If brushes are worn to or
beyond allowable limits, brush
commutator shows evidence
of excessive arcing, or if metal
particles are present, replace
Figure 3-11. Microswitch
e. Switches. Switches control the current flow in
most aircraft electrical circuits. A switch is used to start,
stop, or change direction of current flow.
(1) Types. Toggle (see figure 3-10), push-
button, micro switches (see figure 3-11), rotary-selector
(see figure 3-12), and relay switches are used in Army
aircraft. Toggle switches are used more than any other
type of switch.
procedures for switches are as follows:
(a) Inspect terminals for distortion,
malformed threads, and corrosion.
(b) Operate switch and observe for
(c) Inspect switch and mounting
hardware for malformed threads and damage.
(3) Replacement criteria. Replace switches
when moving parts are binding, scraping, or have dead
spots as evidenced by erratic operation of their
respective components. Replace switches that do not
pass a continuity check.
Replace toggle switches when
dust boots are deteriorated.
f. Built-In Test Equipment. Built-in test equipment
is used to test various systems while installed upon the
aircraft. When button or switch is activated a light
comes on to indicate system continuity or proper
operation. Built-in test equipment is commonly used in
communication systems, fire warning systems, and
g. Electronic Control Units. Electronic control
units provide regulated power and contains the
necessary information to control weapon systems and
other electronic equipment on Army aircraft.
(1) Types. Various types are used to
regulate APU, weapon systems, and other installed
procedures for electronic control units are as follows:
(a) Inspect case for cracks or dents.
(b) Inspect for secure mounting.
(c) Inspect electrical connectors for
broken pins, cracked inserts, or corrosion in accordance
with TM 1-1500-343-23.
(3) Replacement criteria. Electronic control
units shall be replaced if case is damaged or unit is
found to be defective. Perform functional check in
accordance with the applicable technical manual.
Change 3 3-17