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the Pilot’s Operating Handbook (POH) and unintentionally transposed the number 62 to 26. He or she did not mean to make that error but unknowingly and unintentionally did. 

## Intentional 

In aviation, an intentional error should really be considered a flight violation. If someone knowingly or intentionally chooses to do something wrong, it is a violation, which means that one has deviated from safe practices, procedures, standards, or regulations. 

## Human and Physiological Factors that Affect Flight 

## Fatigue 

Fatigue is a major human factor that has contributed to many maintenance errors resulting in accidents. Fatigue can be mental or physical in nature. Emotional fatigue also exists and effects mental and physical performance. A person is said to be fatigued when a reduction or impairment in any of the following occurs: cognitiv e ability, decision-making, reaction time, coordination, spee d, strength, and balance. Fatigue reduces alertness and often reduces a person’s ability to focus and hold attention on the task being performed. [Figure 13-4] 

Symptoms of fatigue may also include short-term memory problems, channeled concentra tion on unimportant issues while neglecting other factors that may be more important, and failure to maintain a situational overview. A fatigued person may be easily distracted or may be nearly impossible to distract. He or she may experience abnormal mood swings. Fatigue results in an increase in mistakes, poor judgment, and poor decisions or perhaps no decisions at all. A fatigued person may also lower his or her standards. 

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Tiredness is a symptom of fatigue. However, sometimes a fatigued person may feel wide awake and engaged in a task. The primary cause of fatigue is a lack of sleep. Good restful sleep free from drugs or alcohol is a human necessity to prevent fatigue. Fatigue can also be caused by stress and by overworking. A person’s mental and physical state also naturally cycles through various levels of performance each day. Variables such as body temperature, blood pressure, heart rate, blood chemistry, alertness, and attention rise and fall in a pattern daily. This is known as one’s circadian rhythm. [Figure 13-5]  A person’s ability to work (and rest) rises and falls during this cycle. Performance counter to circadian rhythm can be difficult. Until it becomes extreme, a person may be unaware that he or she is fatigued. It is easier recognized by another person or in the results of tasks being performed. Flying alone when fatigued is particularly dangerous. 

The best remedy for fatigue is to get enough sleep on a regular basis. Pilots must be aware of the amount and quality of sleep obtained. Countermeasures to fatigue are often used. Effectiveness can be short lived and many countermeasures may make fatigue worse. Caffeine is a common fatigue countermeasure. Pseudoephedrine found in sinus medicine and amphetamines are also used. While effective for short periods, a fatigued person remains fatigued and may have trouble getting the rest needed once they try to sleep. 

