FAA Advisory Circular 43.13-1B
Acceptable Methods, Techniques, and Practices
Aircraft Inspection and Repair
AC 43.13-1B | 4. Metal Structure, Welding, and Brazing | 4. Metal Repair Procedures | 4-60. Steel and Aluminum Fittings
AC 43.13-1B
9/8/98
4-59. REPAIRING CRACKED MEM
BERS. Acceptable methods of repairing vari
ous types of cracks in structural elements are
shown in figures 4-21 through 4-24. The fol
lowing general procedures apply in repairing
such defects.
a. Drill small holes 3/32 inch (or
1/8 inch) at the extreme ends of the cracks to
minimize the possibility of their spreading
further.
b. Add reinforcement to carry the
stresses across the damaged portion and to
stiffen the joints. (See figures 4-14 through
4-17.) The condition causing cracks to de
velop at a particular point is stress concentra
tion at that point in conjunction with repetition
of stress, such as produced by vibration of the
structure. The stress concentration may be due
to the design or to defects such as nicks,
scratches, tool marks, and initial stresses or
cracks from forming or heat-treating opera
tions. It should be noted, that an increase in
sheet thickness alone is usually beneficial but
does not necessarily remedy the conditions
leading to cracking.
4-60. STEEL AND ALUMINUM FIT
TINGS.
a. Steel Fittings. Inspect for the follow
ing defects.
(1) Fittings are to be free from
scratches, vise and nibbler marks, and sharp
bends or edges. A careful examination of the
fitting with a medium power (at least
10 power) magnifying glass is acceptable as an
inspection.
(2) When repairing aircraft after an ac
cident or in the course of a major overhaul, in
spect all highly-stressed main fittings, as set
forth in the manufacturer’s instruction manual.
(3) Replace torn, kinked, or cracked fit
tings.
(4) Elongated or worn bolt holes in fit
tings, which were designed without bushings,
are not to be reamed oversize. Replace such
fittings, unless the method of repair is ap
proved by the FAA. Do not fill holes with
welding rod. Acceptable methods of repairing
elongated or worn bolt holes in landing gear,
stabilizer, interplane, or cabane-strut ends are
shown in figure 4-25.
b. Aluminum and Aluminum Alloy Fit
tings.
(1) Replace damaged fittings with new
parts that have the same material specifica
tions.
(2) Repairs may be made in accordance
with data furnished by the aircraft manufac
turer, or data substantiating the method of re
pair may be submitted to the FAA for ap
proval.
4-61. CASTINGS. Damaged castings are to
be replaced and not repaired unless the method
of repair is specifically approved by the air
craft manufacturer or substantiating data for
the repair has been reviewed by the FAA for
approval.
4-62. SELECTIVE PLATING IN AIR
CRAFT MAINTENANCE. Selective plating
is a method of depositing metal from an elec
trolyte to the selected area. The electrolyte is
held in an absorbent material attached to an in
ert anode. Plating contact is made by brushing
or swabbing the part (cathode) with the elec
trolyte-bearing anode.
a. Selective Plating Uses. This process
can be utilized for any of the following rea
sons.
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