TM 1-1500-204-23-11
(g) Machine Repair Joint. For this repair,
interference between an externally
bonded patch on the part IML surface
and the mating surface on the aircraft
Pressure must be applied to adhesive within
necessitates the use of a lush repair.
pot life of the resin. For ambient temperatures
Select a scarf joint due to ease of
in excess of 90 F, decrease this time by 50%.
machining.
An unsatisfactory repair will result if the resin
gels before adequate pressure is applied and
1
Machine a scarf joint on the IML
may result in loss of structural integrity. Select
skin only. In the edge band area,
and prepare a heat blanket (if required) and
stop the scarf joint at the IML to
all necessary vacuum bag materials prior to
OML adhesive bondline. Use a
mixing resin.
scarf slope as speciied in the sys-
tems speciic technical manual.
Failure to observe the correct number of repair
Refer to paragraph 6-15.
plies, the correct repair ply orientation, the
correct repair ply overlap and removal of all
Inspect the scarf surface as
2
pieces of vacuum bagging ilm will reduce the
described in the criteria of para-
strength of the repair and may result in the
loss of structural integrity.
(h) Dry the repair area to remove subsur-
Failure to properly cure adhesive in accor-
face moisture using per paragraph 6-6.
dance with the speciied cure cycle will result in
Use an envelope vacuum bag. Operate
reduced repair strength may not be detectable
the oven using the guidelines provided
by visual or nondestructive inspection. This
may result in loss of structural integrity.
(i)
Clean per paragraph 6-5. Handle the
(l)
Fabricate & cure the iller patch and
prepared surface of the part wearing
inner patch per the system speciic tech-
powder free latex gloves until after
nical manual and paragraph 6-16.
patch/iller application is complete. If
patch/iller is not to be applied immedi-
(m) Using the part as a guide, edge trim
ately, cover with clean barrier material
the OML and IML patches according
and secure with preservation tape to
to paragraph 6-8 to match part dimen-
prevent contamination.
sions.
NOTE
When fastener holes are affected, redrill fas-
Part to patch alignment must be main-
tener holes.
tained within 2 degree. Fabricated com-
posite patches are orientation sensitive from
(n) Drill fastener holes, if required, in accor-
a strength standpoint. Incorrect alignment
dance with the system speciic technical
of part and patch during layup will result in
manual and paragraph 6-8.
reduced strength and loss of structural integrity
may occur.
(o) Vacuum and wipe with clean, dry wiping
cloth to remove dust and debris.
NOTE
(p) NDI Patch Bond(s).
If part curvature precludes the use of a
pre-cured patch for the OML patch, a wet layup
Visually inspect adhesive squeeze
1
patch must be fabricated using an undamaged
out at patch edge as described in
part as a tool.
(j)
Fabricate and bond OML repair patch
Perform NDI of patch to skin and
2
according to paragraph 7-6. Refer to
patch to iller bond areas to verify
the system speciic technical manual for
bondline integrity.
patch selection.
(q) If applicable, repair lightning mesh per
(k) Calculate the number of iller patch plies
paragraph 7-12 and the system speciic
required per system speciic technical
technical manual.
manual.
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