Specifications

AC 43.13-1B 9/8/98
Page 11-74 Par 11-188
e. Self-tapping screws should not be used
for bonding purposes. Only standard threaded
screws or bolts of appropriate size should be
used.
f. Exposed conducting frames or parts
of electrical or electronic equipment should
have a low resistance bond of less than
2.5 millohms to structure. If the equipment
design includes a ground terminal or pin,
which is internally connected to such exposed
parts, a ground wire connection to such termi-
nal will satisfy this requirement. Refer to
manufacturer’s instructions.
g. Bonds should be attached directly to
the basic aircraft structure rather than through
other bonded parts.
h. Bonds must be installed to ensure that
the structure and equipment are electrically
stable and free from the hazards of lightning,
static discharge, electrical shock, etc. To
ensure proper operation and suppression of ra-
dio interference from hazards, electrical
bonding of equipment must conform to the
manufacturer’s specifications.
i. Use of bonding testers is strongly rec-
ommended.
j. Measurements should be performed
after the grounding and bonding mechanical
connections are complete to determine if the
measured resistance values meet the basic re-
quirements. A high quality test instrument
(AN AN/USM-21A or equivalent) is required
to accurately measure the very low resistance
values specified in this document. Another
method of measurement is the millivolt drop
test as shown in figure 11-19.
k. Use appropriate washers when bond-
ing aluminum or copper to dissimilar metallic
structures so that any corrosion that may occur
will be on the washer.
Figure 11-19. Millivolt drop test.