FAA Advisory Circular 43.13-1B
Acceptable Methods, Techniques, and Practices
Aircraft Inspection and Repair
AC 43.13-1B | 11. Aircraft Electrical Systems | 11. Clamping | 11-147. Wire and Cable Clamps Inspection
9/27/01
SECTION 11. CLAMPING
AC 43.13-1B CHG 1
11-146. GENERAL. Wires and wire bun-
dles must be supported by using clamps meet-
ing Specification MS-21919, or plastic cable
straps in accessible areas if correctly applied
within the restrictions of paragraph 11-158.
Clamps and other primary support devices
must be constructed of materials that are com-
patible with their installation and environment,
in terms of temperature, fluid resistance, expo-
sure to ultraviolet (UV) light, and wire bundle
mechanical loads. They should be spaced at
intervals not exceeding 24 inches. Clamps on
wire bundles should be selected so that they
have a snug fit without pinching wires, as
shown in figure 11-11 through figure 11-13.
CAUTION: The use of metal clamps
on coaxial RF cables may cause prob-
lems if clamp fit is such that RF ca-
ble’s original cross-section is distorted.
a. Clamps on wire bundles should not
allow the bundle to move through the clamp
when a slight axial pull is applied. Clamps on
RF cables must fit without crushing and must
be snug enough to prevent the cable from
moving freely through the clamp, but may al-
low the cable to slide through the clamp when
a light axial pull is applied. The cable or wire
bundle may be wrapped with one or more turns
of electrical tape when required to achieve this
fit. Plastic clamps or cable ties must not be
used where their failure could result in inter-
ference with movable controls, wire bundle
contact with movable equipment, or chafing
damage to essential or unprotected wiring.
They must not be used on vertical runs where
inadvertent slack migration could result in
chafing or other damage. Clamps must be in-
stalled with their attachment hardware posi-
tioned above them, wherever practicable, so
that they are unlikely to rotate as the result of
wire bundle weight or wire bundle chafing.
(See figure 11-11.).
b. Clamps lined with nonmetallic mate-
rial should be used to support the wire bundle
along the run. Tying may be used between
clamps, but should not be considered as a sub-
stitute for adequate clamping. Adhesive tapes
are subject to age deterioration and, therefore,
are not acceptable as a clamping means.
c. The back of the clamp, whenever
practical, should be rested against a structural
member. Stand-offs should be used to main-
tain clearance between the wires and the
structure. Clamps must be installed in such a
manner that the electrical wires do not come in
contact with other parts of the aircraft when
subjected to vibration. Sufficient slack should
be left between the last clamp and the electri-
cal equipment to prevent strain at the terminal
and to minimize adverse effects on shock-
mounted equipment. Where wires or wire
bundles pass through bulkheads or other
structural members, a grommet or suitable
clamp should be provided to prevent abrasion.
d. When wire bundle is clamped into
position, if there is less than 3/8-inch clearance
between the bulkhead cutout and the wire bun-
dle, a suitable grommet should be installed as
indicated in figure 11-14. The grommet may
be cut at a 45 degree angle to facilitate instal-
lation, provided it is cemented in place and the
slot is located at the top of the cutout.
11-147. WIRE AND CABLE CLAMPS
INSPECTION. Inspect wire and cable
clamps for proper tightness. Where cables
pass through structure or bulkheads, inspect
for proper clamping and grommets. Inspect
for sufficient slack between the last clamp and
the electronic equipment to prevent strain at
the cable terminals and to minimize adverse
effects on shock-mounted equipment.
Par 11-146
Page 11-57