•Cell damage - especially within the brain.

•Heat stroke.

•Coma.

•The body loses water through the skin, lungs and kidneys.

Should the blood temperature rise to approximately 43°C (110°F), death will result.

Note: Generally speaking the mind and body need an average of 2 weeks to acclimatise to a hot and humid environment.

Extreme Cold Stress

If the core temperature drops to approximately 35°C shivering declines and eventually ceases. The effects of extreme cold are:

•Uncontrollable shivering and an associated need for more oxygen. Around 34.5°C, the shivering that will have started earlier will tend to cease.

•Cell damage - especially of the brain.

•Sleepiness associated with a feeling of contentment or apathy.

•Circulatory impairment and degradation of the sensory nerves.

•Severe damage to the skin and tissues (frostbite).

•Coma.

•Death.

It is important to stress that the effects of exposure to extreme temperatures are not restricted to the more dramatic conditions described above. Smaller temperature variations within these limits can have a detrimental effect on a person’s ability to perform a task.

Internal Physiological Factors

The most important of these factors are:

•Hunger.

•Thirst.

•Fatigue.

•Lack of sleep.

•Pain.

With the exception of pain, these factors are normally within the control of aircrew. It is of fundamental importance that crews ensure they never start a period of duty with any of these internal physiological stressors.

Stress 7

Stress 7

The Brain’s Ability to Adapt to Physiological Stressors

Repeated exposure to moderate levels of stress from the environment will cause the body to adapt to the stress in order to reduce its impact. For example if an individual lives close to a busy airport the sounds may not be noticed after a time, whereas a visitor might well comment on the noise levels. This ability is limited and varies from person to person.

Cognitive Stress Factors/Stressors

These differ from physiological stressors since they depend on the operator’s professional knowledge, experience and skill.

They can occur in the cockpit under the following conditions:

•When the situation facing the pilot is unexpected and no procedure exists to resolve it.

•When the solution to the unexpected problem is realized but the pilot has insufficient time, or is unable to apply the solution. This can occur when the pilot is “overloaded”.

•When the solution is applied but the results are not as expected and the problem remains unsolved.

Non-professional Personal Factors/StressorTable

Evidence indicates there is a relationship between stress and health and some evidence for a correlation between non-professional stress and the risk of an accident.

Although the stress level caused by a particular stressor will differ from one individual to another, it is possible to make a general assessment of stress levels.

The table below gives a suggested weighting for various incidents in an average westerner’s life. When applying such weighting to other cultures there will be some marked differences. Aircrew must remain sensitive to these cultural differences.

As stress is cumulative, all of the events experienced should be added to give an indication of the total stress acting on any one person.

Stress Table

Stress 7

Stress 7

Imaginary Stress (Anxiety)

Both human beings and animals can suffer from stress without there being a stressor present. It is the anxiety that a future risk exists together with the feeling of an inability to cope or lack of self-confidence. An example of this natural response is when a dog is taken to the vet, having experienced pain during a previous visit. The animal shows signs of anxiety even though no stressor exists. Some of us have similar feelings about a visit to the dentist. Inevitably anxiety will affect our performance.

Unpleasant events in life may be apparently completely forgotten but the anxiety associated with them can be brought to the surface by one of the senses (a scene, noise, smell) and distort perception. This anxious apprehension can be strong enough so as to trigger the GAS response.

Organizational Stress

The Organization

In the aviation industry today, financial pressures on companies can cause pilots to work under considerable pressure. Small unserviceabilities may be carried, duty hours stretched to the limit, checks rushed to make a slot time, and there are many other examples. As an extreme example of stress generated by poor management, the president of an airline which was in financial difficulties, instructed pilots to fly below the legal minima in bad weather. They were also instructed to ignore maximum take-off weights and reduce minimum fuel reserves. As a direct result of these decisions the airline suffered three serious accidents in a short period.

If management continually exerts pressure on its employees to operate in ways that are more consistent with short-term monetary concerns than with safety and good practice, then the whole company will develop ‘organizational stress’.

The symptoms will manifest themselves as:

•Poor industrial relations.

•Absenteeism.

•An increased accident/incident rate.

Aircrew and the Organization

Work stress may be caused by a sudden high work load such as an emergency. The stress experienced will be increased if the pilot is unsure how to react or feels inadequately trained for the specific situation. Realistic simulator training is essential to reduce the impact of any emergency.

Stress may also arise from a long-term high work load. Airlines operate in a competitive world and must make maximum use of staff and equipment. An aircraft and crew standing idle are not producing revenue. Even with the advances of modern ATC there will be times when airspace and airports become overcrowded. Add to this technical delays and additional stress is created.

Rostering of crews can also lead to stress problems. A particular pilot may have to perform an excessive number of night flights and suffer undue disruption to his home life. This, in turn, leads to further cumulative stress.

Poor relationships and/or communications with management and colleagues, both on and off the flight deck, leads to stress. Some cockpit voice recordings, listened to after accidents, have detected crew members arguing on the flight deck just prior to the accident.