clear of internal structure, except for modification of
the doubler.
CHEM-MILLED SKIN REPAIR.—On some
aircraft the fuselage skin is Chem-Milled or machine
tapered and highly stressed. Figure 13-63 shows a
Chem-Milled skin repair in a pressurized fuselage
section. The skin consists of a shim, a doubler, and a
filler. The damage area is trimmed and the inside
corners are filed to one-fourth of an inch in radius.
The replaced metal and rivets or other fasteners must
be equal to or stronger than the original. The
structural repair manual should be consulted for
fastener spacing, edge distance, and repair procedure.
During final assembly of the repair, the fabricated
parts should be bonded together with an adhesive to
ensure pressurization is maintained.
FLUSH ACCESS DOOR.—A flush access door
installation, as shown in figure 13-64, is sometimes
permitted. It is installed to make repair to the internal
structure easier and to permit repair of damage to the
skin in certain areas. The flush access door consists
of a doubler and a stressed cover plate. The cover
plate is normally fabricated from material identical to
the skin. A single row of nut plates is riveted to the
doubler. The doubler is then riveted to the interior
side of the skin with two rows of rivets, staggered as
shown in figure 13-64. The cover plate is attached to
the doubler with machine screws. When an access
Figure 13-63.—Chem-Milled skin repair (fuselage pressurized).
13-46
