Vision
Seeing is a practiced art. The eye sees images that may or may not be transmitted to the brain. The fovea of the retina is the region of sharpest vision. This is only one degree of conical field. By taping a quarter to a window and backing off slightly more than four feet you have measured your fovea vision. Our eye can move and see a vertical arc of 135 degrees, 60 above level and 75 below. Your horizontal field is 160 degrees total with 100 of these to the side and 60 across the nose.

With the best vision in the one-degree fovea cone, at 10 degrees your ability to see is only 1/10 as good. In poor visibility your foveal focus fades in less than 90 seconds to a point just in front of the aircraft. To avoid this it is important that you constantly re-focus your fovea on the most distant object available.

The eye has some functional peculiarities that are of particular importance to the pilot. The eye can see only about a 15-degree arc of space at one time. The eye cannot see while moving. The cone sensors of the eye are centered in the back of the eye. Cones give us color and sharp detail focus in bright light conditions. The rods of the eye are what we use to see in poor light conditions. The rods are to the sides of the eye and to best utilize them we must look slightly to the side of where we actually wish to see. A single flash of white light can destroy the ability of rods to function for over half an hour. The older you are the more time required to adapt to darkness. Red light is still the best light to use if you wish to retain night sight even though it is lacking in color and detail. The preferred color of the Military is now blue.

Objects that are farther away look smaller since they use less of your visual field. We know this because the brain must convert the two-dimensional vision field into three dimensions. This is possible because we have two eyes, which give us stereoscopic views. This binocular ability is good only for about twenty feet.

 Beyond twenty feet we must make use of other abilities. We have acquired a concept of perspective. This makes objects viewed appear to be near or far according to the vanishing lines of perspective. Also, objects that are near or far appear to move in opposite directions as we move. This can be shown by selecting an object across the street and another on your side of the street. As you move your head the objects move in opposite directions. 

The next element of vision has to do with your knowledge of relative size. We know the size of people, cars, most buildings and many airplanes. Their size in relation to other known objects makes it possible to judge distance.

–Vision is source of 80% of your total information
–Visibility--Contrast—movement—window post obstruction.
--You cannot see when moving your eyes, move your head and not your eyes.
--You have 100% vision only in 1-degree of your eye’s focal center.
--You have 20/100 vision in five-degrees of your focal center.
--You have 20/200 vision at 20-degrees of your focal center.
--It takes 10 second to spot, identify and react of what you see.
--If you have a window post where you are looking, your brain cannot correct, move your head.
--If you have nothing distant to see, your eyes will default and focus within 20 feet.
--Normal eyesight will let you detect an aircraft out to about four miles but only if you know where to look.
--A change in eye focus takes one to two seconds.
--Age increases the time required to change the focus of your eyes.
--Knowing where and how to look may compensate for all the other problems of seeing. MAY that is.
--The smoker is far less likely to detect aircraft due to always-present hypoxia.
--At night an aircraft must be much closer before being detected.
--If you look only ten-degrees to the side of an aircraft you will not see it until it is inside a mile.
--In my opinion any evasive maneuver should be up or down. Turning exposes too much airplane.

Where’s Your Balance?
--Whenever you distribute weight evenly so as to insure stability you have created balance.
–The combination of nervous system, muscles and brain form a feedback-loop that make the body system work.
–Orientation comes through vision, vestibular and somatosensory senses.
--Eyes see and inform the brain which give directions to the muscles by processing feedback from the eyes.
--Close your eyes and sound becomes an alternative but inferior system.
--The somatosensory sensory system in our muscles have proprioceptors that give position an movement data.
--The test of somatosensory balance is to close your eyes and touch your nose with one finger.
--Proprioception skills can be trained by musicians, athletes and pilots to give ‘muscle memory’.
--It is the vestibular senses that are the most sensitive balance system of all. the inner ear canals.
--The canals are on three axies, fluid filled with hairy sensors.
–The vestibular senses are those that make you dizzy, airsick and get vertigo.
--Age decreases balance skills. 1/3 of people over 65 fall every year.
--Balance skills can be practiced and improved. Stand on one foot when waiting in line is a start.

Proprioception
Proprioception is what we feel in our muscles. The most sensitive areas are in the neck and knees. Our muscle senses tell us the position of the body.

The vestibular sense is related to our hearing. The vestibular organ gives us balance. It has three semicircular canals which at 90-degrees; each with the others. Additionally, there are two otoliths, nearby. Otoliths are linear accelerometers or motion detectors. We sense gravity through our otoliths. These senses have threshold levels below which they are not able to detect any sensations. Of the two, the otoliths are the more sensitive. Our senses can be dangerously fooled but the vestibular sense is the one most susceptible. Even in VFR conditions we can get the 'leans' when the fluids of the semicircular canals fail to warn us of a slow turn or if a turn continues long enough the hairs in the fluid stabilize and give no sensory indications. A takeoff or climb can, if not countered by noting airspeed and the AI, be felt as an extreme raising of the nose which if countered by lowering the nose can result in an CFIT (Controlled Flight Into Terrain) accident. Reliance on your instruments is most important when you do not have visual cues.

Hearing
Humans detect from 16 to 20,000 Hz but speak between 250 and 2,0000 Hz. The sounds of most G.A. aircraft exceed 90 dB (decibels). Such sound energy is capable of actually breaking the hairs that connect to the cells in the cochlea of the inner ear. These hairs and cells are not replaceable.

Your Inner Ear
--Determines balance, orientation and equilibrium
--About pencil eraser size
--A 3 axis gyro with each canal at right angles to the others.
Canals are filled with fluid the flow of which affects bunches of sensory hairs (cilia) that are capable of sensing only rate changes in fluid acceleration. A steady change will cease to be sensed. Any gentle smooth turn or change below the threshold of inner ear perception will not be detected. If visual reference is obscured then disorientation can/will occur.

Head Cold
The head has eight sinuses paired across the face and extending back to the spinal column. Each cavity is filled with air. They all open to the nose. The air pressure of the cavities is constantly being equalized with the outside atmosphere. Additionally, the eardrum vibrates as sound moves the outside air. On the other side of the membrane the air is equalized by way of the Eustachian tube. For proper hearing the air on either side of the membrane must be equalized. Never take a decongestant that contains antihistamines at altitude. During ascent the air easily leaves the Eustachian tube, it is during descent that a collapsed tube can cause excruciating pain due to the unequal pressures. It is necessary to use a small muscle in the back of the throat to hold the Eustachian tubes open. A 5000' difference in the air pressures can rupture the drum. --You can open your Eustachian tubes by using the Valsava maneuver. Pinch your nostrils, close your mouth and try to exhale through the nose. This should clear your nose. 

--You could try the Frenzel method. This requires you to move your jaw as far forward as you can. Swallowing at the same time will improve your chances of clearing the tube.

Ear Block
Earblock or sinus blockages can cause differential air pressures to exist between cavities of the skull and the exterior. If it is not possible to equalize these pressures by slowing or removing the pressure changes severe pain results. Do not fly if you suspect such a condition exists or above 8,000' within 24 hours of scuba diving. Gum chewing and jaw movement are preventive. The Valsalva maneuver consists of opening the mouth wide with the jaw wide, as though yawning. Do this over and over because opening the mouth helps open the Eustachian tubes. Next, pinch your nose closed, shutting the mouth, and blow gently as through your nose.

How to Reduce Ear Pressure Pain
Blow air into your nose while holding the nostrils closed. Pinch low on your nostrils and blow gently. Be sure that your nose balloons out over your fingers. (Otherwise, blowing lifts your palate, blocking the Eustachian tube that you're trying to de-congest.) If pressure persists in one ear, turn your head, putting that ear forward (this relaxes the throat muscles that may be constricting the Eustachian tube) and blow. 

Continue To Next Page