FAA Advisory Circular 43.13-1B
Acceptable Methods, Techniques, and Practices
Aircraft Inspection and Repair
AC 43.13-1B | 11. Aircraft Electrical Systems | 4. Inspection of Circuit-Protection Devices | 11-52. Circuit Breaker Maintenance
AC 43.13-1B CHG 1
9/27/01
or components. Use of a circuit breaker as a
switch is not recommended. Use of a circuit
breaker as a switch will decrease the life of the
circuit breaker.
b. Electromechanical Switches.
Switches have electrical contacts and various
types of switch actuators (i.e., toggle, plunger,
push-button, knob, rocker).
11-52. CIRCUIT BREAKER MAINTE-
NANCE. Circuit breakers should be periodi-
cally cycled with no load to enhance contact
performance by cleaning contaminants from
the contact surfaces.
11-53. SWITCHES. In all circuits where a
switch malfunction can be hazardous, a switch
specifically designed for aircraft service should
be used. These switches are of rugged con-
struction and have sufficient contact capacity
to break, make, and continuously carry the
connected load current. The position of the
switch should be checked with an electrical
meter.
a. Electrical Switch Inspection. Special
attention should be given to electrical circuit
switches, especially the spring-loaded type,
during the course of normal airworthiness in-
spection. An internal failure of the spring-
loaded type may allow the switch to remain
closed even though the toggle or button returns
to the “off” position. During inspection, at-
tention should also be given to the possibility
that improper switch substitution may have
been made.
(1) With the power off suspect aircraft
electrical switches should be checked in the
ON position for opens (high resistance) and in
The OFF position for shorts (low resistance),
with an ohmmeter.
(2) Any abnormal side to side move-
ment of the switch should be an alert to immi-
nent failure even if the switch tested was
shown to be acceptable with an ohmmeter.
(1) Contacts designed for high-level
loads must not be subsequently used for low-
level applications, unless testing has been per-
formed to establish this capability.
(2) Switches are specifically selected
based on the design for the aircraft service cur-
rent ratings for lamp loads, inductive loads,
and motor loads and must be replaced with
identical make and model switches.
c. Proximity Switches. These switches
are usually solid-state devices that detect the
presence of a predetermined target without
physical contact and are usually rated 0.5 amps
or less.
d. Switch Rating. The nominal current
rating of the conventional aircraft switch is
usually stamped on the switch housing and
represents the continuous current rating with
the contacts closed. Switches should be der-
ated from their nominal current rating for the
following types of circuits:
(1) Circuits containing incandescent
lamps can draw an initial current that is
15 times greater than the continuous current.
Contact burning or welding may occur when
the switch is closed.
(2) Inductive circuits have magnetic en-
ergy stored in solenoid or relay coils that is
released when the control switch is opened and
may appear as an arc.
(3) Direct-current motors will draw
several times their rated current during start-
ing, and magnetic energy stored in their
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