You have several steps to take to find the correct
repair materials and procedures in a structural repair
manual. Figure 13-57 shows each of the steps.
NOTE: The aircraft structural repair manual,
shown in figure 13-57, was selected as a
typical manual. The procedures that follow
are typical but are not standard. Various
manufacturers use different methods to
indicate the types of materials used and
special instructions for using their particular
1. The extent of the damage to the aircraft is
determined by the inspection of the damaged area, as
2. Using a master index
damaged group of the aircraft.
on the diagram, determine the
where the component is found.
diagram, identify the
From the table shown
section of the manual
3. After locating the correct group master index
diagram, obtain the correct item number for the
damaged component from the illustration.
4. Find the index number for the damaged unit
from the component diagram.
5. The index number is (hen matched with the
item number on the repair material chart. This chart
will normally give the parts description, drawing
number, gauge, type of material, and location of
6. You can find the repair diagram by locating
the required section of the manual and turning to the
correct figure in that section. Access provisions and
negligible damage information are given on the repair
diagrams. After the damage has been cleaned,
determine whether or not the damage is negligible
according to the repair diagram. If the damage is
within the limits of negligible damage, it may be
disregarded unless it is necessary to close the hole for
aerodynamic smoothness. If the damage exceeds the
limits of negligible damage, it must be repaired
according to the repair diagram or replaced.
Layout for Repair
Information needed to fabricate replacement parts
is usually found on blueprints, while information
concerning repairs may be found in the aircraft
structural repair manual.
The manual contains
information on extrusions and the necessary data for
the fabrication of various sheet metal equivalents.
The aircraft structural repair manual will indicate
the type of material to be used in each repair. If the
correct material is not available, the General Manual
for Structural Repair should be checked for an
The fabrication of sheet metal parts for internal
structural repair requires careful adherence to the
accepted standards of aircraft sheet metal work. This
includes accurate calculation of bend allowance and
careful layout of all dimensions.
Layout is the
interpreting and transcribing of information from
blueprints, drawings, or written instructions to the
metal that will be made into a part for an aircraft.
If several parts are to be fabricated, the
dimensions may be transferred to a template.
Working from a template ensures a higher degree of
uniformity and speeds production.
The procedure for making a layout either for a
template or for the actual part is essentially the same.
Layout of a part or a template consists principally of
marking the flat sheet so that all drilling, cutting,
bending, and forming operations are indicated on the
sheet. It is a comparable level 3 drawing that has been
marked up in sufficient detail to clearly indicate the
fabrication requirements for each piece/part.
The sheet metal layout may be made from printed
instructions, but it is more often made directly from
the blueprint. Accuracy in all details is essential. You
should not transfer dimensions directly from the
blueprint to the layout because the print material may
have stretched or shrunk, which causes minor distor-
tion of the dimensions. Measurements indicated on
the blueprint are made on the layout.
Details are often left out and must be developed in
the shop. You may, for example, find that you must
add several dimensions, and then figure the bend
allowance for the material consumed in each bend
before you are able to lay out the overall length or
width of a part.
On very accurate layouts, a magnifying glass is
frequently used as an aid to precision work. A
magnifying glass enlarges the graduations on a scale
and makes them easier to read. It helps locate center
punch marks, and it allows a close inspection of the
accuracy of the completed layout.
Earlier in this chapter, we discussed the layout
procedures for sheet metal fabrication. These same
procedures are used to lay out the material that is
going to be used to make the repair.