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Welcome!
This FAQ is a collection of aviation safety articles which I feel are of particular interest to sailplane pilots. A wide range of topics are covered. Any additions or corrections would be appreciated.
This article is Copyright (c) 1994, 1995, 1996 by Michael Steckner. It may be freely distributed in its entirety provided that this copyright notice is not removed. It may not be sold for profit nor incorporated in commercial documents without the author's written permission. This article is provided "as is" without express or implied warranty.
I would like to thank the following people who took the time to send me their comments. Many of them contributed substantial material for this FAQ. Some contributed unknowingly, as I lifted their posts directly from the newsgroup, obtained them from summaries kept by other people, or lifted them out of mailing lists.
Guy Ford Byars, Gosta Arvastson, Noel Matthews, Judah Milgram, Ronnie Moore, Ian Oldaker, Ake Pettersson, John Roake.
Special thanks to the Aviation Safety Institute, publishers of Monitor, for allowing me to reproduce several of their safety articles.
Special thanks to the Flight Training & Safety Committee of SAC (Soaring Association of Canada) and the Chairman, Ian Oldaker, for making the Safety Audit program document available.
I would like to thank John Leibacher for his assistance in producing the html formatted version of this FAQ.
Editor: Michael Steckner Mail address: 418 Eagle Trace Mayfield Heights,
OH 44124 USA Internet: mks@gwis.com
LIGHT POLARIZATION AND SUNGLASSES FOR
PILOTS
From the internet
NEW
FLYING AND DRUGS
New Zealand Gliding Kiwi (Original from Free Flight #3/1993 - Dr Peter
Perry)
Perhaps the key ingredient to an adequate scan is an expectation of danger. The best trained scanners are almost always ex-military pilots who have flown in war zones and lived with an anticipation of hostile aircraft attacks. They know only too well how important it is to see others in time to deal with them successfully. Civilian pilots are more likely to grow up with the "Big Friendly Sky" attitude which says, in effect: "There's tons and tons of airspace out there. How unlikely it is that two little airplanes are going to occupy the some blob of space at the same time!"
What we see is largely what we expect to see.
The human eye is a marvellous instrument, but it is not built like a radar, or even exactly like a camera. Our eyes can observe about a 200 degree arc of the horizon at one glance, but not everything we see will be sharp. In contrast to the camera, which can present all objects that lie within a 10 to 15 degree arc. That is because only a small area at the back of the eye, the fovea, is capable of sending sharp images to the brain. Any image that is not processed directly through the fovea will be blurred.
For example, an airplane that we can see distinctly with the foveal centre at seven miles would have to be as close as 7/10 of a mile in order to be recognized, if the angle of sight caused the image to reach the eye just out- side of the fovea. Hence the first rule of scanning is to examine relatively small blocks of airspace successively -- not all at once.
Another important fact is that it takes some time, as much as several minutes, for our eyes to adjust to the light level outside after a period of studying the instrument panel -- just as, conversely, it takes several minutes for us to adapt to a dimly lit room after having been in full daylight. For that reason bobbing your head in and out of the cockpit does not make for effective scanning. Since we are usually familiar with the instrument panel and we know what is there and what to look for, it is possible with some practice to keep the keep panel gauges and instruments within peripheral view while scanning through the windshield. In any event an exclusive panel scan, important as it is, may be accomplished in a much shorter time than an external scan.
Most experienced (and attentive) pilots can sense changes in the aircraft operation -- such as loss or gain of airspeed, pitch angle changes, etc. -- by means of feeling or sound. This minimizes the number of gauges or instruments that have to be monitored routinely. Ideally a pilot should spend only about one minute looking inside the cockpit for every three or four minutes he is looking outside.
Window panes or windshields obscured with dirt or bug stains make it difficult to scan the adjacent airspace, because our eyes tend naturally to focus on what is close at hand.
Forcing yourself to ignore the windshield distractions and scan beyond them puts a strain on your eyes which may weaken their effectiveness at distance. Cleaning the windows may seem like a rather menial job for a pilot, but if it has not been done before you get into the cockpit and you take off as is, you are burdening your vision unnecessarily.
A different sort of problem occurs when your field of vision contains no distinctive objects, such as during a flight above a cloud layer, or in haze. With nothing of apparent interest to see, your eyes tend to relax and come to rest at a comfortable focal distance of about 15 to 20 feet. This kind of near- sightedness, Or "empty field myopia," as it is formally called, is a dangerous substitute for active scanning. It also probably explains the frequent statement of crewmen following a near midair collision ". . . the plane suddenly materialized out of a clear blue sky." Chances are that the airplane was visible in the distance long before the observer's eyes focused upon it.
To scan apparently empty airspace effectively you have to direct your eyes to move in a slow deliberate pattern. Some pilots like to start at the upper left hand corner of a selected area or block of space and scan left to right, then down, right to left, and back up to the starting point. Then on to the ad- joining block with the same pattern, until the scan is complete. In time, as you learn to control your eye movements, you will see more and more objects that you missed earlier. It is something like looking for a dropped contact lens on a rug: if you examine the rug, imaginary square by square, you stand a much better chance of finding your lost lens than if you just stare at the entire floor covering. Incidently this system also works well for looking over "checkerboard" or mottled terrain that tends to camouflage aircraft.
There is no special scanning technique that works magic; you simply find one that you are comfortable with. Because we are in the habit of absorbing so much information from left to right this kind of motion seems to produce good eye-to-brain teamwork.
After each complete sweep, spend a few seconds looking over the instruments or charts, then resume scanning. Think of it not as a chore to be carried out periodically but as a continuous, ongoing flight activity that you can perform while talking on the radio, making conversation, maneuvering the airplane, drinking coffee, etc. Eventually you may become so accustomed to it that you will feel ill at ease when you are not scanning.
Then you will have the makings of a safe pilot.
WHAT YOU SEE IS NOT ALWAYS WHAT YOU GET (c)
[Reprinted with the kind permission of the Aviation Safety Institute]
This article is taken from the U.S. Naval Safety Center's publication called APPROACH -- February 1983, pp. 12-14. The article was written by Dr. R.A. Alkov of the Naval Safety Center (with the cooperation of Dr. Stanley Roscoe, New Mexico State University).
Although you will see liberal reference to Navy activities and some Navy terminology we felt that this article should be made available to you. Our special thanks to Admiral T.C. Steele, Commander of NSC, for granting us permission to reprint APPROACH articles.
[Edited for Safety FAQ]
Research conducted by Dr. Stanley Roscoe of New Mexico State University and others, notably Dr. Robert Randle of the NASA-Ames Research Center and Dr. Herschel Leibowitz and his students at Penn State, has provided some answers to these questions. To understand the mechanisms involved, let's quickly review the physiology of visual accommodation--the focusing of the eye.
The lens of the eye is elastic and changes its curvature to focus at different distances under the control of the ciliary muscle. This is known as the accommodation of the lens. It was once believed that relaxation of the ciliary muscle caused the eye to focus at optical infinity. We now know it focuses at a relatively short distance when at rest, although this resting distance varies greatly from person to person and moves outward as we get older. The typical result for pilots in flight is space myopia (or nearsightedness) while flying under conditions where there's little or no texture to focus on outside of the aircraft's surfaces. Relatively "empty" visual fields occur when you're flying at night, at high altitudes, over water or snow, or during a hazy day. Also, clouds have surprisingly little effect as stimuli for distant focusing. Under such conditions, the eye relaxes and allows the lens to seek an intermediate curvature that requires no particular focusing effort. This relaxed state is known as the dark focus.
The eyes are constantly involved in a tug-of-war between focusing on some stimulus and returning to the dark focus, with the stimulus normally pulling just hard enough to be seen and recognized. Most of the time in flight, however, there's no stimulus out there to pull the eyes' focus away from the dark focus.
As previously stated, the dark focus varies considerably with the individual, even among those with normal vision. To find your own dark focus, try an experiment first described by Dr. J. Mandelbaum in 1960 (in a ground-breaking article for the "American Medical Association Archives of Ophthalmology") and since called the Mandelbaum effect. From the screened-in porch of his summer cottage, he found he couldn't read a sign on the beach when he stood a certain distance from the screen. All he could focus on was the mesh of the screen. When he moved closer or farther away or moved his head from side to side, he could again read the sign. The distance from his eye to the screen when he couldn't read the sign turned out to be his dark focus, a fact later confirmed experimentally by Dr. Fred Owens at Penn State.
Even if you do have "normal" vision, your dark focus can vary with the time of day, your emotional state, your work- load, and your fatigue and stress levels. Furthermore, it has long been apparent that many naval aviators have much better than 20/20 vision, and there is a wide range of individual differences in perceptual abilities among those considered normal.
Empty-field myopia is reinforced by window posts and frames, some of which are quite close to the eyes. Traffic appearing along a line of sight close to a window post may by virtually invisible to the aviator. There are two main reasons for this. First, the nearby structure can serve as a focus trap. Probably even more important is the normal scan habit of looking to one side of a post with both eyes and then to the other with both eyes.
The two fixations are typically about 30 degrees apart. As a consequence, traffic appearing near one edge of the post will be as much as 15 degrees off the line of sight. Only if targets move, flash, or glisten will they be picked up soon enough in peripheral vision. Even targets that present an extended distinctive shape, such as a long, thin contrail, can be missed when they appear close to a window post. Remember, an aircraft on a collision course stays on the same relative bearing and doesn't appear to move--it only seems to grow. . .
Research reported by Dr. Stanley Roscoe has revealed a high correlation between the size an object is judged to be and the distance at which the eyes are focused. When the eye is focused close-up, we judge the apparent size of a more distant object to be smaller than it really is, and the converse is true when the eye is focused farther away. Since the apparent size of an object serves as a cue to distance, it follows that the perception of depth and distance depends upon where the eyes are focused.
The apparent size of an object is therefore influenced by other objects near the line of sight that also affect focus. Dr. Roscoe believes that this accounts for the popular illusion that the moon seems larger and closer when it is near the horizon than it does when viewed overhead in an empty sky. He's shown experimentally that changes in the apparent size of the moon (or other objects) correlate almost perfectly with the distance at which the eye is focused. When we look at the moon above a horizon, our eyes focus at a great distance; when we look up at the moon in the sky overhead, our eyes relax to a near point close to the dark focus, and the moon appears to shrink accordingly.
If you want to see for yourself, try sticking your thumb out at arm's length and closing one eye. Look at a relatively distant object with your thumb held near the line of view of the open eye and then alternately open and close your other eye while still looking at your thumb and the object. Notice the apparent change in size of the object, shrinking when one eye is closed and expanding when it's opened. The reason for this is that the closed eye tends to return to its dark focus and to pull the open eye with it. The compromise between the two eyes is about halfway between the dark focus and the distance of the object being viewed.
What about the guy landing short at night? When flying over water toward a lighted runway on a dark night, pilots with distant dark focuses, looking at the lights of a runway on the shore with the lights of a city beyond, suffer from the illusion that the runway is larger and therefore closer than it really is, and the runway threshold consequently appears lower in the visual field. An aviator in this situation may take off power too soon and land short (see "The Last Run of Flight 915," APPROACH, April 1974). Dr. Roscoe recommends that lead-in light buoys be used where this problem exists.
As to the overshooting accident, researchers an NASA- Ames have shown that intense stimulation of the inner ears, such as that caused by a sudden increase in cabin pressurization, results in an overaccommodation of the eyes' focusing mechanism. This causes the runway to appear smaller and farther away than it really is (see "The Fallacy of Pilot Error," AVIATION ACCIDENT INVESTIGATOR, December 1982). Outward accommodation is at least partially controlled by the sympathetic branch of the autonomic nervous system That's the one that allows us to run faster and fight harder when we're "psyched up." It increases our visual acuity by magnifying what we see to allow us to detect enemies or sight elusive prey when our adrenaline is pumping This mechanism has helped us since the days of the caveman. Can it be that today this same process causes the attack pilot's visual world to expand, making the ground appear lower and causing him to pull up too late?
It has been demonstrated that some people can be trained more easily than others to control the focal distance of their eyes. This ability is related to a person's dark focus and should be given consideration in the selection and training of aviators. A distant dark focus could be one basis for assigning a flier to fighter or attack aircraft. Individuals with a distant resting focus are not troubled as much by empty- field or space myopia.
Of course, as pilots gain more experience, they learn to compensate for biased distance judgments. As an individual ages, resting focus moves farther away so that target detection tends to improve. In extreme cases, however, a pilot who has "eagle eyes" may have serious problems in making a "black hole" approach at night and may be more likily to land in the water.
The key is detection. Now that we know that certain circumstances can alter our vision, we can take steps to voluntarily control our eyes' accommodation. There you have it; what you see is not always what you get, but you can learn ways to see more than you've ever seen before!
1. Benel, R.A. and Amerson, T.L., Jr., "The Dark Focus of Accommodation and Pilot Performance," In R.S. Jensen (ed.), First Symposium on Aviation Psychology, Columbus, OH, Aviation Psychology Laboratory, The Ohio State University, 1981, 182-191.
2. Clark, B., Randle, R.J., and Stewart, J.D., "Vestibular Ocular Accommodation Reflex in Man," Aviation Space and Environmental Medicine, 1975, 46, 1336-1339.
3. Leibowitz, H.W. and Owens, D.A., Anomalous myopias and the intermediate dark focus of accommodation, Science, 1975, 189,646-648.
4. Leibowitz, H.W., Hennessy, R.T., and Owens, K.A., "The Intermediate Resting Position of Accommodation and Some Implications for Space Perception, Psychologia, 1975, 18,162-170.
5. Owens, D.A., "The Mandelbaum Effect: Evidence for an Accommodative Bias Toward Intermediate Viewing Distances," Journal of the Optical Society of America, 1979, 69, 646-652.
6. Roscoe, S.N., Aviation Psychology, Ames, IA, The Iowa State University Press, 1980, 97-107.
7. Roscoe, S.N., "Landing Airplanes, Detecting Traffic, and the Dark Focus," Aviation, Space, and Environmental Medicine, 1982, 53, 970-976.
COLOUR SCHEMES FOR AIRCRAFT
Australian Gliding June 1990
As all pilots realize, safety in the air depends to a great extent on the ability to see and be seen. To this end, the colour of an aircraft can play an important role. The more easily you can see other aircraft and be seen yourself, the less chance there is of a mid-air collision.
In several parts of the world, experiments have been carried out to develop colours that are highly visible in all the usual flying conditions.
From these experiments have come some interesting results. It has been found that the most visible colours for an aircraft are yellow, orange and silver- grey.
One of the most interesting findings of these experiments was that all the colours outside the blue and orange red range gave a satisfactory visibility result. An aircraft painted sky blue, one would expect, would be invisible against a blue sky. This is not so, the experiments showed.
The real value of colour to an aircraft, it was found, is obtained by the correct use of colour contrast. Already some use has been made of this knowledge in the painting of registration letters. A combination of deep blue letter with a yellow orange border was proved to be visible at distances up to 12 km.
In Australia, several decades ago, we went through a stage of using Dayglo paint on rudders, wingtips and other parts of our sailplanes. The result might have been effective, but it was not particularly attractive to the appearance of the aircraft. Perhaps this was why it was eventually dropped.
One result of experiments in Australia is the realization that an aid to visibility is to have the moving surfaces of a sailplane painted in a dark colour - red, dark blue, brown and dark grey are some of the colour that have been tried.
It has been noted that, when the controls surface is deflected, as when making a turn, it presents a contrasting surface to any aircraft that is behind or in front.
TIPS TO ENHANCE YOUR CHANCES OF DETECTING
OTHER AIRCRAFT
COPA Flight Safety Bulletin Feb/91
The following safety tips do not come with any "iron clad" guarantee. However, if they are followed, your chances of detecting other aircraft that may be on a collision course with you will be enhanced.
If the other aircraft appears to be stuck in the same position on your windshield, you are on a collision course. If it moves you are going to miss it, but take some positive avoidance action just to be on the safe side.
You are looking for a small target which grows rapidly in size only after it is too late to be avoided. It can take a couple of seconds for you to appreciate the situation, make a response and change your course, therefore, minimize the time that you have your head stuck in the cockpit.
Concentrate your search in those areas of potential conflict, which in most situations will be along the horizon. Look for those aircraft at the same altitude as yourself.
Keep your eyes scanning the search areas in quick movements. It is impossible to move your eyes in a smooth, continuous way, unless there is something out there moving in a smooth way which the eye can track.
A pilot who cant see is an accident waiting to happen. Without good glare protection, flying on bright sunny days can be tiring and hazardous. And it can affect night flying too. Exposure to bright sunlight for a whole day without protection interferes with proper night adaptation for 12 to 24 hours! The following brief summary will focus on how to choose your sunglasses and the advantages and disadvantages of the various types.
There are three problems caused by bright sunlight: glare, infrared (IR) radiation and ultraviolet (UV) radiation. Glare, although the most obvious nuisance - causing tearing, distraction and fatigue - is responsible for less serious problems than IR or UV radiation. Cutting down glare by using very dark sunglasses, however, can cause problems because reducing transmitted light reduces visual acuity, as anyone who has driven from a bright road into a dark tunnel whilst wearing sunglasses can verify. Even moderately dark sunglasses can, on a bright day, cut your vision down from 20/20 to 20/40.
On the ground, UV is partially filtered by the earth's atmosphere, but the higher you go, the less the protection. UV light is not filtered equally by all types of sunglasses and can damage the eye, causing early cataracts (lens opacities). Clear plastic sunglasses which only cut down glare allow the pupils to remain dilated in sunlight and may actually increase this risk. Good sunglasses reduce light transmission to 12-20%, but should cut down UV transmission by at least 90%. IR damage, caused by looking directly into the sun, should be avoided as IR can quickly injure the sensitive retina at the back of the eye.
Sunglasses may be constant gradient, photochromic or polarized. Polarized lenses are great for fishing but bad for flying. Due to manufacturing stresses, there may be small areas of polarization in an aircraft canopy or windscreen and, if the angles of polarization in the glasses and the windscreen differ, a blind spot can be produced. Polarization may also interfere with depth and distance perception, particularly during a bank. Just what you need turning on final!
Photochromic lenses which darken with increasing UV light are good for driving, but polycarbonate aircraft canopies shield out much of the ultraviolet rays and may interfere with their proper darkening. Additionally, going from bright sunlight into cloud the glasses may take several minutes to lighten.
Constant gradient glasses come in various colours and are the most commonly used. All are about equally effective for glare, but green or grey lenses have the least adverse effect on your vision. Yellow lenses are good in haze, but less effective in bright sunshine. Sports orange lenses should not be chosen because they interfere with blue green discrimination and may make red warning lights more difficult to see.
What is best? Where vision is concerned there are numerous cheap sunglasses, but few good inexpensive ones. Constant gradient lenses which reduce light transmission to 15-20% and block 90% of UV are ideal. Plastic lenses are lighter in weight, and sometimes less expensive, but tend to scratch. Neutral grey, green or brown lenses are the most popular. Blue, orange or polarizing lenses should not be worn while flying. If in doubt, ask an optometrist or your eye doctor. in the long run, it is wiser to save your eyes than to save your money!
SEE AND AVOID
statistics from Canadian Airspace Newsletter 2/92
Did you realize that pilots need a total of 12.5 seconds to avoid a collision? That is what an American military study concluded was necessary to avoid a collision. That is a lot of time! In 12.5 seconds two sailplanes on a head-on collision course traverse about 0.7 - 1.0 km, assuming closing speeds of 200 - 300 km/hr.
The researchers determined that the 12.5 seconds are broken down as follows:
0.1 seconds to see the threat
1.0 seconds to recognize the threat as an aircraft
5.0 seconds to perceive a collision course
4.0 seconds to decide how to avoid the collision
0.4 seconds for the pilot to move the controls
2.0 seconds for full response from the aircraft.
SUNGLASSES AND POLAROID PROBLEMS
[Canadian] Aviation Safety Letter (unknown issue)
"It was bright but hazy with 40 miles plus visibility. Radar advised me of an aircraft at the same altitude which was slowly overtaking on my left side. Soon it was reported at 9 o'clock and three miles. The sun was behind me. It was near noon. I couldn't see the traffic until I slipped off my polaroid clip-ons and suddenly the image of the other aircraft snapped sharply into view with considerable contrast against the hazy background.
When I put the polaroids back on again, it was a moment or two before I could find it again since there was almost no contrast between the aircraft and sky."
Our Aviation Medicine experts explain this phenomenon:
Sunglasses reduce solar glare from direct, reflected and scattered sunlight. Glare may cause both discomfort and reduced visual acuity. The ideal sunglasses for aviation are neutral grey in colour to avoid affecting colour discrimination, and have a luminous transmittance of between 10 and 15%, that is, they will filter 85 to 90% of the glare effect.
Polaroid lenses are constructed by placing a matrix of minute dichroic (double refracting) crystals between two pieces of glass. The matrix is oriented so that the lens acts as one large crystal which polarizes light in one direction, usually in a horizontal plane. They are therefore very effective in reducing glare. However, since aircraft windscreens are usually made of laminated glass, the combination of a laminated windscreen and a polaroid lens may produce polarization of light in two planes, thus effectively blocking vision.
BETTER GET RID OF THE CHEAP SUNGLASSES,
DILBERT! (c)
[Reprinted with the kind permission of the Aviation Safety Institute]
Edited for Safety FAQ
(Editor Note: This good article was written by Lt. David M. Kennedy (USN), VA-27, appearing in APPROACH Magazine, September 1984. Our thanks to Lt. Kennedy and the Navy Safety Center for the availability of this article. We commend it to your reading).
AS naval aviators, we like to look good. We're also very interested in protecting our precious assets; our "family jewels," so to speak. That's where a solid safety program, thorough preflights, steel toes, NOMEX (Ed: fire resistance flight suits) and sunglasses come into our lives. Sunglasses? Yes, SUNGLASSES. They protect our eyes while producing that unmistakable look that civilians are always trying to copy. But - be honest - how much do you REALLY know about your favorite shades? You wear them as much off the job as on; yet, you probably know very little about what they'e designed to protect you against or exactly how they do it.
First, a little aviation physiology. The sun can do some bad things to your eyes. The known mechanisms of damage are glare, ultraviolet radiation (UV) and infrared radiation (IR). GLARE is the amount of visible brilliant light your eyes have to handle, such as direct light on a sunny day, reflected light from snow or water, or the blinding light from an F-14 burner cat (Ed: catapault) shot at night. Glare can be discomforting or disabling, normally interferes with vision, and individuals have differing sensitivity to differing glare intensity levels. ULTRAVIOLET rays are invisible, potentially harmful and increase in intensity with an increase in level of visible light. UV radiation is the principal cause of high altitude snow blindness and is linked with development of cataracts. INFRARED rays are the sun's heat rays, are also invisible and are a potential cause of retina burns and blindness - (one of the reasons for the warning not to look directly into a solar eclipse even when wearing dark tinted sunglasses). The cumulative effects of glare, UV and IR radiation are fatigue, discomfort, squinting, tearing, distraction and a loss of night vision and dark adaption. Concerning dark adaption, the American Optometric Association counsels that "people who spend an entire day in bright sunlight will not regain their normal night vision even after a full night. Those who spend every day in the sun may require from several days to two weeks of non-exposure to totally regain their normal night vision."
Ideally, sunglasses should provide protection as well as comfort for the wearer -- in our case, the intrepid naval aviator. The rugged, stylish look is just one of the fringe benefits of choosing the "right profession." In flight, the tinted visor, alone or in conjunction with issue sunglasses, works with canopy plexiglas (a UV shield) to provide the required protection. On the ground or at the beach, sunglasses and informed good sense do the job.
The major types of sunglass lenses are CONSTANT GRADIENT, POLARIZING, PHOTOCHROMATIC, REFLECTING and a combination of the previously named types. CONSTANT GRADIENT or TINTED lenses are fixed in color and the amount of ambient light they allow to be passed. They come in various colors, the most popular being gray, green, brown and amber. Although the color of the tint has no effect on the lens' ability to block or absorb UV rays, it does affect the lens' ability to absorb IR rays. The lens' color also affects color perception. POLARIZING lenses absorb some of the light rays reflected from horizontal surfaces, especially water, snow, and sand. Their glare-reducing effectiveness depends upon the light-to-lens angle of incidence. PHOTOCHROMATIC or CHANGEABLE lenses are made of light-sensitive glass which automatically adjusts in density to the level of brightness. Most depend upon UV rays to trigger the darkening reaction. REFLECTING or MIRROR lenses are tinted lenses with a thin metallic coating applied to further reduce light transmission. The coating may be applied to the entire lens or only to the top and/or bottom to combat intense overhead and/or reflected glare.
The only sunglasses authorized for inflight wear by Navy aircrews are the familiar "FG-58" (Flight Goggle 58), introduced in 1958 by American Optical and equipped with neutral gray lenses that block all but 1-18 percent of the ambient light. (This, from the MILSPEC). Neutral gray lenses are stipulated because they don't distort or change colors as most colored lenses do. All things considered, the FG-58 is an excellent pair of sunglasses. Polarized lenses are specifically not authorized for inflight wear due to the possibility of blind spots caused by the cumulative polarizing of canopy/windscreen, visor and sunglass lenses. Photochromatic lenses are not authorized in flight because they are not considered dark enough, even at their darkest, to provide adequate protection. Lenses whose changing density depends upon UV rays are also hampered by the canopy's absortion (sic) of UV rays.
Although naval aviators are encouraged to shun commercially obtainable sunglasses in favor of the FG-58, a simple glance around any naval air station will show a wide variety of sunglasses, most of which are excellent. Some, unfortunately, don't provide the wearer with adequate protection and may be potentially dangerous. By filtering out glare and by tinting the lens, some substandard sunglasses allow your natual squinting impulse to relax and your pupils to dilate. As a result, your eyes become susceptible to retina-damaging IR and UV radiation.
How can you -- the intrepid naval aviator -- best evaluate those shades you're thinking of buying? Only a few manufacturers publish vital statistics with their sunglasses, but those with the best quality lenses do or will gladly provide the information. Additionally the National Society for the Prevention of Blindness suggests several criteria, among them:
1. TRANMISSION FACTOR. For persons engaged in bright work outside or who contemplate night flying, the experts recommend lenses that block 85-90 percent of sunlight, allowing 10-15 percent to reach the eyes.
2. UV TRANSMISSION. The amount of ultraviolet radiation blocked by the sunglass lens varies widely, but all quality lenses rank high in this important category. Studies continue in order to determine the effect of even small amounts of UV radiation over long periods of time.
3. IR TRANSMISSION. Like UV radiation, quality sunglass lenses rank high in this category, measured in terms of IR radiation blocked.
4. COLOR. Neutral gray (or "smoked") is the lens color that retains color fidelity best, but there are advocates of green and brown lenses. The transmission curves of green lenses resemble the color sensitivity of the eye, while brown lenses block scattered blue light rays prevalent with dust or moisture in the air, thereby reducing haziness, improving contrast and sharpening details.
5. OPTICAL QUALITY. Both lenses of your sunglasses should be evenly matched, equal in color and absorptive qualities. The lenses should be free from waves, surface blemishes, scratches or other distortions that can cause eyestrain. To test the lenses, hold the glasses at arm's length, focusing on a distant vertical line. Move the glasses vertically and horizontally. If the line waivers, the lenses contain distortions and should not be used. However, this test is NOT valid for prescription lenses.
6. IMPACT RESISTANCE. The Federal Food and Drug Administration requires that all eyeglass lenses -- including sunglass lenses -- be made of impact-resistant glass or plastic.
The following chart indicates how several popular commercially obtainable sunglasses compare. In no way should be considered complete, or as an advertisement. Optical quality standards of the type set out below, and not mere style and price, should be your guide when buying sunglasses. Also make SURE they are impact resistant.
| Sunglasses | Colour/Type Lens | Transmission (%) | UV (%) | IR (%) |
| FG-58 (American Optical et al) | constant density, neutral gray, N-15 | 15% | 99.8% | 85% |
| Ray Ban Outdoorsman/aviator | Constant density, neutral gray, G-15 | 15% | 99% | 85% |
| Bausch & Lomb | Constant density green | 26% | 99% | 95% |
| Bausch & Lomb | Constant density brown | 15% | 99% | 95% |
| Bausch & Lomb | Reflecting + neutral gray G-31 | top: 4%; center: 23% | 99% | 90% |
| Vuarnet Skilynx Acier (Vuarnet-France) | Reflecting + brown | top: 7.7%; center: 12.2%; bottom: 6.5% | 100% | 90-99% |
| Fishing glasses (Eddie Bauer) | Polarizing | 25% | 84% | 70% |
CAUTION: Although some manufacturers suggest that certain lenses with particularly high transmission factors are "light" enough for use indoors, or while driving at night, such a practice is bad headwork! So, next time you select a set of shades, use these standards of judgment -- and if the bargains you're picking up don't pass, you'd be smart to consider just how much those "cheap sunglasses" might be costing you!
Acknowledgment is given to the National Society for the Prevention fo Blindness, American Optometric Association, Better Vision Institute, Bausch and Lomb, Vuarnet-France, American Optical Company and Navy Opthalmic Support and Training Activity.
(ASI Note: Thanks to Lt. David M. Kennedy for an informative and well-written article.)
LIGHT POLARIZATION AND SUNGLASSES FOR PILOTS
From the internet
This article is written in order to explain the basis for various statements and comments about polarized sunglasses as they apply to aviation. Below are a couple of specific examples that will be addressed in the text following them. My hope is that this article will lead to broader understanding of polarized light effects pertinent to aviation.
Anecdote from the: "SUNGLASSES AND POLAROID PROBLEMS" [Canadian] Aviation Safety Letter (unknown issue) :
"It was bright but hazy with 40 miles plus visibility. Radar advised me of an aircraft at the same altitude which was slowly overtaking on my left side. Soon it was reported at 9 o'clock and three miles. The sun was behind me. It was near noon. I couldn't see the traffic until I slipped off my polaroid clip-ons and suddenly the image of the other aircraft snapped sharply into view with considerable contrast against the hazy background."
Comment from the "BETTER GET RID OF THE CHEAP SUNGLASSES, DILBERT! (c)" article by Lt. David M. Kennedy (USN), VA-27, appearing in APPROACH Magazine, September 1984. :
"Polarized lenses are specifically not authorized for inflight wear due to the possibility of blind spots caused by the cumulative polarizing of canopy/windscreen, visor and sunglass lenses."
POLAROID SUNGLASSES
Polaroids are made of materials typically based on polyvinyl alcohol with iodine or some dyes incorporated into it. These materials exhibit linear dichroism with the direction of the absorbed polarization being set into polaroid sheet by an anisotropic stretching process. In that process the long polyvinyl alcohol molecules are oriented along the stretch direction, and thus the incorporated iodine or dyes become anisotropically active. Good polarizers fabricated this way transmit more than 80% of one polarization while essentially completely eliminating the other. Typical field of view of human eyes is +-35 degrees from the normal to the glasses. For all practical purposes one can consider light viewed through polaroid sunglasses to be incident perpendicularly to lens surface, and dispense with extra complications in discussion.
Most, if not all polaroid sunglasses sold in the stores are set to transmit light polarized vertically (in the frame of a standing person wearing the glasses). This suppresses glare caused by sunlight reflecting off a rear window of a car which is being followed, to darkening of sky toward the zenith when the sun is behind an observer wearing the polarizing sunglasses, and reduces haze with the sun overhead.
POLARIZATION VIA SCATTERING
Direct sunlight is unpolarized. As it traverses the atmosphere it is scattered within it by air molecules, small particles, molecules or tiny droplets of water and so on. For the most part this scattering is strongly, but smoothly, dependent on the wavelength of light. Blue light scatters roughly five times stronger than the red; thus the blue sky. Small particles (smaller than two tenth of a micron in diameter) scatter unpolarized sunlight more or less equally in all directions. However, as the scattering angle approaches 90 degrees the light becomes strongly polarized in the direction perpendicular to the scattering plane. This is strictly true for a "single scattering event". In the atmosphere, light often undergoes multiple scattering events before reaching the observer, thus the polarization due to this effect is not perfect.
Looking through polarized sunglasses perpendicularly to sun rays, an observer with sun behind him will find a band of darker sky. This effect is often used by photographers to increase the contrast of clouds against the sky. This also benefits a glider pilot who is looking for a small whisp of a cloud against the sky's background. When the sun is near to horizon the polarized band is overhead. At noon, with the sun nearing zenith, the polarized band moves towards the horizon. As an observer samples a greater distance through the atmosphere, multiple scattering effects become more important and the degree of polarization is lowered for a band close to the horizon.
The same effects are observed with scattering due to haze. As long as the haze is thin, the scattered light can be eliminated by polarized sunglasses (mostly single scattering events). However, as the haze thickens, multiple scattering destroys the polarization of light coming from further away. Polarized sunglasses now help only with the light scattered close to the observer. As the haze thickens even more, the light from the sun becomes diffuse enough to render polarized sunglasses completely ineffective.
So what is the explanation of the observation in the above anecdote?
I'm going somewhat on a limb but: The sun is overhead (near noon) somewhat to the back, haze is weak (more than 40 miles visibility). The observer is looking for an aircraft to his side, reasonably close to him and near horizon. Aircraft in this configuration does not reflect a lot of light so it is going to be basically a small, dark object against the background. But what is the background? With polaroids on, the observer eliminated light scattered by the haze and suppressed somewhat the intensity of the sky. So he is looking for a basically dark object against darkish background within a predominantly bright scene. I believe that this is one of the worst cases possible for noticing an object. The moment he takes off his polaroids the background lights up increasing the contrast significantly.
But what if the aircraft one were looking for presented itself as a bright object, (e.g. had its lights on, was in a turning bank so that it reflected more light towards the observer). My guess is that the polaroid sunglasses could help in such a case.
POLARIZATION VIA REFLECTION AND TRANSMISSION
About 4% of light incident perpendicularly at a glass surface is reflected on each glass-air interface. As the angle of incidence (half the angle between the incident and reflecting rays) increases, the reflectivity of light polarized perpendicularly to the plane of incidence (plane containing incident and reflecting rays) (s-polarization) increases. However the reflectivity of the light polarized in the plane of incidence (p-polarization) initially slowly decreases, and at a specific angle (Brewster angle) which for glass is about 56 degrees, it reaches zero.
For larger incidence angles, reflectivity of the p-polarized component rises rapidly but is always smaller than that of the s-polarized component until, at glancing incidence (incidence angle approaching 90 degrees) light is completely reflected. At Brewster angle the reflected (not transmitted) light is completely polarized. The reflectivity of the s-polarized component at Brewster angle is about 15% per surface (thus about 70% of this polarization of light is transmitted through a sheet of glass compared to 100% of the other). Metallic surfaces strongly reflect both polarizations.
It is now easy to understand why polarizing sunglasses help eliminate glare from a rear window when one follows a car. With the sun overhead, light reflected from glass surfaces of a car ahead is largely polarized in the plane horizontal to the observer, and that is the polarization that the polaroids absorb. Light reflected off of smooth paint is also to some extent polarized and glare from painted parts can be also suppressed. Note that a slanted windshield of the observer's car also acts as a polarizer (though a very poor one) which is oriented in the same direction as the polarizers of the sunglasses.
What are the implications of that for pilots? I am not sure. In general there appears to be concern about "blind spots" created by cumulative polarizing effects of windows, visors and sunglasses (the windshield effect described above). I do not think this is of any concern for any normal viewing situation. The polarizing effects of the intervening surfaces parallel those of the polaroids. I can imagine however some abnormal viewing conditions in which a "blind spot" might be created, e.g. a pilot tilts his head significantly to look backwards. "Blind spot" in such a case would mean almost total darkness, not loss of contrast. This problem would be exacerbated by a double paned window with an air gap inbetween. Window laminations do not contribute to polarization of light as the bonding materials are usually optically well matched to the glass they join. In my opinion, the "blind spot" effect may be of some concern to fighter pilots in combat, but I doubt very much that they are of any importance to an average pilot; even to a glider pilot who twists his head in a gaggle.
I would be more concerned with a different effect. As mentioned above reflection off paint can be polarized. More often than not I notice other gliders as they flash their wings in a distant turn. With the sun overhead this flash might be lost should I be wearing polaroids.
MY PERSONAL CONCLUSIONS ABOUT USING POLARIZING SUNGLASSES IN FLIGHT
Well, I do not think I want to use them. The variation in their effects is just too great. They definitely help in some situations (e.g. increase contrast of light objects against the sky, help see deeper into haze), but then there are also situations that they might be detrimental (see the anecdote above). In my opinion a pilot is better served by using sunglasses which eliminate the deep blue and thus achieve most of the positive effects of the polaroids by eliminating the radiation that is easiest to scatter, and at the same time help somewhat the visual acuity by limiting chromatic aberration effects (light of different colors comes to focus at different distances from a lens) in the eyes. The UV protection they may offer would be another, and maybe the most important benefit.
THE LANDING FLAREOUT (c)
[Reprinted with the kind permission of the Aviation Safety Institute]
Some pilots have difficulty with the last five to ten feet of altitude just as they progress through the flareout maneuver. It would be well to consider what can be done to improve the flare technique. (Obviously, to judge a pilot primarily on his or her flare skill is not fair.)
It is a well-tested theory that pilots who maximize the use of their extrafoveal or peripheral eye retina during the flare phase generally land better. The use of the peripheral vision results in two important assessments: 1) location in space above the runway, and 2) estimation of vertical speed -- up or down.
Let us assume, a priori, that there is sufficient intelligence out in the real world to give you the cues for making the flare maneuver. When snow cover is covering the runway and lighting environment, or when landing at night with no lights to assist (an unlikely event in today's flying environment), the necessary cues may not be there.
There is normally adequate visual intelligence external to your field of fixated vision, but still within your general view. This is much like having the experience of gazing at an object, and at the same time being aware of something else moving out of the corner of the eye.
The extrafoveal or peripheral retina is particularly sensitive to movement, and, as long as any vision remains, we have movement perception. The readiest explanation of our sense of movement is the successive stimulation of receptors leaving a trail of "on/off" discharges in the eye which gives some indication of direction and total displacement. (Wyburn, Pickford, and Hirst, 1964).
Tests reported by Majendie (1960) demonstrated that significant visual cues were received by pilots landing, from the dynamic pattern of the runway environment. Quoting ."furthermore, it was shown by photographic methods that the pilot did not use a pattern of fixation to assess these cues, but stared fixedly ahead, allowing the dynamic part of the pattern to stream across his field of vision..."
It is not clear what the origin is of this theory. Calvert (1954) credits Majendie for such a suggestion in a personal communication in 1949. However, in passing we might observe that earlier published reports by other investigators (.e.g, Grindley, 1942, Gibson, 1947) certainly dealt with the Parafaveal Streamer Theory of visual judgments made from an aircraft in motion, although they did not use the same terminology.
Sounds technical ? True, but we are giving you a list of references should you want to review the "older" literature -- the basic work that has been done on use of peripheral retina in flying.
Let us consider the task of flaring. The aircraft's speed at the point of entry into the flare maneuver is crucial. Being too slow or fast will profoundly effect the point of touchdown, and your total landing distance, as well as the control applications you apply to touch down for minimum vertical speed and good runway alignment.
We recommend that you bring the aircraft over the runway threshold no faster or slower than 1.3 times the power off stall speed. This would be 1.3Vso. You can determine Vso quite simply for your aircraft by doing a smooth, gentle power off stall(straight ahead) and reading what your airspeed indicator reads at the speed at which control is "lost". This is called the "minimum control speed", which is essentially equivalent to Vso. Multiple that indicated value by 1.3 and you have an acceptable speed over the "fence". Of course, you should add a knot or "MPH" for each knot of headwind speed over 10 knots. This will help keep the aircraft away from the stall regime due to turbulence on final.
Once at that speed and aligned with the aiming point you have chosen on the runway, you should cross the threshold at 1.3 Vso and begin your flare approximately 10 feet above the runway. You should, by now, have fixated on a point near the horizon line easily seen from your position in the cockpit. You may then sense any changes in position above the runway by the apparent motion of the runway edge environment. That is, if the runway edge appears to come up rapidly, you are sinking at the same rate, and you must apply appropriate elevator movements (and-or power) to reduce the rate of sink. Similarly, you should quickly observe any drop of the runway edge environment and take equally appropriate and timely action.
Do not make the common mistake of fixating on the runway below you. To do so will DESTROY the use of the peripheral retina faculties, and you will not effectively observe position changes and vertical rates. We recommend that you try this technique, probably with an instructor or competent pilot aboard as a safety pilot.
Calvert, E. S., Visual Judgments in Motion. Journal of Institute of Navigation, 1954, 7, 233-251.
Gibson, J. J. (ed). "Motion Picture Testing and Research". Amry Air Force Aviation Psychology Reports, Report 7, 1947.
Grindley, G.C. , "Notes on the Perception of Movement in Relation to the Problem of Landing an Airplane". Air Ministry Flying Personnel Research Committee, Report FPRC 426, 1942.
Majendie, A.M.A., "The Para-Visual Director", Jounral of Institute of Navigation, 1960, 13,447-454.
Wyburn, G.M. , Pickford, R. W., and Hirst, J.J., "Human Senses and Perception", Edinburgh and London, Oliver and Boyd, 1964.
Edited for Safety FAQ
The Grob G102 glider has a clear Plexiglas canopy and a black interior, which in the case of strong sunshine can produce a significant greenhouse effect. The pilot normally carried one and one half litres of drinking water when flying in his own glider. However, no water was available in the Grob. The pilot had eaten porridge for breakfast, consumed some fruit for lunch, and had drunk about three glasses of water while working on the flight line. He recalls being hot and tired during the flight. Aircrew rarely experience dehydration by itself, but rather more commonly encounter dehydration in combination with heat stress. Heat stress generally results from rising environmental temperatures and/or increased physical workloads, causing a rise in body temperature. Part of the body's response when heat stress is high is perspiration. The evaporating moisture is an effective cooling mechanism. However, when body moisture is not replenished, dehydration can result. The sweating mechanism can then become ineffective, and the body temperature will continue to rise.
Unchecked heat stress can lead to three conditions of increasing hazard level: heat cramps, heat exhaustion, and heat stroke. Performance affecting symptoms, including loss of concentration or focus on tasks and increasing irritability, become increasingly evident as the body continues to store heat. At low levels of heat stress, the effects on an individual's performance are more subtle, and a pilot being affected may not realize it at the time.
HYPOGLYCEMIC ATTACK CAUSES CRASH
[Canadian] Aviation Safety Letter 5/90
Approximately 45 minutes into a cross country flight, while flying at 4,000 feet above ground level, the pilot felt dizzy and then lost consciousness. He awoke as the aircraft was descending in an unusual attitude toward trees. The pilot was unable to recover from the unusual attitude, and the aircraft flew inverted into the trees. He survived and made his way back to civilization, and was admitted to hospital for tests.
Routine testing showed nothing amiss, but a medical specialist digging into the pilot's history learned that he was a regular consumer of alcohol. His hypothesis was that the pilot suffered a hypoglycemic attack due to fatty-liver disease. The pilot had only toast and coffee in the 18 hours prior to the accident, and a drink of grape juice just before departure. The high sugar content of the grape juice probably triggered the hypoglycemic reaction due to the pilot's liver condition.
Your liver may be in perfect condition, but you can still have hypoglycemic symptoms by not eating adequately prior to going flying, or eating foods that give quick energy (eg chocolate bars) but later lead to feelings of light- headedness, stomach upset and disorientation.
Remember to eat a substantial meal, high in protein, that provides long-term energy - it will make your flying more comfortable.
HEALTH AND WELFARE CANADA COMMENTS ON
ASPARTAME
Canadian General Aviation News Oct/90
In the March 1990 issue of Canadian General Aviation News in this column, a pilot outlined his concerns over questionable adverse effects from the
consumption of diet drinks containing aspartame.
As a result of the article, Health and Welfare Canada referred the pilot's comments to the Bureau of Chemical Safety, Food Directorate. Their finding indicate that aspartame is not a problem for most individuals. They point out that aspartame is composed of two amino acids, aspartic acid and phenylalanine, which are normal constituents of proteins. Aspartame is metabolized inexactly the same manner as any other food protein in the diet. In regard to the formation of methanol, it has long been known that methanol is formed upon degradation and metabolism of aspartame. Methanol however, is not foreign to the human diet. Many common foods, including fruits and fruit juices contain low levels of methanol and substances that are metabolized to methanol. For example, it has been calculated that degradation of all the aspartame in one litre of a soft drink would result in about the same amount of methanol as would be ingested from the consumption of two medium sized apples.
Since the use of aspartame was permitted in Canada, The Health Protection Branch has received as few reports, mostly unsubstantiated, of adverse reactions to this substance. These were generally in the nature of headache, and so called "general malaise" which could not be definitely attributed to aspartame ingestion.
There is however no question that some people do exhibit allergic reactions or hypersensitivities to specific food additives such as aspartame. Monosodium glutamate is a good example. This is the reason that there is a requirement for labelling of the contents of food and beverage preparation.
Dear Editor,
I noted from a recent article in Radio Control Models & Electronics that the author, whilst flying a model helicopter, had experienced a disorientation problem which he accidentally found was related to drinking "diet" soft drinks. Some time later (after laying off the soft stuff) he read a report in the Experimental Aircraft Association's magazine Sport Aviation (February 1985 issue) which explained the problem which could have a lot of relevance to our own sport.
The report, written by Dr. Stanley R. Mohler, concerned a substance called aspartame. This is marketed under the brand name "Nutrasweet" and used in a number of soft drinks. The report states that ... "I found that there are numerous reports by persons who have experienced visual impairment, dizziness, loss of equilibrium or disorientation following its use". The effect is attributed to an allergic reaction which some people may have to the methanol which is produced when aspartame breaks down in the body. The report concludes: "I'am not advocating that you don't drink diet soft drinks - but if you do develop headaches, dizziness, blurred vision or other symptoms, these may be associated with the diet drink. Just be aware of this".
Recently a letter was sent to COPA (the Canadian Owners and Pilots Association) in which a pilot expressed his concerns over questionable adverse effects from consumption of diet drinks containing aspartame. By 1986, the FDA and the Centre for Disease Control in the USA had evaluated 3000 known complaints. Fellow pilots who may have had similar side effects may be interested in the information below.
Plane and Pilot magazine featured an article on drugs and alcohol vis'ê'vis safe flying practises that also talked about food additives. It explained that diet soft drinks are sweetened artificially by "aspartame" (with brand names NutraSweet and Equal), and that aspartame contains 10 per cent methanol. That caught my attention! I know that methanol (sometimes called wood alcohol) is a poisonous substance, which on ingestion causes blindness and death; two teaspoons full are considered lethal.
The article disclosed that methanol destroys the brain, albeit a little at a time, and that effects are cumulative. Depending on a persons physical state and tolerance level, immediate effects can either be severe (resulting in epileptic seizures, including grand mal, blindness, chest palpitations), or less noticeable (causing blurred vision, "bright flashes", tunnel vision, ringing or buzzing in ears, migraine headaches, dizziness, loss of equilibrium, lip and mouth reactions). Less noticeable effects might be passed off as temporary or caused by something else. But everyone is affected in one way or another, since methanol causes toxic reactions, not just allergic ones, in a few unfortunates.
Here are direct excerpts from the article:
"An Air Force pilot traced the patterns of tremors and seizures he suffered for two years directly to his patterns of NutraSweet consumption. When he travelled to areas where diet sodas were not available, he was free of the symptoms. But when he resumed intake of the beverages, his tremors resumed, grew more severe and culminated in a grand mal seizure that ended his flying career. His medical problems ceased when he quit ingesting NutraSweet, but it was too late to restore his flying status."
"Another pilot suffered similar symptoms only when using aspartame products. But FAA revoked his medical certificate when it was informed of the symptoms. After only two cups of artificially sweetened hot chocolate, a pilot experienced blurred vision so severe he was unable, in flight, to read the instruments and very narrowly avoided a tragic landing. Safely on the ground, he related his symptoms to the secretaries in his office. Both of them told of experiencing similar symptoms after ingesting aspartame products."
I, too, had bad experiences with aspartame. It replaced saccharin about 10 years ago; as a marathon runner in my 30s I consumed litres of diet drinks daily at that time. When I first drank pop with aspartame, it had immediate and severe effects upon my consciousness and vision. After a few scary incidents, pop consumption and problems seemed related.
I described symptoms and circumstances to my doctor. He ran tests, but never seriously listened to my concern of relating pop with the effects. He was a reasonably competent GP, but not ready to distrust, let alone blame, an FDA approved sweetener. Eventually I quit ingesting aspartame and have not had incidents since. Employed in the professions and a post-graduate, I conduct research occasionally and am aware of the difficulty of matching cause and effect (and the danger of doing it improperly). But there is no doubt in my mind that "tests" with my body proved that aspartame is bad (at least for me).
Apparently the other main components of aspartame, phenylalanine (50 per cent) and aspartic acid (40 per cent), combined with the methanol (10 per cent), create a witches brew of 16 breakdown products after digestion that cause illness. Animal tests revealed brain tumours, some cancerous; holes in the brain, womb tumours, uterine tumours, and reproductive dysfunctions. Studies on humans indicated that pregnant women and young children run especially high risks.
If pilots want more information, I encourage them to call The Aspartame Consumer Safety Network in Dallas, Mary Nash Stoddard, (214) 352-4268. ACSN promises confidentiality if asked, and will send an eye-opening information package.
Comment by Dr. Peter Perry
Chairman, SAC Medical Committee
This is an interesting article on aspartame and methanol and their side effects, all of which are quite valid. I am sure the aim of the article was to increase pilot awareness of the same. However, I think it has been taken out of context, so to speak, and we have to put the information in the proper perspective. The writer of the article and, I am sure, the other people he has spoken to did indeed have those alarming symptoms, so other users of aspartame should be aware of that possibility, particularly pilots.
If one looked at the full range of side effects of Aspirin and Tylenol, to take two other over-the-counter drugs as an example, one probably wouldn't dream of taking them because they can both produce a wide range of serious side effects, some of which can even be fatal. Even regular coffee is not to be taken lightly - I have seen one authority write that the consumer would be unfit to drive a car after two cups.
Aspartame and the other drugs mentioned have been around for quite some time. They have nasty side effect profiles. But millions of "doses" have been taken. So what is the bottom line. The important thing to consider is not the possibility but the probability of an adverse reaction occurring (bad side effects have low probabilities). Luckily, all the specific cases referred to in the article had dramatic side effects with rapid onset, making it easy to recognize and so respond appropriately. Often we are at more risk from medications with insidious onset of reactions, such as cold remedies and sedating antihistamines, to say nothing of alcohol, smoking, and hypoxia.
ARE YOU A JELLY DONUT?
[Canadian] Aviation Safety Letter (unknown issue)
If it's true that "you are what you eat", then how many of us must stand up and be counted as bacon sandwiches, french fries and jelly donuts?
If you want to stay healthy, you have to give your body the materials it needs to do the work - to produce energy, remove toxic by-products and regenerate itself. Flying puts special demands on you, particularly at high altitudes. The cabin is dry, the temperature tends to be uncomfortable and hypoxia occurs, even in a pressurized cabin which is normally kept between 5000 and 7200 feet. The success you have combatting the stress of this environment depends on your life style - getting the proper rest, exercise and of course nutrition.
The average North American eats too much sugar, too much fat, too much salt and too many refined carbohydrates. The food is nearly always cooked, often overcooked and too often deep fat fried. One nutritional expert suggests, "Avoid as much as possible those foods which have been refined or processed and that contain food additives and chemical pollutants. Foods that increase the likelihood of disease should be avoided, including sugar, white flour, hydrogenated fat, food preservatives and the many artificial flavouring and colour agents."
Airline doctors and aerospace physicians give the same advice. "Crosscheck", a Pan American magazine for pilots, suggests they eat no refined carbohydrates, including sugar and all refined starches. Instead it suggests protein-rich meals eaten every four hours, especially when on flight duty, with fruit or protein snacks for pick-me-ups at odd duty times. It recommends eliminating coffee and soft drinks in favour of low fat milk or fruit juice.
Simply stated, "if many made it, don't eat it" or, more to the point "eat only those foods that spoil. rot or decay, - but eat them before they do."
The secret is not only eating right, but knowing what's good for you. It's a good idea to do some reading on nutrition and if you suspect your present diet many be inadequate, consult a specialist.
Eating regular, healthy meals can be quite a challenge, especially when you're flying the irregular, unpredictable hours of the flying instructor or charter pilot. It's worth the extra effort though. A good start would be to make a habit of keeping a few apples, nuts, and raisins in your flight bag. These will keep you away from those dreadful candy bar machines in airport terminals.
Think of food as your body's fuel. Would you expect your aircraft to perform properly if you ran it continuously on a lower grade fuel than it was designed for? Would you anticipate completing a long cross-country flight if you took off with the fuel low level lights on? If you want to perform at peak efficiency, be particular when you fill your body's "fuel tank". You owe it to yourself as well as your passengers.
QUENCH YOUR FATIGUE
[Canadian] Aviation Safety Letter (unknown issue)
Plain old fatigue can happen from many causes. But one if the most treatable is dehydration. Consider the following:
-we lose about a litre of water a day through normal excretion;
-in hot weather, sweating can cause the loss of up to an unbelievable 4 litres in an hour (In the cockpit, we won't lose that much, but we may lose quite a lot);
-the dehydration effect of pressurization systems (where the humidity can be lower than that of the Sahara Desert); And then there's altitude. As we go to altitude there's less nitrogen, less oxygen, and less water too. The tendency is for the human body to try to share its water with that virtually waterfree atmosphere.
Water loss from low humidity at altitude increases "insensible" perspiration - insensible because we don't notice it. We could call it evaporation just as easily. Our bodies, which are 75-80% water, are like a wet sponge on the desert, continually losing water through evaporation. The rate of insensible perspiration increases when the body goes to altitude.
A lot of dehydration is self-imposed because we probably don't drink enough water in the first place. When the human body gets thirsty it's already about a litre low - drinking sweetened drinks is sometimes the last thing the body needs at this point.
How many of us routinely ask for and drink water with our dinner? Not many ... Why? Because we want something sweet, right? Sure, like cola, ice tea or coffee, milk, etc., in fact almost anything but water. When the human body gets thirsty, sugar can complicate the absorption of water. (And alcohol and coffee can cause the body to lose more water than it gains.)
As if things weren't bad enough, thirst tends to diminish at altitude. Your body, which was created to survive on earth, usually loses most of its water by sweating - not by insensible perspiration. As we sweat on earth, we lose not only water but other body chemicals called electrolytes or "salts". The amount of salt and water lost in the sweat changes the concentration of salts left in the blood. As the blood flows through the brain, it detects the change in salt concentration and decides we've been sweating and have lost some water. Therefore, we must be "thirsty". For pilots, the mechanism must be delayed by the fact that the change in salt concentration is not as dramatic when we lose water through insensible perspiration .. so thirst lags behind. Why haven't we dried up like a piece of jerky by now? Fortunately, we get water in our food and our body produces water as a byproduct of cell respiration. Put those with the water we get the hard way through sweetened drinks, etc., and we manage to stay alive, but we're usually walking around in an almost freeze-dried state. There's no doubt that this dehydration makes us feel fatigued.
Even the early stages of dehydration can lead to emotional alterations and impaired judgment - not the sort of changes that go well with flying. Fatigue through dehydration must be recognized be each pilot and treated - stop and take a couple of swallows of water. Drink more water and quench that fatigue.
THE HANGOVER
[Canadian] Aviation Safety Letter (unknown issue)
No session of "hangar flying" is complete without some "hero" describing the accomplishment of a terrific aeronautical feat while burdened by a massive hangover. Although the air regulations and company operations manuals outline the minimum time from bottle to throttle, little is said about the hazards of flying with a hangover. Studies have shown it can take up to 30 hours for the body to rid itself of all alcohol and the residual symptoms of heavy drinking. In fact, hangovers can affect a pilot's performance just as much as drunkenness.
For those who are not already familiar with them, here are some of the effects that can linger "the morning after".
FATIGUE - The body requires restful sleep, uninterrupted by the presence of foreign chemicals. For this reason a full night's sleep after a binge may not always be restful, even if you are convinced you slept well.
DEHYDRATION - You eliminate fluids often while getting drunk which explains the frequency visits to the washroom during the early stages of a party and the dry feeling the next morning. If you continue to drink beyond the point of intoxication, your kidneys decrease the formation of urine, fluid is retained and you awake feeling waterlogged. In any case, your body's fluid balance is disrupted by drinking and many of its other functions are also affected.
IRRITABILITY - Initially when you drink you feel euphoric. but alcohol is really a depressant. It is also a strong cardiac stimulant that makes you feel like you have had too much coffee or are under stress. The "hyper" feeling can also lead to a "pounding pulse" and elevated blood pressure, the effects of which can last up to 24 hours or more after the party has ended.
HEADACHE - The cause of alcohol-induced headaches is unclear, but one theory says that a drinker's retained fluids may dilate the blood vessels to the brain causing a "vascular-type headache". These symptoms worsen with altitude and can last much longer than 12 hours after the last drink.
The "eight hours from bottle to throttle" rule is the regulatory bare minimum but in many cases it is not enough, so use your common sense.
ALCOHOL AND FLYING IS A DEADLY COMBINATION
[Canadian] Aviation Safety Letter (1/96)
Alcoholic beverages, used by many to "unwind"or relax, act as a social "ice-breaker," a way to alter one's mood by decreasing inhibitions.Alcohol consumption is widely accepted, often providing the cornerstone of social gatherings and celebrations. Along with cigarettes, many adolescents associate the use of alcohol as a rite of passage into adulthood.
While its use is prevalent and acceptable inour society, it should not come as a surprise that problems arise in the use of alcohol and the performance of safety-related activities,such as driving an automobile or flying an air-craft. These problems are made worse by the common belief that accidents happen "to other people, but not to me." There is a tendency to forget that flying an aircraft is a highlydemanding cognitive and psychomotor task that takes place in an inhospitable environment where pilots are exposed to various sources of stress.
Hard facts about alcohol
- It's a sedative, hypnotic, and addicting drug.
- Alcohol quickly impairs judgment and leads to behaviour that can easily contribute to, or cause accidents.
- Alcohol is rapidly absorbed from the stomach and small intestine, and transported by the blood throughout the body. Its toxic effects vary considerably from person to person, and are influenced by variables such as gender, body weight, rate of consumption (time), and total amount consumed.
- The average, healthy person eliminates pure alcohol at a fairly constant rate - about 1/3 to 1/2 oz. of pure alcohol per hour, which is equivalent to the amount of pure alcohol contained in any of the popular drinks. This rate of elimination of alcohol is relatively constant, regardless of the total amount of alcohol consumed. In other words, whether a person consumes a few or many drinks, the rate of elimination of alcohol from the body is essentially the same. Therefore, the more alcohol an individual consumes, the longer it takes his/her body to get rid of it.
- Even after complete elimination of all of the alcohol in the body, there are undesirable effects - hangover - that can last 48 to 72 hours following the last drink.
- The majority of adverse effects produced by alcohol relate to the brain, the eyes, and the inner ear - three crucial organs to a pilot.
- Brain effects include impaired reaction time, reasoning, judgment, and memory. Alcohol decreases the ability of the brain to make use of oxygen. This adverse effect can be magnified as a result of simultaneous exposure to altitude, characterized by a decreased partial pressure of oxygen.
- Visual symptoms include eye muscle imbalance, which leads to double vision and difficulty focusing.
- Inner ear effects include dizziness, and decreased hearing perception.
- If such other variables are added as sleep deprivation, fatigue, medication use, altitude hypoxia, or flying at night or in bad weather, the negative effects are significantly magnified.
The chart summarizes some of the effects of various blood alcohol concentrations. The blood alcohol content values in the table overlapbecause of the wide variation in alcohol tolerance among individuals.
How alcohol affects performance
- Pilots have shown impairment in their ability to fly an ILS approach or to fly IFR, and even to perform routine VFR flight tasks while under the influence of alcohol, regardless of individual flying experience.
- The number of serious errors committed by pilots dramatically increases at or above concentrations of 0.04% blood alcohol. This is not to say that problems don't occur below this value. Some studies have shown decrements in pilot performance with blood alcohol concentrations as low as 0.025%.
Hangovers are dangerous
A hangover effect, produced by alcoholic beverages after the acute intoxication has worn off, may be just as dangerous as the intoxication itself. Symptoms commonly associated with a hangover are headache, dizziness, dry mouth, stuffy nose, fatigue, upset stomach, irritability, impaired judgment, and increased sensitivity to bright light. A pilot with these symptoms would certainly not be fit to safely operate an aircraft. In addition, such a pilot could readily be perceived as being "under the influence of alcohol".
You are in control
Flying, while fun and exciting, is a precise, demanding, and unforgiving endeavor. Any factor that impairs the pilot's ability to perform the required tasks during the operation of an aircraft is an invitation for disaster.
The use of alcohol is a significant self-imposed stress factor that should be eliminated from the cockpit. The ability to do so is strictly within the pilot's control.
Keep in mind that regulations alone are no guarantee that problems won't occur. It is far more important for pilots to understand the negative effects of alcohol and its deadly impact on flight safety.
General Recommendations
1. As a minimum, adhere to the guidelines:
- 8 hours from "bottle to throttle"
- do not fly while under the influence of alcohol,
- do not fly while using any drug that may adversely affect safety
2. A more conservative approach is to wait 24 hours from the last use of alcohol before flying.
This is especially true if intoxication occurred or if you plan to fly IFR. Cold showers, drinking black coffee, or breathing 100% oxygen cannot speed up the elimination of alcohol from the body.
3. Consider the effects of a hangover. Eight hours from "bottle to throttle" does not mean you are in the best physical condition to fly, or that your blood alcohol concentration is below the legal limits.
4. Recognize the hazards of combining alcohol consumption and flying.
5. Use good judgment. Your life and the lives of your passengers are at risk if you drink and fly.
Some of the effects of various blood alcohol concentrations
0.01 - 0.05% (10-50 mg%) average individual appears normal
0.03 - 0.12% (30-120 mg%) mild euphoria, talkativeness, decreased inhibitions, decreased attention, impaired judgment, increased reaction time
0.09 - 0.25% (90-250 mg%) emotional instability, loss of critical judgment, impairment of memory and comprehension, decreased sensory response, mild muscular incoordination
0.18 - 0.30% (180 - 300 mg%) confusion, dizziness, exaggerated emotions (anger, fear, grief) impaired visual perception, decreased pain sensation, impaired balance, staggering gait, slurred speech, moderate muscular incoordination
0.27 - 0.40% (270 - 400 mg%) apathy, impaired consiousness, stupor, significantly decreased response to stimulation, severe muscular incoordination, inability to stand or walk, vomiting, incontinence of urine and feces
0.35 - 0.50% (350-500mg%) unconsiousness depressed or abolished reflexes, abnormal body temperature coma; possible death from respiratory paralysis (450 mg% or above)
* Legal limit for motor vehicle operation in most provinces is .08 or.10c/c (80-100 mg of alcohol per ml of blood).
Reprinted from: Medical Facts for Pilots Publication AM-400-94/2 FAA Civil Aeromedical Institute Aeromedical Education Division AAM-400, P.O. Box 25089 Oklahoma City, Oklahoma 73125
CAFFEINE AND FLYING "TO CAFF OR NOT TO CAFF?" Is That the
Question? (c)
[Reprinted with the kind permission of the Aviation Safety Institute]
[Edited for Safety FAQ]
By Lt. Tom Pokorski, MSC (Ed: This article is borrowed from the Navy Safety Center publication called APPROACH, May 1985, Page 10 to 11.)
Caffeine is a chemical naturally found in several plants that has for centuries been consumed for its stimulant properties. For any chemistry buffs out there, it is a member of the methylxanthine family. In its pure form, it is a white, bitter-tasting crystal. Like many other substances used by our society today, caffeine used moderately(about 200 to 300 mg per day) should have no detrimental efect on MOST people. I stress MOST because individuals with certain medical conditions should use no caffeine at all. Excessive caffeine consumption, however, can cause problems for almost everyone.
The lethal dose for caffeine is 10,000 milligrams, and you won't reach that level unless you're drinking over 70 cups of strong coffee at one sitting. However, many detrimental effects can be observed at much lower levels of intake. Probably the best-known effect that caffeine causes is that of a stimulant. The person who jokingly says, "I just can't function in the morning until I've had my first cup of coffee" probably sums it up the best. Many overconsumers of caffeine can actually develop a physical need for the drug and will exhibit certain withdrawal-like symptoms if they go without any for a few days. This stimulant effect is not always bad. If used properly and at the right time, the effect can help give you the alertness you might need in a tight situation. However, like any stimulant, the "up" period will always be followed by a certain "down" phase when your body has used all the caffeine in the system. Loss of sleep is another problem which often haunts caffeine abusers. Caffeine causes the stomach to increase acid secretions which on an empty stomach can be particularly distressing. It is also a diuretic which, in layman's terms, simply means that the old urine tank reaches the full level faster than it normally would. This can be a big problem on longer flights in some aircraft.
Interestly, studies have shown that caffeine increases the free fatty acid level in the bloodstream. "So what?" you may ask. Some endurance runners think this can be very beneficial for extra energy toward the end of a race. So if you see some runners drinking small amounts of coffee before a race, you know why.
All the stresses caused by caffeine are problems one would probably function much better without, especially when working in an already high-stress occupation such as aviation.
As stated earlier, caffeine is found naturally in a number of plants. Although it can be produced artifically in a laboratory, most of the caffeine marketed is derived from those plants. The coffee bean is probably the first thing that comes to mind, but caffeine is found in various tea leaves and in the kola nut. Table 1 lists some of the more common products that contain caffeine. Since every study differs to some degree on exactly how much caffeine is in each product, I've listed an average taken from several sources.
How Much Caffeine?
| Item | Milligrams of Caffeine |
| Percolated coffee (5 oz) Regular brewed | 90-120 (depends on strength) |
| Drip coffee (5 oz) Regular brewed | 100-150 |
| Instant coffee (5 oz) Regular brewed | 50-90 |
| Decaf brewed coffee (5 oz) Regular brewed | 4 |
| Decaf instant coffee (5 oz) Regular brewed | 2 |
| Tea (5 oz) brewed/instant | 20-80 (depends on strength) |
| Coca Cola | 39 |
| Dr. Pepper | 46 |
| Ginger Ale | 0 |
| Mountain Dew | 51 |
| Pepsi-Cola | 36 |
| 7-Up | 0 |
| Sunkist Orange | 0 |
| Water | 0 |
| Orange juice | 0 |
| MOST herbal teas | 0 |
| Cocoa beverage (6 oz) | 10 |
| Milk chocolate | 6 |
| Excedrin | 64.8 |
| Vanquish | 33.0 |
| Empirin compound | 32.2 |
So, what does this all mean? What can you do to prevent caffeine from being a problem? As stated before, most experts tend to agree that less than about 300 mgs of caffeine per day should not be hazardous, for MOST people. But, YOU must decide what is good for YOU. There are ways to control your caffeine intake. First though, you need to know how much you are using. Do this by making a table similar to Table 1 for a typical day. If you decide that the amount is excessive and want to reduce it, here are some guidelines for you. If you drink coffee, decide how many cups you can drink and keep count each day. If you make your own coffee, remember the stronger the brew, the more caffeine.
Decaffeinated coffees are becoming more and more popular nowadays; however, they can cause problems of their own. Most decaffeinating processes use a solvent (trichloroethylene or methylene chloride, among others) to extract the caffeine. These processes can add to or change the other organic compounds in coffee. Another process which seems safer in Switzerland, using steam only for extraction. This process, however, is more expensive and the coffee is normally sold only in gourmet stores.
All the caffeine extracted goes into medications or soft drinks that don't originally have caffeine. That's right, a lot of the caffeine in soft drinks is added. So again, if you're looking to reduce your caffeine consumption, watch what kind of sodas you drink. There are a lot of drinks on the market now that contain little or no caffeine.
Probably the best way to cut caffeine intake is to drink something which is naturally caffeine-free. Water is great, but people tend to get bored with it. Most fruit juices are also excellent. Many teas are on the market with ingredients containing no caffeine.
As I mentioned before, quitting caffeine will cause withdrawal symptoms. These symptoms often persist for two or three weeks after the last caffeine intake. They range from drowsiness and irritability to severe headaches. Also reported have been fever, chills, nausea, depression and many others. Many people will treat these symptoms with over-the-counter pain medications which normally will be of no help. However, the extra-strength does usually contain caffeine and obviously will help somewhat by satisfying the craving. For heavy caffeine users, the symptoms can be quite severe, indicating a real need to stop. These people should see their flight surgeons for assistance in stopping. For these individuals, after they've controlled their caffeine use and the symptoms have passed, they will find they'll enjoy a better quality of life.
So if you're trying to answer the question "To caff or not to caff?" stop and think of these few things and make the decision that is right for you.
(Lt. Pokorski is the aviation medical safety officer for Training Air Wing 6, NAS Pensacola, FL.)
ED: The author failed to make more than a passing comment about the diuretic effects of caffeine. It is generally accepted amongest the civil flight surgeon community that consumption of one cup of coffee with caffeine results in excretion of slightly more than one cup of urine. If the person fails to compensate for the extra loss of body fluid, there will ultimately be a reduction in brain fluids which are so very essential to proper cerebral functions. Thus, the knowledgeable flight crews who have either learned the lesson or heeded the warnings will consume sufficient non-caffeine liquids to preserve the proper body fluid level.
EATING BEFORE FLYING
(This information is excerpted from "Aviation Safety" [Feb 1/96]. Since
"AS" is copyrighted, I could not directly reproduce the article.)
Does eating before a flight increase or decrease your chances of becoming airsick? It seems to vary from person to person and between the sexes, but for many people an appropriate light meal seems to help. However, there is evidence which suggests that one should not eat immediately before the flight. Research published by the University of North Dakota Center for Aerospace Sciences produced mixed results. Studies showed that women were more likely to become airsick if they ate less than six hours before the flight. (The AS article did not comment on the equivalent male results.)
A number of studies, include the North Dakota study indicated that heavy foods, salty foods, diary products and high protein diets result in an increased risk of airsickness. It would seem that vegetables and complex carbohydrate diets run the lowest risk of producing airsickness. Additionally, males reduced their chances of airsickness if they ate only three or fewer meals a day rather than continual snacking. (The AS article did not comment on the equivalent female results.) Reducing total caloric intake also reduces the risk of airsickness. (It is not clear in the AS article if that trend held for both males and females, or just males.)
It is not wise to avoid food before the flight because then the blood sugar levels might be too low at flight time. Compounding this is the fact that most people drink fluids only during a meal. Therefore, if a meal is avoided, chances are the person is slightly dehydrated as well. Neither a low blood sugar level or dehydrated condition is good for flying! Conversely, a large meal eaten just before the flight can reduce pilot performance because large amounts of blood will then be routed to the gut for digestion.
In any case, the diet suggestions listed above are healthy!
FUEL FOR THOUGHT
- Poor nutrition can turn a pilot into a sick,
confused passenger. Here's how to "refuel" properly.
(This information is excerpted from "Aviation Safety" [March 1/96]. Since
"AS" is copyrighted, I could not directly reproduce the entire article.)
Apparently the human fuel requirement is probably the most frequently overlooked element in good pilot preflight panning.
"Food converted into glucose is the only source of energy for the brain. [ref 1] Neither the brain nor the central nervous system can store blood sugar and, thus, require constant refueling. [ref 2] Physiological responses to a lack of sufficient glucose include fatigue, mental confusion, faintness, headache, forgetfulness, dizziness, blurred vision, coldness in the extremities, low blood pressure, nervousness, depression and, of course, extreme hunger."
Hypoglycemia is not a rare disease which affects only a few. Most people will become hypoglycemic five hours after the last balanced meal. Fasting for 10 hours is almost guaranteed to impair a pilot's mental, physical and perceptive abilities. Therefore, if breakfast is not eaten after a night's sleep you will be in a condition called "fasting hypoglycemia".
A balanced diet is the best defense against hypoglycemia. Such a balanced diet will also provide the neuronutrients which assist in mental functioning and the proteins and fats containing essential vitamins, nutrients and minerals recommended by the FAA Civil Aeromedical Institute. Neuronutrients are vitamins and minerals that are chemically converted into neurotransmitters. Neuronutrients are required for regulating body temperature and metabolism as well. For example, chromium, which is found in whole-grain cereals, bran, and wheat germ, poultry, beef and broccoli stabilizes the burning of sugar for energy. Eggs, fish and whole wheat also provide the B vitamins which are necessary for proper mental functioning. The latest research suggests that a larger than normal dietary dose of neurotransmitters can actually enhance mental functioning and improve memory. These neurotransmitters, like zinc and iron, can be found in fish, meat and leafy green vegetables.
High sugar intake diets comprising of refined sugar and white flour are bad for you because they cause the pancreas to secrete excessive amounts of insulin, a hormone which causes the body to burn sugar. [ref 2] Consequently sugar levels will drop to low levels and starve the brain. In addition, the consumption of alcohol, caffeine and nicotine compound the problem.
The article suggests that the "I'M SAFE (Illness, Medication, Stress, Alcohol, Fatigue, Emotion) personal preflight acronym checklist become I'M SAFER (R = Re-energize, Refuel or Revitalize) in recognition of the importance of proper nutrition.
If you find that you frequently suffer the symptoms of hypoglycemia you might want to have a glucose tolerance test.
So next time you go flying, remember to eat a proper meal before the flight, and carry some water and nutritious snacks for the flight.
REFERENCES
1) Michael LaCombe, MD "Medicine Made Clear," 1989, Diringo Books, Woodstock, Maine
2) Maura Zack, Wilber Currier, MD, "Sugar Isn't Always Sweet," 1983, Uplift Books, Brea, CA.
Many safety devices and procedures that are developed for air carriers and commercial aviation are resisted by other general aviation pilots because of the expected increase in operating costs. However, there is one procedure practised by large operators that private pilots might consider adopting, since it costs nothing more than a little time--and in the long run could save both lives and money.
That practice is the postflight inspection. Preflight inspections are a time-honoured and widely accepted procedure, directly tied to the Federal Aviation Regulations that make the pilot responsible for not taking off in an aircraft unless it is airworthy. But many people in aviation feel that mechanical deficiencies which arise during a flight can best be identified and attended to at the completion of the flight, rather than before takeoff.
To some extent this reasoning is psychological. The pilot who is eager to be airborne is looking ahead in thought, which may reduce the acuity of one's near vision. Unconsciously you may overlook items which on closer inspection might call for immediate maintenance work. You may have invested considerable time in weather briefing and flight planning; and you hate to disappoint passengers or friends you expect to meet at your destination. You are, in a phrase, "departure-oriented."
This is in sharp contrast to the frame of mind of the pilot conducting a postflight checkup at the destination airport, when all of the pressures of being a pilot-in-command are over for the moment. You tend to relax, when you finally shut down the engine and fasten the tie-downs, basking in a glow of satisfaction at having completed another flight safely and effectively. You may feel a sense of gratitude toward the faithful "old bird" that has carried you swiftly and obediently through hostile elements of the environment.
This is an ideal moment to take a slow walk around to see how your faithful old bird has faired en route. You are not looking for anything as obvious as arrow shafts or bullet holes (not usually) but more subtle signs of strain or wear, such as the following:
Wrinkled skin. Could indicate internal structural damage, following exposure to severe turbulence or airspeeds in excess of limitations for a given manoeuvre. Require immediate examination by an appropriately qualified technician.
Metal damage from stones or other debris. Propellers are especially vulnerable, also the underside of the fuselage and the airfoils.
Mud, ice, etc. clogging up small opening, such as pitot tubes or vent holes, may give you distorted readings on vacuum pressure instruments.
Scuffed or torn tire surfaces. Can occur even on paved runways, as a result of potholes or metal parts dislodged from aircraft.
Uneven landing gear extension. Could be caused by loss of tire pressure, improper pressure in struts, leaks, etc.
Fuel stains, or other signs of leakage of fuel, oil, or hydraulic fluid. The source of a leak should be found and corrected by a qualified mechanic prior to further operation of the aircraft.
Your experience during the flight may direct your attention to other potential trouble areas. Excessive fuel consumption en route? Check the fuel caps seating, the fuel drains, underneath tanks and line fittings. High oil consumption? Look for drips around engine seals. Uneven braking or steering on the ground. Take a good look at the undercarriage. And so on.
After any long cross country flight the chances are good that you will find at least some minor problems if you conduct a postflight examination while the flight experience is still fresh in your mind. The chances are equally good that if you just "let it go for later" you will forget about whatever concerned you during the flight. You may have urgent business in town, but that is hardly ever so pressing as to justify not putting together a squawk list before you leave the aircraft. The time you take to do so could save you hours or days of delay the next time you get ready to fly the aircraft. It might also save your life.
This is not to suggest that a postflight inspection should take the place of a pre-flight inspection--both are important. There are special problems which occur typically during periods of disuse. Corrosion or rot may develop. Insects or rodents may nest in engine tubing. Water may condense in the fuel. Tire pressure may go down. Inspections may become overdue. And so forth.
Problems surfacing during preflight could be said to be more of a passive nature than those which may be found immediately after a flight. Both are important.
A pilot's mental condition or attitude is just as important a preflight item as the aircraft, engine, parachutes, etc. A pilot's actions can be completely altered by various attitude changes, such as: daydreaming, family trouble, money trouble, desire to show off, overconfidence, under confidence, vexations - many others. We cannot eliminate family troubles, money troubles. They are part of life. We don't want to eliminate completely the desire to show off, for without it, there would be no aerobatics, airshow, or competition. There will always be times when we are depressed, others when we're just mad at someone, so we must be aware of the fact that they do exist, they change from hour to hour, and that
we must compensate for them as we must compensate for a crosswind.
To have the ability to accurately and honestly appraise one's own mental attitude, allow for a margin of error in his appraisal and then take just reasonable steps to cause this attitude to help, rather than hurt him should be the goal of every pilot. He should then, prize this possession and regularly
preflight it as the most important part of his safety equipment.
YOU AND YOUR "ENVELOPE" (c)
[Reprinted with the kind permission of the Aviation Safety Institute]
Edited for Safety FAQ
By Lcdr. John Wilckens, MC, USN VP-17
(Editor's Note: Commander Wilckens has done a masterful job of describing to Navy flight personnel some of the important facets of their aviation lives. We present this article taken from APPROACH Magazine, May 1984 issue, published by the U.S. Navy Safety Center at NAS Norfolk, VA. Our thanks to NAVSAFECENTER for the priviledge of reprinting Dr. Wilckens' fine work.)
From the title you are probably expecting some technical article updating existing ejection parameters of your aircraft. Instead, this article will discuss YOUR "envelope", the safe operating limits of YOU, the naval aviator. More specifically, I would like to discuss one determinant of that envelope - stress.
Yes, aviators know and handle stress better than most, but you also see a lot more stress. That stress pushes you to the edge of that envelope. That's okay, too. Stress motivates life and nature in the evolution process. Stress is adaptive, the vital force that heightens our response to meet any challenge.
But modern society has evolved through technology to pose a whole new dimension of stress which we are just beginning to understand. The stress response, that rush you feel on final approach, prepares us for the "fight or flight" syndrome which allows you to bring the aircraft aboard in the worst circumstances. That same stress response is working when the skipper calls you in on the carpet about Petty Officer Jone and his fifth rubber check. "Fight or flight" - who are you going to fight? Or, where are you going to run?
If stress continues for a period of time, it can fatigue you and later damage the body to the point of disease or disfunction. You can feel the "hunkydory", flying on top of the world, and be in a state of dysfunction. To make things worse, the closer you are to that point, the less aware of it you are. It's this point, the envelope, we should concern ourselves with.
Stress is a well-described physiologic process. It directly involves the brain, the autonomic and central nervous systems and the endocrine system.
The brain is a very complex organ, but for simplicity let's consider three separate parts of it. The brain stem, the most primitive part of the brain, is concerned with our basic self-preservation. As we moved up the "evolutionary" ladder, we developed the limbic system. It refines basic instincts. As man, we developed a third part of the brain, the cortex. This is where we think and act. It compromises the majority of our conscious thought.
Physiologically, our body has not kept pace with our mind's development. The stress response, engineered for our brainstem concerns, is triggered also by our limbic system and cortex. So while the response was designed for action, it's often triggered when action is not required.
Okay, so we trigger the stress response - what happens then? The stressor, the threat (again, real or imagined) is received through stimulation of one of our many sensory pathways, i.e., we see a fire warning light. A lot of filtering and circuiting is done in the brain. That red light, through your training, puts you at physiological "general quarters". Your hypothalamus becomes stimulated which next triggers the pituitary gland. The pituitary gland secretes Adrenal Cortistraphic Hormone (ACTH), which circulates in the blood and stimulates our adrenal glands. Once in the adrenals, the ACTH stimulates the production of cortisol, aldosterone and epinerphrine, commonly thought of as the stress hormones.
Cortisol prepares for increased energy with its effect on metabolism. Blood sugar, the fuel for the stress response, increases. A snapshot of the body's and blood's chemistry at the height of stress response would resemble the clinical condition, diabetes. The short term effects of cortisol provide a lot of energy to meet a particular demand. Prolonged cortisol stimulation had many effects that are not so beneficial.
Aldostreone stimulates that kidneys to hang on to sodium. This has the effect of increasing the circulating blood volume, increasing blood pressure and increasing stroke volume - the heart pumps more blood. Again, in the short term, this is a beneficial response. The long term aldosterone effect is hypertension with its attendant complications.
The circulating epinephrine, or adrenaline, potentiates the above effects. Along with the triggerd sympathetic autonomic nervous system, cardiac output increases. There is increased excitability of the nervous system and increased metabolism.
All these things help put you at alert to handle some stress demand. Using the fire warning light again, the stress response speeds up your metabolism and your ability to work through the emergency. You're thinking quickly, going through the checklists, with your hands swiftly enacting the steps. Your visual acuity sharpens; your reaction time quickens, and you become more sensitive to your aircraft's performance. Through training, stressful training, your body has channeled the generalized stress response to effect a positive controlled execution of procedures to handle an emergency.
Most of you have noticed that if you stay ahead of the aircraft and execute your mission to the standards expected, you are exhausted after a flight. That is the effect of the stress response as it moves from the "alarm stage" to the stage of "adaptation". Some of you adapt well and the stress demand lessens. But physiologically, the response is going on regardless of how you feel. Even in positive control and ahead of the aircraft, you are stressed. As the body and its systems approach exhaustion, the stress response becomes maladaptive.
We have all experienced these prolonged stress symptoms but do we appreciate the toll they take on the body? Ninety percent of all hypertension has "no specific cause" and is labeled essential hypertension. Hypertension, regardless of the source, is a major risk factor for heart disease. More subtly, the prolonged stress response affects the body's natural immune or self-defense system. The immune system is not a target organ of the stress response per se. The prolonged stress response marches on at the expense of the immune system, making us more susceptible to all kinds of diseases, both infectious and noninfectious. A body not only has to be exposed, it also needs to be susceptible to become infected by some "bug".
You may all say "well and good", or "that's interesting", "But what does that do for me?" Flying is stressful, and you do a good job with it. The stress of flying you feel confortable with, but what about all those other stresses? "What stresses?" Well, there are lots. They are subtle. They are insidious. they are accumulative. And physiologically, they are dangerous.
So what are these other stresses? There are psychosocial stresses, bioecological stresses, and the stresses of our own behavior and personality. Keep in mind they trigger all those hormones and systems the same as the fire warning light. Let's look at some of the psychosocial stresses:
Two big ones are PCS orders and deployments. these changes are stressful, triggering the stress response, even if those orders are your first choice or the deployments is a "liberty run". Remember, any change is stressful.
Then, there is frustration. How many times are you tasked with more than is reasonable? Sometimes it seems like the whole U.S. Navy is meeting commitments that exceed its capability. That's not without a price. Frustration triggers the stress response and can overload you.
Personality and behavior patterns are stress-related. That agressive, dominating personality you are so proud of can go a little too far, emerging as hostilty. Rigid and unbending profiles will trigger the stress response when you find yourself between the proverbial "rock and a hard place". Another typical stress provoking personality trait you may exhibit is you obsessive compulsiveness and your attention to detail. For the most part, that perfectionism keeps you alive and allows you to overachieve. Just realize that physiologically it can be triggering the stress response. To a point it is adaptive, but past that point it is maladaptive.
Some of the last stresses I want to discuss are bioecological. Some may seem obvious, but few are really appreciated. How about noise? Those 120 dB on the flight deck or 85 dB in your office at the hangar trigger a stress response. In your office, you close the window to close out noise only to experience another, heat. Dehydration and fatigue are all stresses in their own right. If your environment is not comfortable, it is stressful.
Another factor we ignore, usually because we don't understand it, is biological rhythms. We are aware of circadian rhythms, our 24-hour biological clock. Aviators have to cross time zones and fly at night. You can't change that, but keep a mental note you are triggering a physiological response.
While aviators do well with stress, nutritionists and physiologists would wonder how, because of your "stress prone diet". Starved and hypoglycemic, you show up for your brief with a "fighter pilot's breakfast", coffee and a candy bar. It provides instant energy until your pancreas squeezes out healthy amounts of insulin. That insulin pushes most of that sugar into your starving cells causing rebound hypoglycemia. Hypoglycemia produces a stress response. The coffee can also be a problem. Caffeine is a stimulant, acts as a sympathomimetic. It kind of triggers a stress response without even a stressor. One, two, maybe three cups a morning are fine (six-ounce cups); any more is unhealthy and counterproductive.
If breakfast is bad, lunch and or dinner are probably worse. All that processed food has little nutritional content, is high in salt and has tons of fat. Only when you drag that burger through the garden do you get any compensation. What you eat and drink is important.
If that's not enough, some of you tend to add insult to injury with a smoke or a chew, or whatever. Tobacco nicotine also ignites a stress response.
The psychosocial, bioecological and personality stress can be very insidious. The stress response is generally the same, regardless of the trigger. The stress response was designed for action, not for writing evals, passing an NTPI or driving to work. It was designed for night hovers over an overboard sailor in sea state 5, fire warning lights and combat. Cortisol, enephrine and aldosterone don't help family fights, command selection boards or flat tires.
Many of you are probably thinking you have got it all "compartmentalized". "That's how I can live in this stressed and insane world and still fly". Compartmentalization is protective and certainly explains how you can leave the XO, wife, car and kids on the deck while you fly. I feel it's a rather new evolutionary tool. To a point it short circuits cerebral thoughts and stressors, shelving them for a more opportune time. But it's short term, too. Like stress, it can be adaptive if used as designed and maladaptive if used in a prolonged sense. Your brain has only so many shelves, and it can get overloaded. Also, you can't compartmentalize something forever. That stuff has to surface some time and needs to be dealt with. Pushing problems continually under conscious thought becomes stressful in itself.
So what now? Well, half the battle is won. Knowing you're close to the edge of the envelope and how you got there is important. You may not be able to change that. You may not want to change that. But you also want to know when you're over, what got you there, and how to get back in the envelope.
As aviators, you understand systems. You are sensitive to system malfunctions. Popped circuit breakers, vibrations or annunciator panel lights trigger a dissection of the system involved trying to figure out the particular malfunction. You appreciate indications of impending engine failure long before the engine actually fails. In fact, you shut the engine down before it fails. You need that same sensitivy about your own biological systems. Appreciate the ping or vibration in your own body. Don't ignore headaches, low back pain or eye strain. Don't discount high blood pressure readings, allergy flare-ups or recurrent illnesses. Your GI system bears particular attention. Your body deserves the same careful appreciation as your aircraft.
If we insist on pushing our bodies like machines, we need to treat them with similar care. Schedule maintenance, do preventive work or perform corrosion control. After so many hours the aircraft and engines are inspected, put into phase, go to NARF, etc. Take leave. You shouldn't be flying if you haven't taken leave in over a year. If you work hard, play hard. But that play should not reinforce the stress response, it should release it. On occasion you need something mindless and non-ego-serving. You should come off the golf course more relaxed than when you went on it; if not, you need a new sport.
Identify the stressors. You can't always change them, but there may be alternatives. Much of our stress is mental or psychological. Is it necessary? Are things prioritized in your life? The big picture helps. Goals help. A spiritual experience may help. Look at your day. Could it use a little more structure and management? Does everything have to be done by crisis management? If you're spending long hours at work, there's a good chance things aren't organized, running efficiently, or you're doing somebody else's work. Delegate responsibility. Learn to say no. Don't over-commit yourself. Take your horrendous workload and divide it into several manageable parts. Set goals, plot progress, document work. Try avoiding all other unnecessary stress. Accept help, accept fallibility. Plan ahead, anticipate and realize vulnerabilities. A big misconception is that boredom is relaxation, but it is not. It happens to be very stressful. Vacation and leave doesn't always mean relaxation either, with taxis, airports, lost travelers checks, etc. And you diet. Do your diet justice. Make every effort to modify it to some healthy standard. You put "high-test" in your aircraft and your sportscar. Why not put some good "fuel" into your own body's engine?
Another myth is that alcohol relieves stress. When you come home each night, before you kiss the wife or kick the dog, how many of you grab for a beer from the fridge? Somehow that first beer puts things into perspective. If one does it for you - great. But if it takes many more, you've got a problem! Alcohol is a chemical depressant. In small amounts it acts like a stimulant because it depresses the restraining neurotransmissions. In larger amounts it depresses the brain in general, including those stress response activators.
Alcohol doesn't make problems go away. If you thought you had brushfires before, DWI or an alcohol-related incident will certainly complicate you life more. Physiologically, alcohol inhibits other systems, the immune system in particular, which is already under attack from your stress. Your gastrointestinal system, to include the liver, is tested. Long after your blood alcohol level returns to zero from an overindulgence, your brain suffers from lost neurons and neurotransmitters. In the final analysis, if not a stress itself, alcohol interferes with your body's abilities to handle stress. It certainly is not a remedy.
What is a good prescription for stress? One of the best is exercise, aerobic exercise in particular. Yes, exercise is a stress, but it's used as designed, mobilization for action with action. A good aerobic routine makes the body systems more efficient. Excess fat and sugar are burned as fuel. The body changes its metabolism and attempts to realign itself with natural cues. Sleep becomes better, if not more. Diet becomes healthy. Excess stress metabolites are burned off, allowing the body as a whole to rest and recuperate after exercise. You gradually obtain the physical and mental ability to do more work in less time.
But exercise is not a panacea. Again, it's also a stress, and to extremes it can precipitate failure in the body. As your percent body fat drops way off, your immune system suffers. World class athletes are intimately aware of this. They train to peak for the big event. If they peak too early, they experience illness or injury at game time. After the big event, athletes reduce or stop training for a period of time to recover. This is sort of