make sure that your aircraft and your clubhouse are equipped with a first aid kit whose contents meets the
recommendation of the air navigation order and that you know what those contents are.
Be sure, too, that you know how to locate the first aid kit.
We receive information from the world around us through our senses, sight, hearing, touch, smell and taste.
When flying an aircraft, the pilot must observe and react to events both in the cockpit and in the environment
outside the aircraft.
The information from our senses must be interpreted in order to make decisions and take actions to ensure the safety
of the aircraft at all times.
In this lesson, we'll lay out the basic systems by which we receive and process information in order to make
decisions and recognise where errors in the system may be the cause of accidents.
We need to build a functional model of the various stages of our reasoning.
The model we'll use here is not the sophisticated one used in universities to teach the whole subject of human
performance.
However, it will suffice to teach those aspects of the stages of reasoning most important to private pilots.
These stages are detection, information is received in the receptors, perception, decisions are taken, action, responses are selected and executed,
feedback.
This model is of great importance when errors are considered. We can determine if the errors result from a failure
of perception, a failure of memory or even if, in spite of having correctly interpreted the information, we've just failed
to take the correct action.
The functional model also helps in understanding other factors, such as stress, that may influence our performance.
The model is based on a series of stages that occur between receiving information and the response being made.
The various sections of the model will be discussed both individually and as part of the full mechanism.
Once information has been perceived, a decision must be made as to the response.
For example, on hearing a warning sound, the operator may hold the information in memory while a search is made
for the problem which has triggered the warning.
Or switch off the affected system, a selected response.
Information is continuously entered into and withdrawn from both the long and short term memories to assist the decision process.
For example, air traffic control may require that the radio frequency be changed.
The frequency required will be stored in the short term memory, whilst the actions to enable us to select a
frequency will be stored in the long term memory.
We sometimes feel that we can make several decisions at the same time.
This is strictly untrue, since the central decision maker can only process one decision at a time, and this is
its chief limitation.
This is known as single channeled processing.
Because humans are limited to single channeled processing, multitasks, such as flying an aircraft and holding a conversation, are not
possible without the central decision maker getting further assistance.
So to enable us to carry out multitasks, we must learn skills through motor programs.
Motor programs, or skills, are behavioral subroutines which are learnt by practice and or repetition, and are held within the
long term memory, and can be carried out without conscious thought.
For instance, when a fully functional adult human walks, the action requires little conscious attention.
The skills required to walk have been stored in long term memory as behavioral subroutines.
For clarity, the information processing model shows them separated from the long term memory, although subsequently in this lesson you'll
find we have included motor programs inside the long term memory.
A skill is an organized and coordinated pattern of activity. It may be physical, social, linguistic, or intellectual.
There are three distinct phases involved in developing a motor program or skill.
A cognitive phase, in which the learner thinks consciously about each individual action.
The associative phase, in which the separate components of the overall action become integrated.
The automatic phase, when the total manoeuvre can be executed smoothly without conscious control.
Although reflexes do depend on the nerves in the body, they occur with little or no involvement of the central
nervous system.
When a reflex action is required, such as when part of the body touches something very hot, the motor nerve,
which controls muscular action, that is movement, is linked very closely to the sensory nerve which felt the heat, so
that the central nervous system is essentially bypassed, and the muscular action occurs before hardly any processing within the central
nervous system can be carried out.
There is a delay between detection, stimulus, and muscle contraction. This delay is called reaction time.
Reaction time depends on the type of reflex action being used. There are three types of reflex action.
Unconditioned, conditioned, and trained.
Unconditioned reflexes are instinctive, natural reflexes, such as blinking when there is a movement towards eyes or jerking back from
a hot surface.
This type of reflex has the shortest reaction time, since the brain does not process it.
Conditioned reflexes are reflexes that may be learned. An example of a conditioned reflex is that of Pavlov's dogs.
Dr. Pavlov sounded a bell at the same moment that food was offered to a dog. Over time the dog
became so conditioned that its mouth would water any time it heard the bell, even when food was not present.
This type of reflex has the second fastest reaction time, since the brain does not have to process sensory input.
It is conditioned to respond directly to the input without conscious thought.
Trained reflexes are reflexes that may be improved by repeated practice. The crew of a large aircraft might practice emergency
drills in the flight simulator. This will make them more proficient.
The trained reflex is a conscious reaction to a sensory input. This type of reflex has the slowest reaction time,
but with continuous training over a long period it may be developed to almost an instinctive reaction time.
However, in the aviation context there is a danger that emphasis may be placed more on the importance of the
speed of the reaction rather than the accuracy of the action.
This may cause problems. For instance, although this example might not apply to the private pilot, if the drill is
concerned with an engine fire in a multi-engined aircraft and an incredibly quick fire drill is carried out on
the wrong engine.
The senses, sight, hearing, taste, smell and touch, provide inputs, stimuli, to our brain. Most stimuli are stored for a
brief time after the input has finished. The ability to retain these stimuli for a short time is essential, because
when they first arrive we may not have the processing capacity to deal with them.
Stimuli must be of a certain strength for the sensory receptors to pick them up. In other words, a sound
must be sufficiently loud to be heard, or a light bright enough to be seen. This minimum strength is known
as the sensory threshold.
There are three types of memory. Sensory memories, sometimes referred to as ultra-short-term memories.
Short-term or working memory. Long-term memory.
The key features of the sensory memories are, there is a separate memory store for each sensory system. The input
decays rapidly. The sensory stores for touch, taste and smell are of little significance in aviation. However, those of sight
and sound are important, and knowledge of these is necessary.
The longest lasting sensory store is the echoic memory, which can last for between two and eight seconds. The echoic
memory retains sounds, and for example, it's possible to record the chimes of a clock that have struck, when realising
you want to know the time, but only after the third or fourth stroke.
In these circumstances, echoic memory can be interrogated or replayed to enable the strokes to be counted consciously. The echoic
memory needs to last long enough for input to be scanned for relevance. If an input is of interest, then
it's called into the short-term memory.
The iconic memory is the visual sensory store, and it only lasts for between a half and one second. 80
% of the information processed by humans enters the brain through the visual channel.
A special characteristic of all sensory receptors is that they adapt, either partially or completely, to their stimuli after a
period of time. That is, when a continuous stimulus is first applied, the receptors respond at a very high impulse
rate at first, then progressively less rapidly, until finally many of them no longer respond at all.
This is why, once you get dressed, you do not continue to feel your clothes against the skin. The classic
example of this is when, having moved into a house close to a railway line or airport, the noise of
passing trains or arriving aircraft can cause extreme stress. However, having lived for a month or so under these conditions,
the noise may be hardly sensed, if at all.
Sensory adaptation is sometimes referred to as habituation.
Perception involves the conversion of the sensory information received into a meaningful structure. For example, a pattern of vibrations in
the air becomes recognised as a particular message. The percept, what we perceive, is not a complete representation of the
information in the sensory store, but an immediate interpretation of it.
Read the following words out loud. When you've done so, continue with the lesson.
The words actually read, a bird in the the hand. Most people will read the sign incorrectly the first time,
and perhaps for a few more times. The reason in this case is simple. It's the beginning of a well
-known phrase, and having read the first three lines, the reader believes he knows what's coming next, and may automatically
pass on to the last word to confirm his belief.
Missing out the extra the.
It follows that the sensory information that we expect to receive is more easily perceived and integrated when it actually
occurs, compared with totally unexpected information. This should serve to warn us to guard against having a mindset.
Anticipating receiving sensory information is good, for instance a particular radio message, but we must beware making up our minds
what the message says before we've fully interpreted it.
It's true that we can perceive only that which we can conceive. It's also true that we perceive only a
fraction of the information reaching our senses at any moment. Therein lies the importance of the attention mechanism in our
model.
The process of perception is greatly assisted by our ability to form mental and three-dimensional visual models.
Perception of a situation can differ depending upon the starting point of an observer. Imagine two men are walking through
some woods and they see a family group having a picnic. The first may perceive the overall picture of a
family enjoying themselves together in the open air, whereas his companion may first perceive details of the image.
The wording on the young boy's t-shirt, or perhaps the uniqueness of the picnic basket that the family is
using. It's possible of course that with time both observers will eventually arrive at the same conclusion, the first narrowing
his overall perception to include the details of the scene, and the second expanding his perception to include the overall
picture. However the initial perception of the two men, of exactly the same situation, will be quite different.
Attention is the deliberate devotion of the cognitive resources to a specific item. Man must be alert to be attentive,
but being alert is not sufficient guarantee that attention will be paid to the right item at the right time.
Due to the limitations of the central decision maker, we're generally unable to pay attention to a number of different
items at any given time. Although attention can move very quickly from item to item, it can only deal with
one at a time, and thus the need for the pilot to consciously prioritise.
The attention mechanism is required because of the two potentially limiting stages in processing information. There is a limit to
the number of items held or maintained in short-term memory, or working memory.
Our channel capacity is limited. We cannot devote conscious thought or simultaneously attend to all of the stimuli entering our
senses.
This limited channel capacity means that there must be an apparatus at an early stage of the whole process which
allows us to select those stimuli which will be perceived consciously, and used as a basis for our consideration and
our decisions.
Some stimuli are extremely efficient for getting our attention, for example the cocktail party effect, which relates to hearing our
own name in a background of many conversations.
In aviation, this may be hearing our RT call sign among a lot of radio chatter, or detecting a smell
of burning on the flight deck. Each will focus our attention in an attempt to get more information.
Attention is the process of directing and focusing psychological resources to enhance perception, performance, and mental experience. It has three
characteristics. It improves mental processing. It requires effort. It's limited.
There are two types of attention. Selective attention, when inputs are sampled continually to decide their relevance to the present
task in hand, our names or call signs have been particularly attention-getting.
Divided attention, when our central decision-making channel can timeshare between a number of tasks.
The pilot flying a visual approach will be dividing his attention between looking out to maintain his approach and checking
his flight instruments for airspeed, height, engine power, etc.
Whereas it would appear that the pilot is working on a number of tasks simultaneously, in reality the central decision
-maker is spending a fraction of every second on a different problem in turn, in effect a timesharing system.
It's important to remember that the mind always pays attention to something, except during sleep. Therefore the major danger for
pilots is the poor management of attention. That's to say paying attention to the wrong item at any given time.
Stress can have a significant effect on attention, especially during times of low and high arousal. Our limited ability to
process information under stress has implications for the level of performance we're able to achieve.
At times of low arousal, such as in the cruise, our attention can wander, with the result that information is
either missed or misinterpreted. Generating artificial cockpit workloads or flight deck visits are methods of addressing this problem.
At optimum arousal level, the central decision-maker is at its most efficient.
At times of high arousal, because of the limited channel capacity of the central decision-maker, there is a real
danger of attention becoming narrowed, so that important information is disregarded. Indeed, if overloaded, the attention mechanism may even reject
additional information.
This overload can be of two types. Qualitative overload. The information is perceived to be beyond our attentional capacity when
the task too difficult.
Quantitative overload. There are just too many responses to be made in the time available. Most certainly a very high
workload can be interpreted as stress, and the relationship between stress and performance can be represented as an inverted U
-curve as shown here.
The symptoms of overload will vary from individual to individual. Among the most common symptoms are a sharp degradation of
performance, funneling of attention or focus, regression where the correct actions are forgotten and procedures learnt in the past are
substituted, mental blocking where it becomes impossible to review or even to consider other solutions, mood swings.
Some individuals becoming aggressive towards others in the aircraft or air traffic control, restlessness and trembling, even a nervous laugh,
panic.
Human reliability can be defined as the individual functioning in the manner in which he or she is supposed to
function.
Studies of human error rates during the performance of a simple and repetitive task show that an error can normally
be expected to occur about once in 100 actions.
This error rate is built into the human system and can increase rapidly when stress, fatigue or low morale may
be added factors.
It has been demonstrated that with practice human reliability can be improved by several orders of magnitude.
Frank Hawkins who was the human factors consultant to KLM quotes that an error rate of 1 in 1000 might
be thought of as pretty good in most circumstances.
Error is a generic term which describes all those occasions when a series of mental or physical activities do not
achieve their intended effect.
Human error ranges from the mere step of the tongue to those which can cause a terrible cost in human
life in disasters such as the Tenerife runway collision in 1977,
the Bhopal methyl isocyanate tragedy in 1984 and the Challenger and Chernobyl catastrophes in 1986.
The aviation industry is currently investing large amounts of funding in human error research and national authorities have all included
the study of human error in human performance syllabi.
Although it is possible to have isolated errors that have neither consequence or influence on any further elements, errors in
general tend to be cumulative, one error leads to a second which in turn can lead to a third and
so on.
This is commonly known as the error chain. A simple example of an isolated error would be to take out
a young plant from a flower bed mistaking it for a weed.
A cumulative error would, for example, be to issue an incorrect aircraft maintenance procedure which results in a series of
accidents.
The attention mechanism selects the information which is passed to the short-term memory.
The short-term memory enables information to be retained for a short period of time.
Unless this information is actively rehearsed and deliberately placed in our long-term memory, it will be lost in 10
to 20 seconds.
Unless rehearsed, these items are lost by interference from new information or even from information previously stored.
Auditory information is considered easier to retain than visual information as it's easier to rehearse sounds than data in a
visual form.
The capacity of our short-term memory is limited.
The maximum number of unrelated items which can be maintained in the short-term memory is about 7 +/- 2.
Once this limit is exceeded, one or more of the items are likely to be lost or transposed.
This is of importance when designing checklists or deciding on the contents of an RT message.
As anyone who has received a complicated departure clearance is aware, much of the information cannot be memorized but must
be written down.
Short-term memory is also highly sensitive to interruption.
For example, if a frequency is passed to a pilot and very soon after its reception an interruption occurs,
although instant retention does occur, the information is then immediately lost because of the interruption and the pilot has to
request that the frequency be retransmitted.
There are two main tools which may be used to increase short-term memory. They are chunking and association.
Chunking
We can expand the number of items retained in our short-term memory by a system of chunking any related
material.
Chunking works best when the individual is familiar with the information. He already has a mental model.
A long telephone number may contain ten or more digits, for example 0123571762, but it can be chunked to 0123571762,
only three items to be held.
Association
This technique is used by many when remembering spoken lists of items. A wild and bizarre association is imagined and
attached to each item on the list.
Many politicians make use of this method when putting faces to names. Typical examples of items stored in the short
-term memory in flight are
radio frequencies, heights and pressure settings prior to selection, short air traffic control instructions, and verbal responses to checklists prior
to their execution.
If the information in the short-term memory is rehearsed, it will then be transferred into the long-term memory.
It's believed that information is stored in the long-term memory for an unlimited time period, although frequently there can
be retrieval problems.
One major disadvantage of long-term memory is the time that it takes to access it.
The long-term memory contains information which can be classified into three types. Semantic memory, episodic memory, procedural memory.
Semantic memory stores general knowledge of the world, storing information to such questions as are fish minerals, do birds fly,
do cars have legs.
It's believed that semantic memory holds concepts that are represented in a dense network of association.
Language is also held in semantic memory.
It's generally thought that once information has entered semantic memory, it's never lost.
It is certainly more accurate than episodic memory.
When we are unable to remember a word, it's because we are unable to find where the item is stored,
not because it's been lost from the store.
Episodic memory is a memory of events or episodes in our life, a particular flight, a meeting or incident.
Although some experts in the field of information processing agree that long-term memory consists of only episodic and semantic
memories, there are those that include skills within the makeup of the long-term memory.
We've already discussed the learning process in acquiring skills and skill development. However, the learning process also allows us to
gain intellectual advance.
In its simplest form, learning is an internal process which allows the mental acquisition and retention of data.
Here are some of the types of learning and also brief examples of those types.
Classical or operant conditioning, which is the behavioristic approach of Pavlov, where the recipient is taught through, principally, physiological responses,
for example, an experienced pilot's reaction to a fire warning.
Insight, where the data is intellectually and cognitively understood and is retained, for example, a pilot setting up the radios
before flight.
Observational learning or imitation, where the data from an outside source is replicated, for example, a student pilot following through
the instructor approach and then executing the approach on his own shortly afterwards.
Experience, sometimes called learning from our mistakes.
Skill learning or observational learning, along with practice, plays an important role in the learning of skills, motor programs. It
involves motivation, attention, observation, much practice, and corrective feedback.
Some of the factors affecting the quality of learning are
The intellectual capacity of the recipient
The quality of communication between transmitter and recipient
The applicability of the data
The motivation of both the transmitter and the recipient
Overlearning
Overlearning is simply carrying the training process beyond what is required to perform to the minimum acceptable level. Overlearning not
only improves the chances of recall, but makes the performance of the task more resistant to stress.
Information retention can be increased by the use of
Mnemonics, for example,
Hazel, people, or freedom
Memory training
Among the methods commonly used in memory training are
Word or phrase or object association
Chunking
Repetition
Revision
Attention
Whereas it is possible to learn without motivation, attention is essential. However, having said this, the learning process is vastly
improved with motivation, and high performance is rarely achieved without it. However, motivation is always enhanced by reinforcing successful endeavors.
We all have the ability to learn from our experiences and mistakes, and from those of others.
An interesting reality is that, in spite of the fact that age not only severely affects pilots' learning abilities but
slows both mental and physical reactions, their performance decreases by only a very small amount, if at all, with advancing
years.
Studies have led to the conclusion that the deficiencies in older pilots' learning abilities and mental and physical reactions are
compensated for by experience.
Thus it can be stated that sensory information is more easily perceived and integrated if it is recognized through experience.
Actions can be carried out as a result of information emanating from
Motor programs via the attention mechanism, for example, a skilled pilot flying straight and level
Motor programs via the central decision maker, for example, when carrying out an engine fire in the air drill
Directly from the central decision maker, for example, when solving a non-routine or unfamiliar problem
The feedback mechanism is continually in use. Even when motor programs are being used to fly the aircraft in straight
and level flight, and in visual conditions, the senses continually scan the environment to maintain the desired configuration.
Any action undertaken will cause a detectable change which, in turn, will be noted by the senses. This feedback may
alter the action being taken.
As an example, a pilot banking the aircraft will receive feedback from the visual or artificial horizon.
From the rate of bank detected, the pilot may increase or decrease the control forces, and when the desired angle
of bank is reached, the feedback will cause the pilot to return the controls to the neutral position.
When there is pressure to make a rapid response, perhaps in an emergency, there are a number of factors to
be borne in mind which include
There will frequently be a trade-off between speed and accuracy. A delay in some situations could be dangerous, as
with an engine fire after take-off.
There will also be pressure to make a response before sufficient information has been processed.
High arousal levels lead to faster, but less accurate responses.
Auditory stimuli, noises, are more likely to attract attention than visual stimuli, but they are also more likely to be
responded to in error.
An increase in age between 20 and 60 years tends to lead to slower, but more accurate responses.
If we expect a stimulus, like the starting gun when we're on the blocks at the start of a race,
and we prepare a response, like diving in, we'll respond more quickly if the expected stimulus occurs.
If, however, an unexpected stimulus occurs, we'll be more likely, under pressure, to make the prepared response and dive in
anyway, an error of commission.
For example, a pilot may have noticed engine instrument variations, showing parameters approaching out of limits.
He'll mentally prepare to do the engine shutdown drill if the limits are exceeded, and any stimulus, perhaps as little
as the noise of his passenger coughing, may be sufficient to trigger the pilot to shut down the engine.
Response, or reaction time, is the time interval between the onset of a given signal and the production of response
to that signal.
In the simplest case, such as pushing a button when the light illuminates, the reaction time is about two tenths
of a second.
If we complicate the task by having two lights and two buttons, the reaction time will increase, the increase being
due to the increase in loading on the central decision maker.
In aviation, the reaction times will be even longer, since the decision element of the task is likely to be
more complex.
It's important to remember that reaction times are important, but in general it's of paramount importance to make the correct
response rather than a fast response.
Human beings have evolved to function at sea level, and at speeds achievable on two legs.
Flight puts the pilot into an environment which can distort sense organs. In addition, the changed perspective which is experienced
in flight can result in information being presented which is outside the individual's expectations.
A hallucination is a false perception characterized by a distortion of real sensory stimuli.
Common types of hallucination are auditory, that is hearing voices or noises, and visual, that is seeing things that are
not actually there.
A hallucination is also a mental state of being mistaken or deluded. Hallucinations may indicate the presence of a mental
or physical disorder.
However, normal people also may have auditory or visual hallucinations when deprived of stimuli.
We use mental models as frameworks to make sense of the world and guide our actions. Mental models can be
incomplete and thus faulty.
This diagram may look like a group of spirals, but in fact it's a group of concentric circles.
In aviation, any mismatch between what we sense and what we expect is an illusion, in other words the difference
between perception and reality.
Objects seen from the air look quite different than when viewed on the ground.
Because of the lack of stable visual references and the erroneous mental models that may be produced, the pilot is
at a disadvantage.
In addition, in flight the pilot's cognitive and sensory orientation mechanisms have to try and cope with a third dimension
for which they have not been designed.
This will lead to both mental and physical illusions.
Illusions may occur during all stages of the flight, and to pilots of every experience and skill level.
The pilot, therefore, should be aware of the possibility of misinterpreting the information received.
Illusions can affect all of our senses, but a particular concern in aviation are those which affect our visual sense
and those affecting the balance organs in the middle ear.
We also possess a position sensing system derived from nerve endings in the skin, muscles and joints, which can be
a source of incorrect information passed to the brain.
Visual illusions are particularly dangerous in aviation as we normally consider our visual input to be the most reliable of
our senses.
Most people are familiar with the two-dimensional figures shown here.
In A, the figure with the outgoing fins appears to contain a longer line than the other, although both are
exactly the same length.
We're not often going to see large finned lines on our airfields, but the natural scenery, the junction of two
roads or railways, the alignment of valleys, even a small runway running into the corner of a field where hedges
meet, can give a false impression of runway length.
In B, the upper of the two horizontal lines appears the longer, but they are both the same length.
In C, the vertical straight lines appear curved, but they're straight.
In D, which line passes through the red block? It is in fact the top line.
All of the illustrations shown here can be visualized as a model, but none could exist in real life.
Visual illusions in flying are often associated with inappropriate experiences. For example, the pilot who has done most of his
flying in relatively polluted air may have learned to use atmospheric perspective as a good cue to range.
If the pilot then operates in a very clear atmosphere, he may believe distant objects, because of their clarity, to
be much closer than they actually are, or mistake the distant object for a similar, smaller object he was expecting
to see close by.
Both the expected and the actual object would give the same angular size on the retina. A number of accidents
have occurred in polar regions when pilots flying in very clear conditions have miscalculated the distance to a landing spot
situated close to a landmark, with the result that the aircraft have run out of fuel.
Our senses—sight, hearing, touch, etc.—do not account for all the sensory illusions. Sometimes the perception is correct, but comprehension and
identification may be in question.
The human brain is continually working on the construction of mental models. The Gestalt theory of learning—the word comes from
the German word gestalt, meaning shape—proposes that any individual's understanding of the world results from them sorting out and combining
multiple cues perceived in the environment, until a coherent whole appears that is acceptable, according to the individual's standards as
regard the world.
Gestalt psychologists propose that perception, rather than being a simple, repeated association between a stimulus and a response, is an
active construction of an object by the brain.
To reach this coherent whole that we spoke of, the brain has developed a set of rules about the combination
of all the cues available. These rules are the laws of perceptual organization of the Gestalt theory, and they deal
with factors such as proximity, continuity, similarity, symmetry, simplicity, and closure.
In many cases, an individual will add cues which are not in the environment, but which the brain thinks are
hidden or not visible in what has been perceived.
Basically, Gestalt laws formulate basic principles governing how objects are organized and perceived.
Consider the following letters and consider what they mean to you.
A psychology student would probably read it as psychologist, whereas a biology student might read physiologist.
We must use extreme caution to ensure that we do not construct our mental model according to our wishes or
desires.
Even on the ground we are not free of illusions. Another aircraft moving slowly past our aircraft may give an
illusion that it is our aircraft that is moving. Blowing snow may give a false impression of relative speed.
When an aircraft is taxiing with a tailwind, the snow may appear to be falling vertically, giving the impression that
the aircraft has stopped, when in fact it may still have a relatively fast taxiing speed. Application of the parking
brake in these circumstances could have serious consequences.
Alternatively, the aircraft could creep forward, colliding with an obstacle, when it was thought to be stationary.
When taxiing into a headwind, the blowing snow will give the illusion that the aircraft is taxiing faster than it
is. In either case the pilot must look out of the side cockpit windows to gain an accurate assessment of
taxi speed.
In commercial flying, the major accelerations in the longitudinal and rotational planes occur on the take-off and go-around.
An acceleration gives the pilot an impression of the nose of the aircraft pitching up, and this encourages the pilot
to push forward the stick with the resultant danger of flying into the ground. The effect is due to the
brain resolving the weight, acting vertically downwards, and the acceleration into a single resultant force.
The fact that this phenomena is exacerbated by the information supplied by the otoliths of the inner ear makes it
particularly dangerous.
Outside references, vectional false horizons, may give false impressions within the cockpit. Among these are
Immediately after take-off, a false horizon may be perceived when surface lights are confused with stars.
Over water, the reflection of the moon off the water or ice, or the lights of fishing boats have been
mistaken for stars and the flight path adjusted inappropriately.
In hilly terrain, it's possible that, emerging from low cloud or mist on take-off, lights on the ground will
be mistaken for stars and the flight path adjusted to a lower and dangerous profile.
Gently sloping terrain, may create an illusion at any time when flying visually at low level.
A bank of sloping cloud across the horizon will give the impression of a wing low.
This is a side elevation, not drawn to scale, of a normal three degree approach path to a runway which
is level. The pilot has an established visual perspective of what he expects to see.
When the ground and the runway slope down away from him, if he's unfamiliar with the approach, in order to
get the same visual perspective that he had on the level runway, the pilot will initiate the approach from a
greater height and fly it at a steeper angle.
A down sloping runway will appear longer than it really is.
When the ground and the runway slope upwards, if he's unfamiliar with the approach, in order to get the same
visual perspective that he had on a level runway, the pilot will initiate the approach from a lower height and
fly it at a shallower angle.
An up sloping runway will appear shorter than it really is.
Staring at an isolated and stationary light when other visual references are inadequate or absent may cause autokinetic movement of
the eyes. This gives the illusion that the light is moving and can lead the pilot to believe that a
single star is another aircraft.
Numerous cases have been reported of mistaken identity of lights. These illusions can be avoided by shifting the gaze to
eliminate staring. The illusion is created by small movements of the eye ignored by the brain and interpreted as motion
of the object.
A common problem in flight is the evaluation of the relative altitude of approaching aircraft and the assessment of a
potential collision risk.
At a distance an aircraft may appear to be at a higher level, but may eventually pass below the observer.
Mountains or clouds at a distance tend to appear to be above the aircraft, but often pass below.
50% of all airline accidents occur on the approach and landing, and of all the phases of flight this
is the one most prone to human error. In the final stages of a flight the pilot has to cope
with the most critical visual tasks, and these may be divided into three stages.
Initial judgment of glide slope
Maintenance of the glide slope
Ground proximity judgments
The judgment of the glide slope can be made easier by the use of vases or pappies at the airfield,
or by positioning the aircraft at a predetermined height above known ground features.
However, often the judgment must be made without such aids.
To judge the approach path, normally 3 degrees, the pilot is attempting to establish an angle. This angle is the
visual angle, and is measured at the pilot's eye down from the horizon to the visual aiming point on the
runway.
This of course is equal to the approach angle.
The width of the runway may also cause incorrect height judgments on the final approach.
A pilot used to a standard-width runway, 150 feet or 46 metres, may, when approaching an unfamiliar airfield with
a narrow runway, judge he's too high, and therefore round out too low on approach.
At an airfield with a wider runway than the pilot is used to, the tendency will be to round out
too high on an approach, in an attempt to match the visual scene to the pilot's expectation.
When approaching an airfield at night over water, jungle or desert, the only lights visible may be the distant runway
or airfield lights, with an apparent black hole between them and the aircraft.
This absence of visual cues leads to an illusion that the aircraft is too high, and as a result the
approach path may be flown at too shallow an angle, the aircraft touching down short of the runway.
Once the aircraft is established on the glide path and is in the landing configuration, it's relatively easy to visually
maintain the glide path by keeping the aiming point at a fixed position on the windscreen.
A situation can arise on the approach such that, with an inadvertent speed loss and a gradual loss of altitude,
the runway could remain in the same position on the windshield, giving the impression of a safe, stabilised approach, until
the aircraft touches down some distance before the threshold.
This should be remembered in particular when visual flying at night around airports, where the surrounding terrain is without lights.
Clearly this technique of using the visual angle will only work, providing the speed and configuration are maintained.
If the speed decreases, the nose-up attitude of the aircraft will increase, and the selected spot on the windscreen
will move towards the overshoot end of the runway.
The danger exists in descending to regain the position of the selected spot on the windscreen, whilst maintaining the lower
speed, and vice versa.
As long as visual texture flows away from the aiming point, and the visual angle between this point and the
horizon remains constant, the approach will progress normally.
The texture change is particularly important when landing on a grass field.
In the final stage of the approach, the pilot will be required to make an assessment of his height above
the ground to initiate the flare or power reduction.
The pilot will use a number of cues in this height assessment, among which will be
That the apparent speed of objects on the ground will increase as the height reduces.
That the size of objects, such as runway lights etc, will increase with decreasing distance, both height and range of
the aircraft.
That the apparent width of the runway will increase.
That the texture of the ground will change.
At height, grass will appear only as a green surface, only at low level does it look like grass.
There are recorded cases where pilots with engine failure have mistaken the green jungle canopy for a flat green field,
and attempted to land.
It is sometimes said that as visual illusions result from an unconscious process within the brain, there is nothing that
can be done about providing protection against them.
This is not true. Effective steps can be taken to substantially reduce the risks associated with visual illusions.
Organised and formal training is the best protective measure, and it has been recommended that this should be used to
educate pilots to recognise
that illusions are natural phenomena, the different types of illusions and their effects.
That the supplementation of other visual cues with information from other sources is the most effective counter to the effects
of illusions.
The need for comprehensive flight briefing should the occurrence of illusions be known to exist or anticipated at particular geographic
locations.
That special care must be taken by pilots during accelerations and particularly when instrument flying.
That head movements, fatigue, night and conditions of reduced visibility are all factors that can promote visual illusions.
A pilot's best performance occurs when he has suitable levels of skill, knowledge and experience for the situation he is
in.
His mental workload is such that he is neither over nor underworked.
If his workload increases too much, as a result of deteriorating weather or tiredness for example, it is highly likely
that his performance will decrease.
Conversely, if a pilot's workload is too low, he may get bored and be understimulated, leading to carelessness and inattention.
Several types of situations can cause mental overload, and this invariably leads to degraded performance.
It's important to know your capabilities and plan to stay within them.
Too many concurrent stimuli can cause the sensory memory to overload, effectively cutting out a proportion of the stimuli.
A pilot coping with an emergency situation may not hear other important information or warnings.
As we've seen previously, the short-term memory only has a limited capacity of about 7 items for 10 to
20 seconds.
New information replaces or confuses that already there.
The central decision maker can also become overloaded if you are required to make too many decisions in a short
time or receive conflicting information.
Our bodies are continuously receiving numerous stimuli from our five senses.
This information is stored briefly in our sensory memory, and if we perceive it to be important, given enough attention
for us to become aware of it and for it to be transferred to our short-term memory or central
decision maker.
Some stimuli are better than others at getting our attention.
It's quite common for example to clearly hear your name mentioned if someone's talking about you in a crowded room,
and people rarely ignore the smell of smoke if they don't know its cause.
Making good decisions is one of the most important aspects of piloting an aircraft.
Good decisions can help lead to safe, successful flights, whereas bad decisions and even indecision have led to many aircraft
accidents.
As a new pilot you may find it difficult to make the right decisions in a timely manner, but with
practice and experience you'll find it gets easier as the tasks involved become more and more automatic.
You'll find it easier when you are yourself in a situation you have seen before or have heard about.
Talk to your instructor and other pilots about different flying situations to obtain advice about what a good decision would
be in a given circumstance.
In multi-crew aircraft or when flying with another pilot, it's possible to increase the chance of a good decision
being made by discussing it.
However, there are factors that can affect whether the correct solution is found and agreed upon.
These factors include things such as the status of the various members of the group making the decision, whether individuals
feel they need to conform to the group decision, and how long the crew or group has been together.
Status of the members of the crew or group is particularly worth noting, as a relatively inexperienced pilot might be
reluctant to question a more experienced pilot.
If, as an inexperienced pilot, you're flying with someone of more experience and you see them doing something you consider
to be dangerous, you should immediately question their course of action.
Even with experience and training errors can sometimes be made.
Being tired or overloaded can easily lead to errors being made, as can overconfidence and complacency.
A good pilot is one who always realizes there is more to learn.
When making a decision, a pilot will also be influenced by his previous experience, the probability of an occurrence, and
whether the information he is receiving matches that expected.
When using judgment to come to a decision, it's often necessary to weigh up the risk involved.
The risk assessment is based on the probability of the risk occurring and the impact of that risk if it
did occur.
You will often have to balance risks against each other to determine your course of action.
For example, you've planned to take a couple of friends on a flying outing.
On the day, however, the weather reports are unfavourable and there is a strong crosswind on the runway.
There's a risk that by postponing the flight you'll disappoint your friends.
However, this is far outweighed by the possible dangers you may well encounter if you continue as planned.
Remember, making good decisions is one of the most important aspects of piloting an aircraft.
Good decisions can help lead to safe, successful flights, whereas bad decisions and even indecision have led to many aircraft
accidents.
Always strive to make good decisions.
Many companies, including airlines, use personality profiling in their selection schemes to assess individuals' aptitude for a particular job.
They've learnt that people with particular personalities, attitudes and behaviours are more likely to perform well as pilots.
Someone who is too introvert or anxious, for example, may find it difficult.
Examples of good behaviour are the ability to cope with stress and remain calm, good management of tasks, time and
people,
a well-placed sense of self-confidence and adventure and the ability to assess and control risks.
As captain of an aircraft, you'll need to show good leadership skills.
This will inspire confidence in both passengers and crew.
Such skills include the behaviours just mentioned, as well as being able to communicate and listen well,
to understand others and help them develop, to be able to delegate, to behave well in the air and on
the ground,
and to maintain a good overview of the situation and set priorities.
A captain should show leadership without being aggressive or dictatorial and so maintain authority without losing the respect of the
crew.
While acting as pilot in command, you should ensure that you stay in command. You should be properly organised and
prepared.
Give yourself enough time for planning both before you get to the airfield and after you've arrived and are preparing
the aircraft for flight.
Perform your checks thoroughly and don't get distracted, as this can easily lead to overlooking items.
Remain professional in dealing with others and give good radio calls.
Always be aware of your surroundings and your capabilities and don't allow yourself to get into situations that are beyond
you.
As captain of an aircraft, you should always show captaincy.
In the previous section, we mentioned that a good leader is one who can maintain an overview of his situation.
He can show good situational awareness.
This means he can, at all times, retain an accurate mental model of his environment, making sure that his perception
matches the reality of the situation.
He must also remain aware of his own performance.
There are a number of factors that can interfere with accurate situational awareness.
Stress, boredom, fatigue and emotion can all have a negative effect, as can poor communication and interruptions.
To maintain good situational awareness, you should gather as much information as possible.
Don't rush into making a decision and make sure you consider all the alternatives.
Don't make the mistake of seeing something that is not really there, just because you want it to be there.
As you progress, occasionally evaluate your decision against further information to check your accuracy.
Sound decision making is the result of a logical process.
The process is shown in the table and should be followed meticulously.
Pilots operate in a dynamic and constantly changing environment.
A good decision reached a minute ago will not necessarily be the same good decision in two minutes time.
So constantly review.
If the situation has changed, the whole process starts again from the beginning.
There are some forms of psychiatric illness that are associated with loss of contact with reality.
These are so serious as to be totally incompatible with flying, for example manic depression or schizophrenia.
Less serious states such as depression or obsessional disorders can be treated,
and once the treatment has finished and the pilot has returned to good health, most will be able to fly
again.
At a busy airport communication is fast and concise.
With aircraft landing and taking off every few minutes, it's important that no time is wasted by hesitating unnecessarily,
and even more important, that the calls are understood and accurate.
Using your aircraft radio, which you'll learn more about from Oxford's CBT on RT communications,
is only one example of when good verbal communication is necessary.
When piloting an aircraft, whether with passengers, another pilot or an instructor,
good verbal communication will help the flight go more smoothly and aid aircraft safety.
Over the last few years, the number of communications courses aimed at professional pilots has increased.
This reflects the need for good communication at all levels of aviation.
In this lesson, we'll look at a number of circumstances that may occur in the cockpit.
Why good briefings are necessary? What can cause barriers to good communication and good teamwork?
This should help you understand there are many times when clear, concise and unambiguous communication is essential to the safe
conduct of aviation traffic.
You may find yourself in a number of different situations where good cockpit communication is necessary.
Here are three examples.
Before a flight, it should be established between the two pilots what action should be taken by whom in an
emergency situation,
such as an engine failure on take-off.
As things can happen very fast in an emergency, there'll be no time to decide who does what at the
time.
In the event of an emergency before reaching the take-off speed, I will bring the aircraft to a halt
on the runway.
If we have taken off, if possible, I will land back on the runway, otherwise I will attempt a forced
landing.
This can be even more dangerous if a less experienced pilot relies on a more experienced one without first letting
him know.
In the event of an emergency, I will ask you to unlatch the door and tighten your seat belt.
After an emergency landing, you should exit the aircraft to the rear.
You can talk to me during the flight, but at busy times I may ask you to refrain for a
while.
Again, whilst in the air, you'll not have time to brief your passenger in the event of an emergency.
The pilot's attention should be on flying the aircraft.
At any point in the flight with a student and instructor, the instructor may take control of the aircraft to
demonstrate a manoeuvre or technique,
and then hand control back to the student.
Whenever control of the aircraft changes hands, the student and instructor should be clear on who has control.
This should always be said out loud to avoid confusion, so before a demonstration, I have control.
You have control.
And after the demonstration has ended, you have control.
I have control.
Briefings can be an excellent way of transferring information, and are often used by instructors before flights with students.
Good briefings will help tremendously in the understanding of information.
On the other hand, bad briefings can cause confusion and actually make communication worse.
A good briefing should fit several criteria. It should be short.
This allows the person being briefed to remember what has been covered.
It should be individual for each flight, and it should be thoroughly understood.
This can be achieved by both parties asking and answering questions.
The following attitudes and behaviour have proved to be especially dangerous when flying.
Anti-authoritarian behaviour, impulsiveness, feelings of invulnerability, aggressiveness, arrogance, resignation.
Several things can be done by team leaders to facilitate good teamwork.
These include building a self-controlled team whose members are willing to listen to one another's opinions.
Feelings of mutual trust and confidence should be developed among team members.
Teams need to be aware of the skills and knowledge possessed by individual members.
Expectation is when the pilot is expecting to hear a particular response, and then assumes that he has heard what
he is expecting.
For instance, he may expect his request to ATC to be approved.
Should the controller's reply be clipped, unclear, too soft or too quick, there is a danger that the expected approval
is assumed, when it has not in fact been given.
With possible catastrophic consequences.
Do not assume you have heard what you are expecting to hear.
Actively listen.
This takes concentration and diligent effort, and is the first casualty in times of stress.
In this lesson we have looked at a number of circumstances that may occur in the cockpit.
Why good briefings are necessary?
What can cause barriers to good communication and good teamwork?
This should help you understand there are many times when clear, concise and unambiguous communication is essential to the safe
conduct of aviation traffic.
Stress is commonly defined as the body's responses to the demands placed upon it.
Thus it is the reaction to events and circumstances which may truly be defined as stressful, not the events and
circumstances themselves.
Events and circumstances which cause stress are known as stress factors or stressors.
Stress can be physical, where the body is exposed to excess heat, cold or force.
This is often called distress.
Or stress can be mental or emotional, when circumstances are such that our reasoning and decision-making faculties cease to
function effectively.
Mental and emotional stressors are much harder to quantify than physical stressors.
But stress is recognised as being a natural condition of life, and is a normal reaction to demanding situations.
We also know that while stress is a necessary condition for coping with life's demands, too much stress is harmful.
Thus, while a certain amount of stress is of fundamental importance in keeping us aware and vigilant,
too much stress will degrade the performance of both body and mind, and can eventually lead to catastrophic decision-making,
mental breakdown and long-term serious illness.
The different stress levels generated within individual persons by a particular stressor will differ from one individual to another.
Thus some people are more tolerant of stress than others.
The response of a person to the event or circumstances to which he is exposed is known as arousal.
One way of defining arousal is to say that it is a measure of the human being's readiness, fitness and
ability to respond effectively to a given stress factor.
The level of arousal of different human beings will depend on both their inborn and acquired characteristics, as well as
their state of health.
Inborn characteristics may include an individual's personality or character.
Among acquired characteristics, we may identify an individual's level of training and experience in a given field of activity.
In an active, outward-going, highly trained person, too little stimulation or stress arousal will lead to the onset of
boredom and even drowsiness.
Such a person might need significant challenges in his specialist field in order to function optimally.
Conversely, an introspective, underconfident person, if over-aroused, might be unable to function at all, even in circumstances that he
is competent to deal with.
If such a person is undertrained, his level of arousal and the stress that he feels might cause him serious
problems.
Thus, whilst flying in challenging meteorological conditions may be even a welcome occurrence for a skilled and experienced pilot and
stimulate him to demonstrate extraordinary skill,
such conditions may cause unbearable stress in an underconfident, low-hours pilot and lead to the temporary loss of even
basic flying skills.
Here is a graph depicting the relationship between levels of arousal and performance.
Evidently, the first pilot is in a state of optimal arousal where a human being operates at his most efficient.
The second pilot may be considered as being in a state of high arousal.
Here, a person's performance starts to deteriorate.
He will begin to commit errors and overlook items of information.
His attention span will narrow and he will tend to focus on a limited source of data.
If very high arousal levels are reached, the pilot may experience overload and reach the limit of his information processing
capacity and ability to cope with the task in hand.
It is easy to see how such a high state of arousal might result in a pilot-induced accident.
At the other extreme of the graph is that of low arousal, for example when we are relaxing on a
sun-soaked airfield following a satisfying flight.
Our information processing capacity is again low and our immediate performance potential poor.
But there is no doubt that training and experience help to ward off stress and high levels of arousal.
Successful completion of a stressful task will reduce the amount of stress experienced when a similar situation arises in the
future.
The level of stress felt by any individual is a function of the demands which he perceives to be placed
upon him and of the ability he perceives he has to cope with the demand.
It is then the person's evaluation of the demands imposed upon him rather than actual demands which will determine the
level of stress he feels.
Similarly, it is a person's perception of his own ability to cope with a given demand rather than his actual
measured ability which determines the amount of stress he feels.
The body's feedback mechanism is of great importance in determining the amount of stress experienced by an individual on subsequent
performances of the task.
Successful completion of a given task will cause a person to perceive that the demand placed on him fell within
his ability to accomplish the task.
His original evaluation of the task will thus be changed and the level of stress he feels will be reduced.
Similarly, of course, the opposite is also true.
Failure to complete a task will induce high stress levels in an individual if the task has to be repeated.
There are many recognised causes of stress, stress factors or stresses, some of the most common of which are shown
on the screen.
An important fact to remember about stress factors is that they are cumulative.
If a pilot happens to be subject to a minor stress factor and then another stressor kicks in, his stress
level will increase out of proportion to the stress he would feel if the second stress factor were the only
one affecting him.
Thus, if a pilot, having had an argument with a colleague on the ground, then flies and encounters another small
problem on the flight deck, his stress level will rise to a higher level than if the argument had not
taken place.
The most common stress factors likely to affect a pilot in the cockpit are health, heat or cold, noise, vibration,
workload, anxiety, lack of training, lack of experience, fatigue and emergency.
Health emergencies and fatigue are dealt with elsewhere in this course.
As far as cockpit workload is concerned, thorough flight planning is the key to reducing this, as is the efficient
organisation of all charts and documents that are to be referred to in flight.
Make sure then that your cockpit housekeeping is of a high order and that all documents, charts and associated equipment
are appropriately stored and accessible in accordance with the principles of flight safety.
High quality headsets will reduce cockpit noise levels.
Temperature can often be regulated using the cabin heating or ventilation system.
If this is not an option, make sure that you are wearing appropriate clothing for the altitude and season.
Factors such as training, experience and anxiety are interrelated.
Stress caused by these factors can really only be avoided, not solved immediately once the problem has arisen.
The best way of avoiding such stress is to know your limits and fly well inside them.
Do not attempt to fly sorties or routes which impose demands on you but which you have not been trained.
If you are trained but lack experience, fly with a more experienced colleague until you have gained confidence.
If you are aware that you are under stress because of any of the factors listed, consider whether it would
not be wiser for you to stay on the ground rather than to fly when you are not up to
it.
Stress in everyday life can affect piloting performance, as indeed piloting performance can cause stress in the pilot's work and
home life.
Pilots suffering from life stresses should be aware that this can affect their concentration and performance when at the controls
of an aircraft.
There is some evidence for a relationship between life stress and flying accidents.
Attempts have been made to assess stress levels in general and though reaction to stress levels varies from individual to
individual, the table on the screen gives a suggested stress weighting for various incidents that can occur in an average
person's life.
As stress is cumulative, all of the events should be totaled to give an indication of the stress acting on
any given person.
As a pilot, you can learn to avoid stress in the cockpit and to reduce the effect of the more
common stress factors associated with flight and aircraft operations.
First of all, let us look at how to avoid coming under stress when you fly.
Adopt a professional approach to all your flying activities. There will then be little possibility of your being surprised by
situations or developments in the air.
Whatever your level of experience as a private pilot, ensure that you fly with an instructor at least twice a
year.
Ask him to comment on your general and procedural flying and get him to give you practice emergencies to deal
with such as getting lost, engine failure after take-off or fire in the air.
You should learn from the past, including from the experience of others.
If you have committed a piloting error therefore, discuss it with an instructor or with your fellow pilots.
Write down what you and others perceive to have been the causes of your error. This way you will be
less likely to reoffend.
Be thorough in your pre-flight briefing and preparation. This will enable you to anticipate in-flight events and will
contribute greatly to reducing workload in the cockpit.
In order to cope with stress, it is fundamental that you should be aware that you are under stress in
the first place.
Only then can you identify the stress factors and either remove yourself from them or modify them in order to
reduce your stress level.
So, in order to help reduce the impact of flying-related stress factors and to avoid or mitigate stress in
the cockpit, consider the following advice.
Do not let people or circumstances rush you into acting before you are ready.
Air traffic control and ground-based duty personnel are understandably keen to get you airborne.
But while remaining mindful of the necessity to work expeditiously, do not be pressed by outside influencers into committing an
error of airmanship.
If necessary, ask ATC to stand by.
Do not be distracted from your pre-flight checks.
If you are interrupted during your checks, go back several items before continuing to work through the checklist.
When airborne, stick to your pre-flight plan unless a change is absolutely necessary.
Ask ATC to say again if you do not understand an RT transmission.
However, make sure that you learn your RT well.
If faced with bad weather or with flying conditions that you are not trained, qualified or equipped to deal with,
make an early decision to turn back or divert.
Finally, if you are planning to fly with another qualified pilot, during the pre-flight briefing agree on who will
be the designated pilot-in-command and which principal in-flight tasks each of you will perform.
This will prevent either one of you becoming overloaded and will avoid confusion in the air about who is responsible
for the various piloting tasks and for the aircraft in general.
The design of the human body is for life on the ground, but aviation has transported mankind into the air.
Our survival in this new dimension depends upon the effectiveness of the design and manufacture of not only the aircraft
in which we travel, but of the systems by which they are flown and controlled.
It is therefore important that the relationship of this dichotomy is considered and studied.
It is useful to construct a simple model to show the relationship of man to all the factors with which
he has to relate.
The shell concept, shown here, is named after the initial letters of its components and was proposed in 1972 by
a psychologist named Edwards.
At the centre of the model is the pilot, man, the most valuable and flexible component of the system.
The second L represents other humans in contact with the pilot, whether inside or outside the aircraft such as ground
crew, tower personnel, radar control or even the passengers.
The S represents such things as procedures, manuals, checklist layouts, symbology, computer programs, maps and charts, all those things with
which the pilot must interact in order to plan and carry out the flight.
Hardware encompasses the design of flight decks, the physical structure of the aircraft, presentation of instruments, positioning and operating sense
of controls.
Once again the pilot must interact with all of these in order to carry out the flight.
The conditions, both inside and outside the cockpit.
The edges of the blocks which comprise the concept are not simply straight lines and so each component of the
system must be carefully matched to the others if stress in the system is to be avoided and eventual breakdown
prevented.
Man has adapted the environment within the aircraft to match human requirements in the air through systems such as pressurisation,
soundproofing and air conditioning to control temperature and humidity.
The two remaining interfaces to be considered are those of hardware and software.
The most important factor that determines the overall size of an aircraft and its flight deck is the size of
people.
People vary greatly in size. Even within a specific group or nation there are large differences within the general population.
Anthropometry is the study of human measurement and a great deal of data has been made available to aircraft designers
on various aspects of the sizes of different populations.
The information is grouped into static measurements are those such as height, ankle to knee distance, shoulder width etc.
Dynamic measurements refers to those within the reach envelope.
Contour surface measurements, those measurements from fingertip to elbow for example.
With the wide range of different measurements that exist within any population the designers must decide which percentage of the
population they will provide for on the flight deck.
It is neither feasible nor desirable to attempt to allow for all of the different sizes of adults.
It is certainly not practical to design a cockpit which can be operated by both the very short and the
very tall individual.
A common decision made by aircraft designers is that all those in the central 90% of size distribution should
be catered for.
Those in the lowest 5% and those in the highest 5% are not considered.
In the United Kingdom the 5th percentile of height for adults males is 5 foot 4 inches 1.625 meters
that is 5% of adult males are shorter than this.
And the 95th percentile is 6 foot 1 inch 1.855 meters that is 5% of adult males are
taller than this.
One of the basic features of cockpit design is that the pilot should be able to view all of the
important displays within the aircraft and still maintain an adequate view of the world outside without the need to make
more than the minimum of head movements.
It follows that the cockpit space must be designed around a defined position of the pilot's eye.
This position can be called variously the eye datum, the design eye position or the reference eye point.
And it is sometimes indicated in the cockpit by the provision of an indicator on the central windscreen pillar which
only appears to be aligned when the pilot's eye is at the designed point.
If the pilot is sitting too high in the cockpit then he will have a good downward view but his
view of the flight instruments and his high view will be less than optimum.
As the external view is of particular importance the pilot must without strain be able to look over the top
of the instrument panel and see sufficient of the ground ahead to enable him to land the aircraft.
If the pilot is sitting below the eye datum then the undershoot will be obscured.
If he is sitting higher than the datum then not only may the overshoot area be invisible but also the
aircraft instruments may be difficult to read accurately.
Once the design eye position has been set and the anthropometric range of pilots has been determined, the size of
the cockpit workspace and the amount of adjustment to seat, rudder pedals etc. can be established.
Pilots, if they are lucky, will spend a long time sitting in the cockpit and thus it is of the
utmost importance that the seating is comfortable and adjustable to the individual pilot's size and shape.
Flight deck seating must have a lumbar support to maintain the natural spine shape and thereby reduce the chances of
lower back pain caused by a failure of the shock absorbing discs between the vertebrae.
Additionally the seat should, if possible, be isolated from vibration of the airframe.
When adjusting their seats pilots should attempt to establish a comfortable position that facilitates full control movement together with a
balance between a full instrument scan and outside visibility.
This desired position should be used for all phases of the flight.
Restraint should be provided by a five-point harness with a negative G-strap to hold the harness in position
during negative G manoeuvres and prevent submarineing under the lap strap during rapid deceleration.
When deciding on the best way to display information the basic choice is between a digital or analogue display.
However, even when using a cathode ray tube to show information the choice between a digital or an analogue display
is still available to us.
Experiments have shown that for the display of purely quantitative information, the amount of fuel in a tank for example,
then digital displays give the better results.
For displaying qualitative or comparison information then an analogue display provides more easily assessed information.
An aircraft using conventional displays would usually have a standard T layout in which the most important instrument, the artificial
horizon or attitude indicator, is at the centre.
The other primary flight instruments, altimeter, airspeed indicator and direction indicator, are grouped around it.
Roll over the labels with the mouse to see the instruments.
The conventional analogue type compass card gives a better picture of the aircraft orientation than would a digital readout.
A digital readout for heading makes it more difficult to determine such factors as the shortest way to turn onto
a new heading.
It is practical in some instances to combine both digital information and analogue information in a single instrument as seen
here, in which the thousands and hundreds of feet are displayed digitally.
The hundreds of feet are also shown by a single pointer.
The use of a single moving pointer against a fixed scale will give a much better mental picture to the
pilot when approaching the end of the scale, that is approaching the ground.
This form of display is also excellent for showing small changes, such as when levelling off or departing inadvertently from
the selected altitude.
The three-pointer altimeter shown here has been in use for more than 50 years and is still the most
commonly used principal altimeter fitted to the light aircraft blown by private pilots, despite the fact that it can easily
be misread and that it produces significantly more reading errors than the single pointer altimeter.
Experiments have shown that the three-pointer altimeter is three times more difficult to read than a digital display, with
a reading error rate of up to 20%.
With the digital altimeter there is a zero reading error rate.
Instrument displays enable information to be passed from the aircraft to the pilot.
The controls enable instructions to be passed from the pilot to the aircraft.
There are certain basic considerations which govern the way controls should be both designed and arranged. Here are some of
them.
Most importantly, controls should be standardised in their location and sense of use from one aircraft to another, and between
different aircraft types.
For example, in both the aircraft pictured here, to bank the aircraft to the right, the control wheel should be
rotated in the same direction, that is, to the right.
Controls should be located such that they are within the easy reach envelope of all designed users of the aircraft.
Controls that are used frequently or for protracted periods should be located so that they do not require the pilot
to adopt an awkward or fatiguing posture.
Controls that should normally be used in a given order should be laid out so that the sequence of use
is represented in that layout.
As well as being ergonomically convenient, the order of the layout itself will act as a prompt for the pilot
to operate the controls in the correct sequence.
Important controls must be located in easily reached and unobstructed positions.
Switches and knobs that control different systems or functions should look and feel different from each other, thus reducing the
chances of inadvertent operation.
Controls, if possible, should be designed to contain some reference to their function, thus undercarriage levers can be shaped like
a wheel, and flap levers may resemble the cross-section of the flap.
Those controls which may require simultaneous use, such as the throttle and mixture controls, should be located in order to
enable this to take place.
It is essential that all warnings should be attention-getting, without being startling.
As well as attracting attention, the warning should inform the pilot of what is wrong and, if possible, guide the
pilot to take the correct actions.
The alerting function for all important failures should be fulfilled by an audio warning.
Even the most conspicuous visual warnings rely on head and gaze orientation.
In a more extreme example, the use of any visual warning is rendered useless if the pilot should be asleep.
The ideal warning system would have a single audio warning to first of all alert the pilot to a failure
and subsequently direct his attention to a single central warning panel that would announce the nature of the problem with
a suitably illuminated caption.
The importance of good design in checklists is fundamental to the safe operation of aircraft.
Aircrew must be afforded rapid accessibility to accurate information in manuals and checklists.
There is plainly a requirement for crews to be sufficiently familiar with their documentation so that they know where to
find relevant information in the shortest possible time.
The main requirements for the design of checklists are that they should be
Unambiguous
Presented in easily understood language
Kept to a manageable size for easy use on the flight deck
Pages colour-coded by topic
Divided with protruding thumb locators
Easy to read
To make the checklist easy to read, the text should be managed so that
Its size should be kept well above the minimum required for bare legibility, since it may have to be read
in poor lighting conditions by a crew that already has a high workload.
The typeface should maximise legibility
A mix of upper and lower case together with bold and italics should be used with care to maximise clarity
and emphasis.
Uppercase text, and the use of italics, may be useful in conveying emphasis, but neither of these are as fast
to read as normal text.
Thus, long messages in uppercase such as this should be avoided, since word shape which acts as a clue in
reading may be lost.
Here are some common problems associated with checklists.
A major source of error in using routine checklists is that they may be responded to automatically rather than diligently.
It is tempting for pilots to regard a rapid dismissal of checklist items as indicative of their skill and familiarity
with the aircraft,
but if checklists are dealt with in this automatic way, it is very easy for individuals to see what they
expect to see, rather than what is there.
Pilots must be aware of this tendency and devote particular care to this aspect of checklist action.
The progress of the checklist is interrupted by an external event, the offer of refreshments or a radio call for
example, when items may be omitted or,
simply because a pilot who is using his thumb as a marker adjusts his grip on the checklist, items may
be missed.