FAA Advisory Circular 43.13-1B
Acceptable Methods, Techniques, and Practices
Aircraft Inspection and Repair
AC 43.13-1B | 3. Fiberglass and Plastics | 3. Transparent Plastics | 3-20. Forming Procedures and Techniques
9/8/98
SECTION 3. TRANSPARENT PLASTICS
AC 43.13-1B
3-18. GENERAL. Plastics cover a broad
field of organic synthetic resin and may be di
vided into two main classifications – thermo
plastics and thermosetting plastics.
location away from heating coils, radiators, or
steam pipes, and away from such fumes as are
found in paint spray booths or paint storage ar
eas.
a. Thermoplastics. Thermoplastics may
be softened by heat and can be dissolved in
various organic solvents. Two kinds of trans
parent thermoplastic materials are commonly
employed in windows, canopies, etc. These
materials are known as acrylic plastics and
cellulose acetate plastics.
(1) Cellulose acetate was used in the
past but since it is dimensionally unstable and
turns yellow after it has been installed for a
time, it has just about passed from the scene
and is not considered an acceptable substitute
for acrylic.
(2) Acrylic plastics are known by the
trade names of Lucite or Plexiglas and by the
British as Perspex and meet the military speci
fications of MIL-P-5425 for regular acrylic,
MIL-P-8184 for craze-resistant acrylic.
b. Thermosetting Plastics. These plas
tics do not soften appreciably under heat but
may char and blister at temperatures of
240 to 260 °C (400 to 500 °F). Most of the
molded products of synthetic resin composi
tion, such as phenolic, urea-formaldehyde, and
melamine formaldehyde resins, belong to the
thermosetting group. Once the plastic be
comes hard, additional heat will not change it
back into a liquid as it would with a thermo
plastic.
3-19. STORAGE AND HANDLING. Be
cause transparent thermoplastic sheets soften
and deform when they are heated, they must be
stored where the temperature will never be
come excessive. Store them in a cool, dry
a. Paper-masked transparent sheets
must be kept out of the direct rays of the sun,
because sunlight will accelerate deterioration
of the adhesive, causing it to bond to the plas
tic and making it difficult to remove.
b. Plastic sheets should be stored with the
masking paper in place, in bins that are tilted
at a ten-degree angle from the vertical. This
will prevent their buckling. If the sheets are
stored horizontally, take care to avoid getting
dirt and chips between them. Stacks of sheets
must never be over 18 inches high, with the
smallest sheets stacked on top of the larger
ones so there will be no unsupported overhang.
Leave the masking paper on the sheets as long
as possible, and take care not to scratch or
gouge the sheets by sliding them against each
other or across rough or dirty tables.
c. Formed sections should be stored with
ample support so they will not lose their shape.
Vertical nesting should be avoided. Protect
formed parts from temperatures higher than
120 °F (49 °C), and leave their protective
coating in place until they are installed on the
aircraft.
3-20. FORMING PROCEDURES AND
TECHNIQUES. Transparent acrylic plastics
get soft and pliable when they are heated to
their forming temperatures and can be formed
to almost any shape. When they cool, they re
tain the shape to which they were formed.
Acrylic plastic may be cold-bent into a single
curvature if the material is thin and the bend
ing radius is at least 180 times the thickness of
the sheet. Cold bending beyond these limits
Par 3-18
Page 3-15