Physiological Factors Affecting Pilots

14 CFR part 107 does not allow operation of small UA if the remote pilot in command, the person manipulating the controls, or visual observer is unable to safely carry out his or her responsibilities. It is the remote pilot in command’s responsibility to ensure that all participating crewmembers are not impaired. While drug and alcohol use are known to impair judgment, certain over-the-counter (OTC) medications and medical conditions could also affect the ability to safely operate a small UA, such as certain antihistamines and decongestants which may cause drowsiness. Part 107 prohibits a person from serving as a remote pilot in command, person manipulating the controls, visual observer (VO), or other crewmember if he or she:

Has consumed any alcoholic beverage within the preceding 8 hours.
Is under the influence of alcohol.
Has a blood alcohol concentration of .04 percent or greater.
Is using a drug that affects the person’s mental or physical capabilities.

There are certain medical conditions such as epilepsy which may also create a risk to operations. Again, it is the remote PIC’s responsibility to determine that their medical condition is under control and they can safely conduct a small UA operation. Important medical factors that a pilot should be aware of include the following:

Hyperventilation
Stress
Fatigue
Dehydration
Heatstroke

Effects of Alcohol and Drugs

Hyperventilation: Hyperventilation is the excessive rate and depth of respiration leading to abnormal loss of carbon dioxide from the blood. This condition occurs more often among pilots than is generally recognized. It seldom incapacitates completely, but it causes symptoms such as increased breathing rate and anxiety, leading to unconsciousness. Pilots encountering an unexpected stressful situation may subconsciously increase their breathing rate.  Common symptoms of hyperventilation include:

Visual impairment
Unconsciousness
Lightheaded or dizzy sensation
Muscle Spasms
Hot and Cold Sensations
Tingling Sensations

The treatment for hyperventilation involves restoring the proper carbon dioxide level in the body. Breathing normally is both the best prevention and the best cure for hyperventilation. In addition to slowing the breathing rate, breathing into a paper bag or talking aloud helps to overcome hyperventilation. Recovery is usually rapid once the breathing rate is returned to normal. Conversely, breathing too slow or shallow results in hypoventilation.

Stress: Stress is the body’s response to physical and psychological demands placed upon it. The body’s reaction to stress includes releasing chemical hormones (such as adrenaline) into the blood and increasing metabolism to provide more energy to the muscles. Blood sugar, heart rate, respiration, blood pressure, and perspiration all increase. The term “stressor” is used to describe an element that causes an individual to experience stress. Examples of stressors include physical stress (noise or vibration), physiological stress (fatigue), and psychological stress (difficult work or personal situations). Stress falls into two broad categories: acute stress (short term) and chronic stress (long term).

Acute stress involves an immediate threat that is perceived as danger, and this type of stress triggers a fight or flight response in an individual, whether the threat is real or imagined. Normally, a healthy person can cope with acute stress and prevent stress overload. However, ongoing acute stress can develop into chronic stress.

Chronic stress can be defined as a level of stress that presents an intolerable burden, exceeds the ability of an individual to cope, and causes individual performance to fall sharply. Unrelenting psychological pressures, such as loneliness, financial worries, and relationship or work problems can produce a cumulative level of stress that exceeds a person’s ability to cope with the situation. When stress reaches these levels, performance falls off rapidly. Pilots experiencing this level of stress are not safe and should not exercise their airman privileges. Pilots who suspect they are suffering from chronic stress should consult a physician.

Fatigue: Fatigue is frequently associated with pilot error. Some of the effects of fatigue include degradation of attention and concentration, impaired coordination, and decreased ability to communicate. These factors seriously influence the ability to make effective decisions. Physical fatigue results from sleep loss, exercise, or physical work. Factors such as stress and prolonged performance of cognitive work result in mental fatigue. Fatigue falls into two broad categories: acute fatigue and chronic fatigue.

Acute fatigue is short term and is a normal occurrence in everyday living. It is the kind of tiredness people feel after a period of strenuous effort, excitement, or lack of sleep. Rest after exertion and 8 hours of sound sleep ordinarily cures this condition. A special type of acute fatigue is skill fatigue. This type of fatigue has two main effects on performance:

Timing disruption – appearing to perform a task as usual, but the timing of each component is slightly off. This makes the pattern of the operation less smooth because the pilot performs each component as though it were separate, instead of part of an integrated activity.
Disruption of the perceptual field, concentrating attention upon movements or objects in the center of vision and neglecting those in the periphery. This is accompanied by loss of accuracy and smoothness in control movements.

Acute fatigue has many causes, but the following are among the most important for the pilot:

Mild hypoxia (oxygen deficiency)
Physical stress
Psychological stress
Depletion of physical energy resulting from psychological stress
Sustained psychological stress

Acute fatigue can be prevented by proper diet and adequate rest and sleep. A well-balanced diet prevents the body from needing to consume its own tissues as an energy source. Adequate rest maintains the body’s store of vital energy. If suffering from acute fatigue, a remote pilot should not operate a small UA. If fatigue occurs during the operation of a small UA, no amount of training or experience can overcome the detrimental effects. Getting adequate rest is the only way to prevent fatigue from occurring.

Chronic Fatigue: Chronic fatigue, extending over a long period of time, usually has psychological roots, although an underlying disease is sometimes responsible. Continuous high-stress levels produce chronic fatigue. Chronic fatigue is not relieved by proper diet and adequate rest and sleep, and usually requires treatment by a physician.

An individual may experience this condition in the form of weakness, tiredness, palpitations of the heart, breathlessness, headaches, or irritability. Sometimes, chronic fatigue even creates stomach or intestinal problems and generalized aches and pains throughout the body. When the condition becomes serious enough, it leads to emotional illness. Remote pilots should avoid flying their small unmanned aircraft without a full night’s rest, after working excessive hours, or after an especially exhausting or stressful day. Remote pilots who suspect they are suffering from chronic fatigue should consult a physician.

Dehydration: Dehydration is the term given to a critical loss of water from the body. Causes of dehydration are hot temperatures, wind, humidity, and diuretic drinks such as coffee, tea, alcohol, and caffeinated soft drinks. Some common signs of dehydration are headache, fatigue, cramps, sleepiness, and dizziness. The first noticeable effect of dehydration is fatigue, which in turn makes top physical and mental performance difficult, if not impossible. Flying a small UA for long periods in hot summer temperatures or at high altitudes increases the susceptibility to dehydration because these conditions tend to increase the rate of water loss from the body.

Dehydration is the term given to a critical loss of water from the body. Causes of dehydration are hot temperatures, wind, humidity, and diuretic drinks such as coffee, tea, alcohol, and caffeinated soft drinks. Some common signs of dehydration are headache, fatigue, cramps, sleepiness, and dizziness. The first noticeable effect of dehydration is fatigue, which in turn makes top physical and mental performance difficult, if not impossible. Flying a small UA for long periods in hot summer temperatures or at high altitudes increases the susceptibility to dehydration because these conditions tend to increase the rate of water loss from the body.

The key for pilots is to be continually aware of their condition. Most people become thirsty with a 1.5 quart deficit or a loss of 2 percent of total body weight. This level of dehydration triggers the “thirst mechanism.” The problem is that the thirst mechanism arrives too late and is turned off too easily. A small amount of fluid in the mouth turns this mechanism off and the replacement of needed body fluid is delayed. Other steps to prevent dehydration include:

Carrying a container in order to measure daily water intake.
Staying ahead and not relying on the thirst sensation as an alarm. If plain water is not preferred, add some sport drink flavoring to make it more acceptable.
Limiting daily intake of caffeine and alcohol (both are diuretics and stimulate increased production of urine).

Heatstroke: Heatstroke is a condition caused by any inability of the body to control its temperature.  Onset of this condition may be recognized by the symptoms of dehydration, but also has been known to be recognized only upon complete collapse. To prevent these symptoms, it is recommended that an ample supply of water be carried and used at frequent intervals, whether thirsty or not.  The body normally absorbs water at a rate of 1.2 to 1.5 quarts per hour. Individuals should drink one quart per hour for severe heat stress conditions or one pint per hour for moderate stress conditions. For more information on water consumption, refer back to the “Dehydration” section of this chapter.

Drugs

The Federal Aviation Regulations include no specific references to medication usage. Title 14 of the CFR prohibits acting as a remote pilot or in any other capacity or crewmember while that person: Knows or has reason to know of any medical condition that would make the person unable to meet the requirement for the medical certificate necessary for the pilot operation, or is taking medication or receiving other treatment for a medical condition that results in the person being unable to meet the requirements for the medical certificate necessary for the pilot operation.

14 CFR part 107 and 14 CFR part 91, sections 91.17 and 91.19 prohibit the use of any drug that affects the person’s faculties in any way contrary to safety. If a remote pilot is in question regarding the effects of any over-the-counter (OTC) medicine, they should consult with the Pilot Handbook of Aeronautical Knowledge. So the safest rule is not to fly as a remote pilot in command or crewmember while taking any medication, unless approved to do so by the FAA. And if there is any doubt regarding the effects of any medication after reviewing the Pilot handbook of Aeronautical Knowledge, consult an Aeronautical Medical Examiner (AME) before flying.

Alcohol

Alcohol impairs the efficiency of the human body, and studies have shown that consuming alcohol is closely linked to performance deterioration. Pilots must make hundreds of decisions, some of them time-critical, during the course of a flight and the safe outcome depends on the ability to make correct decisions and take the appropriate actions during both routine and abnormal situations.

The influence of alcohol drastically reduces the chances of completing a flight without incident, and even small amounts of alcohol can impair judgment, decrease sense of responsibility, affect coordination, constrict visual field, diminish memory, reduce reasoning ability, and lower attention span. And as little as one ounce of alcohol can decrease the speed and strength of muscular reflexes, lessen the efficiency of eye movements while reading, and increase the frequency at which errors are committed.

While experiencing a hangover, a pilot is still under the influence of alcohol. And although a pilot may think he/she is functioning normally, motor and mental response impairment are still present. Considerable amounts of alcohol can remain in the body for over 16 hours, so pilots should be cautious about flying too soon after drinking. Intoxication is determined by the amount of alcohol in the bloodstream, and this is usually measured as a percentage by weight in the blood.

14 CFR part 91 requires that blood alcohol level be less than .04 percent and that 8 hours pass between drinking alcohol and piloting an aircraft. Even though blood alcohol may be well below .04 percent, a pilot cannot fly sooner than 8 hours after drinking alcohol.

Congratulations! You’ve completed Lesson 11 on Physiology of Operating an sUAS. Be sure to click the COMPLETE button to register your progress.

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