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11.13.3 Human Factor Considerations


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Stress affects all human beings. It is the perception of what the stress is that determines whether the human copes. Overstress a person and their ability to reason and function correctly is reduced. Not enough stress will cause boredom and complacency. The right amount of stress and optimum performance levels are achieved.

Stress can be defined as:

Excessive and aversive environmental factors that produce physiological responses in an individual

The strain and pressure that is exerted on a human can be related to the scientific use of the term where effectively a body is bent and eventually breaks if overstressed.

Stress is present in all humans. It is important to accept that in all walks of life that we all suffer some stress whether good or bad. The pilot needs to be aware of the problems of stress and how to cope with the rigours it puts the body through. This helps the person recognise the negative impact on performance caused by overstress such as:

  • Fatigue
  • Personal problems
  • High workload

Remember, the pilot is his own worst enemy. Peer pressure over the years has instilled in most pilots a fear that admission of overload is a weakness.

The stress that the body is subjected to can be broken down into three areas. Remember that these problems may be singular or cumulative, for simplicity we look at each separately.

Physical: Environment we live in; conditions such as, noise, vibration and stages of hypoxia.

Physiological: Fatigue, physical fitness, poor diet.

Emotional: The domestic, social and emotional factors related to living. Work related activity such as leadership or decision making.

Stress can be defined as either:

Chronic Stress: The long term demands of a person's lifestyle such as work, health or domestic security

Acute Stress: Short term stress caused by the issues of the day.

Effects of Stress

Acute stress is dealt with by the body immediately. Adrenaline is released into the bloodstream and charges the body:

  • Raising the heart rate.
  • Increasing the blood pressure.
  • Increasing the breathing rate.
  • Increasing the blood sugar level.

A condition known as the "fight or flight" syndrome. This allows the person to react quickly to a given situation.

Chronic stress is different, the body has to take a long term view of the stress that it is being put under. Chronic stress can make a situation that we normally cope with difficult. Chronic stress will exaggerate the effects of acute stress and in the long term threatens a person's health.

Stress is Cumulative

Long term stress over a period of time can affect the individual's ability to perform in stressful situations. In a pilot this can result in:

  • Inaccurate flying.
  • Communication difficulties.
  • Leadership and command problems.

Simple points can help describe the effects of stress:

  • Stressor:
    • Change
    • Frustration
    • Conflict
    • Pressure
    • Boredom
    • Trauma
  • Stress Mediation:
    • Coping Skills
    • Perception of Stress
    • Predictability
  • Stress Reaction:
    • Physical
    • Psychological
    • Emotional


  • Stressor: A situation or event that causes a stress.
  • Stress Reaction: The physical, physchological or emotional response of the body.

The interaction of stressors and the resultant stress reactions are not straightforward. We all react differently to different stresses in life. What seems minor to one person may be a life crisis in another.

Any stress reaction is related directly to the evaluation of the stress and the perceived ability a person has in coping. Solely psychological these are our stress mediators and can be good or bad depending on our perception of the problem.

Listed are some of the major stressors in life. These pass through a mediation phase that then is felt by the body as a stress reaction.

Mediation should lessen the effect of stress. As we learn to cope with the R/T and flying the aircraft at the same time both become inbuilt into our sub-conscious and are no longer worried about.

However mediation may not work:


Assume that you are on an approach to London Heathrow. The weather is poor. The cloud base is on the ground, the crosswind is on limits.

There are two possibilities:

  • One: You cope with the approach and do a good job.
  • Two: You "cock it up"

One week later you are flying into London Heathrow in exactly the same conditions.

If you succeeded last time stress mediation will have taken place and you will not be so worried about the approach and most probably you will make a good approach again.

If you failed last time your brain will be telling you that you failed last time and that you can't do it. In this case mediation is worse and you will most likely fail.

Psychological Stressors

The stressors that are related in the simple stress model can be experienced as shown below:

  • Frustration: Where obstacles stand in the way of our progress such as holding because of problems on the ground.
  • Pressure: Whether self inflicted or external we all get the feeling, "so much to do and so little time to do it"
  • Boredom: A problem in that a bored person does not work at peak performance and can be left wanting in an emergency.
  • Trauma: A physical or emotional experience that leaves the body in shock.
  • Conflict: Domestic or work, conflict can make the life of the sufferer miserable.
  • Change: Change is related in this chapter by the use of Life Change Units. The events listed are measured relative to each other for a Northern European adult. If you accumulate more than 120 LCU's/12 months or 200 LCU's/2 years, then you may suffer a minor life crisis.

For the pilot, as well as the domestic changes that are listed above there are certain events specific to the job in hand:

  • Medicals.
  • Training and line checks.
  • Time schedules and late passengers.
  • Other crew members.
  • Company pressure.
  • Fatigue etc.

There are many more, these are but a few.

Effects of Stress

Stress affects our motivation and performance. Small amounts of stress are needed to make the body move. This can be related in a simple performance/ arousal graph. As the amount of stress increases we are initially:

In a low arousal state. This can be thought of as just waking up or being over fatigued. The central nervous system is not functioning fully and any information processing is slow and inaccurate.

Motivation to react to stimuli is low and the body is inattentive. Think about what your actions are when you wake to the alarm clock. Get up straight away or press the snooze button?

As the day progresses the arousal increases as does the performance. Under optimum conditions the central nervous system is functioning correctly. To carry out complicated tasks the body needs to be in this state of optimum arousal:

  • One where a task will stimulate and interest the brain but not be so omplicated so as to push us into an overload situation.

Once the limit of capacity is reached then the performance falls rapidly.

Physical and Psychological Stress Reactions

Stress reactions are the physical, psychological or emotional response to the stressor. The reactions are not independent of each other but can be interrelated. For simplicity each is discussed separately.

Physical Stress Reactions

Think of what happens to you when you have a sudden shock. Pulse and breathing become rapid, possible sweating and trembling. The fight or flight syndrome is an animal reaction to danger and results in the release of certain hormones (Adrenaline and Nor-adrenaline) into the bloodstream.

The commands to release these hormones come from the Sympathetic Branch of the Autonomic Nervous System. As the danger passes, the Parasympathetic Branch calms the body down.

The long term effects of stress are better explained by the General Adaptation Syndrome.

Three stages occur:

  • The Alarm Stage: A stressor causes a fall in our resistance. Defensive measures are taken by the body and it starts to act against the stress.
  • The Resistance Stage: Once mediation has taken place the body prepares a resistance phase. This is a time limited phase as the body can only cope with so much.
  • The Exhaustion Stage: Eventually resistance will fail if the mediation has not been successful. Prolonged exhaustion can be fatal. More common are ailments such as hypertension, organ failure, cardiac arrest, ulcers, or renal failure.
Psychological Stress Reactions

Stress is related as the way that a person feels and responds to a situation. These feelings are divided into three simple categories:

  • Emotional Responses: Common emotional reactions to stress include anger, anxiety, fear, depression etc. In extreme cases emotional responses can be come uncontrollable and cause such problems as anxiety attacks.
  • Cognitive Responses: Stress affects the ability to concentrate on the task in hand. To think clearly and logically defence mechanisms are used to cope with the stressors.
  • Behavioural Responses: The changes in the way a person acts when stressed. Fidgeting or shaking when worried is just one example. In the pilot the most common response to stress is the use of alcohol.
Domestic Stress

The one stress we all suffer from at some stage in life. By using the LCU table you can determine how life is affecting you. Domestic stress does affect the workplace no matter who you are.

Clinical Effects of Stress

The body reacts in differing ways to cope with stressors. Both psychological and physiological responses are made:

  • Physical Effects: The "Fight or Flight" syndrome where the Sympathetic Branch of the Autonomic Central Nervous System is activated.
  • Health Effects: Increased heart rates and the release of adrenaline will cause hypertension.
  • Behavioural Effects: The problems of the over use of drugs or alcohol.
  • Cognitive Effects: Lack of concentration and lack of attention to detail lead to the inability to deal with problems clearly and logically.
  • Emotional Effects: The body releases tension in many ways which may include aggression or moodiness etc.
Coping Skills

To cope with stress the person needs to accept that a stress is causing problems. The next stage is to choose a coping strategy that best helps. Some coping is carried out subconsciously. If the sub-conscious does not work then there are strategies that can be adopted. To cope with a stress the person must accept that they are under stress and want to do something about it.

These conscious coping strategies are:

Action Coping

The reduction of stress by direct action. Implementation usually includes some or all of the following:

  • Assessment: Find the sources and effects of the stress.
  • Set Goals: Find the stressors and stress reactions that need to be attacked.
  • Plan: Make a plan of action on how to cope.
  • Action: Carry out the plan.
  • Evaluation: Check to see if the plan is working. If not, try again or revise the plan.
Cognitive Coping

Cognitive coping is a method in changing the way we think about a problem. Methods used include:

  • Distraction: Concentrate on other tasks to take away the pressure of the stressor.
  • Redefining the Situation: Try to make the stress more acceptable.
  • Direct Action: By thought the decision may be to use action planning.
  • Catharsis: An emotional outburst to release the stress.
  • Acceptance: Decide to accept the problem and do nothing about it.
Symptom-Directed Coping

The use of external coping skills

  • Physical Exercise: A healthy person copes with stress better than an unfit person. Stress can be released in the aggression of sport.
  • Relaxation Techniques: Use of areas such as meditation or hypnosis to counteract the ravages of life.
Other Coping Strategies

Other Coping Strategies include:

  • Religion: The help of the church and someone to talk to is a good way of helping with stress.
  • Counselling: Not only professional counselling but talking with a friend can help.
Stress Management

The way that a person decides to cope with a stress. To carry out stress management the person must first accept that stress is causing a problem.

It is easy to recognize the signs of stress in oneself, but what about others?

If a person does not manage stress, stress will manage the person. Life events do not create stress; the perception of the stress is created in our minds. The source must be identified before it can be addressed and reduced or eliminated.

Make a plan and stick to it. The aim is to control or to eliminate the effects of stress. Be realistic and practical. This may call for you to be flexible and willing to adapt. Rest is essential as a tired mind and body give quickly. Humour and perseverance help.