Patching is one method used in repairing a
Still another way to locate the rivet holes without a
damaged stringer (fig. 4-67). The repair consists of a
template is to use a hole finder similar to the one shown
reinforcement splice and a filler splice. The
in figure 4-66.
reinforcement splice should be long enough to extend a
After all the holes have been drilled, the temporary
minimum of four times the width of the leg of the
fasteners are taken out and the sheet is removed from
stringer on each side of the damaged area. The
the framework. The burrs left by drilling must be
cross-sectional area of the reinforcement splice must be
removed from both sides of all holes in the skin, the
equal to or greater than the stringer itself. The damage
stringers, and the rib flanges. Burring may be
is cleaned to a smooth contour with corner radii, and a
accomplished with a few light turns of a deburring tool
filler of the proper thickness is prepared to fit in the
or drill bit. In this way, particles of metal left around the
cleaned area. If possible, you should always make both
edges of the drilled holes are eliminated. If they were
ends of the cutout midway between two rivets so that
not removed, the joint would not be tight and rivets
the existing rivet pattern can be maintained in the repair.
might expand, or flash, between the parts being riveted.
Cut the filler splice one thirty-second of an inch shorter
in length than the cutout section. This will allow a
1/64-inch clearance stringer between each end of the
filler splice and the stub ends of the stringer. This
The repair of internal structures concerns the repair
eliminates the possibility of stress developing from
or replacement of extruded parts used as stringers, webs
contact between the two parts.
used as bulkheads, and formed parts, such as ribs and
After the damage has been inspected and classified,
the next consideration is to plan the repair so that it may
be assembled in the proper sequence. Before the
removal, repair, or replacement of a structural member
is undertaken, the adjacent structural members of the
aircraft must be supported so that proper alignment is
maintained throughout the operation.
STRINGERS.--A stringer is a spanwise
structural member designed to stiffen the skin and aid
in maintaining the contour of the structure. Stringers
also transfer stresses from the skin to the bulkheads and
ribs to which they are attached. Stringers are not
continuous throughout the structure as are longerons
and are not subject to as much stress. Stringers are
made from both extruded and rolled sections, and are
usually in the form of C-channels, angles, or hat
Figure 4-67.--Stringer repair by patching.
Figure 4-66.--Using a hole finder.