Technical data

13773-001
20-10
Page 1330 Nov 2000
CAUTION: Sealant which does not wet properly or which is difficult to extrude from the
sealing gun must be discarded. Sealant should never be applied at temper-
atures below 60° F (15.5° C) or to a structure that is below 60° F (15.5° C).
Sealed structures must be handled with care and should never be moved
until sealant has achieved a tack-free surface. Pressure testing, if required,
must never be performed, until all sealant has cured.
(f) Using an extrusion gun, roller, or spatula, apply sealant to one mating surface. Spread
sealant over entire faying surface.
(g) Place parts in assembly position and install fasteners within the sealant work life.
Note: Sufficient sealant shall have been applied so that the space between the
faying surfaces is completely filled with sealant and a small amount of seal-
ant is extruded continuously along the joint.
(h) Fair out extruded sealant to leave a smooth fillet along joint.
(i) Inspect seal for poor adhesion and evidence of air bubbles. Evidence of air bubbles is
cause to rework the seal.
(j) Allow sealant to cure.
(2) Repairing an Injection Seal
Injection seals are used to fill holes, joggles, channels and other voids. Injection seals may be
applied to provide continuity where fillet seals are interrupted by structure. Injection sealing
forces air out of a cavity and fills the vacated space with sealant. Injection seals are accom-
plished by injecting the area with an extrudable sealant through an extrusion cartridge or a tube.
An example of an injection seal is the seal applied in the fuel tank where the joggle at the end of
a rib intersects the wing skin interior and the spar or shear web.
(a) If not already accomplished remove all sealant from damaged seal with cutting tools and
suitable hardwood or plastic scrapers as described in paragraph A (Preparation for Seal-
ing).
Note: The injection channel must be cleared all the way through as trapped air will
prevent complete filling of the channel. A pipe cleaner or hooked wire may
be used to clear sealant debris from inside the seal channel.
(b) Refinish damaged surface.
CAUTION: After thoroughly cleaning surfaces to be sealed, wear clean, white, cotton
gloves to prevent contaminating the surfaces to be sealed.
Use care in selecting solvent. Do not use acetone to clean acrylic. Use only
isopropyl alcohol for solvent cleaning acrylic surfaces.
(c) Solvent clean joints to be sealed. Remove all solvent residue and thoroughly dry area.
(Refer to 20-30)
CAUTION: Ensure that extrusion gun cartridge has sufficient sealant to make a com-
plete seal with one injection without any break. Stopping and starting an
injection seal will cause air to be entrapped in the seal and is cause for
rework.