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HUMAN PERFORMANCE AND LIMITATIONS
ROBERT JURCA
HUMAN PERFORMANCE AND LIMITATIONS ATPL Exam preparation 1
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HUMAN PERFORMANCE AND LIMITATIONS
Table of Contents
HUMAN FACTORS IN AVIATION.........................................................................3 FLIGHT PHYSIOLOGY........................................................................................... 5 NERVOUS SYSTEM...............................................................................................21 THE EYE...................................................................................................................23 THE EAR................................................................................................................... 27 SPATIAL DISORIENTATION................................................................................29 HEALTH....................................................................................................................35 HUMAN INFORMATION PROCESSING.......................................................... 41 HUMAN ERROR.....................................................................................................52 FLIGHT DECK MANAGEMENT..........................................................................63 PERSONALITY........................................................................................................ 74 STRESS..................................................................................................................... 77 SLEEP........................................................................................................................84 AUTOMATION........................................................................................................88
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HUMAN FACTORS IN AVIATION All flight crew should be proficient in the English Language as it is the common aeronautical language. Trend in aeroplane hull loss rate is related mainly to the crew. 70 - 80% of accidents caused by the crew – there is hardly ever a single cause responsible. However, everyone in the Aviation Industry is responsible for flight safety 1:000 000 chance of being killed in a flying accident. Good safety record – GPWS gone a long way to reduce accidents since the 1980’s Poor judgment main cause of crew error. CRM (Crew Resource Management) training is intended to develop effectiveness of crew performance by improving attitudes towards flight safety and human relationship management SHELL Concept
Designed by Edwards in 1972; shows the mismatches between each component
S SOFTWARE
H
L
L
HARDWARE
LIVEWARE
LIVEWARE
E ENVIRONMENT
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Component Liveware
Other humans
Software
Procedures, SOPs, manuals, checklists – conceptual aspects
Hardware
Aircraft and the equipment (three pointer altimeter)
Environment
Outside environment, Biological rhythms (fatigue, sleep)
Pilot Competency
A competent pilot: • Trains and practices regularly and learns from past experiences • Have the confidence to carry out the task and has good self management skills • Have something in reserve for the unexpected
Pilot Training
When training a pilot: • Not confident in their own ability and generally have nervousness and focused attention • Not confident in the aircraft • Can fly it though – but likely to be rough on the controls
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FLIGHT PHYSIOLOGY ISA
Atmosphere
Pressure
1013.25 hPa
Nitrogen
78%
Temperature
+15ºC
Oxygen
21%
Density
1225 g/m3
CO2
0.03%
Lapse Rate
-1.98°C/1000 ft
Argon
0.9% Rest rare gases
21% O2 constant for all altitudes Reduction in Atmospheric Pressure
The changes in atmospheric gas pressure with altitude are nonlinear, with a higher rate of change at lower levels. Sea Level
1013 hPa
8000 ft
750 hPa
¾ atmospheric pressure
18 000 ft
500 hPa
½ atmospheric pressure
26 500 ft
350 hPa
1/3 atmospheric pressure
33 500 ft
250 hPa
¼ atmospheric pressure
Partial pressures of the individual gases will also fall at the same rate GAS LAWS Boyle’s Law
At constant temperature the volume of a gas varies inversely with its pressure Trapped gases, expansion in the body due to decompression
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Charles’s Law
The physical law that states the volume of a fixed mass of gas held at a constant pressure varies directly with the absolute temperature. Volume/temperature relationship
Dalton’s Law
The total pressure of a mixture of gases is the sum of the partial pressures of each gas in the mixture Respiration and Hypoxic Hypoxia
Henry’s Law
The mass of a gas dissolved by a given volume of liquid at a constant temperature is directly proportional to its pressure Decompression sickness
Fick’s Law
The law of diffusion The rate of gas transfer through a tissue is proportional to the difference between the partial pressures of a gas on the two sides of the tissue. Diffusion of gases
RESPIRATION AND CIRCULATION The gases of physiological importance to man are oxygen and carbon dioxide Metabolism
Sum of physical and chemical changes that take place to provide energy for the body.
External Respiration
Exchange of gases between the body and the atmosphere
Internal Respiration
Oxidation process in the cells liberating energy where oxygen is being transferred from the blood into the tissues and carbon dioxide from the body cells into the blood.
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Internal Respiration
Oxidation process in the cells liberating energy where oxygen is being transferred from the blood into the tissues and carbon dioxide from the body cells into the blood.
Respiration
The diffusion of oxygen through the respiratory membranes into the blood, transportation to the cells, diffusion into the cells and elimination of carbon dioxide from the body.
Gaseous exchange in the human body depends on: • Diffusion gradients between the participating gases • Permeable membranes • Partial pressure of oxygen in the alveolus air • Acid-base balance in the blood Lungs
Air breathed in and is warmed, filtered and moistened by the pharynx at the back of the throat. It goes down the trachea which then splits into two bronchi, which in turn split into the bronchiole tree at the end of which are the alveoli.
Alveoli
Sac like structures surrounded by capillaries. The thin walls of the capillaries allow gas diffusion to take place. O2 diffuses into the blood because the partial pressure is higher in the alveoli than in the blood. CO2 diffuses into the alveoli because the partial pressure in the alveoli is less than in the blood.
Normal rate of breathing 10 to 20 cycles per minute • •
Lung Volume Tidal volume
6 litres 500 ml
Volume of gas in the lung during normal breathing is 2.4 litres. Half the lung capacity. Rest known as the residual capacity. Expire further such that the last remaining amount is about 1.2 litres and is the residual volume. Difference between the total lung volume and the residual capacity is the vital capacity and is approximately 4.8 litres.
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Total Gas Volume: • Tidal volume • Inspiratory reserve volume • Expiratory reserve volume • Residual volume Control of Respiration
Controlled by the CO2 pressure in the blood. CO2 balance checked by chemoreceptors in the carotid artery and aortic arch. Increased CO2 in blood Increased acidity (less alkaline) – increased respiration rate Decreased CO2 in blood Decreased acidity (more alkaline) – decreased respiration rate
Oxygen Saturation
Normally 98% - tails off quickly with height, decreasing pressure or carbon monoxide poisoning
Circulation
The circulatory system allows for the: • Transportation of oxygen combined with haemoglobin as oxy-haemoglobin • Transportation of carbon dioxide dissolved in the blood as carbonic acid • Transportation of information by chemical substances • Transportation of nutrients to the cells • Transportation of waste products
Heart
Supplied with blood by the Coronary Arteries. • Oxygenated blood carried from the lungs via the pulmonary veins • Goes into the left atrium. Flows through a one way valve • Goes into the left ventricle, where it is pumped under pressure • Goes into the aorta which pumps the blood into the main arteries. The main arteries split into the arterioles and then into capillaries.
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Capillaries
Capillaries are neither arteries nor veins. All you can say is that the artery splits into a capillary at the tissue and rejoins after diffusion to form a vein. • Deoxygenated blood is returned to the heart by veins to the right atrium which passes it through a one way valve. • Goes into the right ventricle which pumps it to the lungs • Through the pulmonary artery.
Arteries
Strong muscular vessels that carry blood under pressure. All arteries flow away from the heart and mainly carry oxygenated blood. The exception is the pulmonary artery that carries deoxygenated blood to the lungs.
Veins
All veins flow towards from the heart. Have one way valves to stop flow back and mainly carry deoxygenated blood. The exception is the pulmonary vein that carries oxygenated blood to the lungs.
Cardiac Output
• • • •
Pulse Rate
Increased by: • Release of Adrenalin • Physical exercise • Increase of glucose concentration in the body
Coronary Arteries
Heart has its own arteries. Failure of enough blood to reach the heart causes a Myocardial Infarct or heart attack
Heart rate x stroke volume Normal heart rate – 60 to 80 beats per minute Stroke volume – 70 ml Cardiac output about 5 litres per minute
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Blood
Transports oxygen and nutrients to the body cells; withdraws waste from the body cells Plasma – Fluid constituent of blood without the cells Red Blood Cells – Contain haemoglobin - Iron rich compound Anaemia – Lack of iron (haemoglobin) in the blood – can be a cause of hypoxia White Blood Cells – Immune system Platelets – Clotting system All blood cells are produced in the bone marrow.
Blood Pressure
Measured in the upper arm – represents the pressure at heart level Systolic Pressure – Ratio of the pressure exerted when the heart pumps blood Diastolic Pressure – Pressure in the arterial system when the heart relaxes between beats Normal blood pressure – 120/80
Blood pressure depends on: • The cardiac output – the work rate of the heart • Elasticity of the arterial wall • Blood volume and viscosity • The resistance of the capillaries Changes in blood pressure measured by pressoreceptors in the carotid artery and aortic arch. Lowering of blood pressure the adaptation mechanisms affect the following: • Arterioles constrict • Cardiac output increases and • Heart rate increases High and low blood pressure as well as a poor condition of the circulatory system can lead to medical certificate disqualification.
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Hypertension – High blood pressure
Where BP exceeds 160 mmHg Systolic, or 95 mmHg Diastolic, treatment is required before a medical certificate is issued.
Hypotension
Too low a blood pressure - Will also mean withdrawal of the medical certificate
Oxygen Needs Sea level to 10 000 ft
Breathe air
ppO2 103 mm Hg at sea level ppO2 55 mm Hg at 10 000 ft
10 000 ft to 33 700 ft
Increase in O2 100% O2 by 33 700 ft
PpO2 103 mm Hg at 33 700 ft
33 700 ft to 40 000 ft
100% O2 breathed. Above 40 000 ft pressure breathing
PpO2 55 mm Hg at 40 000 ft
Breathing 100% O2:
• 33 700 ft is equivalent to sea level • 40 000 ft is equivalent to 10 000 ft
Hypoxia A potential threat to flight safety. Healthy people are usually capable of compensating for a lack of oxygen up to 10 000 to 12 000 feet. A human can survive at any altitude provided that enough oxygen, pressure and heat available. Hypoxia is a lack of Oxygen to meet the body’s needs and can be caused by: • Low partial pressure of oxygen in the atmosphere when flying at high altitudes without pressurisation and supplemental oxygen • A decreased saturation of oxygen in the blood due to »» Lack of haemoglobin in the red blood cells »» Carbon monoxide attached to the haemoglobin where there is a decreased ability to transport the oxygen • Blood pooling in the lower extremities due to inertia (+ Gz) • Malfunction of the body cells to metabolise oxygen Hypoxia is especially dangerous where the reasoning and perceptive functions are degraded and euphoria occurs.
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Dangerous to single pilot operations as the first signs of Hypoxia are hard to detect. Sensitivity and reaction to hypoxia varies from person to person. Four types:
Hypoxic Hypoxia Insufficient ppO2.
Also when there is insufficient O2 in the air
Hypemic Hypoxia Reduction of the O2 carrying capability of the blood. Such as CO poisoning or Anaemia, a lack of red blood cells Stagnant Hypoxia Inadequate circulation
Heart failure.
Histotoxic Hypoxia Toxins that reduce the body’s ability to use the O2 Severity depends on the rate of decompression HYPOXIC HYPOXIA 20% of O2 breathed used by the brain. Sufficient cover to 10 000 ft where the critical oxygen tension is reached. Start to feel the effects above this altitude. Initial symptoms: • Drowsiness or fatigue • Headache • Difficulty in performing simple tasks – lack of concentration and impaired judgment • Euphoria – leading to error proneness • Visual disturbance and dizziness The most dangerous being Euphoria and Impairment of judgment. Indifferent
0 – 10 000 ft Dark adaptation affected as low as 5000 ft Visual acuity reduced by up to 10% - night vision is the most sensitive to hypoxia Performance starts to be impaired – short term memory begins to be affected Euphoria may be experienced Increased heart rate and pulmonary ventilation
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Compensatory
10 – 15 000 ft Short term memory loss becomes apparent Body provides some protection Pulse rate, systolic pressure, circulation rate and cardiac output increased. Effects on the Central Nervous System more apparent Drowsiness, errors of judgment Difficulty in performing simple tasks – loss of coordination Easy to overlook at this stage
Disturbance
15 – 20 000 ft No physiological protection Headache, dizziness, euphoria and fatigue. Cyanose extremities – blue lips and fingernails Tunnel vision
Critical
20 – 23 000 ft Confusion and dizziness. Total incapacitation very quickly.
Hypoxia compared to the initial stages of drunkenness. Susceptibility to Hypoxia Sensitivity and reaction to hypoxia varies from person to person, other factors include, the severity depends upon the following factors: • Altitude – Lower ppO2 the greater the effect • Time – Rate of decompression and the time a person is affected • Exercise and Physical Fitness – the fitter the person the less the effect • Cold • Illness • Fatigue • Stress • Increased Gz – Pooling of the blood in the lower body • Alcohol – Brain cells become more susceptible to hypoxia • Smoking • Drugs - All have an adverse effect
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Treatment of Hypoxia • Immediately don the oxygen mask and check that 100% O2 flow is available. • Descend to a safe altitude • Reduce physical activity Pressurisation Helps to Prevent: • Decompression sickness • Expansion of gases in the body • Hypoxia Time of Useful Consciousness (TUC) Can also be known as the Effective Performance Time and is the time a pilot has to recognise the onset of the symptoms of Hypoxia and can act with both mental and physical efficiency. It is not the time to unconsciousness and is measured from the moment where the individual is exposed to hypoxia. TUC varies between individuals and depends upon the cabin altitude, for a person at rest. Altitude
TUC
20 000
30 minutes Moderately active person 5 minutes
25 000
3 – 5 minutes
30 000
1 – 2 minutes
35 000
30 – 90 seconds
40 000
15 – 20 seconds
45 000
9 – 12 seconds
TUC is dependent on the strength and time of decompression and the physical activity of the crew. HYPERVENTILATION With hyperventilation, caused by high levels of arousal or overstress an increased amount of carbon dioxide is exhaled causing muscular spasms and even unconsciousness
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Hyperventilation
Breathing in excess of the body’s needs. Expelling CO2 at a greater rate than is needed. Makes the body more alkaline. Some vasoconstriction occurs which means: • Less O2 is diffused into the cells, but • The rapid breathing causes more O2 to attach to the haemoglobin
Hyperventilation can cause unconsciousness, because blood circulation to the brain is slowed down. Symptoms and Causes Similar to Hypoxia. Do not get Cyanose extremities. Hyperventilation is likely to occur when a person is emotionally aroused. SYMPTOMS
CAUSES
Dizziness
Fear, anxiety, distress and emotional arousal
Increased tingling sensation
Overstress
Increased sense of body heat
Motion sickness
Increased heart rate
Vibration
Muscle cramps and spasms
Heat
Vision disturbance – clouding or tunneling
G manoeuvring
Nausea
Pressure breathing
Loss of consciousness
Hypoxia Pain
Difference between Hypoxia and Hyperventilation You can die from Hypoxia. Cyanosis only occurs in Hypoxia. Treatment Decrease the rate and depth of breathing which is done by breathing into a paper bag or oxygen mask. The intention being to raise the level of CO2 in the blood as fast as possible. Treatment of Hypoxia or Hyperventilation • Below 10 000 ft treat for Hyperventilation • Above 10 000 ft treat for Hypoxia
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