Vision in Flight

Vision

Of all the senses, vision is the most important for safe flight. Most of the things perceived while flying are visual or heavily supplemented by vision. As remarkable and vital as it is, vision is subject to limitations. Two limitations are illusions and blind spots. The more a pilot understands about the eyes and how they function, the easier it is to use vision effectively and correct for potential problems.

The eye functions like a camera. Its structure includes an aperture, a lens, a mechanism for focusing, and a surface for registering images. Light enters through the cornea at the front of the eyeball, travels through the lens, and falls on the retina. The retina contains light sensitive cells that convert light energy into electrical impulses that travel through nerves to the brain. The brain interprets the electrical signals to form images. There are two kinds of light-sensitive cells in the eyes: rods and cones. 

The cones are responsible for all color vision, from appreciating a glorious sunset to discerning the subtle shades in a fine painting. Cones are present throughout the retina, but are concentrated toward the center of the field of vision at the back of the retina. There is a small pit, called the fovea, where almost all the light sensing cells are cones. This is the area where most “looking” occurs (the center of the visual field where detail, color sensitivity, and resolution are highest).

While the cones and their associated nerves are well suited to detecting fine detail and color in high light levels, the rods are better able to detect movement and provide vision in dim light. The rods are unable to discern color but are very sensitive at low light levels. The trouble with rods is that a large amount of light overwhelms them, and they take a long time to “reset” and readjust to a dim light environment. There are so many cones in the fovea that the very center of the visual field contains virtually no rods at all. In low light conditions the middle of the visual field is not very sensitive, but farther from the fovea, the rods are more numerous and provide the major portion of night vision.

The area where the optic nerve enters the eyeball has no rods or cones, leaving a blind spot in the field of vision. If an image falls on the "blind spot" the brain does not sense the image. Normally, each eye compensates for the other’s blind spot.  Cover the right eye and hold a page at arm’s length. Focus the left eye on the X on the right side of the windshield and notice what happens to the airplane while slowly bringing the page closer to the eye.

The importance of the blind spot and the physiological nature of the brain creates a dangerous potential for collisions between aircraft.

If a plane's image is focused on your you blind spot, and you don't effect a proper scan for aircraft in your vicinity, you will not see the aircraft you are about to collide with. the reason is easy. There aren't any nerve receptors for the image to stimulate.

If the image is not located on the area of the blind spot then another phenomenon of vision, and the nervous system, is the brain slowly "adjusts down" its reception of the image in the brain.

Think about eating a nice, pungent yellow onion. For the first few minutes the smell is overpowering. After a short period of time, you hardly notice the smell received from the onion by the olfactory sensors in your nasal epithelium. The first rush of impulses to the brain are fully analyzed as a strong onion odor. In a few minutes the brain decreases its interpretation of the impulses. You don't have the same harsh onion smell you first received.

Your vision reacts the same way. You receive the visual signals of a plane spotted in your field of vision but the brain reacts like it was never there. Not a good situation for collision avoidance.

I will continue to write about selected areas of sensory input to the brain for more interpretation.

Enjoy

"The Bends" - Altitude-Induced Decompression Sickness (DCS)

Decompression Sickness in Aircraft

Decompression sickness (DCS) describes a condition characterized by a variety of symptoms resulting from exposure to low barometric pressures. The low pressure allows inert gases (mainly nitrogen normally dissolved in body fluids and tissues) to come out of physical solution and form bubbles. Nitrogen is an inert gas normally stored throughout the human body (tissues and fluids) in physical solution. When the body is exposed to decreased barometric pressures (as in flying an unpressurized aircraft to altitude, or during a rapid decompression), the nitrogen dissolved in the body comes out of solution. If the nitrogen is forced to leave the solution too rapidly, bubbles form in different areas of the body, causing a variety of signs and symptoms. The most common symptom is joint pain, which is known as “the bends.”

What to do when altitude-induced DCS occurs:

• Put on oxygen mask immediately and switch the regulator to 100 percent oxygen.
• Begin an emergency descent and land as soon as possible.
• Upon landing seek medical assistance from an FAA medical officer, AME, military flight surgeon, or a hyperbaric medicine specialist. 
• Definitive medical treatment may involve the use of a hyperbaric chamber operated by specially trained personnel.
• Delayed signs and symptoms of altitude-induced DCS can occur after return to ground level regardless of presence during flight.

Even if the symptoms disappear during descent, land and seek medical evaluation while continuing to breathe oxygen. If one of the symptoms is joint pain, keep the affected area still; do not try to work pain out by moving the joint around.

Be aware that a physician not specialized in aviation or hypobaric medicine may not be familiar with this type of medical problem.

DCS After Scuba Diving

Scuba diving subjects the body to increased pressure, which allows more nitrogen to dissolve in body tissues and fluids. The reduction of atmospheric pressure that accompanies flying can produce physical problems for scuba divers. A pilot or passenger who intends to fly after scuba diving should allow the body sufficient time to rid itself of excess nitrogen absorbed during diving. If not, DCS due to evolved gas can occur during exposure to high altitude and create a serious inflight emergency.

The recommended waiting time before going to flight altitudes of up to 8,000 feet is at least 12 hours after diving that does not require controlled ascent (nondecompression stop diving), and at least 24 hours after diving that does require controlled ascent (decompression stop diving). The waiting time before going to flight altitudes above 8,000 feet should be at least 24 hours after any scuba dive. These recommended altitudes are actual flight altitudes above mean sea level (AMSL) and not pressurized cabin altitudes. This takes into consideration the risk of decompression of the aircraft during flight.

Drugs

Your performance is degraded by both prescription and over-the-counter medications. Drugs to treat medical conditions like tranquilizers, sedatives, strong pain relievers, and cough suppressants have primary effects. These include:

• Impair judgment
• Memory
• Alertness
• Coordination
• Vision
• Ability to make calculations.

These chemicals affect the same critical functions:

• Antihistamines
• Blood pressure drugs
• Muscle relaxants
• Agents to control diarrhea
• Motion sickness

Medications that depresses the nervous system like  sedatives, tranquilizers and antihistamines make you more susceptible to hypoxia.

You group painkillers into two broad categories: analgesics and anesthetics. Analgesics are drugs that reduce pain while anesthetics are drugs that deaden pain or cause loss of consciousness.

Over-the-counter analgesics like acetylsalicylic acid (aspirin), acetaminophen (Tylenol), and ibuprofen (Advil) have few side effects when you take them in the correct dosage.

Flying restrictions for some people that are allergic to certain analgesics or may suffer from stomach irritation are not restricted when taking these drugs. 

Restrictions are in place for flying while using the prescription analgesics listed below:

• Propoxyphene (e.g., Darvon)
• Oxycodone (e.g., Percodan)
• Meperidine (e.g., Demerol)
• Codeine

Drugs
These drugs are known to cause side effects like mental confusion, dizziness, headaches, nausea and vision problems.

You use anesthetic drugs for dental and surgical procedures. These local anesthetics wear off within a short period of time. The anesthetic itself may not limit flying as much as the actual procedure and subsequent pain.

Stimulants drugs excite the central nervous system and produce an increase in alertness and activity. 

Amphetamines, caffeine, and nicotine are all forms of stimulants. Common uses of these drugs include appetite suppression, fatigue reduction, and mood elevation. Some drugs cause a stimulant reaction even though this reaction is not their primary function. In some cases stimulants produce anxiety and mood swings, both of which are dangerous when flying.

Depressants drugs reduce your body’s functioning in many areas. These drugs:

• Lower blood pressure
• Reduce mental processing
• Slow motor responses
• Slow reaction responses.

Depressants act on your body to slow it down. These include  tranquilizers, motion sickness medication, some types of stomach medication, decongestants and antihistamines. The most common depressant is alcohol. Some drugs that are classified as neither stimulants nor depressants have adverse effects on flying. 

Some antibiotics produce dangerous side effects that include balance disorders, hearing loss, nausea and vomiting. While many antibiotics are safe for use while flying, the infection requiring the antibiotic may prohibit flying. In addition, unless specifically prescribed by a physician, do not take more than one drug at a time and never mix drugs with alcohol. The effects on you are often unpredictable.

The known dangers of illegal drugs  are well documented. Certain illegal drugs can have hallucinatory effects that occur days or weeks after the drug is taken. Obviously, these drugs have no place in the aviation community.

Clipped Wing 1946 Piper Cub

Nostalgia

Another plane that dropped like a "Rock." It was modified! Had a 90 hp Continental and was certified for aerobatics. The wingspan was a Lippert-Reed modification. The clipped wing original Cub was like the tricycle-landing gear version that came out much later.  A modification that wasn't allowed was the fuel system. In the wing was a fuel tank reserve that was connected to the "cork gauge" fuel tank by a fuel line. When you wanted an hour or two more of great flying just open the fuel valve and wait until a little fuel splashed on the windshield.  Now, isn't that a great way to catch a little more flying?

Needless to say I never knew that modification existed. Someone else discovered it on a routine servicing. Lucky for me the cork fuel gauge was only an inch or two from the windshield and the fuel evaporated quickly.

Since I was not qualified for aerobatics I wasn't sure how the modified fuel system worked in unusual attitudes.

Dawn patrols! Wonderful. Open up the doors to let the air rush thru and the smell of fresh hay sifting up to tantalize your thoughts of days long gone. The slow leisurely pace of the little Cub made a perfect perch to spot a farmers grass strip and the chance discovery what treasure was hidden in the overgrown hanger. Pilots being pilots spin wonderful stories, over a cup of Joe (wonder where I got the idea for a Blog?) When you drop in, so to speak, to talk with the farmer in person.

Flying at five hundred feet you sense so much more than a Bonanza at cruise at altitude. Its a barnstorming experience. Its a happening! God Bless the Antique Air shows. 

Work hard to preserve an age that would quickly disappear if not for the wonderful restorations of beautiful aircraft.

The EAA is commended for their outstanding contributions to aviation. Unique, well thought out plans for a lifetime dream coming true. What an experience.

I was lucky enough to be a small part of that experience when Bob Nichols, the Manager of the Gaylord, Michigan Otsego County Airport, introduced me to the art of recovering the fabric on a Cub.

Flying took on a brand new feel for me. "Keep em flying" has a new meaning when you are a part of that experience.

Alcohol

Alcohol

Alcohol impairs your bodies efficiency. Studies  prove that drinking and performance deterioration are closely linked. You make hundreds of decisions, some of them time-critical, during the course of a flight. The safe outcome of any flight depends on you to make the correct decisions and take the appropriate actions during routine occurrences, as well as abnormal situations.

The influence of alcohol drastically reduces the chances of completing a flight without incident. In small amounts, alcohol can:

•  impair judgment
•  decrease sense of responsibility 
• affect coordination
•  constrict vision 
• diminish your memory 
• reduce reasoning power 
• lowers attention span 

One ounce of alcohol can:

•  decrease the speed and strength of muscular reflexes
•  lessen the efficiency of eye movements while reading
•  increase the frequency at which errors are committed

Impairments in vision and hearing occur at alcohol blood levels as little as one drink. The alcohol you consume in beer and mixed drinks is ethyl alcohol, a central nervous system depressant. From a medical point of view, it acts on your body much like a general anesthetic. The “dose” is generally much lower and more slowly consumed in the case of alcohol, but the basic effects on your body are similar. Alcohol is easily and quickly absorbed by the digestive tract. The bloodstream absorbs about 80 to 90 percent of the alcohol in a drink within 30 minutes when ingested on an empty stomach. Your body requires about 3 hours to rid itself from alcohol contained in one mixed drink or one beer.

When you experience a hangover, your still under the influence of alcohol. Although you think you're functioning normally, the impairment of motor and mental response is still present. Considerable amounts of alcohol can remain in you for over 16 hours, so pilots should be cautious about flying too soon after drinking.

Altitude multiplies the effects of alcohol on the brain. When combined with altitude, the alcohol from two drinks may have the same effect as three or four drinks. Alcohol affects your brain’s ability to utilize oxygen. It produces a form of histotoxic hypoxia. The effects are rapid because alcohol passes quickly into the bloodstream. In addition, your brain is a highly vascular organ that is immediately sensitive to changes in the blood’s composition. For you, the lower oxygen availability at altitude and the lower capability of the brain to use what oxygen is there, add up to a deadly combination.

You determine intoxication by the amount of alcohol in the bloodstream. You measure it as a percentage, by weight, in the blood. Flying an aircraft requires that blood alcohol level be less than .04 percent and, to pilot an aircraft, 8 hours must pass between that drink and flying an airplane. A pilot with a blood alcohol level of .04 percent or greater after 8 hours cannot fly until the blood alcohol falls below that amount. Even though blood alcohol may be well below .04 percent, a pilot cannot fly sooner than 8 hours after drinking alcohol. Although the regulations are quite specific, it is a good idea to be more conservative than the regulations.

"Stay away from the bottle when you want to hit the throttle" is a good slogan to remember.

One point indicates altitude contributes to the effect of alcohol. Lowered oxygen partial pressure from high altitudes affects other body system functions that lead to visual illusions and other phenomenon that are not pleasant experiences.

Dehydration and Heatstroke

Dehydration

A critical loss of water from the body is dehydration. Causes of dehydration are hot flight decks, flight lines, wind, humidity, and diuretic drinks. Coffee, tea, alcohol, and caffeinated soft drinks fall into the category of diuretic drinks.. 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 for long periods in hot summer temperatures or at high altitudes increases the susceptibility to dehydration. The conditions above increase the rate of water loss from the body.

To help prevent dehydration, drink two to four quarts of water every 24 hours. Since each person is physiologically different, this is only a guide. Most people are aware of the eight-glasses-a-day guide. If each glass of water is eight ounces, this equates to 64 ounces, which is two quarts. If you don't replace the fluid the fatigue progresses to dizziness, weakness, nausea, tingling of hands and feet, abdominal cramps, and extreme thirst.

Hot weather, like this summer, requires vigilance for the symptoms ofdehydration . 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 will turn 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—not relying on the thirst sensation as an alarm. If plain water is offensive, 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

Your inability to control body temperature is heatstroke.   You can recognize the onset of heatstroke by the symptoms of dehydration. Complete collapse of your heat control efforts can occur without warning.

Carry an ample supply of water to prevent these symptoms. Use the water at frequent intervals on, long flight, whether thirsty or not. The body normally absorbs water at the 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. If your aircraft has a canopy or roof window then wearing light-colored, porous clothing and a hat will help provide protection from the sun. 

Keeping the flight deck well ventilated aids in dissipating excess heat. Phoenix, Arizona warns newcomers to stop frequently to drink water. Numerous drinking fountains are strategically placed to encourage you to drink. In very hot and arid conditions you lose water quickly and heatstroke is a constant danger. Same thing occurs in your plane.

Fatigue

Fatigue

Fatigue is frequently associated with pilot error. Some of the effects of fatigue include loss of attentiveness 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.

Like stress, fatigue falls into two broad categories: acute and chronic. 

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

Sustained psychological stress increases the glandular secretions that prepare the body for quick reactions during an emergency. These secretions make the circulatory and respiratory systems work harder, and the liver releases energy to provide the extra fuel needed for brain and muscle work. When this reserve energy supply is depleted, the body lapses into generalized and severe fatigue.

Acute fatigue can be prevented by proper diet and adequate rest and sleep. A well-balanced diet prevents the body from the need to consume its own tissues as an energy source. 

Adequate rest maintains the body’s store of vital energy.

Chronic fatigue, that extends over a long period of time, usually has psychological roots. Underlying disease is sometimes responsible. Continuous high stress levels produce chronic fatigue. Chronic fatigue is not relieved by proper diet, adequate rest and sleep. Chronic fatigue 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 with generalized aches and pains throughout the body. When the condition becomes serious enough, it leads to emotional illness.

If you suffer from acute fatigue, stay on the ground. If fatigue occurs in the flight deck, no amount of training or experience can overcome the detrimental effects. Getting adequate rest is the only way to prevent fatigue from occurring. Avoid flying without a full night’s rest, after working excessive hours, or after an especially exhausting or stressful day. Pilots who suspect they are suffering from chronic fatigue should consult a physician.

Stress

Stress

Stress is the body’s response to physical and psychological demands. Your 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 from stress. Use the term “stressor” 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 (short term) and chronic (long term). Acute stress involves an immediate threat you perceive as danger. This is the 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.

You define chronic stress as a level of stress that presents an intolerable burden, exceeds the ability of an individual to cope and causes individuals performance to fall sharply. 

Continuous psychological pressures, like loneliness, work, financial worries and relationships problems  produce a cumulative level of stress which 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.

Motion Sickness

Motion Sickness

The sensation of airsickness results from the brain receiving conflicting messages about the state of your body. A pilot may experience motion sickness during initial flights, but it generally goes away within the first few lessons. 

Anxiety and stress, which you experience at the beginning of flight training contributes to motion sickness. Symptoms of motion sickness include discomfort, nausea, dizziness, paleness, sweating, and vomiting. Avoid these physiological symptoms if possible. It is important to remember that experiencing airsickness is no reflection on one’s ability as a pilot. If you're prone to motion sickness let the flight instructor know. There are techniques you can use to overcome this problem. 

For example, avoid lessons in turbulent conditions until becoming more comfortable in the aircraft. Start with shorter flights and graduate to longer instruction periods. If you experience symptoms of motion sickness during a lesson, open the fresh air vents. Focus on objects outside the airplane. Avoid unnecessary head movements. These may  alleviate some of the discomfort.

Medications like Dramamine can prevent airsickness in passengers. Dramamine causes drowsiness and other symptoms. Avoid this drug if you are the pilot. 

More Illusions During Instrument Flight

Instrument Flight Illusions

The sensations that lead to illusions during instrument flight conditions are normal perceptions experienced by pilots. 

These undesirable sensations cannot be completely prevented, but through training and awareness, pilots can ignore or suppress them by developing absolute reliance on the flight instruments.

As pilots gain proficiency in instrument flying, they become less susceptible to these illusions and their effects.

Optical Illusions

Of the senses, vision is the most important for safe flight. However, various terrain features and atmospheric conditions can create optical illusions. These illusions are primarily associated with landing. Since pilots must transition from reliance on instruments to visual cues outside the flight deck for landing at the end of an instrument approach, it is imperative they be aware of the potential problems associated with these illusions, and take appropriate corrective action. The major illusions leading to landing errors are described below.

Runway Width Illusion

A narrower-than-usual runway can create an illusion the aircraft is at a higher altitude than it actually is, especially when runway length-to-width relationships are comparable.  The pilot who does not recognize this illusion will fly a lower approach, with the risk of striking objects along the approach path or landing short.

 A wider-than-usual runway can have the opposite effect, with the risk of the pilot leveling out the aircraft high and landing hard, or overshooting the runway.

Runway and Terrain Slopes Illusion

An upsloping runway, upsloping terrain, or both, can create an illusion that the aircraft is at a higher altitude than it actually is. The pilot who does not recognize this illusion will fly a lower approach. Downsloping runways and downsloping approach terrain can have the opposite effect.

Featureless Terrain Illusion

An absence of surrounding ground features, as in an over water approach, over darkened areas, or terrain made featureless by snow, can create an illusion the aircraft is at a higher altitude than it actually is. This illusion, sometimes referred to as the “black hole approach,” causes pilots to fly a lower approach than is desired.

Water Refraction

Rain on the windscreen can create an illusion of being at a higher altitude due to the horizon appearing lower than it is. This can result in the pilot flying a lower approach. 

Haze

Atmospheric haze can create an illusion of being at a greater distance and height from the runway. As a result, the pilot will have a tendency to be low on the approach.

Bright Clear Air

Conversely, extremely clear air (clear bright conditions of a high attitude airport) can give the pilot the illusion of being closer than he or she actually is, resulting in a high approach, which may result in an overshoot or go around. 

Diffusion of Light

The diffusion of light due to water particles on the windshield can adversely affect depth perception. The lights and terrain features normally used to gauge height during landing become less effective for the pilot.

Fog

Flying into fog can create an illusion of pitching up. Pilots who do not recognize this illusion will often steepen the approach quite abruptly.

Ground Lighting Illusions

Lights along a straight path, such as a road or lights on moving trains, can be mistaken for runway and approach lights. Bright runway and approach lighting systems, especially where few lights illuminate the surrounding terrain, may create the illusion of less distance to the runway. The pilot who does not recognize this illusion will often fly a higher approach.

Safety factors in flight depend on recognizing and avoiding these illusions before they disorient you.

What to Expect from Unusual Attitudes in Flying

Unusual Attitudes in Flight

Climbing While Accelerating

With your eyes closed, the instructor pilot maintains approach airspeed in a straight-and-level attitude for several seconds, then accelerates while maintaining straight-and-level attitude. The usual illusion during this maneuver, without visual references, is that the aircraft is climbing.

Climbing While Turning

With your eyes still closed and the aircraft in a straight-and-level attitude, the instructor pilot now executes, with a relatively slow entry, a well coordinated turn of about 1.5 positive G (approximately 50° bank) for 90°. While in the turn, without outside visual references and under the effect of the slight positive G, the usual illusion produced is that of a climb. Upon sensing the climb, you should immediately open your eyes to see that a slowly established, coordinated turn produces the same sensation as a climb.

Diving While Turning

Repeating the previous procedure, except your eyes should be kept closed until recovery from the turn is approximately one-half completed, can create the illusion of diving while turning.

Tilting to Right or Left

While in a straight-and-level attitude, with your eyes closed, the instructor pilot executes a moderate or slight skid to the left with wings level. This creates the illusion of the body being tilted to the right.

Reversal of Motion

This illusion demonstrates any of the three planes of motion. While straight and level, with the your eyes closed, the instructor pilot smoothly and positively rolls the aircraft to approximately 45° bank attitude while maintaining heading and pitch attitude. This creates the illusion of a strong sense of rotation in the opposite direction. After this illusion is noted, you should open your eyes and observe that the aircraft is in a banked attitude.

Diving or Rolling Beyond the Vertical Plane

This maneuver may produce extreme disorientation. While in straight-and-level flight, you should sit normally, either with eyes closed or gaze lowered to the floor. The instructor pilot starts a positive, coordinated roll toward a 30° or 40° angle of bank. As this is in progress, you tilt your head forward, look to the right or left, then immediately returns his or her head to an upright position. The instructor pilot should time the maneuver so the roll is stopped as you return your head upright. An intense disorientation is usually produced by this maneuver, and you experiences the sensation of falling downward into the direction of the roll. After a short time, you will become disoriented and the instructor pilot then tells the pilot to look up and recover.

The benefit of this exercise is that the pilot experiences the disorientation while flying the aircraft.

In the descriptions of these maneuvers, the instructor pilot is doing the flying, but having you do the flying can also be a very effective demonstration. You should close your eyes and tilt the head to one side. The instructor pilot tells you what control inputs to perform. The pilot then attempts to establish the correct attitude or control input with eyes closed and head tilted. While it is clear you have no idea of the actual attitude, you will react to what the senses are saying. 

This makes you experience your actual sensations to the unusual attitude your instructor created and made it possible to see what the actual attitude your plane was flying.

Postural Considerations - "Seat of Pants" Sensations

Posture Signals to Flight Attitude

Your skin, joints and muscles all send signals to the brain that interpret them with respect to the Earth's gravitational pull. This updating is on a constant basis.

The "Seat of the pants" flying is dependent upon these signals. The gravitational signals, along with the input from visual and vestibular clues, give a fairly reliable attitude position of your plane. 

If visual input is impaired from the deterioration of flying conditions the present of illusions is magnified. Instrument training is vital to overcome the false attitudes formed from the illusions.

However, because of the forces acting upon the body in certain flight situations, many false sensations can occur due to acceleration forces overpowering gravity. 

These situations include uncoordinated turns, climbing turns, and turbulence. Be aware of how you may react when faced with unusual flying conditions.

If you enjoy roller-coasters, you can experience acceleration forces that overpower gravity in a variety of unusual attitudes of your body. 

Somatogravic Illusion

Somatogravic Illusions

The otolith organs respond to acceleration situations while flying. A rapid tilting of your head backward will stimulate the otolith organ. 

A rapid takeoff acceleration stimulates the otolith organ and creates the  "nose up" somatogravic illusion. In situations with limited visual references, the disoriented pilot may push the airplane into a "nose-down" or "dive" attitude.

In takeoff mode you may inadvertently crash into the runway before you recognize the illusion. If you know your plane and expect the illusion, especially with a high performance plane, it may prevent such an accident.

A rapid deceleration by the quick reduction of the throttle(s) can have the opposite effect. The disoriented pilot may pull the plane into a nose-up or stall attitude.

A more pronounced deceleration may occur when reverse thrusters are powered up, after landing a commercial jet, with moderate braking applied simultaneously. If you are a passenger you may feel this illusion from the safety of your seat.

Another situation that causes deceleration is lowering the landing gear or deploying flaps.

For Instructors - Demonstration of Spatial Disorientation

Spatial Disorientation

Writing about and just reading about spatial disorientation is difficult to understand. Instructors are excellent resources to demonstrate, for their students, what to expect.

There are several instructor controlled aircraft attitudes that demonstrate spatial disorientation. The flight attitudes are designed to create a specific illusion. The teaching point is experiencing a false attitude that demonstrates disorientation.  

There are a number of controlled aircraft maneuvers a pilot can perform to experiment with spatial disorientation. While each maneuver will normally create a specific illusion, any false sensation is an effective demonstration of disorientation.

One example that involves no detection of change is the "death spiral." Trying to convince a pilot that he is indeed in a steep turn is nearly impossible. We are unable to detect a bank or roll after a few seconds. More information on the "spiral" later. 

Why demonstrate these controlled attitudes for students?

1. They teach you to understand how the human system reacts to spatial disorientation.

2. They demonstrate that judgments of aircraft attitude based on bodily sensations are frequently false.

3. They help lessen the visual illusion that caused your disorientation. It gives you a better understanding of the relationship between aircraft motion and head movements that results in disorientation.

4. They instill, in you, more confidence in relying on your flight instruments for assessing true aircraft attitude.

You should not attempt any of these maneuvers at low altitudes, or in the absence of an instructor pilot or an appropriate safety pilot.

Each staged maneuver illustrates illusions that may cause loss of control. Use common sense. Have a well trained instructor as a passenger.

Spatial Disorientation and Illusions

Spatial Disorientation - Attitude Illusions

Spatial disorientation occurs when your orientation differs with regard to the actual position, attitude, or movement of your airplane in space. 

Your body uses three systems, working together, to ascertain orientation and movement in space. They are, respectively:

• Vestibular system—organs found in the inner ear that sense your position by the way you are balanced.

• Somatosensory system—the nerves in your skin, muscles, and joints, which, along with hearing, sense position based on gravity, feeling, and sound.

• Visual system—your eyes, which sense position based on what you see.

All this information comes together in the brain and, most of the time, the three streams of information give you a clear idea of where and how your body is moving. 

Flying may cause these systems to supply conflicting information to your brain, which can lead to disorientation.

During flight in VFR conditions, your eyes are the major orientation source and usually take preference over false sensations from your other sensory systems. When these visual cues are removed, as they are in instrument conditions, false sensations can cause you to quickly become disoriented.

The vestibular system in the inner ear allows you to sense movement and determine orientation in the surrounding environment. It is like a gyroscope in the way it maintains it's orientation.

In both the left and right inner ear, three semicircular canals are positioned at approximate right angles to each other.

Each canal is filled with fluid and has a section full of fine hairs. Accelerated motion of the inner ear in any direction causes the tiny hairs to deflect, which in turn stimulates nerve impulses, sending messages to the brain. The vestibular nerve transmits the impulses from the utricle, saccule, and semicircular canals to the brain to interpret motion.

The somatosensory system sends signals from the skin, joints, and muscles to the brain that you interpret in relation to the Earth’s gravitational pull. These signals determine your posture.

Inputs from each movement update your body’s position to the brain on a constant basis. “Seat of the pants” flying is largely dependent upon these signals. Used in conjunction with visual and vestibular clues, these sensations can be fairly reliable. 

However, your body cannot distinguish between acceleration forces due to gravity and those resulting from maneuvering the aircraft which leads you to  to sensory illusions and false impressions of an aircraft’s actual orientation and movement. 

Under normal flight conditions, when there is a visual reference to the horizon and ground, the sensory system in the inner ear helps you to identify the pitch, roll, and yaw movements of the aircraft. Think of how the walls of a room and the ceiling meet at a specific corner of the room. The two walls are pitch and roll. The ceiling represents the yaw.

When you lose visual contact with the horizon , your vestibular system becomes unreliable. Without visual references outside the aircraft, there are many situations in which combinations of normal motions and forces create convincing illusions that you find difficult to overcome.

Prevention is usually the best remedy for spatial disorientation. Unless you have many hours of training in instrument flight, flight should be avoided in reduced visibility or at night when the horizon is not visible.

You can reduce susceptibility to disorienting illusions through training and awareness. Instrument training is the key to avoid the temptations offered by illusions. You learn to rely totally on flight instruments.

Revisiting Medical Certification for Pilots

Medical Certification

First up is a valid medical certificate. You need this to obtain an airman certificate. Glider and free balloon pilots are not required to hold a medical certificate. If your a sport pilot you can hold either a medical certificate or a valid state drivers license.

To qualify for a medical certificate requires an examination by an aviation medical examiner (AME), who is trained in aviation medicine designated by the Civil Aerospace Medical Institute (CAMI).

There are three classes of medical certificates. Which one you have to qualify for depends on the type of flying the pilot plans to do.

Starting from the simplest to the more complex certificate, the first is a third-class medical certificate. It is required for a private or recreational pilot certificate. It is valid for three years (3) for those pilots under the age of forty (40). For those over forty (40) the certificate is valid for two (2) years.

A commercial pilot requires at least a second-class medical certificate which is valid for one (1) year

A first-class medical certificate is required for airline transport pilots and are valid for six (6) months. 

The standards are tougher for the higher classes of certificates. A pilot with a higher class medical certificate has met the requirements for the lower classes as well.

Since the required medical class applies only when exercising the privileges of the pilot certificate for which it is required, a first-class medical certificate would be valid for 1 year if exercising the privileges of a commercial certificate, and 2 or 3 years, as appropriate, for exercising the privileges of a private or recreational certificate. The same applies for a second-class medical certificate.  

The standards for medical certification are contained in Title 14 of the Code of Federal Regulations (14 CFR) part 67 and the requirements for obtaining medical certificates can be found in 14 CFR part 61.

Students who have physical limitations, such as impaired vision, loss of a limb, or hearing impairment may be issued a medical certificate valid for “student pilot privileges only” while learning to fly. 

Pilots with disabilities may require special equipment installed in the aircraft, such as hand controls for pilots with paraplegia. Some disabilities necessitate a limitation on the individual’s certificate; for example, impaired hearing would require the limitation “not valid for flight requiring the use of radio.” When all the knowledge, experience, and proficiency requirements have been met and a student can demonstrate the ability to operate the aircraft with the normal level of safety, a “statement of demonstrated ability” (SODA) can be issued. This waiver, or SODA, is valid as long as the physical impairment does not worsen. Contact the local Flight Standards District Office (FSDO) for more information on this subject.

Pilot certification is important, for obvious reasons, and you should know the qualifications and limitations for the certificate you need.

Middle Ear and Sinus Problems in Flying

Middle Ear and Sinus Problems in Flying

During climbs and descents, the air in our closed cavities expands or contracts due to a difference between the pressure of the air outside the body and that of the air inside the body. 

If the air expands pressure builds up within the cavity and pain is experienced if it can't escape. Trapped gas expansion accounts for ear and sinus pain, as well as a temporary reduction in the ability to hear.

The physical ear consists of an outer conical shaped structure called external pinna. A middle chamber, that connects to the outside atmosphere, and the inner ear. 

The middle and inner ear are located in a small cavity in the bone of the skull. The tympanic membrane separates the outer ear and middle ear. The Eustachian tube connects the middle ear to the outside atmosphere. Pressure differences between the middle ear and the outside atmosphere are equalized by the Eustachian tube.There is a right and left Eustachian tube. They are normally shut but they open during chewing, yawning or swallowing to equalize the pressure.

A slight difference in external pressure and middle ear pressure can cause discomfort.

During a climb, middle ear air pressure may exceed the pressure of the air in the external ear canal, causing the eardrum to bulge outward. Pilots become aware of this pressure change when they experience alternate sensations of “fullness” and “clearing.”

 During descent, the reverse happens. While the pressure of the air in the external ear canal increases, the middle ear cavity, which equalized with the lower pressure at altitude, is at a lower pressure than the external ear canal. This results in the higher outside pressure, causing the eardrum to bulge inward.

This condition can be more difficult to relieve where the partial vacuum tends to constrict the walls of the Eustachian tube. To remedy this often painful condition, which also causes a temporary reduction in hearing sensitivity, pinch the nostrils shut, close the mouth and lips, and blow slowly and gently in the mouth and nose.

This procedure forces air through the Eustachian tube into the middle ear. It may not be possible to equalize the pressure in the ears if a pilot has a cold, an ear infection, or sore throat. A flight in this condition can be extremely painful, as well as damaging to the eardrums.

If experiencing minor congestion, nose drops or nasal sprays may reduce the risk of a painful ear blockage. Before using any medication, check with an AME to ensure that it will not affect the ability to fly.

In a similar way, air pressure in the sinuses equalizes with the pressure in the flight deck through small openings that connect the sinuses to the nasal passages. An upper respiratory infection, such as a cold or sinusitis, or a nasal allergic condition can produce enough congestion around an opening to slow equalization. As the difference in pressure between the sinuses and the flight deck increases, congestion may plug the opening. This “sinus block” occurs most frequently during descent. Slow descent rates can reduce the associated pain. A sinus block can occur in the frontal sinuses, located above each eyebrow, or in the maxillary sinuses, located in each upper cheek. It will usually produce excruciating pain over the sinus area. A maxillary sinus block can also make the upper teeth ache. Bloody mucus may discharge from the nasal passages.

Sinus block can be avoided by not flying with an upper respiratory infection or nasal allergic condition. Adequate protection is usually not provided by decongestant sprays or drops to reduce congestion around the sinus openings. Oral decongestants have side effects that can impair pilot performance. If a sinus block does not clear shortly after landing, a physician should be consulted.

Travelers on commercial planes, where pressurization is set at 6,000 feet, may experience pain if the passageways are blocked before takeoff.  Techniques described above, if not illegal, can alleviate the expected difficulty before takeoff.