Aviation Fatigue Is a Complex

Aviation Fatigue

Fatigue is a complex phenomenon that has been ascribed to various causes. The underlying reasons for fatigue are investigated in this paper and the focus of the research is on solutions to the problem as well as on the importance of understanding the causative factors. Fatigue has also been singled out by the aviation industry and the Air Force as one of the most pervasive reasons for in-flight errors and loss of concentration in operational conditions. The seriousness of the issue of fatigue and fatigue related problems are indicated by the numerous studies, reports and seminars that have been conducted over the past decade. In this investigation into the solutions to the problem of fatigue, the study also finds that the solutions are extremely dependent on the full understanding of fatigue and the way that this phenomenon relates to other factors. Solutions to the problem of fatigue, such as the management of sleep and duty times during operational conditions, are also dependent on a holistic view of the phenomenon and the variables that affect fatigue.

1, Introduction

Fatigue is a factor that is being increasingly seen as a threat and a problem in the aviation industry and the Air Force. In financial terms it has been estimated that problems caused by fatigue costs American industry more than $18 billion a year in terms of lost productivity." (Military Aviation Fatigue Countermeasures workshop)

Numerous studies have shown that there is a direct correlation between fatigue and aviation accidents. "...there is mounting evidence that pilot/aircrew fatigue is a causative factor in many civilian and military aviation mishaps." (ibid) There is also a long history of accidents that have been positively linked to fatigue in aviation; for example, fatigue has been cited as causative factor in the 1196 Korean disaster where 228 people were killed on Korean Air Flight 801 in 2002. Furthermore, fatigue has been identified as a contributing cause in 9.6% of all Air Force Class a mishaps over the past 30 years, and aircrew fatigue has been associated with approximately four percent of all Army Class a-C accidents during the period from 1990-2000.

These statistics and other supporting data are indicative of the seriousness in which fatigue as a causative factor in aviation errors is being taken by modern researchers. This has resulted in an increasing emphasis on research into the causes of fatigue and the preventative measures that can be taken to combat fatigue - related errors in aviation. This is particularly important when it comes to military operations with an increasing emphasis on the importance of research into the prevention of combat fatigue during these operations. Donald Rumpsfeld, the present Defense Secretary of the United States, has emphasized this fact by promoting a policy to reduce air mishaps by 50% within the next two years. (ibid)

Fatigue as a factor in aviation accidents is also being recognized throughout the world as an important factor in aviation safety, as the following report attests:

Airline pilots have called for an urgent investigation after it was revealed those crews who fall asleep in the cockpit are to blame for up to one in 12 plane crashes.

The British Air Line Pilots Association (BALPA) is demanding more research into flight-deck fatigue and an overturning of new European legislation that allows airlines to make pilots fly longer with shorter breaks.

A www.questia.com/PM.qst?a=o&d=5008711166"("One in Twelve Plane," 2005, p. 26)

The phenomenon of fatigue has a number of central characteristics that have been emphasized by researchers and psychologists. "

Fatigue is characterized by (1) a decreased capacity for work, known as work decrement; (2) modifications in the physiological state of the individual; and (3) a feeling of weariness. " (Bartley, Chute & Ivy, 1947, p. 6)

Fatigue also results from prolonged working hours and has a measurable effect and change on the body and other aspect of the physiology.

Feelings of weariness are "the subjective sign of deep-seated bodily changes and decreased capacity for work which characterize fatigue. The feeling of fatigue may be accompanied by irritability, anxiety, excessive worry, disturbed emotional states of all kinds..." (Bartley, Chute & Ivy, 1947, p. 6)

This paper will provide an overview of the problem and discuss the meaning and importance of fatigue as it relates to aviation accidents and mishaps. The definition and understanding of fatigue as both a physiological and psychological issue will be discussed. The paper will also provide an intensive discussion of research tests and experiments that have been conducted in these areas, in order to provide a comprehensive view of the latest strategies for alleviating fatigue related problems.

2. Method

The central method used in this paper was to research and compile results of views and findings on the subject from a variety of database and data sources. Sources and studies on fatigue, focusing on the impact of fatigue on aviation and aviation accidents is the Air Force, were firstly researched. These sources included Internet databases as well as offline and online academic journals, magazines and books that offered insight into the issue of fatigue within the parameters mentioned.

While it was found that there was a plethora of data relating to the effects of fatigue in general, the issue of fatigue as it relates specifically to aviation was not as prolific. However, it was noticed during the research process that there were considerably more reports and studies on the subject during the past decade.

These data sources were then analyzed and used as a basis for which to draw up an overview, firstly of the causes and reasons for fatigue and secondly to discuss the various views and facts relating to way in which the issue of fatigue was linked to operational situations. The focus here was on the prevention of fatigue in the Air Force, particularly under combat situations. An attempt was also made in the study to maintain a balance between positive and negative studies of the implications of fatigue.

3. Results

The result obtained from an investigation and analysis of these various sources seem to overwhelmingly indicate that there is a significant problem that has to be addressed with regard to acute fatigue. Tests and research show that while fatigue is not always a factor influencing judgment errors, yet it has been conclusively shown, as the following section will attest to, that fatigue is a major factor in aviation errors.

The research also suggests that the problem is been taken very seriously by the Air Force and the aviation industry, with numerous papers, studies and seminars on the subject. Studies also suggest various methods of dealing with the problem, as will be outlined in the following section. The results of these investigations also point to the fact that fatigue is a complex issue that cannot be understood or dealt with in isolation from other concomitant factors, such as stress. Solutions to the problem of fatigue are therefore also dependent on a full and wide ranging assessment of the problem.

4. Discussion comprehensive and in-depth understand of fatigue requires that various related and concomitant factors need to be taken into account in order to fully comprehend the phenomenon. This has been realized especially by researchers concerned with improving the accident rate in the Air Force as a result of fatigue. The importance of adequate levels of performance during combat and in war situations is a central concern for the military, and researchers have realized that there is a complex interrelationship between fatigue and aspects such as stress and sleep deprivation that have to be taken into account.

Other factors such as the environment and the physiological effects of altitude, as well as other variables, have also to be included in an assessment and understanding of the nature of fatigue.

Reviews of the literature (Heslegrave & Angus, 1985; Hockey, 1986; Holding, 1983; Johnson & Naitoh, 1974; Naitoh, 1981) show that this relation is complex, involving characteristics of the individual (e.g., restedness, skill level, motivation), task variables (e.g., type, duration, repetitiveness), and the environment (e.g., temperature, altitude, noise). (Neri & Shappell, 1994, p. 141)

There have been numerous attempts and studies both in the field and in simulated experiments to determine the degree of performance degradation due to fatigue and sleep deprivation. The results from these studies have often produced mixed and sometimes ambiguous results. For example a study by Fraser (1952) showed significant vigilance degradation in aircrew after long flights; and Haslam (1981) also detected vigilance degradation with sleep loss. Storm (1980) (Neri & Shappell, 1994, p. 142)

In another study it was demonstrated that "...performance in a simulator was significantly degraded for transport crews given only onboard rest after flying 8- to 9-hr missions. (Neri & Shappell, 1994, p. 142)

However there are also other reports that indicate that fatigue as a result of sleep deprivation is not always a certain or critical factor and that there are various factors that are interrelated and can effect the assessments of fatigue of aviation issues.

Nonetheless, the magnitude of performance degradation after partial, or even total, sleep deprivation is often small (Johnson & Naitoh, 1974; Krueger, Armstrong, & Cisco, 1985). Furthermore, subjective feelings of fatigue can be inconsistent with performance (Holding, 1983), sometimes exhibiting a greater sensitivity to sleep loss than the performance measures (Haslam, 1981).

While different studies have produced variable results about the effects of fatigue inducing elements in flight performance and aviation errors, yet there is on the whole general agreement among researchers that fatigue is negative factor in aviation, particularly when it comes to military operations. "Despite the mixed findings, there is agreement on the importance of adequate sleep management and sleep logistics for military troops in wartime (Johnson & Naitoh, 1974; Naitoh et al., 1986; Nicholson & Stone, 1987). (ibid)

Researchers also point out that the varying results obtained from studies are related to and dependent on the type of experiments and the situations in which the testing takes place. They note that the best data and sources of information on the true effects of fatigue are often taken from actual combat situations and conditions; while many state that the results from simulations and laboratory experiments do not produce an accurate picture of the reality of fatigue and fatigue-induced errors in aviation. (ibid)

Many studies on fatigue focus on the effects on the body and the physiological implications of flying at high altitudes; as well as the way that this effects the inducement of bodily fatigue. A recent study on aviation fatigue states that, "exhaustion among flight crew is a significant but often underreported problem in civilian and military air operations.

As many as eight per cent of all plane crashes and near-misses in both civilian and military aviation are the result of pilot fatigue." ("One in Twelve Plane," 2005, p. 26)

The study looked at the results of investigations into accidents involving passenger aircraft over the past 30 years, records of crashes by U.S. Army, Navy and Air Force planes in peacetime, and war operations such as Desert Storm." Report author John Caldwell, of the U.S. Air Force Research Laboratory in San Antonio, Texas, says more effort must be made by airlines to ensure crew get enough sleep between flights."

Fatigue can result from facing stressful situations in difficult conditions for long periods of time, a situation that many Air Force pilots face in combat situations. Besides these factors, fatigue can result from and be complicated by physiological disruptions in the body "clock " and timing mechanisms. Sleep deprivation has been shown to be one of the central facets in the impacts on fatigue, especially under stressful conditions. This type of situation is obviously a central concern for the Air Force, and various methods including GO Pills have been used as a means of alleviating the problem. (Brown, L. 2003) However, there are many other strategies that can be implemented and which will be discussed in this section.

The exact nature of fatigue is a contentious issue among many researchers. There is considerable debate as to the interrelationship between the different types and definitions of fatigue that have to be taken into account. The studies of fatigue are essentially concerned with various manifestations of the phenomenon. These include changes in the level of aviation performance which are expressed in the decreased capacity for work. This is usually referred to as objective fatigue. This muscular fatigue is measured by the use of the finger ergograph. (Bartley, Chute & Ivy, 1947, p. 7)

Secondly there is physiological fatigue which refers to "...the physiological changes due to the chemical products of fatigue" and the metabolic rate of energy consumption which "... measures this real basis of physical fatigue and also mental fatigue in so far as it can be determined physiologically." (ibid) the third working definition of fatigue that is recognized is more psychological and relates to ennui or weariness and boredom. (ibid) All of these various definitions of fatigue are not mutually excusive have to be considered in the overall assessment of the effects of aviation fatigue.

Studies of fatigue have dealt the problem from three quite different angles. Some have defined fatigue in terms of the subjectively observed feelings of fatigue as these show themselves in ennui, boredom, dissatisfaction with the task, and feelings of bodily weariness and an unpleasant affective tone. All these can be grouped under the term Subjective Fatigue. Others have been concerned with changes in the level of performance or output as a result of continuous work. This can be called Objective Fatigue. Still others have taken the position that physiological changes within the organs constitute the real basis of fatigue, and that the term should be applied to them. This can be spoken of as Physiological Fatigue.

The problem with the measurement and assessment of fatigue in terms of these three central definitions is that their interactions are not always constant and each type of fatigue may operate independently of the other. This has led to the following assessment of fatigue.

If any two of these three variables were correlated with one another the problem would be simplified, but as a matter of fact, each one is to a certain extent independent of every other. Neither subjective feeling nor output is highly correlated with physiological condition; nor are subjective feeling and output closely related. Output has a much less rapid decrement than subjective feeling. As a result of these discrepancies some psychologists, notably Muscio and Watson, have argued that the term fatigue is essentially ambiguous and should be eliminated from discussions of work and fatigue. (ibid)

In the light of the above view it seems obvious that each type of fatigue and its variables will have to be considered both in isolation as well as in conjunction with one another in order for the comprehensive picture of fatigue to emerge.

Flying at high altitudes is a central factor which affects the pilot and can lead to the physiological symptoms of fatigue. In investigating the effects of altitude on body functioning we first must understand what is defined as high altitude and then observe the important changes that occur in the internal environment of the human body. Exposure to changes in altitude has a profound effect on the human body. External conditions inhibit the body to provide sufficient oxygen for cellular respiration, causing the body to go into a state of homeostasis in an attempt to maintain life.

The effects of high altitude on the human body is hypoxia, hyperventilation, changes in lung volume, changes in pulmonary diffusing capacity, changes in number of red blood cells, changes in hemoglobin concentration, and changes in cardiac output. The human body is also prone to high altitude stress which includes effects like increased secretion of ADH, redistribution of body fluids, and impairment of mental reactions.

Human Ecology)

The relationship between altitude and fatigue as a result of the decrease in oxygen intake has been associated with symptoms of fatigue.

Generally the human body acclimatizes to high altitudes and begins to function differently to compensate for the change in atmospheric gases. Yet, the performance of body systems may decline rapidly and if prolonged and may be fatal. In order to sustain life the human body must absorb oxygen; it also expels carbon dioxide from the body. With an increase in elevation, the body is forced to adjust in order to provide adequate oxygen needed for internal respiration. One of the major effects that the body experiences when there is a reduction of oxygen is known as hypoxia.

The condition the body experiences when there is less oxygen available in the air, as at high altitude, is known as hypoxia. The condition in which the arterial blood contains lower than normal partial pressure of oxygen is sometimes known as hypoxemia. "The condition the body experiences when there is less oxygen available in the air, as at high altitude, is known as hypoxia. The condition in which the arterial blood contains lower than normal partial pressure of oxygen is sometimes known as hypoxemia." (Deitz & Thoms, 1991, p. 32)

Normal symptoms of acclimatization to altitude include increased heart and exhalation rates to rid the body of the increased amounts of carbon dioxide being inhaled; Increased bladder activity caused by increased levels of sodium bicarbonate due to the higher than normal levels of carbon dioxide in the bloodstream; Insomnia; Slight swelling of the feet and knees; and Breathlessness; and fatigue. "As a result of the lack of oxygen the muscles quickly become tired. Muscle glycogen, the muscles' energy store, decreases." (Clarke, 2003) Other symptoms are also indicative of symptoms related to extreme fatigue and can seriously impair an aviator's judgment.

In war and operational situations there are many stressful aspects that are often labeled as fatigue. This particularly refers to the syndrome of chronic nervous fatigue in pilots in operational conditions and relates to the more psychological aspects of fatigue. Researcher's state that this understanding of fatigue in military personnel is known as aeroneurosis, as described in a study by Armstrong.

The symptoms he described are more or less identical with those of the syndrome variously called "situational neurosis," "chronic exhaustion state," "anxiety state," "anxiety neurosis," or "chronic nervous exhaustion." We use the term chronic exhaustion state because we do not believe the functional disturbances encountered in a pilot are any different from the functional disturbances encountered in any other hightensioned person subjected to overwork and prolonged emotional strain." (Bartley, Chute & Ivy, 1947, p. 39)

This sort of fatigue is due to the fact that the nervous system can be overtaxed and lose its potential energy through continuous strain. If this occurs then the symptoms of exhaustion become evident.

Another aspect that creates intense fatigue in military situations is sustained and continuous flight operations which are often tactically necessary in order to apply pressure on the enemy. This form of stress and fatigue can lead to detrimental impact on military aviation. "It is well established that sustained wakefulness and the resulting sleep debt increase the likelihood that personnel will briefly (and uncontrollably) nod off on the job, even during flights (Dinges, 1995). (Brown, L. 2003).

These factors apply as well to commercial aviation accidents and their role in error judgments. For example, "Although predictions about the exact effects of fatigue are difficult to make, most researchers agree that fatigue-related performance and alertness decrements follow a fairly reliable time course. (ibid) This is supported by other reports and studies that state, for example, that military personal lose about 25% of their performance ability for every twenty four hours without sleep. (Belenky et al. 1994. 127-135) Another study also suggests that the ability of soldiers drops by as much as 80% after four consecutive days without sleep. (Roussel, B. 1995.)

Another aspect which has received attention is sleep deprivation. Sleep deprivation and studies of the body's 'Circadian Clock' refers to the body's internal rhythms which are often 'programmed' to change and decrease in intensity at night.

Disruptions to the body's clock compound the fatigue associated with long hours of wakefulness so that someone who is trying to work early in the morning (after being awake since the previous day) is suddenly vulnerable to involuntary "sleep attacks" even though they were fine just a few hours before. These same people might deceive themselves into thinking they've overcome fatigue after the sun comes up even though they haven't slept a wink during the night. (Brown, L. 2003).

The search for solutions to the problem of fatigue during operations has resulted in some in-depth studies and experimental reports. In studies of Air Force fatigue is was found that in disruption in sleep routines and sleep deprivation "...performance...would have declined until it degraded to less than 50% of optimal levels. Decrements of this magnitude could create serious problems in the operational environment unless a proven fatigue countermeasure is implemented." (ibid) Therefore this study suggests that," it is for this reason that feasible countermeasures must be developed and implemented." (ibid)

These results and the necessity for intensive research into fatigue are also underlined in a paper entitled Simulated Sustained Flight Operations and Performance, Part 1: Effects of Fatigue by Neri et al. Of the Naval Aerospace Medical Research Laboratory Pensacola, Florida

The results of their study indicates that continuous flight operations are likely to produce fatigue and performance decrement in aviators. (Neri, Shappell & Dejohn, 1992, p. 137)

The data in this study were obtained from simulated sustained operations, and the subjects were subjected to a variety of tests to determine the effects of fatigue on performance across a wide range of variables. The result indicated that,

Planning and performance demands combined with stress and fatigue probably result in fragmented sleep and, if continued, circadian rhythm desynchronization.... Task repetitiveness and the extent to which it requires sustained effort, attention, activity, and stamina are important (Krueger, 1991). Individual characteristics of age, temperament, personality, and intelligence also can affect performance (Neri, Shappell & Dejohn, 1992, p. 138)

The study also notes the increase in errors that occur as fatigue inducing factors worsen. Among there ways that are suggested by the study of dealing with fatigue is the balancing of effort and predicted results. This refers to a practical strategy of using less effort for tasks that have a lower probability of success, and in this way conserving energy. These results point to the fact that better planning and management of situation can be effective in reducing workload, stress and fatigue.

The study also found that the error rate also increased linearly with time. For these tests, increasing response rate was due, in part, to an increase in error rate.... The error rate increase was enough to cause a significant decline in accuracy. This is an important finding because errors in the cockpit can have dire consequences and, depending on their severity and timing, may not always be correctable. (ibid)