Cessna 172 Skyhawk SERIES, Maintenance Manual

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CESSNA AIRCRAFT COMPANY
SINGLE ENGINE
STRUCTURAL REPAIR MANUAL
PLASTIC WINDOW SURFACE REPAIR
1. Repair of Plastic Window Surfaces
A. Damaged window panels and the windshield on the airplane are normally removed and replaced
if the damage is extensive. However, certain repairs as described in the following paragraphs can
be accomplished without removing the damaged part from the airplane. Three types of temporary
repairs for cracked plastic are possible. No repairs of any kind are recommended on highly stressed
or compound curves or where the repair would be likely to affect the pilots or copilot's
fi eld of vision
during normal fl ight or landing operations. Curved areas are more dif fi cult to repair than fl at areas,
and any repaired area is both structurally and optically inferior to the original surface. Refer to Figure
801 for an illustration of typical windshield and window repair.
NOTE: If temporary repairs are made, operations should be kept to a minimum until replacement
of window can be made.
2. Tools and Materials
NAME NUMBER MANUFACTURER USE
Novus 1 Novus Co.
Minneapolis, MN 55435 To polish scratches
out of windows.
Novus 2 Novus Co. To polish scratches
out of windows.
Methylene Chloride Commercially Available Solvent for repair of
windows.
3. Stop-Drilling
A. The following procedure should be used when stop-drilling.
(1)
When a crack appears in a panel, drill a hole at the end of the crack to prevent further spreading.
The hole should be approximately 1/8 inch in diameter, depending on the length of the crack and
the thickness of the material. This is a temporary repair.
NOTE: If temporary repairs are made, operations should be kept to a minimum until
replacement of window or windshield can be made.
4. Surface Patch
A. The following procedure should be used when preparing a surface patch.
(1)
Trim away damaged area and round all corners.
(2) Cut a piece of plastic of suf fi cient size to cover the damaged area and extend ¾ inch on each
side of crack or hole.
(3) Bevel edges as shown in Figure 801.
NOTE: If section to be repaired is curved, shape surface patch to the same contour by
heating it in an oil bath at a temperature of 248°F to 302°F, or it may be heated on a
hotplate until soft. Boiling water should not be used for heating.
(4) Coat surfaces to be bonded evenly with plastic solvent adhesive (acrylic chips dissolved in
methylene chloride) and place immediately over the hole.
(5) Maintain a uniform pressure of 5 to 10 pounds per square inch on the surface patch for a
minimum of 3 hours. Allow surface to dry 24 to 36 hours before sanding or polishing is attempted.
5. Insert (Plug) Patch
A. The following procedure should be used when preparing a plug patch.
(1)
Trim hole to a perfect circle or oval and bevel edges slightly.
56-10-00
Page 801
© Cessna Aircraft Company
Jun 1/2005