FAA Advisory Circular 43.13-1B
Acceptable Methods, Techniques, and Practices
Aircraft Inspection and Repair
AC 43.13-1B | 11. Aircraft Electrical Systems | 14. Terminal Repairs | 11-174. General
9/27/01
SECTION 14. TERMINAL REPAIRS
AC 43.13-1B CHG 1
11-174. GENERAL. Terminals are attached
to the ends of electrical wires to facilitate con
nection of the wires to terminal strips or items
of equipment. The tensile strength of the wire
to-terminal joint should be at least equivalent
to the tensile strength of the wire itself, and its
resistance negligible relative to the normal re
sistance of the wire.
a. Selection of Wire Terminals. The
following should be considered in the selection
of wire terminals.
(1) Current rating.
(2) Wire size (gauge) and insulation
diameter.
(3) Conductor material compatibility.
(4) Stud size.
(5) Insulation material compatibility.
(6) Application environment.
(7) Solder/solderless.
Pre-insulated crimp-type ring-tongue terminals
are preferred. The strength, size, and support
ing means of studs and binding posts, as well
as the wire size, should be considered when
determining the number of terminals to be at
tached to any one post. In high-temperature
applications, the terminal temperature rating
must be greater than the ambient temperature
plus current related temperature rise. Use of
nickel-plated terminals and of uninsulated ter
minals with high-temperature insulating
sleeves should be considered. Terminal blocks
should be provided with adequate electrical
clearance or insulation strips between mount
ing hardware and conductive parts.
b. Terminal Strips. Wires are usually
joined at terminal strips. A terminal strip fit
ted with barriers should be used to prevent the
terminals on adjacent studs from contacting
each other. Studs should be anchored against
rotation. When more than four terminals are to
be connected together, a small metal bus
should be mounted across two or more adja
cent studs. In all cases, the current should be
carried by the terminal contact surfaces and not
by the stud itself. Defective studs should be
replaced with studs of the same size and mate
rial since terminal strip studs of the smaller
sizes may shear due to overtightening the nut.
The replacement stud should be securely
mounted in the terminal strip and the terminal
securing nut should be tight. Terminal strips
should be mounted in such a manner that loose
metallic objects cannot fall across the termi
nals or studs. It is good practice to provide at
least one spare stud for future circuit expan
sion or in case a stud is broken. Terminal strips
that provide connection of radio and electronic
systems to the aircraft electrical system should
be inspected for loose connections, metallic
objects that may have fallen across the termi
nal strip, dirt and grease accumulation, etc.
These type conditions can cause arcing which
may result in a fire, or system failures.
c. Terminal Lugs. Wire terminal lugs
should be used to connect wiring to terminal
block studs or equipment terminal studs. No
more than four terminal lugs or three terminal
lugs and a bus bar should be connected to any
one stud. Total number of terminal lugs per
stud includes a common bus bar joining adja
cent studs. Four terminal lugs plus a common
bus bar thus are not permitted on one stud.
Terminal lugs should be selected with a stud
hole diameter that matches the diameter of the
stud. However, when the terminal lugs at
tached to a stud vary in diameter, the greatest
Par 11-174
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