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 | 11-175. Attachment of Terminals to Studs
AC 43.13-1B CHG 1
9/27/01
diameter should be placed on the bottom and
the smallest diameter on top. Tightening ter
minal connections should not deform the ter
minal lugs or the studs. Terminal lugs should
be so positioned that bending of the terminal
lug is not required to remove the fastening
screw or nut, and movement of the terminal
lugs will tend to tighten the connection.
d. Copper Terminal Lugs. Solderless
crimp style, copper wire, terminal lugs should
be used and conform to MIL-T-7928. Spacers
or washers should not be used between the
tongues of terminal lugs.
e. Aluminum Terminal Lugs. The alu
minum terminal lugs conforming to
MIL-T-7099 (MS-25435, MS-25436,
MS-25437, and MS-25438) should be crimped
to aluminum wire only. The tongue of the
aluminum terminal lugs or the total number of
tongues of aluminum terminal lugs when
stacked, should be sandwiched between two
MS-25440 flat washers when terminated on
terminal studs. Spacers or washers should not
be used between the tongues of terminal lugs.
Special attention should be given to aluminum
wire and cable installations to guard against
conditions that would result in excessive volt
age drop and high resistance at junctions that
may ultimately lead to failure of the junction.
Examples of such conditions are improper in
stallation of terminals and washers, improper
torsion (“torquing” of nuts), and inadequate
terminal contact areas.
f. Class 2 Terminal Lugs. The Class 2
terminal lugs conforming to MIL-T-7928 may
be used for installation, provided that in such
installations, Class 1 terminal lugs are ade
quate for replacement without rework of in
stallation or terminal lugs. Class 2 terminal
lugs should be the insulated type, unless the
conductor temperature exceeds 105 °C. In that
case uninsulated terminal lugs should be used.
Parts’ lists should indicate the appropriate
Class 1 terminal lugs to be used for service re
placement of any Class 2 terminal lugs in
stalled.
g. Termination of Shielded Wire. For
termination of shielded wire refer to
MIL-DTL-27500.
11-175. ATTACHMENT OF TERMI-
NALS TO STUDS. Connectors and terminals
in aircraft require special attention to ensure a
safe and satisfactory installation. Every possi
bility of short circuits, due to misinstallation,
poor maintenance, and service life, should be
addressed in the design. Electrical equipment
malfunction has frequently been traced to poor
terminal connections at terminal boards.
Loose, dirty, or corroded contact surfaces can
produce localized heating that may ignite
nearby combustible materials or overheat adja
cent wire insulation. (See paragraph 11-178)
11-176. STUDS AND INSULATORS. The
following recommendations concerning studs
also apply to other feed-through conductors.
a. Current Carrying Stud Resistance.
Due to heat loss arising from wire-to-lug and
lug-to-stud voltage drop, the resistance per unit
length of a current carrying stud should not be
greater than that of the wire.
b. Size of Studs. In designing the stud for
a feed-through connection, attention should be
given to the higher resistance of brass, as com
pared to copper. A suggested method of de
termining the size is to use a current density in
the stud equivalent to that of the wire, com
pensating for the difference of resistance of the
metals. Consideration should also be given to
mechanical strength.
c. Support for Studs. The main stud
support in the feed-through insulation should
be independent of the attachment of the lugs to
the stud. Therefore, loosening of the insula
tion support of the stud will not affect the
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