TM 1-1500-204-23-11
2
Perform NDI of patch to skin and
materials igure 7-8 shows a cross section of a
patch to iller bond areas to verify
typical stepped repair. Cutting steps in a laminate of
bondline integrity.
unidirectional plies can take three to four times as
long as sanding a comparable scarfed joint. Even with
careful workmanship and frequent micrometer depth
measurements, steps typically fail to fall on the correct
ply by one to three plies. A router can be used for any
DO NOT sand into laminate near patch edge
step repair and must be used on boron. A stepped
when sanding adhesive squeeze out.
repair is usually not performed in unidirectional plies
of iberglass. In this method, the plies are removed in
a stepped pattern (igure 6-23) rather than the tapered
(m) If applicable, repair the outer lightning
pattern used in the scarf method. The step can be
mesh according to paragraph 7-12 and
achieved by physically cutting and peeling the plies
the system speciic technical manual.
or by machining with a router and template. The ield
will generally only perform the step repair by cutting
(n) Reinish.
and peeling which can be performed on laminates
made with woven materials. Laminates made with
Sand the area smooth with 180
1
unidirectional materials have a tendency to separate
grit abrasive paper. Vacuum the
within a ply; therefore, the plies should be removed by
sanding dust from the repair area.
machining with a controlled depth router and templates
Wipe with clean, dry wiping cloth to
to ensure the proper step depth and length is achieved.
remove sanding residue.
The router method is dificult to perform on complex
contours and is usually limited to depot level repairs.
Apply inish system in accordance
2
This repair procedure is not necessarily applicable to
with paragraph 7-13b or the system
a particular weapon system. The applicability of this
speciic technical manual.
repair depends upon additional factors such as loading
conditions and laminate thickness. Refer to igure 7-7
c. Full Thickness Step Repair. The step (or step-
for the Process Flow Diagram for Penetration Damage
lap) repair is almost identical to the scarf repair
Repair. Consult the system speciic technical manual
except that each ply is removed separately and is
or engineering for further guidance.
stepped or terraced accordingly. A stepped repair is
used primarily on boron, aramid, and polyethylene
Figure 7-8. Cross Section of Typical Stepped Repair
(1) Facilities, Equipment and Materials. The
Technical Manual), Vacuum Bag Repair Materials Kit,
following equipment and materials are required: Vac-
Copper Sheet.
uum Cleaner, HEPA Filter, Dual Action Sander or 90
degree die-grinder and sanding mandrel, Utility Knife
(2) Full Thickness Step Repair Procedure.
or Single Edge Razor Blade, Temperature/Vacuum
Controller, Heat Blanket, Flash breaker Tape, Sili-
(a) Remove dirt, grease and aircraft luids
con Carbide Abrasive Paper, Wiping Cloth, Release
from repair area as described in para-
Film, Spatula, Adhesive, Liquid (See System Speciic
Technical Manual), Fabric (See System Speciic Tech-
nical Manual), Lightning Mesh (See System Speciic
