Purpose
Conduit comes in two basic types--flexible
and rigid. Its chief functions are to act as radio
An aircraft can become highly charged with
shielding and as a support and protection for
wires.
doesn't have a proper bond, all metal parts won't
Conduit fittings attach either flexible or rigid
conduit to junction boxes and other equipment,
have the same charge. A difference of potential
will then exist between various metal surfaces.
and usually include ferrules and coupling nuts.
Various forms of both are in use along with
variable resistance produces electrical disturbances
special designs of locknuts, box connectors, and
coupling adapters.
Couplings are straight or angular in design so
between isolated metal surfaces is large enough,
they fit all needs. Ferrules are bushings or flanges
charges can collect, causing a spark, which is a
applied to the ends of the conduit to give greater
fire hazard. If lightning strikes the aircraft, a good
conducting path lessens severe arcs and sparks that
strength and support to the coupling nuts. They
could damage the aircraft and possibly injure its
are either crimped or swagged on by the use of
crimping or swaging tools.
occupants.
The aircraft structure is also the ground for
the radio. For the radio to function properly, a
SAFETY WIRE
proper balance is necessary between the aircraft
structure and the radio antenna. This means the
There are three types of safety wire:
surface area of the ground must be constant.
Control surfaces, for example, may become
1. Lockwire is a heavy wire used to secure
partially insulated from the remaining structure.
parts against accidental opening. Use lockwire in
This is caused by a film of lubricant building up
all areas of high vibration such as an aircraft's
on the hinges. This would affect radio operation
compartment. Electric connectors are lockwired
if bonding did not take care of the condition.
in high-vibration areas that are inaccessible for
Bonding also provides the necessary low-resistance
periodic maintenance and inspection.
return path for single-wire electrical systems. The
2. Shear wire is a lighter wire used to secure
reasons for bonding are summed up as follows:
parts subject to periodic disconnection, mainte-
nance and inspection, or for parts you need to
remove quickly.
3. Seal wire is a thin, easily breakable wire
used as a seal on fire-extinguishing systems,
To reduce the fire hazard by preventing
oxygen regulators, and other emergency devices
static charges from accumulating between
that need a quick release for use. You use seal wire
two isolated members and creating a spark
to show whether these devices have been used or
tampered with.
aircraft and its occupants
BONDING AND BONDING DEVICES
To provide the proper ground for proper
functioning of the aircraft radio
A bond is a union that exists between two
metallic objects and results in electrical con-
ductivity between them. Aircraft electrical
To provide a low-resistance return path for
single-wire electrical systems
bonding is the process of obtaining electrical
between the aircraft structure and installed
To provide a means of bringing the entire
equipments. An isolated conducting part or object
aircraft to the earth's potential and keeping
is one physically separate from the aircraft
it that way while it is grounded to the earth
structure and other conductors bonded to the
Parts Requiring Bonding
structure. A bonding connector provides the
The design in current naval aircraft is to keep
the number of bonding jumpers to a minimum.
and bonding clamps are examples of bonding
As a result, jumpers are very important and need
connectors.