Zlin Aviation
Section 2
Maintenance Manual Line Maintenance, Repairs and Alterations
Issued: 01/02/2006
QAP-AMM-Rev02
Date of latest Revision: 23/01/2013
Page Number: 2-14
2.3.3.4 STOP DRILLING OF CRACKS
This is an extract of FAA AC 43.13-1B Chapter 3.
Replace, rather than repair extensively damaged transparent plastic, whenever possible, since even a
carefully patched part is not the equal of a new section, either optically or structurally. At the first
sign of crack development, drill a small hole with a # 30 or a 1/8-inch drill at the extreme ends of
the cracks as shown in figure 3-21. This serves to localize the cracks and to prevent further splitting
by distributing the strain over a large area. If the cracks are small, stopping them with drilled holes
will usually suffice until replacement or more permanent repairs can be made. The following
repairs are permissible; however, they are not to be located in the pilot’s line of vision during
landing or normal flight.
CLEANING AND POLISHING TRANSPARENT PLASTIC.
Plastics have many advantages over glass for aircraft use, but they lack the surface hardness of
glass and care must be exercised while servicing the aircraft to avoid scratching or otherwise
damaging the surface.
a. Clean the plastic
by washing it with plenty of water and mild soap, using a clean, soft, grit-free
cloth, sponge, or bare hands. Do not use gasoline, alcohol, benzene, acetone, carbon tetrachloride,
fire extinguisher or deicing fluids, lacquer thinners, or window cleaning sprays. These will soften
the plastic and cause crazing.
b. Plastics should not be rubbed
with a dry cloth since this is likely to cause scratches, and also to
build up an electrostatic charge that attracts dust particles to the surface. If after removing dirt and
grease, no great amount of scratching is visible, finish the plastic with a good grade of commercial
wax. Apply the wax in a thin even coat and bring to a high polish by rubbing lightly with a soft
cloth.
c. Do not attempt hand polishing
or buffing until the surface is clean. A soft, open-type cotton or
flannel buffing wheel is suggested. Minor scratches may be removed by vigorously rubbing the
