is perfectly clean, don’t use it. Soft cloths such as cotton
diapers also work well, but avoid using polyester or rayon; it
can scratch unprotected plastics. To eliminate any chance of
scratching, use only disposable cloths. DuPont makes special
disposable windshield wipes under the brand name Sontara.
Technique matters, too. A number of cleaner and polish manufacturers recommend applying their products in a
straight back-and-forth pattern in line with the airflow over
the window or windshield, so as to avoid swirl marks that
will reflect the sun at any angle.
Keeping your windows clean and polished also has the
Aviation-specific products are available
for both cleaning and polishing plastic
windows and windshields. The simplest
ones consist of only acrylic-safe clean-
ers and anti-static compounds.
advantage of making it much more difficult for future
contaminants to stick. A simple, once-a-month cleaning
and polish should make it easy to remove almost all
bugs and grime with simple water and your bare hand.
Repairing Versus Replacing
Most window damage can be categorized as cracks, crazing, hazing, or scratches. There are no long-term solutions
to cracks. You can stop-drill the crack to deter progression, but the bottom line is that the window needs to be
replaced. Depending on the crack type and location, there
might also be an airworthiness issue.
Crazing refers to the myriad of “spider webs” that one
would see through the glass when looking at the sun. It is
caused by thousands of minute fractures in the plastic and
typically occurs toward the surface of the window. Crazing
can be caused by stress, UV exposure, or chemical damage from cleaning products containing ammonia, MEK,
or other solvents. It can sometimes be treated by removing the damaged outer layer of the window. There are a
number of excellent products on the market that do just
that, but the labor is extremely intensive and has several
risks. If not done properly, the process can result in optical
distortion and/or losing critical window thickness during
Hazing refers to a window that has lost its clarity.
Hazing is caused by internal degradation of the plastic,
making the window look milky or cloudy. It is most often
caused by UV or chemical damage. Since hazing occurs in
the core of the plastic, it cannot be repaired.
The most common window repairs are those to remove
scratches. So long as they are localized, and the window itself
isn’t suffering from hazing or crazing, there are some great
systems out there to remove minor scratches.
Novus No. 2 and No. 3 as well as “210 Plus” Plastic Scratch
Remover are mildly abrasive creams that can help with small
scratches that you can just barely feel with your finger-
Eight Tips for Window Replacement
If you do have to resort to complete window replacement,
here are a few tips you can use to make the job easier:
• Consider installing thicker glass than the original.
Thicker windows and windshields can greatly reduce
cabin noise, are much stronger, and should last longer in
service. Many window manufacturers have supplemental
type certificates to make this possible.
• Always work in a warm environment, above 70°F if
possible. The warmer the windows, the less likely they
will be to crack or chip while trimming and flexing them
• Remove the protective film from the new window
carefully and inspect the window for any manufacturing defects before starting work. After inspection,
replace the protective film, leaving only the perimeter
areas (that must be worked) unprotected.
• If the original glass can be removed intact and fits the
aircraft well, trace its outline on the new glass with a
china crayon as a guideline. Don’t make this your ultimate guide, as the curvatures may vary. But, use it as a
reference point for your trimming job.
• For any holes that need to be drilled in the window,
be sure to use a special acrylic drill bit. These bits are
specially sharpened to scrape a clean hole in the window
and will not chip or crack the plastic like standard drill
bits. Keep in mind that acrylic expands and contracts, so
the holes should generally be drilled oversize.
• Be sure to bevel and sand all cut window edges slightly
and remove any tooling marks that may act as stress
risers for future cracks.
• Use the proper sealing materials, as specified by
both the window and aircraft manufacturers. Some
of the adhesives, tapes, and sealing materials have
evolved over the years, and there may be more than
one option available.
• If the window installation requires flexing the window
or feeding it into a channel frame, the process can
often go smoother by spraying the window edges liberally with an approved window cleaner. This can act as
a lubricant during installation, and most will evaporate
quickly once the job is complete.