FAA Advisory Circular 43.13-1B
Acceptable Methods, Techniques, and Practices
Aircraft Inspection and Repair
AC 43.13-1B | 3. Fiberglass and Plastics | 4. Windshields, Enclosures, and Windows | 3-40. General
9/8/98
AC 43.13-1B
SECTION 4. WINDSHIELDS, ENCLOSURES, AND WINDOWS
3-40. GENERAL. These repairs are appli
cable to plastic windshields, enclosures, and
windows in nonpressurized airplanes. For
pressurized airplanes, replace or repair plastic
elements in accordance with the manufac
turer’s recommendation. When windshields
and side windows made of acrylic plastics are
damaged, they are usually replaced unless the
damage is minor and a repair would not be in
the line of vision. Repairs usually require a
great deal of labor. Replacement parts are
readily available, so replacement is normally
more economical than repair.
a. Minor Repairs. There are times, how
ever, when a windshield may be cracked and
safety is not impaired. In that case, repairs can
be made by stop-drilling the ends of the crack
with a # 30 drill (1/8 inch) to prevent the con
centration of stresses causing the crack to con
tinue. Drill a series of number 40 holes a
half-inch from the edge of the crack about a
half-inch apart, and lace through these holes
with brass safety wire (see figure 3-24) and
seal with clear silicone to waterproof.
b. Temporary Repairs. One way to
make a temporary repair is to stop-drill the
ends of the crack, and then drill number
27 holes every inch or so in the crack. Use
AN515-6 screws and AN365-632 nuts with
AN960-6 washers on both sides of the plastic.
This will hold the crack together and prevent
further breakage until the windshield can be
properly repaired or replaced. (See fig
ure 3-24.)
c. Permanent Repairs. Windshields or
side windows with small cracks that affect
only the appearance rather than the airworthi
ness of a sheet, may be repaired by first
stop-drilling the ends of the crack with a
# 30 or a 1/8-inch drill. Then use a hypoder
mic syringe and needle to fill the crack with
polymerizable cement such as PS-30 or
Weld-On 40, and allow capillary action to fill
the crack completely. Soak the end of a
1/8-inch acrylic rod in cement to form a cush
ion and insert it in the stop-drilled hole. Allow
the repair to dry for about 30 minutes, and then
trim the rod off flush with the sheet.
d. Polishing and Finishing. Scratches
and repair marks, within certain limitations,
can be removed from acrylic plastic. No
sanding that could adversely affect the plas
tic’s optical properties and distort the pilot’s
vision should be done on any portion of a
windshield.
(1) If there are scratches or repair marks
in an area that can be sanded, they may be re
moved by first sanding the area. Use 320- or
400-grit abrasive paper that is wrapped around
a felt or rubber pad.
(2) Use circular rubbing motions, light
pressure, and a mild liquid soap solution as a
lubricant. After the sanding is complete, rinse
the surface thoroughly with running water.
Then, using a 500-grit paper, continue to sand
lightly. Keep moving to higher grit paper and
sand and rinse until all of the sanding or repair
marks have been removed.
(3) After using the finest abrasive pa
per, use rubbing compound and buff in a cir
cular motion to remove all traces of the sand
ing.
e. Cleaning. Acrylic windshields and
windows may be cleaned by washing them
with mild soap and running water. Rub the
surface with your bare hands in a stream of
water. Follow with the same procedure but
with soap and water. After the soap and dirt
have been flushed away, dry the surface with a
soft, clean cloth or tissue and polish it with a
Par 3-40
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