Originally Posted by
marquette42
I often hear inexperienced or poorly educated opticians say pilots can never wear polarized. There is little farther from the truth. There certainly are a segment of the piloting community who would have their flight performance hampered by polarized, but to make a blanket statement that no pilot should ever wear polarized is incorrecr.
Australian Government.........Civil Aviation Authority,
2.1.13 Sunglasses
Glare is often a cause of significant discomfort when flying above cloud or when flying intothe sun. Sunglasses may be required in such circumstances.
There are two basic factors to consider when selecting sunglasses, namely the frame andthe lenses.
Any spectacle frame reduces the field of vision. Narrow frames that carry large lenses aredesirable. The most critical problem with frames arises from the presence of wide sidearmswhich significantly impair the peripheral visual field.
Sunglass lenses should protect the eyes from glare while not adversely affecting the visualcues necessary for safe flight. Accordingly, lenses should not be too dark, and shouldtransmit at least 15% of incident light. The tint used should be "neutral density" (N.D.),that is, a greyish tint that does not distort colour perception or adversely affect red signaldetection and recognition. The recommended tint is N.D.15.
Lenses of polycarbonate are preferred because of their impact-resistance and ability toabsorb ultra-violet and infrared rays. However, these lenses can scratch readily and anyscratched spectacles should be discarded.
To ensure that sunglasses provide adequate protection from solar radiation that maydamage the eyes, only those sunglasses that conform to the current Australian Standardshould be worn.
Sunglasses that conform to the current Australian Standard also meet acceptablestandards for lens quality, frame strength and lens retention.For aviation use, those sunglasses marked "Specific Purpose Sunglasses" arerecommended, provided their frames are appropriate. The lenses of these sunglasseshave been specifically designed for use in conditions of intense glare, such as in flightabove cloud. At high altitude, atmospheric absorption of ultra-violet radiation is reduced.
Polarising sunglasses should
not
be used when flying. The polarising filter interacts withthe cockpit transparency to produce a distorted and degraded visual field that poses athreat to air safety.
The pilot who already wears prescription spectacles for flying can choose from a numberof options for glare protection. Prescription sunglasses with N.D.15 lenses can beobtained, or N.D.15 clip-on or flip-up sunglasses may be worn over prescriptionspectacles.
Pilots who require correction of their near vision only and who wear "look-overs" areadvised to obtain bifocals and a plano upper segment. Clip-on or flip-up sunglasses can
then be worn. However, the dangers of flip-ups previously mentioned should be recalled.
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