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Human Factors and Pilot Performance Section 1 Human Physiology and the affects of altitude
Human Factors and Pilot Performance Often shortened to “Human Performance” The exam is 30 mins, 16 questions, need to get 12 right Quite simple but need to know subject – not more than 4 answers wrong or FAIL Three sessions/sections 1.Human Physiology and the affects of altitude 2. Seeing, Hearing, Fitness 3. Brain and information processing Based on Thom Vol 6. Will refer to specific sections
Human Factors and Pilot Performance 1. Human Physiology 1.1. Nervous system Thom Fig 1.1 Central nervous system – brain and spinal cord Peripheral Nervous system – all nerves running off or to spinal cord These operate in three different ways: Autonomic Nervous system – automatic controls – e.g heartbeat, peristalsis, sweating, blushing Motor Nervous system – nerves that consciously control muscle movements. Sensory Nervous system – nerves that send sensations (heat, cold, pain, sound etc) to the brain, which may send motor signal to appropriate muscles in response. e.g fight or flight response (run or interact with e.g. fight/eat/have sex with More about brain control mechanisms in Section 3.
Human Factors and Pilot Performance 1. Human Physiology 1.2 Circulatory System (Cardiovascular system) Heart – central pump Arteries – take blood from heart to organs) BLOOD Veins - bring blood back to heart ) VESSELS Note: Pulmonary Artery takes blood from the lungs to the heart Pulmonary Vein takes blood from the heart to the lungs Blood – CORPUSCLES, red and white cells. RED cells transport OXYGEN round the body (HAEMOGLOBIN – iron rich). Used to produce energy by “burning” sugars in the different muscles and organs. WHITE cells (many different types) mainly concerned with protection against foreign substances (VIRUSES, BACTERIA). PLASMA salty fluid, corpuscles suspended in it.
Human Factors and Pilot Performance 1. Human Physiology 1.3 BLOOD VESSELS ARTERIES and VEINS are big ones, but these get smaller in the different organs and tissues and end up as CAPILLARIES. These make sure there is an efficient blood supply and removal system to organs and tissues Simple system above is SYSTEMIC CIRCULATION. Note: In tissues, where arterial and venous capillaries meet, blood goes from Arteries to Veins (higher pressure in Arteries) PULMONARY CIRCULATION. Local circulation of blood to and from the lungs VENOUS (“used”) blood pumped from heart via PULMONARY ARTERY to the lungs, CARBON DIOXIDE is removed and OXYGEN added Oxygenated blood returns through the PULMONARY VEIN to the HEART Then recirculates round the body through the ARTERIES.
Human factors and pilot Performance 1. Human Physiology 1.4 HEART – see Thom Fig 1.2. Left side of midline, just below breastbone. Contracts as a unit. Pumps blood through non-return valves. Special groups of muscle cells contract together. 4 chambers 2 each side. Left – receives venous blood coming back from organs/extremities, pumps it to lungs Right – receives oxygenated blood from lungs, pumps it into main artery or aorta BLOOD PRESSURE. Measure of pressure of blood against walls of the main arteries(elastic) Highest when heart is contracting (SYSTOLIC pressure) Lowest when resting (not contracting – DIASTOLIC pressure) Varies with age. Increases as get older (arteries “ harden” – walls lose elasticity.). Expressed as mm mercury, systolic/diastolic. Typical normal values are 120/80. Limiting values for pilots under JAR is160/95 – medically unfit if above this.
Human Factors and Pilot Performance 1. Human Physiology 1.4 Respiration RESPIRATION. Brings in oxygen, removes carbon dioxide, according to reaction below: Sugar + oxygen(O2) carbon dioxide (CO2) + water (cells) (blood brings) (blood takes away) This is INTERNAL RESPIRATION EXTERNAL RESPIRATION is a continuous process involving lungs, where CO2 is given out and fresh O2 taken (Thom 1.3)
Human Factors and Pilot Performance 1. Human Physiology 1.5 Lungs STRUCTURE (Thom 1.3, 1.4) In chest cavity, one each side, surrounded by rib cage Open to atmosphere at top (windpipe) Muscle across the bottom (diaphragm) Windpipe divides into increasingly small tubes (bronchii, bronchioles) These terminate in air sacs (alveoli) which have CAPILLARIES that transport blood to and from the alveoli O2 diffuses through alveolus wall into capillary, CO2 goes other way Both are following concentration gradients
Human Factors and Pilot Performance 1. Human Physiology 1.6 BREATHING MECHANISM Diaphragm goes down, rib cage (chest cavity) expands air is drawn IN through the bronchii etc Diaphragm goes up, rib cage (chest cavity) contracts air is forced OUT Lung capacity ca. 5L but only 0.5 L replaced with each breath. Small amount of gas exchange due to importance of CO2 in keeping blood pH balance Therefore amount is kept nearly constant in lungs The amount of CO2 in blood varies with muscular activity To cope with this, breathing rate is controlled by blood CO2 content (higher O2, faster breathing rate)
Flying and Altitude Composition of dry air: 78% nitrogen, 21% oxygen, 1% other gases (carbon dioxide 0.03%) Total air pressure falls with altitude, (approx 1hp/30 ft). Relative composition stays constant Can have oxygen deficiency at high altitudes Additional supply of oxygen essential over 10,000 ft (legal requirement) Note: Air also contains variable amounts of water vapour – varies with temperature and altitude.
Flying and Altitude LACK OF OXYGEN (HYPOXIA) Due to deficient oxygen supply to brain. Onset of symptoms depends of pilot’s condition as well as altitude e.g. smoker, unfit, tired can be as low as 4000ft. No smoking in cabin! Be fit! Use oxygen if necessary! May also be caused by inability of blood to carry enough oxygen (anaemic hypoxia) which may be due to carbon monoxide poisoning (see below) SYMPTOMS False sense of security and wellbeing Faulty judgement Clumsiness Headache Blurred vision Rapid pulse Blue lips/fingers
Flying and Altitude Time of Useful Consciousness (TUC) Affect of sudden failure of oxygen supply Altitude Moderate Activity Minimal Activity 22000 ft5 mins10 mins 25000 ft2 mins 3 mins 28000 ft1 min 1.5 mins 30000 ft45 secs75 secs 35000 ft30 secs45 secs 40000 ft12 secs15 secs
Flying and Altitude Other effects of altitude/flying Barotrauma pain caused by trapped gases Gases trapped in your body expand with altitude – stomach, guts, sinuses, middle ear, decaying tooth. Blocked Eustachian tube (links middle ear to back of throat, discomfort/pain often sensed on descent from high altitudes, e.g on commercial flight). Due to unequal air pressure on each side of eardrum. Chewing, swallowing or yawning usually gives relief. Unwise to fly with headcold, sinusitis etc
Decompression sickness. caused by gases dissolved in the blood – pain in joints Example: divers, if they surface too rapidly (and/or fly too soon after diving) Dissolved gases released can cause severe pain, especially in joints (the bends) Depends on depth dived to. General rule - don’t fly within 12 h of a shallow dive (less than 30ft (10m)) - don’t fly within 24h (or more) if surfacing from a greater depth
Flying and Altitude Carbon monoxide (CO) poisoning. Usually from engine exhaust via cabin heating system Very dangerous – colourless, tasteless and odourless (but usually accompanied by other exhaust gases which have odour e.g. nitrogen oxides) Reacts with haemoglobin in blood and prevents oxygen attaching to it
Flying and Altitude SYMPTOMS of Carbon Monoxide (CO) Poisoning headache etc. blurred vision impaired judgement and memory slower breathing loss of muscle power convulsions coma and death Note: no blues (lips may turn cherry red)! No euphoria! Remedy – shut off cabin heat, open fresh air vents/windows, land ASAP Useful – have carbon monoxide sensor in cockpit (turns brown if CO present)
Flying and Altitude HYPERVENTILATION. Shallow overbreathing – usually due to anxiety or fear often cumulative (anxiety overbreathing breathlessness greater anxiety etc). Due to CO2 balance being upset.
Flying and Altitude HYPERVENTILATION Symptoms. Numbness and tingling of extremities Palpitations, ringing in ears Faster pulse Sweating Blurred vision Dizziness/fainting/unconsciousness R EMEDY Slow person down (talk down, reassure) Breathe into a bag (increases carbon dioxide in blood) Give person something to do (take mind off whats making them anxious or afraid)
Flying and Altitude Another altitude affect Blocked ears – due to unequal pressure each side of eardrum (blocked Eustachian tube). Often associated with a cold, hayfever, sinusitis etc (variation on barotrauma) and linked to rapid descent. REMEDY Chewing or swallowing usually relieves the pressure, but it will gradually return to normal anyway
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