FAA Advisory Circular 43.13-1B
Acceptable Methods, Techniques, and Practices
Aircraft Inspection and Repair
AC 43.13-1B | 11. Aircraft Electrical Systems | 6. Aircraft Electrical Wire Selection | 11-77. Aircraft Wire Materials
9/8/98
SECTION 6. AIRCRAFT ELECTRICAL WIRE SELECTION AC 43.13-1B
11-76. GENERAL. Aircraft service im
poses severe environmental condition on elec
trical wire. To ensure satisfactory service, in
spect wire annually for abrasions, defective in
sulation, condition of terminations, and poten
tial corrosion. Grounding connections for
power, distribution equipment, and electro
magnetic shielding must be given particular
attention to ensure that electrical bonding re
sistance has not been significantly increased by
the loosening of connections or corrosion.
a. Wire Size. Wires must have sufficient
mechanical strength to allow for service con
ditions. Do not exceed allowable voltage drop
levels. Ensure that the wires are protected by
system circuit protection devices, and that they
meet circuit current carrying requirements. If
it is desirable to use wire sizes smaller
than #20, particular attention should be given
to the mechanical strength and installation
handling of these wires, e.g. vibration, flexing,
and termination. When used in interconnect
ing airframe application, #24 gauge wire must
be made of high strength alloy.
b. Installation Precautions for Small
Wires. As a general practice, wires smaller
than size #20 must be provided with additional
clamps, grouped with at least three other wires,
and have additional support at terminations,
such as connector grommets, strain-relief
clamps, shrinkable sleeving, or telescoping
bushings. They should not be used in applica
tions where they will be subjected to excessive
vibration, repeated bending, or frequent dis
connection from screw terminations.
c. Identification. All wire used on air
craft must have its type identification im
printed along its length. It is common practice
to follow this part number with the five
digit/letter Commercial and Government En
tity (C.A.G.E). code identifying the wire
manufacturer. Existing installed wire that
needs replacement can thereby be identified as
to its performance capabilities, and the inad
vertent use of a lower performance and unsuit
able replacement wire avoided.
(1) In addition to the type identification
imprinted by the original wire manufacturer,
aircraft wire also contains its unique circuit
identification coding that is put on at the time
of harness assembly. The traditional “Hot
Stamp” method has not been totally satisfac
tory in recent years when used on modern, ul
tra-thin-walled installations. Fracture of the
insulation wall and penetration to the conduc
tor of these materials by the stamping dies
have occurred. Later in service, when these
openings have been wetted by various fluids,
serious arcing and surface tracking have dam
aged wire bundles.
(2) Extreme care must be taken during
circuit identification by a hot stamp machine
on wire with a 10 mil wall or thinner. Alter
native identification methods, such as “Laser
Printing” and “Ink Jet,” are coming into in
creasing use by the industry. When such mod
ern equipment is not available, the use of
stamped identification sleeving should be con
sidered on thin-walled wire, especially when
insulation wall thickness falls below 10 mils.
11-77. AIRCRAFT WIRE MATERIALS.
Only wire, specifically designed for airborne
use, must be installed in aircraft.
a. Authentic Aircraft Wire. Most air
craft wire designs are to specifications that re
quire manufacturers to pass rigorous testing of
wires before being added to a Qualified Prod
ucts List (QPL) and being permitted to produce
the wire. Aircraft manufacturers who maintain
their own wire specifications invariably exer
cise close control on their approved
Par 11-78
Page 11-35