Chapter 17 Aeromedical Factors Introduction It is important for a pilot to be aware of the mental and physical standards required for the type of flying performed. This chapter provides information on medical certification and on a variety of aeromedical factors related to flight activities. 17-1 Obtaining a Medical Certificate demonstrated ability” (SODA) can be issued. This waiver, or SODA, is valid as long as the physical impairment does Most pilots must have a valid medical certificate to exercise not worsen. Contact the local Flight Standards District Office the privileges of their airman certificates. Glider and free (FSDO) for more information on this subject. balloon pilots are not required to hold a medical certificate. Sport pilots may hold either a medical certificate or a valid The FAA medical standards, 14 CFR part 67, specify fifteen state driver’s license. Regardless of whether a medical medical conditions that are considered disqualifying by certificate or drivers license is required, 14 CFR 61.53 “history or clinical diagnosis.” Regardless of when one of requires every pilot not to act as a crewmember if they know, these conditions was diagnosed and treated, an airman may or have reason to know, of any medical condition that would not be issued a medical certificate except through a process make them unable to operate the aircraft in a safe manner. called a “Special Issuance Authorization,” as explained in 14 CFR part 67, section 67.401. A special issuance is a Acquisition of a medical certificate requires an examination discretionary issuance by the FAA Federal Air Surgeon and by an aviation medical examiner (AME), a physician requires satisfactory completion of special testing determined with training in aviation medicine designated by the Civil by the FAA to demonstrate that an airman is safe to fly for Aerospace Medical Institute (CAMI). There are three classes the duration of the medical certificate issued. The specific of medical certificates. The class of certificate needed disqualifying conditions include: depends on the type of flying the pilot plans to perform. • Diabetes mellitus requiring oral hypoglycemic A third-class medical certificate is required for a private or medication or insulin recreational pilot certificate. It is valid for 5 years for those • Angina pectoris individuals who have not reached the age of 40; otherwise it • Coronary heart disease that has been treated or, if is valid for 2 years. A commercial pilot certificate requires at untreated, that has been symptomatic or clinically least a second-class medical certificate, which is valid for 1 significant year. First-class medical certificates are required for airline transport pilots and are valid for one year if the airman is 40 • Myocardial infarction or younger; 40 and older it is valid for 6 months. • Cardiac valve replacement • Permanent cardiac pacemaker The standards are more rigorous for the higher classes of certificates. A pilot with a higher class medical certificate • Heart replacement has met the requirements for the lower classes as well. Since • Psychosis the required medical class applies only when exercising the privileges of the pilot certificate for which it is required, a • Bipolar disorder first-class medical certificate would be valid for 1 year if • Personality disorder that is severe enough to have exercising the privileges of a commercial certificate and 2 or 5 repeatedly manifested itself by overt acts years, as appropriate, for exercising the privileges of a private • Substance dependence (including alcohol) or recreational certificate. The same applies for a second-class medical certificate. The standards for medical certification • Substance abuse are contained in Title 14 of the Code of Federal Regulations • Epilepsy (14 CFR) part 67 and the requirements for obtaining medical • Disturbance of consciousness and without satisfactory certificates can be found in 14 CFR part 61. explanation of cause Students who have physical limitations, such as impaired • Transient loss of control of nervous system function(s) vision, loss of a limb, or hearing impairment may be issued without satisfactory explanation of cause a medical certificate valid for “student pilot privileges only” while learning to fly. Pilots with disabilities may require However, this list includes only the mandatory disqualifying special equipment to be installed in the aircraft, such as conditions. There are many other medical conditions that fall hand controls for pilots with paraplegia. Some disabilities into the General Medical Condition section of the regulations necessitate a limitation on the individual’s certificate; for that are considered by the FAA to be disqualifying even example, impaired hearing would require the limitation though they are not stated in the regulations. Conditions “not valid for flight requiring the use of radio.” When all the such as cancer, kidney stones, neurologic and neuromuscular knowledge, experience, and proficiency requirements have conditions including Parkinson’s disease and multiple been met and a student can demonstrate the ability to operate sclerosis, certain blood disorders, and other conditions that the aircraft with the normal level of safety, a “statement of 17-2 may progress over time require review by the FAA before a to pass between the membranes in the respiratory system. medical certificate may be issued. This decrease in number of oxygen molecules at sufficient pressure can lead to hypoxic hypoxia. The important thing to remember is that with very few exceptions, all disqualifying medical conditions may Dangers of Transporting Dry Ice be considered for special issuance. If you can present Sublimation is a process in which a substance transitions satisfactory medical documentation to the FAA that your from a solid to a gaseous state without passing through condition is stable, the chances are good that you will be an intermediate liquid state. Dry ice sublimates into large able to qualify for an Authorization. quantities of CO gas, which can rapidly displace oxygen- 2 containing air and potentially cause hypoxia via carbon Health and Physiological Factors dioxide intoxication. Case studies have shown that both illness Affecting Pilot Performance and death can be caused by occupational and/or unintentional exposure when transporting dry ice in small, confined A number of health factors and physiological effects can be spaces such as a flightdeck or airplane. Exposure to high linked to flying. Some are minor, while others are important concentration of CO gas may lead to increased respiration, enough to require special attention to ensure safety of flight. 2 tachycardia, cardiac arrhythmia, and unconsciousness. In some cases, physiological factors can lead to inflight Exposure to concentration of CO gas in excess of 10 percent emergencies. Some important medical factors that a pilot 2 may cause convulsions, coma, and/or death. should be aware of include hypoxia, hyperventilation, middle ear and sinus problems, spatial disorientation, motion The tendency of dry ice to rapidly sublimate also means that sickness, carbon monoxide (CO) poisoning, stress and without proper ventilation, it can rapidly pressurize. For fatigue, dehydration, and heatstroke. Other subjects include this reason, dry ice should never be placed inside a sealed the effects of alcohol and drugs, anxiety, and excess nitrogen transport container (i.e., leak-proof secondary container) in the blood after scuba diving. and must be placed within an outer shipping container or storage container that allows adequate ventilation to release Hypoxia the CO gas and avoid pressurization. Sealing dry ice within a Hypoxia means “reduced oxygen” or “not enough oxygen.” 2 leak-proof container may result in explosion of the container Although any tissue will die if deprived of oxygen long potentially leading to serious physical injury or death. enough, the greatest concern regarding hypoxia during flight is lack of oxygen to the brain, since it is particularly Hypemic Hypoxia vulnerable to oxygen deprivation. Any reduction in mental function while flying can result in life-threatening errors. Hypemic hypoxia occurs when the blood is not able to take Hypoxia can be caused by several factors, including an up and transport a sufficient amount of oxygen to the cells insufficient supply of oxygen, inadequate transportation of in the body. Hypemic means “not enough blood.” This type oxygen, or the inability of the body tissues to use oxygen. of hypoxia is a result of oxygen deficiency in the blood, The forms of hypoxia are based on their causes: rather than a lack of inhaled oxygen, and can be caused by a variety of factors. It may be due to reduced blood volume • Hypoxic hypoxia (from severe bleeding), or it may result from certain blood • Hypemic hypoxia diseases, such as anemia. More often, hypemic hypoxia • Stagnant hypoxia occurs because hemoglobin, the actual blood molecule that transports oxygen, is chemically unable to bind oxygen • Histotoxic hypoxia molecules. The most common form of hypemic hypoxia is CO poisoning. This is explained in greater detail later in this Hypoxic Hypoxia chapter. Hypemic hypoxia can also be caused by the loss Hypoxic hypoxia is a result of insufficient oxygen available of blood due to blood donation. Blood volume can require to the body as a whole. A blocked airway and drowning several weeks to return to normal following a donation. are obvious examples of how the lungs can be deprived of Although the effects of the blood loss are slight at ground oxygen, but the reduction in partial pressure of oxygen at high level, there are risks when flying during this time. altitude is an appropriate example for pilots. Although the percentage of oxygen in the atmosphere is constant, its partial Stagnant Hypoxia pressure decreases proportionately as atmospheric pressure Stagnant means “not flowing,” and stagnant hypoxia or decreases. As an aircraft ascends during flight, the percentage ischemia results when the oxygen-rich blood in the lungs of each gas in the atmosphere remains the same, but there are is not moving, for one reason or another, to the tissues that fewer molecules available at the pressure required for them 17-3 need it. An arm or leg “going to sleep” because the blood endurance or acclimatization. When flying at high altitudes, flow has accidentally been shut off is one form of stagnant it is paramount that oxygen be used to avoid the effects of hypoxia. This kind of hypoxia can also result from shock, hypoxia. The term “time of useful consciousness” describes the heart failing to pump blood effectively, or a constricted the maximum time the pilot has to make rational, life-saving artery. During flight, stagnant hypoxia can occur with decisions and carry them out at a given altitude without excessive acceleration of gravity (Gs). Cold temperatures supplemental oxygen. As altitude increases above 10,000 can also reduce circulation and decrease the blood supplied feet, the symptoms of hypoxia increase in severity, and the to extremities. time of useful consciousness rapidly decreases. [Figure 17-1] Since symptoms of hypoxia can be different for each Histotoxic Hypoxia individual, the ability to recognize hypoxia can be greatly The inability of the cells to effectively use oxygen is defined improved by experiencing and witnessing the effects of it as histotoxic hypoxia. “Histo” refers to tissues or cells, and during an altitude chamber “flight.” The Federal Aviation “toxic” means poisonous. In this case, enough oxygen is being Administration (FAA) provides this opportunity through transported to the cells that need it, but they are unable to make aviation physiology training, which is conducted at the FAA use of it. This impairment of cellular respiration can be caused CAMI in Oklahoma City, Oklahoma, and at many military by alcohol and other drugs, such as narcotics and poisons. facilities across the United States. For information about the Research has shown that drinking one ounce of alcohol can FAA’s one-day physiological training course with altitude equate to an additional 2,000 feet of physiological altitude. chamber and vertigo demonstrations, visit the FAA website at www.faa.gov. Symptoms of Hypoxia High-altitude flying can place a pilot in danger of becoming Hyperventilation hypoxic. Oxygen starvation causes the brain and other vital Hyperventilation is the excessive rate and depth of respiration organs to become impaired. The first symptoms of hypoxia leading to abnormal loss of carbon dioxide from the blood. can include euphoria and a carefree feeling. With increased This condition occurs more often among pilots than is oxygen starvation, the extremities become less responsive and generally recognized. It seldom incapacitates completely, but flying becomes less coordinated. The symptoms of hypoxia it causes disturbing symptoms that can alarm the uninformed vary with the individual, but common symptoms include: pilot. In such cases, increased breathing rate and anxiety further aggravate the problem. Hyperventilation can lead to • Cyanosis (blue fingernails and lips) unconsciousness due to the respiratory system’s overriding • Headache mechanism to regain control of breathing. • Decreased response to stimuli and increased reaction Pilots encountering an unexpected stressful situation may time subconsciously increase their breathing rate. If flying at • Impaired judgment higher altitudes, either with or without oxygen, a pilot may • Euphoria have a tendency to breathe more rapidly than normal, which often leads to hyperventilation. • Visual impairment • Drowsiness Since many of the symptoms of hyperventilation are similar • Lightheaded or dizzy sensation to those of hypoxia, it is important to correctly diagnose and treat the proper condition. If using supplemental oxygen, • Tingling in fingers and toes check the equipment and flow rate to ensure the symptoms are • Numbness Altitude Time of useful consciousness As hypoxia worsens, the field of vision begins to narrow and instrument interpretation can become difficult. Even with all 45,000 feet MSL 9 to 15 seconds these symptoms, the effects of hypoxia can cause a pilot to 40,000 feet MSL 15 to 20 seconds have a false sense of security and be deceived into believing 35,000 feet MSL 30 to 60 seconds everything is normal. 30,000 feet MSL 1 to 2 minutes 28,000 feet MSL 2½ to 3 minutes Treatment of Hypoxia 25,000 feet MSL 3 to 5 minutes Treatment for hypoxia includes flying at lower altitudes and/ 22,000 feet MSL 5 to 10 minutes or using supplemental oxygen. All pilots are susceptible 20,000 feet MSL 30 minutes or more to the effects of oxygen starvation, regardless of physical Figure 17-1. Time of useful consciousness. 17-4 not hypoxia related. Common symptoms of hyperventilation include: Middle ear Eustachian tube • Visual impairment • Unconsciousness Eardrum • Lightheaded or dizzy sensation • Tingling sensations • Hot and cold sensations • Muscle spasms Auditory canal The treatment for hyperventilation involves restoring the proper carbon dioxide level in the body. Breathing Outer ear Opening to throat 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 Figure 17-2. The Eustachian tube allows air pressure to equalize overcome hyperventilation. Recovery is usually rapid once in the middle ear. the breathing rate is returned to normal. sensitivity, pinch the nostrils shut, close the mouth and lips, Middle Ear and Sinus Problems and blow slowly and gently into the mouth and nose. During climbs and descents, the free gas formerly present in various body cavities expands due to a difference between This procedure forces air through the Eustachian tube into the the pressure of the air outside the body and that of the air middle ear. It may not be possible to equalize the pressure in inside the body. If the escape of the expanded gas is impeded, the ears if a pilot has a cold, an ear infection, or sore throat. pressure builds up within the cavity and pain is experienced. A flight in this condition can be extremely painful, as well as Trapped gas expansion accounts for ear pain and sinus pain, damaging to the eardrums. If experiencing minor congestion, as well as a temporary reduction in the ability to hear. nose drops or nasal sprays may reduce the risk of a painful ear blockage. Before using any medication, check with an The middle ear is a small cavity located in the bone of the AME to ensure that it will not affect the ability to fly. skull. It is closed off from the external ear canal by the eardrum. Normally, pressure differences between the middle In a similar way, air pressure in the sinuses equalizes with ear and the outside world are equalized by a tube leading the pressure in the flight deck through small openings from inside each ear to the back of the throat on each side that connect the sinuses to the nasal passages. An upper called the Eustachian tube. These tubes are usually closed but respiratory infection, such as a cold or sinusitis, or a nasal open during chewing, yawning, or swallowing to equalize allergic condition can produce enough congestion around an pressure. Even a slight difference between external pressure opening to slow equalization. As the difference in pressure and middle ear pressure can cause discomfort. [Figure 17-2] between the sinuses and the flight deck increases, congestion may plug the opening. This “sinus block” occurs most During a climb, middle ear air pressure may exceed the frequently during descent. Slow descent rates can reduce the pressure of the air in the external ear canal causing the associated pain. A sinus block can occur in the frontal sinuses, eardrum to bulge outward. Pilots become aware of this located above each eyebrow, or in the maxillary sinuses, pressure change when they experience alternate sensations located in each upper cheek. It usually produces excruciating of “fullness” and “clearing.” During descent, the reverse pain over the sinus area. A maxillary sinus block can also happens. While the pressure of the air in the external ear make the upper teeth ache. Bloody mucus may discharge canal increases, the middle ear cavity, which equalized with from the nasal passages. the lower pressure at altitude, is at lower pressure than the external ear canal. This results in the higher outside pressure Sinus block can be avoided by not flying with an upper causing the eardrum to bulge inward. respiratory infection or nasal allergic condition. Adequate protection is usually not provided by decongestant sprays This condition can be more difficult to relieve due to the or drops to reduce congestion around the sinus openings. fact that the partial vacuum tends to constrict the walls of Oral decongestants have side effects that can impair pilot the Eustachian tube. To remedy this often painful condition, performance. If a sinus block does not clear shortly after which also causes a temporary reduction in hearing landing, a physician should be consulted. 17-5 Spatial Disorientation and Illusions ear in any direction causes the tiny hairs to deflect, which Spatial disorientation specifically refers to the lack of in turn stimulates nerve impulses, sending messages to the orientation with regard to the position, attitude, or movement brain. The vestibular nerve transmits the impulses from of the airplane in space. The body uses three integrated the utricle, saccule, and semicircular canals to the brain to systems that work together to ascertain orientation and interpret motion. movement in space. The somatosensory system sends signals from the skin, joints, • Vestibular system—organs found in the inner ear that and muscles to the brain that are interpreted in relation to the sense position by the way we are balanced Earth’s gravitational pull. These signals determine posture. • Somatosensory system—nerves in the skin, muscles, Inputs from each movement update the body’s position to the and joints that, along with hearing, sense position brain on a constant basis. “Seat of the pants” flying is largely based on gravity, feeling, and sound dependent upon these signals. Used in conjunction with visual • Visual system—eyes, which sense position based on and vestibular clues, these sensations can be fairly reliable. what is seen However, the body cannot distinguish between acceleration forces due to gravity and those resulting from maneuvering All this information comes together in the brain and, most the aircraft, which can lead to sensory illusions and false of the time, the three streams of information agree, giving impressions of an aircraft’s orientation and movement. a clear idea of where and how the body is moving. Flying can sometimes cause these systems to supply conflicting Under normal flight conditions, when there is a visual information to the brain, which can lead to disorientation. reference to the horizon and ground, the sensory system in the During flight in visual meteorological conditions (VMC), inner ear helps to identify the pitch, roll, and yaw movements the eyes are the major orientation source and usually prevail of the aircraft. When visual contact with the horizon is lost, over false sensations from other sensory systems. When the vestibular system becomes unreliable. Without visual these visual cues are removed, as they are in instrument references outside the aircraft, there are many situations in meteorological conditions (IMC), false sensations can cause which combinations of normal motions and forces create a pilot to quickly become disoriented. convincing illusions that are difficult to overcome. The vestibular system in the inner ear allows the pilot to Prevention is usually the best remedy for spatial disorientation. sense movement and determine orientation in the surrounding Unless a pilot has many hours of training in instrument flight, environment. In both the left and right inner ear, three flight should be avoided in reduced visibility or at night when semicircular canals are positioned at approximate right angles the horizon is not visible. A pilot can reduce susceptibility to each other. [Figure 17-3] Each canal is filled with fluid to disorienting illusions through training and awareness and and has a section full of fine hairs. Acceleration of the inner learning to rely totally on flight instruments. Ampulla of semicircular canal YAW Semicircular canals Otolith organ ROLL PITCH ROLL PITCH YAW Endolymph fluid The semicircular tubes are arranged Cupola at approximately, right angles to each other in the roll, pitch, and yaw axes. Vestibular nerve Hair cells Figure 17-3. The semicircular canals lie in three planes and sense motions of roll, pitch, and yaw. 17-6 Vestibular Illusions direction causing the disoriented pilot to return the aircraft The Leans to its original turn. Because an aircraft tends to lose altitude in turns unless the pilot compensates for the loss in lift, A condition called the leans, is the most common illusion the pilot may notice a loss of altitude. The absence of any during flight and is caused by a sudden return to level flight sensation of turning creates the illusion of being in a level following a gradual and prolonged turn that went unnoticed by descent. The pilot may pull back on the controls in an attempt the pilot. The reason a pilot can be unaware of such a gradual to climb or stop the descent. This action tightens the spiral turn is that human exposure to a rotational acceleration of 2 and increases the loss of altitude; this illusion is referred to degrees per second or lower is below the detection threshold as a “graveyard spiral.” [Figure 17-5] This may lead to a of the semicircular canals. [Figure 17-4] Leveling the wings loss of aircraft control. after such a turn may cause an illusion that the aircraft is banking in the opposite direction. In response to such an Somatogravic Illusion illusion, a pilot may lean in the direction of the original turn in a corrective attempt to regain the perception of a correct A rapid acceleration, such as experienced during takeoff, vertical posture. stimulates the otolith organs in the same way as tilting the head backwards. This action may create what is known as Coriolis Illusion the “somatogravic illusion” of being in a nose-up attitude, especially in conditions with poor visual references. The The “coriolis illusion” occurs when a pilot has been in a turn disoriented pilot may push the aircraft into a nose-low or long enough for the fluid in the ear canal to move at the same dive attitude. A rapid deceleration by quick reduction of the speed as the canal. A movement of the head in a different throttle(s) can have the opposite effect, with the disoriented plane, such as looking at something in a different part of the pilot pulling the aircraft into a nose-up or stall attitude. flight deck, may set the fluid moving, creating the illusion of turning or accelerating on an entirely different axis. This action causes the pilot to think the aircraft is performing a maneuver it is not. The disoriented pilot may maneuver the aircraft into a dangerous attitude in an attempt to correct the aircraft’s perceived attitude. Graveyard spin For this reason, it is important that pilots develop an instrument cross-check or scan that involves minimal head movement. Take care when retrieving charts and other objects in the flight deck—if something is dropped, retrieve it with minimal head movement and be alert for the coriolis illusion. Graveyard Spiral As in other illusions, a pilot in a prolonged coordinated, constant-rate turn may experience the illusion of not Graveyard spiral turning. During the recovery to level flight, the pilot will then experience the sensation of turning in the opposite Figure 17-5. Graveyard spiral. Endolymph Cupola Tube No turning Start of turn Constant rate turn Turn stopped No sensation. Sensation of turning No sensation after fluid Sensation of turning in as moving fluid deflects accelerates to same opposite direction as moving hairs. speed as tube wall. fluid deflects hairs in opposite direction. Figure 17-4. Human sensation of angular acceleration. 17-7 Inversion Illusion Autokinesis An abrupt change from climb to straight-and-level flight can When flying in the dark, a stationary light may appear to stimulate the otolith organs enough to create the illusion of move if it is stared at for a prolonged period of time. As tumbling backwards, known as “inversion illusion.” The a result, a pilot may attempt to align the aircraft with the disoriented pilot may push the aircraft abruptly into a nose- perceived moving light potentially causing him/her to lose low attitude, which may intensify this illusion. control of the aircraft. This illusion is known as “autokinesis.” Elevator Illusion Postural Considerations The postural system sends signals from the skin, joints, and An abrupt upward vertical acceleration, as can occur in an muscles to the brain that are interpreted in relation to the updraft, can stimulate the otolith organs to create the illusion Earth’s gravitational pull. These signals determine posture. of being in a climb. This is known as “elevator illusion.” Inputs from each movement update the body’s position to The disoriented pilot may push the aircraft into a nose-low the brain on a constant basis. “Seat of the pants” flying is attitude. An abrupt downward vertical acceleration, usually largely dependent upon these signals. Used in conjunction in a downdraft, has the opposite effect with the disoriented with visual and vestibular clues, these sensations can be pilot pulling the aircraft into a nose-up attitude. fairly reliable. However, because of the forces acting upon the body in certain flight situations, many false sensations Visual Illusions can occur due to acceleration forces overpowering gravity. Visual illusions are especially hazardous because pilots rely [Figure 17-6] These situations include uncoordinated turns, on their eyes for correct information. Two illusions that lead climbing turns, and turbulence. to spatial disorientation, false horizon and autokinesis, affect the visual system only. Demonstration of Spatial Disorientation There are a number of controlled aircraft maneuvers a pilot False Horizon can perform to experiment with spatial disorientation. While A sloping cloud formation, an obscured horizon, an aurora each maneuver normally creates a specific illusion, any false borealis, a dark scene spread with ground lights and stars, sensation is an effective demonstration of disorientation. and certain geometric patterns of ground lights can provide Thus, even if there is no sensation during any of these inaccurate visual information, or “false horizon,” when maneuvers, the absence of sensation is still an effective attempting to align the aircraft with the actual horizon. demonstration because it illustrates the inability to detect The disoriented pilots as a result may place the aircraft in a bank or roll. dangerous attitude. Level Coordinated turn Pull out Level skid Forward slip Uncoordinated turn Skid, slip, and uncoordinated turns feel similar. Pilots feel they are being forced sideways in their seat. Figure 17-6. Sensations from centrifugal force. 17-8 There are several objectives in demonstrating these various aircraft to approximately 45° bank attitude while maintaining maneuvers. heading and pitch attitude. This creates the illusion of a strong sense of rotation in the opposite direction. After this illusion 1. They teach pilots to understand the susceptibility of is noted, the pilot should open his or her eyes and observe the human system to spatial disorientation. that the aircraft is in a banked attitude. 2. They demonstrate that judgments of aircraft attitude based on bodily sensations are frequently false. Diving or Rolling Beyond the Vertical Plane 3. They help decrease the occurrence and degree This maneuver may produce extreme disorientation. While of disorientation through a better understanding in straight-and-level flight, the pilot should sit normally, of the relationship between aircraft motion, head either with eyes closed or gaze lowered to the floor. The movements, and resulting disorientation. instructor pilot starts a positive, coordinated roll toward a 4. They help instill a greater confidence in relying on 30° or 40° angle of bank. As this is in progress, the pilot flight instruments for assessing true aircraft attitude. tilts his or her head forward, looks to the right or left, then immediately returns his or her head to an upright position. A pilot should not attempt any of these maneuvers at The instructor pilot should time the maneuver so the roll is low altitudes or in the absence of an instructor pilot or an stopped as the pilot returns his or her head upright. An intense appropriate safety pilot. disorientation is usually produced by this maneuver, and the pilot experiences the sensation of falling downward into the direction of the roll. Climbing While Accelerating With the pilot’s eyes closed, the instructor pilot maintains In the descriptions of these maneuvers, the instructor pilot is approach airspeed in a straight-and-level attitude for several doing the flying, but having the pilot do the flying can also seconds, then accelerates while maintaining straight-and- be a very effective demonstration. The pilot should close his level attitude. The usual illusion during this maneuver, or her eyes and tilt the head to one side. The instructor pilot without visual references, is that the aircraft is climbing. tells the pilot what control inputs to perform. The pilot then attempts to establish the correct attitude or control input with Climbing While Turning eyes closed and head tilted. While it is clear the pilot has no With the pilot’s eyes still closed and the aircraft in a straight- idea of the actual attitude, he or she will react to what the and-level attitude, the instructor pilot now executes, with a senses are saying. After a short time, the pilot will become relatively slow entry, a well coordinated turn of about 1.5 disoriented and the instructor pilot will tell the pilot to look positive G (approximately 50° bank) for 90°. While in the up and recover. This exercise allows the pilot to experience turn, without outside visual references and under the effect of the disorientation while flying the aircraft. the slight positive G, the usual illusion produced is that of a climb. Upon sensing the climb, the pilot should immediately Coping with Spatial Disorientation open the eyes to see that a slowly established, coordinated To prevent illusions and their potentially disastrous turn produces the same sensation as a climb. consequences, pilots can: Diving While Turning 1. Understand the causes of these illusions and remain Repeating the previous procedure, but with the pilot’s constantly alert for them. Take the opportunity to eyes should be kept closed until recovery from the turn is experience spatial disorientation illusions in a device, approximately one-half completed, can create the illusion of such as a Barany chair, a Vertigon, or a Virtual Reality diving while turning. Spatial Disorientation Demonstrator. 2. Always obtain and understand preflight weather Tilting to Right or Left briefings. While in a straight-and-level attitude, with the pilot’s eyes 3. Before flying in marginal visibility (less than 3 miles) closed, the instructor pilot executes a moderate or slight skid or where a visible horizon is not evident, such as flight to the left with wings level. This creates the illusion of the over open water during the night, obtain training and body being tilted to the right. maintain proficiency in aircraft control by reference to instruments. Reversal of Motion 4. Do not fly into adverse weather conditions or into This illusion can be demonstrated in any of the three planes dusk or darkness unless proficient in the use of flight of motion. While straight and level, with the pilot’s eyes instruments. If intending to fly at night, maintain closed, the instructor pilot smoothly and positively rolls the 17-9 night-flight currency and proficiency. Include cross- is. [Figure 17-7] The pilot who does not recognize this country and local operations at various airfields. illusion will fly a lower approach. Downsloping runways and downsloping approach terrain can have the opposite effect. 5. Ensure that when outside visual references are used, they are reliable, fixed points on the Earth’s surface. Featureless Terrain Illusion 6. Avoid sudden head movement, particularly during An absence of surrounding ground features, as in an takeoffs, turns, and approaches to landing. overwater approach over darkened areas or terrain made 7. Be physically tuned for flight into reduced visibility. featureless by snow, can create an illusion that the aircraft is Ensure proper rest, adequate diet, and, if flying at at a higher altitude than it actually is. This illusion, sometimes night, allow for night adaptation. Remember that referred to as the “black hole approach,” causes pilots to fly illness, medication, alcohol, fatigue, sleep loss, and a lower approach than is desired. mild hypoxia are likely to increase susceptibility to spatial disorientation. Water Refraction 8. Most importantly, become proficient in the use of Rain on the windscreen can create an illusion of being at a flight instruments and rely upon them. Trust the higher altitude due to the horizon appearing lower than it is. instruments and disregard your sensory perceptions. This can result in the pilot flying a lower approach. The sensations that lead to illusions during instrument Haze flight conditions are normal perceptions experienced by Atmospheric haze can create an illusion of being at a greater pilots. These undesirable sensations cannot be completely distance and height from the runway. As a result, the pilot prevented, but through training and awareness, pilots can has a tendency to be low on the approach. Conversely, ignore or suppress them by developing absolute reliance extremely clear air (clear bright conditions of a high attitude on the flight instruments. As pilots gain proficiency in airport) can give the pilot the illusion of being closer than instrument flying, they become less susceptible to these he or she actually is, resulting in a high approach that may illusions and their effects. result in an overshoot or go around. The diffusion of light due to water particles on the windshield can adversely affect Optical Illusions depth perception. The lights and terrain features normally Of the senses, vision is the most important for safe flight. used to gauge height during landing become less effective However, various terrain features and atmospheric conditions for the pilot. can create optical illusions. These illusions are primarily associated with landing. Since pilots must transition from Fog reliance on instruments to visual cues outside the flight Flying into fog can create an illusion of pitching up. Pilots deck for landing at the end of an instrument approach, it who do not recognize this illusion often steepen the approach is imperative that they be aware of the potential problems abruptly. associated with these illusions and take appropriate corrective action. The major illusions leading to landing errors are Ground Lighting Illusions described below. Lights along a straight path, such as a road or lights on moving trains, can be mistaken for runway and approach lights. Bright Runway Width Illusion runway and approach lighting systems, especially where A narrower-than-usual runway can create an illusion that the few lights illuminate the surrounding terrain, may create the aircraft is at a higher altitude than it actually is, especially illusion of less distance to the runway. The pilot who does when runway length-to-width relationships are comparable. not recognize this illusion will often fly a higher approach. [Figure 17-7] The pilot who does not recognize this illusion will fly a lower approach, with the risk of striking objects How To Prevent Landing Errors Due to Optical along the approach path or landing short. A wider-than- Illusions usual runway can have the opposite effect with the risk of To prevent these illusions and their potentially hazardous the pilot leveling out the aircraft high and landing hard or consequences, pilots can: overshooting the runway. 1. Anticipate the possibility of visual illusions during approaches to unfamiliar airports, particularly at night Runway and Terrain Slopes Illusion or in adverse weather conditions. Consult airport An upsloping runway, upsloping terrain, or both can create an illusion that the aircraft is at a higher altitude than it actually 17-10