TO 35-1-3 - Robins Air Force Base

TO 35-1-3
with AMS 3367, Class A or B or PR-1773, Class B sealant or
Av-DEC TM HT3935-7 or HT3000FR sealant tape in the joints
as specified by the system specific maintenance manual. In
addition to faying surface sealing, fillet seal all interior seams
and all exterior seams (those exposed to the outside environment)
that would allow water intrusion using MIL-PRF-
81733, Type II, Class 1 or 2, Grade A sealant.
NOTE
The following does not apply to parts that are lubricated
in the joint areas immediately before or after
installation, or to close tolerance bolts and parts that
are removed frequently for maintenance requirements.
3.8.3.3.1 Attaching parts, such as nuts (standard, speed, and
self-locking), bushings, spacers, washers, screws (standard
and self-tapping), sleeves for shake-proof fastener studs,
clamps, bolts, etc., do not need to be painted in detail except
when dissimilar metal or wood contact is involved with the
materials being joined or exposure to a corrosive interior environment
or the exterior environment will occur in service.
However, all parts shall be installed wet with sealant. For permanent
installations, use MIL-PRF-81733, Type I or IV, Class
1 or 2, Grade A sealant and coat the entire mating surface of
the parts. For removable installations, use SAE AMS 3367,
Class A or PR-1773, Class B sealant and coat only the lower
side of the heads of screws and bolts with sealant. For removable
installations, do not coat the threads and shanks of screws
and bolts or the holes into which they are inserted because this
will make future removal almost impossible without damaging
the parts. As an alternate for removable installations, the
shanks, threads, and lower side of the heads of standard
screws and bolts may be coated with MIL-PRF-63460, MIL-
PRF-16173, Class II, Grade 3 before they are installed. Close
tolerance bolts and parts shall be coated with corrosion inhibiting,
solid film lubricant. Use MIL-L-23398 or MIL-PRF-
46147 (air curing type) on aluminum parts and on all types of
metallic parts. The solid film lubricant shall be applied and
completely cured prior to assembly. Bolts shall be coated on
shanks and threads only. A thin bead of sealant shall be
applied under the bolt head to impart a wet seal.
3.8.3.3.2 All rivets shall be installed wet with MIL-PRF-
81733, Type I or IV, Class 1 or 2, Grade A sealant. In fuel
contact areas, the exposed rivet head and approximately 1/4-
inch of the adjacent structure shall be brush over coated with
SAE AMS-S-8802 Class A sealant.
3.8.3.3.3 All machine screws, countersunk fasteners, bolts
(head end) and nuts which are used in contact with magnesium
shall be installed with 5056 aluminum alloy washers. These
parts, including the washers, shall be installed wet with MIL-
PRF-81733, Type II, Class 1, Grade A sealant and shall be
completely fillet sealed with the same material after installation.
3.8.3.3.4 Adjustable parts, such as tie rod ends and turnbuckles
shall be installed as follows: (1) If possible, surfaces and
threads shall be lubricated and protected before assembly with
a film of MIL-L-23398 or MIL-PRF-46147 (air curing type)
corrosion inhibiting, solid film lubricant which shall be completely
cured prior to assembly. After installation, apply a thin
coating of MIL-PRF-63460; MIL-PRF-16173, Class II, Grade
3; or MIL-PRF-81309, Type II, water displacing, corrosion
preventive compound (CPC), to all surfaces of these parts. (2)
If solid film lubricants cannot be applied, use a thin coating of
MIL-PRF-63460; MIL-PRF-16173, Class II, Grade 3; or MIL-
PRF-81309, Type II water displacing, corrosion preventive
compound (CPC) after assembly.
3.8.3.3.5 When practical, slip fit parts shall be assembled
with mating surfaces wet with MIL-PRF-81733, Type I or IV,
Class 1 or 2, Grade A sealant. If this process is not practical,
coat the interior diameter (ID) of the holes in the receiving
part, which is normally the larger structure with a corrosion
inhibiting, solid film lubricant conforming to MIL-L-23398 or
MIL-PRF-46147 (air curing types) and the outer diameter
(OD) of the mating part with one conforming to MIL-L-23398
or MIL-PRF-46147 (air curing types). The solid film lubricant
shall be applied and completely cured prior to assembly.
3.8.3.3.6 All cut edges and holes drilled or reworked for
bolts, screws, rivets, studs, and bushings of aluminum alloy
structures or parts shall receive a chemical conversion coating
treatment prior to the installation of the fasteners or bushings
and prior to installing or refinishing the structure or parts.
Apply a conversion coating to aluminum surfaces, using
Touch-N-Prep pen containing Alodine TM 1132. On steel surfaces
use the appropriate primer to coat the cut edges of holes
prior to reinstallation of the parts.
3.8.3.4 Sealant may be applied by brush, spatula, or caulking
gun application.
3.8.3.5 To prevent sealant from contacting adjacent areas
during application and smoothout, outline the areas being
sealed with masking tape (AMS-T-21595, Type I) so that each
tape strip is 1/8 to 1/4 inch from the edge of the seams.
3.8.3.5.1 Apply the sealant between tapes with a nonmetallic
spatula or spreader, brush or caulking gun. Avoid the entrapment
of air. Work sealant into recesses by sliding the edge of
the spatula firmly back over the recesses. Smoothing will be
easier if the nonmetallic spatula is first dipped in water.
3.8.3.5.2 Remove masking tape after the sealant has been
applied and before it begins to set. Cure time will depend upon
the application life of the materials used.
3-5