Technical data

13773-001
20-10
Page 4 30 Nov 2000
(3) Injection Seals
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.
(4) Brush Seals
Brush sealing is used in the fuel tank to reseal surface areas after a structural repair to the wing
exterior skins. The wet area inside the tank must be sanded, cleaned and free of all dust and
contaminates. The sealant is applied using a stiff-bristle brush to the repair and surrounding
area.
H. Method of Application
Sealants may be applied with a brush, a roller, an extrusion gun, or with a spatula. Extrusion guns are
available as either hand operated or pneumatic powered. Some extrudable sealants are also available
in squeezable tubes. Each application method has advantages in particular situations.
(1) Brush Application
A stiff-bristle brush (not nylon) is used to apply the sealant to the surface to be sealed. Brushed
on sealant application may be used for faying surface sealing, fastener sealing, and surface
sealing.
(2) Roller Application
Faying surface and brushable sealant may be applied using a roller. For some applications
where a thin even coat of sealant is to applied, a roller is the preferred method of application.
(3) Extrusion Application
Fillet and faying surface seals may be applied with an extrusion gun. Injection seals must be
applied using an injection gun. Some extrusion guns are available with a variety of nozzles for
various applications. Nozzle tips may be shaped as required by the mechanic to provide a bead
of sealant with the shape and dimensions for the specific seal.
(4) Spatula Application
A spatula is used to spread sealant material for faying surface and fillet seals. Normally, a spat-
ula cannot be used to provide an injection seal. Small repair fillet seals may be applied with a
spatula if an extrusion gun is not available or will not fit in the area to be sealed. Spatulas may be
manufactured by the mechanic to tool fillet seals applied with a extrusion gun to fill voids, even
the bead, and/or to remove bubbles.