Human Factors PDF

2 Human Factors 2.1 Vision Vision is a pilot’s most important sense to obtain reference information during flight. 2.1.1 The Anatomy of the Eye The Cornea The cornea is a transparent window of about 10-12mm which seals the front of the eye and allows light to pass through it. The surface of the corn...

2 Human Factors 2.1 Vision Vision is a pilot’s most important sense to obtain reference information during flight. 2.1.1 The Anatomy of the Eye The Cornea The cornea is a transparent window of about 10-12mm which seals the front of the eye and allows light to pass through it. The surface of the cornea is curved and some refraction of the light rays takes place. The Iris The iris is a coloured muscular membrane, situated behind the cornea that contains the pupil. The iris is the first means of enabling the eye to adapt to changing light conditions. - Poor light conditions → the iris expands - Bright light conditions → the iris contracts The Lens Located behind the iris, the lens is supported by ciliary muscles which are used to change the lens’ shape. If the muscles relax the lens will flatten, and if the muscles contract the lens will become more curved. The flattening and contracting of the lens is known as accommodation. Accommodation reduces with an increase in age and is easily corrected through the wearing of glasses or contact lenses. The Retina The retina is a soft transparent layer of light-sensitive nervous tissue located at the rear of the eye. It contains two types of photoreceptor cells, known as rods and cones. Copyrighted - ISBN: 978-1-64008-188-8 Rev4 ©UAV Industries Training P a g e 22 | 182 Rods: the primary function of rods is to define vague movement. Rods have no perception of colour, only in shades varying from black to white, thus they are unable to define detailed movement. They are able to function in dim light and are therefore instrumental in our peripheral vision, the function of which is essential for both orientation and night vision. Cones: cones provide the best visual acuity or accuracy. They achieve maximum efficiency in conditions of good illumination and become less effective in poor light and darkness. The Fovea The fovea is the small depression located in the exact centre of the macula that contains a high concentration of cones but no rods. This is where our vision is sharpest. The Anatomical Blind Spot There are no photoreceptors (i.e. rods or cones) in the optic disk and therefore there is no image detection in this area. The blind spot of the right eye is located to the right of the centre of vision and vice versa in the left eye. With both eyes open, the blind spots are not perceived because the visual fields of the two eyes overlap. Copyrighted - ISBN: 978-1-64008-188-8 Rev4 ©UAV Industries Training P a g e 23 | 182 The Night Blind Spot The “Night Blind Spot” appears under conditions of low ambient illumination due to the absence of rods in the fovea, and involves an area 5 to 10 degrees wide in the centre of the visual field. Therefore, if an object is viewed directly at night, it may go undetected or it may fade away after initial detection due to the night blind spot. 2.1.2 Types of vision Myopia – short-sightedness Myopia is the term used to define short-sightedness. Light from a distant object forms an image before it reaches the retina. Hypermetropia – long-sightedness Hypermetropia means long sight and is where the image of a nearby object is formed behind the retina. 2.1.3 Empty field myopia This is caused by flight at high altitude or at night, when there is nothing to look at. The eyes tend to adopt a resting focus at a point approximately two metres away, with the result that a distant object has to be fairly large in order to be seen, which is an obviously dangerous situation. This can be overcome by actively refocusing the eyes on distant objects such as the ground, clouds or stars. Risk scenarios The following list consists of several identified conditions where the eyes tend to repeatedly revert to their natural resting state: a) in VMC, when the sky is featureless and visibility is 10km or more b) in very dark night with no stimuli to focus on c) in hazy conditions Copyrighted - ISBN: 978-1-64008-188-8 Rev4 ©UAV Industries Training P a g e 24 | 182 d) in bright light and glare e) flying over snow-covered or desert surfaces with predominantly featureless ground. 2.1.4 Night vision Physiologically, night vision is achieved through the rods because of their greater sensitivity. Greatest night visual acuity is achieved by looking slightly off-centre at an object, due to the fact that the rods are concentrated away from the centre of the retina. Maximum night efficiency of the rods may take as much as 45 minutes to achieve and therefore a period of dark adaption may be necessary to acquire good night vision. Factors which can adversely affect night vision include: a) Mild hypoxia (oxygen deficiency) b) Smoking c) Alcohol d) Stimulants e) Increasing age Copyrighted - ISBN: 978-1-64008-188-8 Rev4 ©UAV Industries Training P a g e 25 | 182 2.1.5 Colour vision Although normal colour vision is not necessarily essential for a pilot, the ability to distinguish between these colours is mandatory: RED WHITE GREEN 2.1.6 Optical illusion False horizon: Common during flight in partial IMC, the pilot observes sloping cloud formations and an obscured horizon. Alternatively, at night, this optical illusion can also be caused by a combination of stars, ground lights and geometric ground light patterns Ground lighting: Many pilots, especially in unfamiliar areas, have mistaken lights along a straight road or on a moving train as approach or runway lights. The effect of a bright runway: The pilot thinks he is close to the runway, which results in a high approach. The effect of an unlit runway: The lack of lights reduces height cues and the pilot may fly a low approach. Auto-kinesis: This is an illusion that makes a static light appear to be moving when stared at for a period of 8-10 seconds in a dark environment. To prevent auto-kinesis, do not stare/focus on a source of light and expand your visual field. Copyrighted - ISBN: 978-1-64008-188-8 Rev4 ©UAV Industries Training P a g e 26 | 182 2.2 STRESS 2.2.1 Background Every person has experienced some form of stress in his life, but understanding exactly what stress is and how it affects an individual’s performance can be difficult. Stress is the logical result of an overload of mental and/or physical pressure and can be divided into either physical or emotional stress. 2.2.2 Types of stress Physical stress: Physical stress can be caused by prolonged physical discomfort, such as flying an aeroplane through turbulence for any length of time. Emotional stress: With regard to flying, emotional stress is considered to be the more important of the two and can broadly be categorized as either acute or chronic. Stress inducing factors are referred to as stressors. 2.2.3 Categories of stress Acute stress: Acute stress is considered to be relatively short-term and occurs as a result of immediate demands placed on the body, such as: a) Bad weather b) Diversion c) Flight deck crisis Acute stress is often short term. Once the pilot has safely landed the aircraft, this type of stress is likely to dissipate. Chronic stress: Chronic stress is more serious as it is usually longer term and may be brought about by both positive and negative events, such as: a) Marriage b) Death of a close friend or family member c) Divorce d) Concern over employment security e) Health f) Product of an entire lifestyle Copyrighted - ISBN: 978-1-64008-188-8 Rev4 ©UAV Industries Training P a g e 27 | 182 Both of these stress conditions will impact on flying performance. Stressors: These are generally placed in three categories: a) Physical b) Physiological c) Emotional Physical stressors: These comprise environmental conditions such as: a) Extremes of both temperature and humidity b) Lack of oxygen c) Noise and vibration Physiological stressors: These include, but are not limited to: a) Sleep deprivation (fatigue) b) Hunger, which may result in low blood sugar c) The discomfort of a full bladder or bowel d) A mild infection, e.g. flu e) Pain, e.g. chronic backache Emotional stressors: These are usually associated with social interaction – problems related to the home and work environment. 2.2.4 Stimulation and stress It is a generally accepted principle that in order to act we need a stimulus and this often takes the form of pressure, as we tend to react to demand. The danger is not so much the demand, but rather how we cope with it. Our ability to handle stress varies from person to person, but there are a number of factors which determine our response to stress. Health: Is the person well rested or not, in good physical condition with a happy and relaxed external life? Personality: Is the person outgoing, confident and does he make decisions easily? Copyrighted - ISBN: 978-1-64008-188-8 Rev4 ©UAV Industries Training P a g e 28 | 182 Preparation: Has the person adequately prepared for the flight? Does he know all the theory for the exam? Intelligence: Is the person right for the job? Is he qualified for the job? 2.2.5 Stages of stress The human response to sudden demands is almost instinctive and is often referred to as the fight or flight response. The fight or flight reaction comprises three stages: a) The alarm stage b) The resistance stage c) Exhaustion The alarm stage: The immediate reaction to a stressor is to either confront it or flee from it. During this stage, adrenaline is released into the bloodstream. The adrenaline increases the heartbeat, the rate of breathing and the body’s blood sugar. At the same time, it is common to experience improved vision, hearing and muscular strength – all of which may be fundamental responses for finding a solution to the alarm. The resistance stage: The body enters a recovery cycle and starts to repair the damage, either physiologically or by adapting to the new situation (learning to cope). Exhaustion stage: No doubt you will already have recognized these first two stages simply because you will have experienced them many times during your life. The third stage is more complex. If the body is continually subjected to a stressor, it will remain in the alarm stage for a prolonged period of time. Aviation-related examples include bad weather experiences without an instrument rating. A prolonged alarm condition means that the body may eventually be unable to keep up with the demands placed on it, resulting in exhaustion. In this condition, control is lost because the mind is unable to keep a correct perspective of Copyrighted - ISBN: 978-1-64008-188-8 Rev4 ©UAV Industries Training P a g e 29 | 182 matters. In really extreme cases the person may simply abandon themselves to fate. 2.2.6 Anxiety This is a condition which usually results from excessive worry. Symptoms of anxiety range from uneasiness to fear. During anxiety, a person may perform poorly and the following signs may display: Physical signs: Breathing difficulties, nervous twitches, dry mouth, stomach pains, headache and an increased heart rate. Behavioural signs: Mood changes from being light-hearted to depressed, sudden changes in emotion, laughing at inappropriate times, being over co-operative, impatience, unwarranted anger, rudeness, smoking, drinking and even eating excessively. Fatigue: Being extremely tired from lack of sleep and/or over-worked and/or chronically stressed. 2.2.7 Managing stress Stress is a mechanism that can sometimes over-stimulate the nervous system, making it hard to address serious threats to flight safety. It is difficult to control stress reactions, but it is not entirely impossible. Coping efforts can be focused toward the stressor or the emotions that arise as a result of stress, but the most effective strategy is to deal with both the stressor and its emotional impact. Reducing the negative emotional impact of the stressor removes many of the barriers that obstruct the problem-solving thought processes. Incorrect stress management Ego can be our biggest enemy. We are all subject to stress – it is a necessary catalyst for action. Copyrighted - ISBN: 978-1-64008-188-8 Rev4 ©UAV Industries Training P a g e 30 | 182 This person may try to avoid stress by ignoring it or by resorting to alcohol, drugs or medication, which may relieve the symptoms but not the cause. Clearly these are unacceptable methods of dealing with stress. They are referred to as defence mechanisms and may be joined by other subconscious actions. Stress defence mechanisms include: a) Giving up or accepting whatever outcome presents itself b) Trying to rationalise or justify incorrect actions, when more often these are excuses c) Anger, which may include bad language and even violent behaviour d) A lack of awareness, a condition where the brain subconsciously refuses to recognise a stressor Recognising a stressful condition The first step in effective stress management is to train yourself to be able to recognise the symptoms that signal the onset of stress before stress levels get too high. Some common signals of stress include: a) Physical signs: cold, sweaty hands, headache, tension b) Behavioural changes: irritability, anger, hurriedness, fixation c) Speech patterns: fast and/or irregular speech, non-standard phrases, voice tone or loudness. Dealing with stress during flight It is important to know how to deal with acute stress taking place during flight and chronic stress that may have been around for an extended period of time. Reactive and preventative measures are available to deal with both acute and chronic stress. Very often the preventative measures help to improve reactive coping techniques. For example, practicing a certain emergency technique or making good backup plans are both preventive and make it much easier to deal with an emergency. Copyrighted - ISBN: 978-1-64008-188-8 Rev4 ©UAV Industries Training P a g e 31 | 182 In general, preparation and practice create competence and confidence and greatly reduce stress levels. Some stressors that are faced in flight cannot be avoided. The best way of coping with such stressors involves a combination of preparation (pre-flight) and duringflight corrective actions: a) Preparation: Knowledge of techniques for dealing with certain flight situations that are not frequently encountered. The ability to apply these techniques proficiently is crucial for safety. b) Anticipation: It is good to anticipate possible scenarios and threats that could arise during the flight, even if they are very unlikely to happen. This will reduce the surprise factor if something does happen. c) Planning: Anticipating what might happen is not enough. It is important that once all reasonable scenarios and threats are identified, a sound plan for dealing with them is made on the ground before flight. This further increase preparedness. d) Communication: Briefings both before the flight and during flight are critical. Letting other crew members know what the plans are will ensure that everyone knows what to do and that no one will be surprised or will do anything that is contrary to the planned action. e) Use of resources: Make the best use of all available resources. This includes careful distribution of tasks at the operational area and other resources, such as equipment and ATC, which can always help by providing information and advice that will help you deal with the situation and reduce stress levels. f) Crew Resource Management (CRM): Share tasks to avoid work overload. If you are overloaded with too many tasks, do not avoid asking for assistance. Learn to recognise the symptoms of stress, not only in yourself, but also in other crew members. Provide advice or assistance when necessary. A good workplace atmosphere with plenty of humour always helps, but remember there is a time to joke and a time to be serious. g) Time management: Always do things in advance whenever possible. Do not leave tasks until the last moment (e.g. asking ATC for clearances). Whenever Copyrighted - ISBN: 978-1-64008-188-8 Rev4 ©UAV Industries Training P a g e 32 | 182 possible, buy yourself more time to analyse and solve a situation properly in order to avoid rushed actions. Should you still be faced with a totally unexpected stressful situation despite all your careful planning and anticipation, the keys are to recognise the symptoms, remain calm and buy yourself as much time to think as possible. By understanding stress mechanisms, you can control negative emotions resulting from stress such as irritation, nervousness and anxiety and attempt to solve the problem in the most logical and safe way possible. Dealing with long-term and chronic stress No matter how much you try to avoid certain stressful situations in flight, there will always be personal or other stressors, some outside your control that will affect you. Some of these stressors may be chronic. The most basic elements of coping with these chronic stress issues are: a) Taking care of the physical causes of stress: This includes ensuring you get enough sleep, eat properly and exercise. Hunger and fatigue are some of the most obvious stressors and their effects are well known. Climbing stairs is a very good way of eliminating excess toxins in the body and swimming helps restore equilibrium to the nervous system. b) Continuous professional training: Training ensures currency and competence in all standard and emergency operating procedures. c) Social interaction: It is not good to allow personal problems and worries to build up. Communicating them with others is very important as it offers partial relief and also because people may be able to offer help and advice. d) Workload: Do not allow yourself to take on too many tasks and responsibilities (both work and non-work related) that can cause work overload. It is important to learn to say “no” when asked to do too many tasks. Copyrighted - ISBN: 978-1-64008-188-8 Rev4 ©UAV Industries Training P a g e 33 | 182 2.3 FATIGUE 2.3.1 Introduction Fatigue can be best described as a very deep tiredness. It can be caused by the same factors which lead to stress and can also be divided into two types. a) Acute fatigue b) Chronic fatigue Acute fatigue: This condition can occur as a result of intense and undivided mental concentration or physical activity over a prolonged period. The cure is relatively straightforward: restful and uninterrupted natural sleep, uninfluenced by alcohol or drugs. Chronic fatigue: This condition occurs over a longer period as a result of lack of sleep, excessive workload stress and even jet lag. It cannot be as easily cured as acute fatigue as it requires a prolonged recovery period. The laws regarding flight and duty time are regarded as a preventative measure against the occurrence of chronic fatigue. Symptoms of fatigue: a) Obvious tiredness: slow and frequent yawning, drooping head b) Decreased awareness resulting in lack of response c) Much slower reactions d) Poor concentration (noticeable in instrument flying) e) Forgetfulness f) Being unable to sleep g) Reduced short-term memory (e.g. forgetting clearances) h) Tending to make more mistakes i) Loss of appetite and increased reliance on alcohol and drugs such as caffeine. Prevention and treatment of fatigue The most obvious prevention and treatment for fatigue is sleep, combined with a proper balance between work and rest. A well-balanced diet and regular exercise also reduces fatigue. Excessive alcohol, caffeine and drugs should be avoided. Copyrighted - ISBN: 978-1-64008-188-8 Rev4 ©UAV Industries Training P a g e 34 | 182 2.3.2 Sleep Sleep is the body’s method of recharging and revitalising itself. The amount and quality thereof ultimately determine how well we can perform both mentally and physically. Stages of sleep: a) REM sleep b) Non-REM sleep REM sleep This commences some 90 minutes after falling asleep and is characterised by the sleeper’s eyes moving rapidly back and forth beneath closed eyelids. REM sleep is closely related to wakefulness. This is due to the high frequency electrical waves which occur during this condition. REM sleep is believed to be the sleep period that rejuvenates the brain. Non- REM Sleep: This comprises four distinct stages: Stage 1 is the transition between waking and sleeping. It is characterised by decreasing brain wave activity and slow rolling eye movements. It can last from one to 10 minutes. Stage 2 sleep continues for approximately 10 minutes, during which time brain wave activity declines further. Stages 3 and 4 are referred to as slow wave sleep, which is characterised by very low frequency brain waves. It is thought to be associated with physical restoration. 2.3.3 Sleeping problems a) Nervous insomnia b) Situational/acute insomnia c) Clinical/chronic insomnia Nervous insomnia: The most common insomnia of all and probably one to which we are all subjected to at some time or another, nervous insomnia is based on the Copyrighted - ISBN: 978-1-64008-188-8 Rev4 ©UAV Industries Training P a g e 35 | 182 anticipation of a near-future event such as a major flight test in the case of aircrew. Acute insomnia: This is the result of a disturbance in body rhythms, which is also referred to as jet lag. Similarly, recovery is relatively easy and will take place within one week. Clinical insomnia: This refers to a difficulty in sleeping under normal circumstances when the body requires sleep. The person can be affected for weeks or months. 2.3.4 Sleep management Clearly, sleep is a vital part of our well-being and should be managed carefully, with the emphasis on natural sleep rather than on drug-induced sleep. This will involve calculated scheduling in both normal and long-distance flight operations. The following recommendations are noted: 1. Stay relaxed. Avoid strenuous physical or mental exercise and refrain from alcohol, caffeine and large meals before going to bed. 2. Maintain a regular sleep schedule. 3. The ideal sleeping environment should consist of a comfortable bed in a dark, quiet room at a pleasant temperature, with fresh air. Copyrighted - ISBN: 978-1-64008-188-8 Rev4 ©UAV Industries Training P a g e 36 | 182 2.4 SELF-HEALTH ASSESSMENT I.M.S.A.F.E Illness – is the pilot suffering from any illness or symptom of an illness which might affect them in flight? Medication – is the pilot currently taking any drugs (prescription or over-thecounter)? Stress – is the pilot overly worried about other factors in his life? The psychological pressures of everyday living can be a powerful distraction and consequently affect a pilot's performance. Alcohol – although legal limits vary by jurisdiction (0.04 BAC, any consumption in the past 8 hours or current impairment in the USA[2]), the pilot should consider their alcohol consumption within the last 8 to 24 hours. Fatigue – has the pilot had sufficient sleep and adequate nutrition? Emotion – has the pilot fully recovered from any extremely upsetting events, such as the loss of a family member? Copyrighted - ISBN: 978-1-64008-188-8 Rev4 ©UAV Industries Training P a g e 37 | 182