liquids. Figure 2-19 shows a representative
junction box for housing and protecting several
terminal blocks.
When you install a junction box, make sure
the screw or bolt heads are inside the box. Don't
install attaching hardware so the threaded part of
the screw or bolt protrudes inside the junction
box. The sharp thread edges of protruding
hardware may damage wire insulation.
SUPPORT CLAMPS
Figure 2-20.-Cable clamps.
Clamps provide support for conduit and open
wiring and serve as lacing on open wiring. Clamps
usually have a rubber cushion, or they are of
away from lines, surface control cables, pulleys,
all-plastic construction. When used with shielded
and all movable parts of the aircraft. Use these
conduit, the clamps are of the bonded type
clamps only as a temporary measure. Replace with
(fig. 2-20, view A); that is, there is a provision
a permanent installation as soon as possible.
for electrical contact between the clamp and
When cables pass through lightening holes, the
conduit. Use unbended clips for the support of
installation should conform to the examples
open wiring.
shown in figure 2-21. In each case, the AN 742
A strap-type clamp (fig. 2-20, view B) or an
cable clamp holds the cable firmly. Route the
AN 742 (fig. 2-20, view C) is used for long cable
cable well in the clear of the edges of the lightening
runs between panels. The preferred method for
hole to avoid any chance of chafing the insulation.
supporting cable runs of all types is using AN 742
If any wire is closer than one-fourth inch to the
clamps. MS 25281D plastic clamps are for use
edge of the lightening hole, use a grommet
where the maximum temperature does not exceed
(a rubber cushion) to protect the wires.
250F. When using the strap-type clamp, you
Protect wire bundles from the following:
must make sure the clamps hold the cable firmly
High temperature
Battery acid fumes, spray, or spillage
Solvents or fluids
Abrasion in wheel wells where exposed to
rocks, ice, or mud
Damage due to personnel using the wire
bundle as handholds or footsteps
Damage due to shifting cargo
Figure 2-21.-Routing cables through lightening holes.
Figure 2-19.-Aircraft junction box.
