FAA Advisory Circular 43.13-1B
Acceptable Methods, Techniques, and Practices
Aircraft Inspection and Repair
AC 43.13-1B | 11. Aircraft Electrical Systems | 9. Environmental Protection and Inspection | 11-117. Minimum Wire Bend Radii
9/27/01
AC 43.13-1B CHG 1
SECTION 9. ENVIRONMENTAL PROTECTION AND INSPECTION
11-115. MAINTENANCE AND OPERA-
TIONS. Wire bundles must be routed in ac-
cessible areas that are protected from damage
from personnel, cargo, and maintenance activ-
ity. They should not be routed in areas in
where they are likely to be used as handholds
or as support for personal equipment or where
they could become damaged during removal of
aircraft equipment. Wiring must be clamped
so that contact with equipment and structure is
avoided. Where this cannot be accomplished,
extra protection, in the form of grommets,
chafe strips, etc., should be provided. Protec-
tive grommets must be used, wherever wires
cannot be clamped, in a way that ensures at
least a 3/8-inch clearance from structure at
penetrations. Wire must not have a preload
against the corners or edges of chafing strips or
grommets. Wiring must be routed away from
high-temperature equipment and lines to pre-
vent deterioration of insulation. Protective
flexible conduits should be made of a material
and design that eliminates the potential of
chafing between their internal wiring and the
conduit internal walls. Wiring that must be
routed across hinged panels, must be routed
and clamped so that the bundle will twist,
rather than bend, when the panel is moved.
FIGURE 11-7. Group and bundle ties.
FIGURE 11-8. Comb for straightening wires in bundles.
11-116. GROUP AND BUNDLE TIES. A
wire bundle consists of a quantity of wires
fastened or secured together and all traveling
in the same direction. Wire bundles may con-
sist of two or more groups of wires. It is often
advantageous to have a number of wire groups
individually tied within the wire bundle for
ease of identification at a later date. (See fig-
ure 11-7.) Comb the wire groups and bundles
so that the wires will lie parallel to each other
and minimize the possibility of insulation
abrasion. A combing tool, similar to that
shown in figure 11-8, may be made from any
suitable insulating material, taking care to
ensure all edges are rounded to protect the wire
insulation.
11-117. MINIMUM WIRE BEND RADII.
The minimum radii for bends in wire groups or
bundles must not be less than 10 times the out-
side diameter of their largest wire. They may
be bent at six times their outside diameters at
breakouts or six times the diameter where they
must reverse direction in a bundle, provided
that they are suitably supported.
a. RF cables should not bend on a radius
of less than six times the outside diameter of
the cable.
Par 11-115
Page 11-51