Well, Tom Cruise looked great in his aviators in Top Gun, no ifs and buts about that. Just cool or do sunglasses really serve a purpose for pilots?
Pilots form an integral part of the economy, transporting people and goods all over the world. In uniform, smart and ready to do the job, the sunglass is, on almost all occasions, hanging from the front shirt pocket of the aviator. Our discussion here will focus on commercial airliners only.
Flight decks, or cockpits, are mostly of two types. The first is the normal instrument panel which consists of analog dials and gauges. These are found in older generation aircraft such as the McDonnell Douglas DC 8, 9 and 10 as well as the earlier Boeing aircraft (707, 727). These may or may not be flying anymore in our skies as the retirement age of these classics is pretty much now. The latter type is referred to as Glass Cockpit, where aircraft systems and dials show up across a range of LCD screens spread out in the instrument panel. Modern jets across the board, including Airbus, Boeing as well as others, fit into this category.
For a pilot flying at altitudes of between 2,000 to 41,000 feet, the choice of sunglasses is an important one. The higher the altitude, the brighter the sun as cloud cover is nonexistent at higher altitudes. Given that cockpit windows have UV protection as well sun visors for protection, there are always instances where some UV light may penetrate through and sunlight will always pass through the glare shield and the visors, hence complete eye protection is only possible with sunglasses.The choice now, for our pilot friend, is between polarized and non polarized sunglasses.
Polarized sunglasses have a filter between the lenses, chemical in nature, which absorbs horizontal light waves. A horizontal light wave is mainly reflection and/or glare and hence a clearer picture is perceived by the wearer when wearing these polarized lenses. Non polarized lenses do not have this filter and are basically lenses with an added tint of choice of color. Note that depth perception and color is maintained in both choices of lenses.
Instruments in a glass cockpit run on the principle of glare. Information showing up on LCD screens is visible to the pilot because of glare that is emitted by them. Hence, if a pilot was to wear polarized sunglasses, he or she would not be able to read the instruments clearly. Secondly, aircraft bodies and windscreens, when in sunlight, give off glare. Again, polarized sunglasses will hamper the pilot’s vision in being able to see this off any aircraft, especially when flying under VFR (visual flight rules) in a busy airspace.
Which leads us to one conclusion only: Today’s modern aircraft are all equipped with a glass cockpit. LCD screens from left to right display vast amounts of avionic information for the safe passage of flight. A modern day pilot can only wear non polarized sunglasses.
What color lenses one may ask? Although all colors will do a good job of protecting the eyes against harmful light, there are colors which may be more suitable for flying. In my opinion as a part time aviator, I find the Gray color the best as it is a neutral density filter, i.e. distorts the colors the least. However, green and brown tints are excellent as well.
As far as material of the lenses is concerned, my preference is definitely glass. Glass lenses are the best for optical clarity and resistance against scratches, but not for UV protection. A layer of UV 400 protection coating must be applied. Plastic lenses and Polycarbonate lenses are also quite good and can be used anytime. Utmost care must be taken to make sure that lenses are UV 400 protected.
So next time you see a pilot wearing sunglasses, remember that there is a science behind it!