nuts & bolts
maintenance & restoration
Aircraft Windshields and Windows
Critical components that shouldn’t be neglected
JEFF SIMON, EAA 478233
Of all the devices at a pilot’s disposal, none are as important as your eyeballs. It’s equally critical that he windshield and windows of the aircraft remain
in top condition. After all, the last thing you need on
approach is to be blinded by the sun through spider-web
micro-cracks and crazing in your windshield. And, when
advised by approach control of converging traffic, you
don’t want to spend precious seconds figuring out if those
are bugs on a windshield or a Mooney coming at you at a
closing rate of 250 knots.
Aircraft windshields and windows are critical components in an aircraft. In some cases, they even serve as
structural components of the airframe. Like many airframe
components on general aviation (GA) aircraft, windows
and windshields are custom-fitted to a particular aircraft.
Light aircraft are hand-built, and regardless of the amount
of tooling and jigs used to produce them, they inevitably vary from one to the next. Because of this, aircraft
“glass” manufacturers produce oversized windows and
windshields, leaving the installer the challenging job of
measuring, trimming, and fitting for each unique installation. In most cases, the cost of labor far outweighs the cost
of the parts.
Because of this, it makes good sense to protect the
“glass” that you already have, before you get to the point
that replacement is your only option.
The Basics of Aircraft “Glass”
Most aircraft windows and windshields are not made
from glass at all. Traditional glass is far too heavy for most
aircraft. So, the windows and windshields of most light
aircraft are made from an acrylic plastic, most commonly
known by the Rohm and Haas Company trade name
Plexiglas. Acrylic plastics are easily heat-formed using a
process known as cell casting, which produces a very clear
product with no grain (lines) within the base material.
Acrylic is an excellent material for aircraft use because it is
relatively hard and more scratch-resistant than other forms
of plastic, such as Lexan.
…well-intentioned aircraft owners can
be the primary source of damage to
windows and windshields. Without using
the proper procedures and chemicals,
it’s easy to do a lot of damage in a
short amount of time.
The term Lexan refers to the trade name established by General Electric for its polycarbonate plastics.
Polycarbonate plastic is much softer than acrylic, very flexible, and extremely resistant to cracking. For this reason, it
has been used in instances where the part must be formed
by installation or continue to flex in use, such as the side
windows on an Ercoupe that flex each time the windows
are raised or lowered. Unfortunately, the same softness that
makes Lexan so flexible also makes it vulnerable to scratching and chemical damage from fuel.
Care and Preventive Maintenance
Unfortunately, well-intentioned aircraft owners can be the
primary source of damage to windows and windshields.
Without using the proper procedures and chemicals, it’s easy
to do a lot of damage in a short amount of time.