Technical data

13773-001
20-10
Page 1930 Nov 2000
(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
Sealing.”
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.
(b) Solvent clean area and fitting to be sealed. The fastener and surrounding area should be
cleaned at least twice and all residue removed. (Refer to 20-30)
(c) Apply a small amount of sealant on fitting threads before installing nut. Ensure that bulk-
head fitting is properly installed with O-ring and nut is on wet side of bulkhead and nut is
properly torqued.
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. Sealant must never be
applied after usable application time.
Note: Application time is the period in which the sealant can be satisfactorily
applied. After this point, the material does not “wet” properly and may fail in
adhesion (sealant “rolls up” ahead of the sealing gun or “draws up” behind
the gun).
(d) Use extrusion gun or spatula to apply sealant around the base and over the nut on the wet
side. If necessary, the sealant may be worked with a tool so that the sealant has a mini-
mum thickness as specified.
Note: Sealant must be applied so that it provides an airtight seal. Care must be
exercised so that folds, laps, and entrapped air are not created during the
process. All air bubbles must be worked out of the sealant. The fillet can be
moved slightly to insure that the highest portion of the fillet is over the edge
of the structure.
(e) Work out all entrapped air and remove excess sealant with a fairing tool.
(f) Inspect seal for poor adhesion and evidence of air bubbles. Evidence of air bubbles is
cause to rework the seal.
(g) Allow seal to cure.
(6) Cable Pass-Through
The heat box control cable, alternate air control cable, mixture control cable, throttle control
cable, and governor control cables all pass-through the firewall. When any of these cables are
removed, the cable pass-through must be properly fillet sealed to assure an airtight seal.