What It Looks Like

See-and-avoid is the primary method that we use to avoid conflicts with other aircraft when we fly in visual meteorological conditions. Our ability to scan for and spot traffic depends on a lot of factors, including the angle of the sun, the clarity of the air, aircraft attitude, the amount of window area in the airplane, and the condition of the windows themselves.

Most light general aviation airplanes have a windshield and side windows made from acrylic plastic, which is far lighter and cheaper than glass, easier to cut and fit during the installation process, and more easily repaired. Acrylic plastic also is more pliable than glass - an important consideration given the amount of flexing that light airplanes undergo during turbulence and maneuvering.

The big drawback of acrylic plastic is that it is relatively soft and therefore vulnerable to scratching from improper cleaning. According to Federal Aviation Administration (FAA) Advisory Circular 43.13-1B, acrylic windshields and windows may be cleaned by washing with plenty of water and mild soap, using a clean, soft, grit-free cloth, sponge, or bare hands. Do not use gasoline, alcohol, benzene, acetone, carbon tetrachloride, fire-extinguishing chemicals, deicing fluids, lacquer thinners, or window cleaning sprays. These will soften the plastic and cause minute cracking, called crazing.

Plastics should not be rubbed with a dry cloth because this is likely to cause scratches and build up an electrostatic charge that attracts dust particles to the surface. If, after removing dirt and grease, no great amount of scratching is visible, finish the plastic with a good grade of commercial wax. Apply the wax in a thin, even coat and bring to a high polish by rubbing lightly with a soft cloth. Some scratches may be removed using special sanding techniques, but this is best left to a mechanic or a window specialist.

Excessive heat can deform an acrylic plastic windshield or window. When an aircraft is parked in direct sunlight, the windshield will absorb heat and will actually become hotter than either the inside of the aircraft or the outside air. At the same time, the sun will cause the inside of a closed aircraft to become extremely hot, and the plastic windshield also absorbs this heat. Prolonged exposure to sunlight over a period of years can lead to crazing and, depending on the quality of the plastic, a milky discoloration.

To protect against the damage this can cause, the FAA recommends that the aircraft should be stored in a hangar or in some type of shade to keep the sun from coming in direct contact with the windshield. Of course, this isn't always possible. A close-fitting canopy cover is effective in reducing heat soak, but if grit blows up under the cover it can scratch the windows and windshield.

The best advice on caring for acrylic plastic aircraft windshield and windows is to treat them the same as you would the exterior finish on an expensive car. Wash and wax carefully, using plenty of water, approved cleaners, wax, and a soft, grit-free cloth. The car will stay nice to look at; the windows will stay nice to look through.