extent of the damage. Inspect the internal structure for
FLUSH ACCESS DOOR.--A flush access door
damage or signs of strain. Members that are bent,
installation, as shown in figure 4-64, is sometimes
fractured, or wrinkled must be replaced or repaired.
permitted. It is installed to make repair to the internal
They may be sheared considerably without visible
structure easier and to permit repair of damage to the
evidence of such a condition. You should drill out rivets
skin in certain areas. The flush access door consists of a
at various points in the damaged area and examine them
doubler and a stressed cover plate. The cover plate is
for signs of shear failure.
normally fabricated from material identical to the skin.
A single row of nut plates is riveted to the doubler. The
During the inspection, note carefully all unusual
doubler is then riveted to the interior side of the skin
riveting problems or conditions that render riveting
with two rows of rivets, staggered as shown in figure
difficult or make rivet replacement impossible. Any
4-64. The cover plate is attached to the doubler with
fixtures that will hinder riveting and prevent the use of
machine screws. When an access door is permitted and
straight bucking bars will be apparent in a thorough
installed over the internal structure, screws should be
inspection. There will also be places where flanges or
installed through the cover plate into the internal
reinforcing members, intersection of stringers,
structural member wherever possible.
longerons, formers, frames, or rings make the bucking
of rivets very difficult. This problem can be solved by
SKIN REPLACEMENT.--Sometimes damage
designing and making bucking bars to suit these
to the metal skin is so extensive that an entire panel
must be replaced. Also, an excessive number of patches
or minor repairs to a section may require the
You must take care to avoid mutilating the damaged
replacement of the entire panel.
skin in the removal process. In some cases, it can be
used as a template for the layout and the drilling of
As in all other forms of repairs, the first step is to
holes in the new piece of skin.
inspect the damaged area thoroughly to determine the
Figure 4-64.--Flush access door installation.