350
14 CFR Ch. I (1–1–24 Edition)
§ 25.1355
(4) No corrosive fluids or gases that
may escape from the battery may dam-
age surrounding airplane structures or
adjacent essential equipment.
(5) Each nickel cadmium battery in-
stallation must have provisions to pre-
vent any hazardous effect on structure
or essential systems that may be
caused by the maximum amount of
heat the battery can generate during a
short circuit of the battery or of indi-
vidual cells.
(6) Nickel cadmium battery installa-
tions must have—
(i) A system to control the charging
rate of the battery automatically so as
to prevent battery overheating;
(ii) A battery temperature sensing
and over-temperature warning system
with a means for disconnecting the
battery from its charging source in the
event of an over-temperature condi-
tion; or
(iii) A battery failure sensing and
warning system with a means for dis-
connecting the battery from its charg-
ing source in the event of battery fail-
ure.
(c) Electrical bonding must provide
an adequate electrical return path
under both normal and fault condi-
tions, on airplanes having grounded
electrical systems.
[Amdt. 25–123, 72 FR 63405, Nov. 8, 2007]
§ 25.1355
Distribution system.
(a) The distribution system includes
the distribution busses, their associ-
ated feeders, and each control and pro-
tective device.
(b) [Reserved]
(c) If two independent sources of elec-
trical power for particular equipment
or systems are required by this chap-
ter, in the event of the failure of one
power source for such equipment or
system, another power source (includ-
ing its separate feeder) must be auto-
matically provided or be manually se-
lectable to maintain equipment or sys-
tem operation.
[Doc. No. 5066, 29 FR 18291, Dec. 24, 1964, as
amended by Amdt. 25–23, 35 FR 5679, Apr. 8,
1970; Amdt. 25–38, 41 FR 55468, Dec. 20, 1976]
§ 25.1357
Circuit protective devices.
(a) Automatic protective devices
must be used to minimize distress to
the electrical system and hazard to the
airplane in the event of wiring faults or
serious malfunction of the system or
connected equipment.
(b) The protective and control de-
vices in the generating system must be
designed to de-energize and disconnect
faulty power sources and power trans-
mission equipment from their associ-
ated busses with sufficient rapidity to
provide protection from hazardous
over-voltage and other malfunctioning.
(c) Each resettable circuit protective
device must be designed so that, when
an overload or circuit fault exists, it
will open the circuit irrespective of the
position of the operating control.
(d) If the ability to reset a circuit
breaker or replace a fuse is essential to
safety in flight, that circuit breaker or
fuse must be located and identified so
that it can be readily reset or replaced
in flight. Where fuses are used, there
must be spare fuses for use in flight
equal to at least 50% of the number of
fuses of each rating required for com-
plete circuit protection.
(e) Each circuit for essential loads
must have individual circuit protec-
tion. However, individual protection
for each circuit in an essential load
system (such as each position light cir-
cuit in a system) is not required.
(f) For airplane systems for which
the ability to remove or reset power
during normal operations is necessary,
the system must be designed so that
circuit breakers are not the primary
means to remove or reset system power
unless specifically designed for use as a
switch.
(g) Automatic reset circuit breakers
may be used as integral protectors for
electrical equipment (such as thermal
cut-outs) if there is circuit protection
to protect the cable to the equipment.
[Doc. No. 5066, 29 FR 18291, Dec. 24, 1964, as
amended by Amdt. 25–123, 72 FR 63405, Nov. 8,
2007]
§ 25.1360
Precautions against injury.
(a) Shock. The electrical system
must be designed to minimize risk of
electric shock to crew, passengers, and
servicing personnel and to mainte-
nance personnel using normal pre-
cautions.
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§ 25.1383
(b) Burns. The temperature of any
part that may be handled by a crew-
member during normal operations
must not cause dangerous inadvertent
movement by the crewmember or in-
jury to the crewmember.
[Amdt. 25–123, 72 FR 63406, Nov. 8, 2007]
§ 25.1362
Electrical supplies for emer-
gency conditions.
A suitable electrical supply must be
provided to those services required for
emergency procedures after an emer-
gency landing or ditching. The circuits
for these services must be designed,
protected, and installed so that the
risk of the services being rendered inef-
fective under these emergency condi-
tions is minimized.
[Amdt. 25–123, 72 FR 63406, Nov. 8, 2007]
§ 25.1363
Electrical system tests.
(a) When laboratory tests of the elec-
trical system are conducted—
(1) The tests must be performed on a
mock-up using the same generating
equipment used in the airplane;
(2) The equipment must simulate the
electrical characteristics of the dis-
tribution wiring and connected loads to
the extent necessary for valid test re-
sults; and
(3) Laboratory generator drives must
simulate the actual prime movers on
the airplane with respect to their reac-
tion to generator loading, including
loading due to faults.
(b) For each flight condition that
cannot be simulated adequately in the
laboratory or by ground tests on the
airplane, flight tests must be made.
§ 25.1365
Electrical appliances, motors,
and transformers.
(a) Domestic appliances must be de-
signed and installed so that in the
event of failures of the electrical sup-
ply or control system, the require-
ments of § 25.1309(b), (c), and (d) will be
satisfied. Domestic appliances are
items such as cooktops, ovens, coffee
makers, water heaters, refrigerators,
and toilet flush systems that are
placed on the airplane to provide serv-
ice amenities to passengers.
(b) Galleys and cooking appliances
must be installed in a way that mini-
mizes risk of overheat or fire.
(c) Domestic appliances, particularly
those in galley areas, must be installed
or protected so as to prevent damage or
contamination of other equipment or
systems from fluids or vapors which
may be present during normal oper-
ation or as a result of spillage, if such
damage or contamination could create
a hazardous condition.
(d) Unless compliance with § 25.1309(b)
is provided by the circuit protective
device required by § 25.1357(a), electric
motors and transformers, including
those installed in domestic systems,
must have a suitable thermal protec-
tion device to prevent overheating
under normal operation and failure
conditions, if overheating could create
a smoke or fire hazard.
[Amdt. 25–123, 72 FR 63406, Nov. 8, 2007]
L
IGHTS
§ 25.1381
Instrument lights.
(a) The instrument lights must—
(1) Provide sufficient illumination to
make each instrument, switch and
other device necessary for safe oper-
ation easily readable unless sufficient
illumination is available from another
source; and
(2) Be installed so that—
(i) Their direct rays are shielded from
the pilot’s eyes; and
(ii) No objectionable reflections are
visible to the pilot.
(b) Unless undimmed instrument
lights are satisfactory under each ex-
pected flight condition, there must be a
means to control the intensity of illu-
mination.
[Doc. No. 5066, 29 FR 18291, Dec. 24, 1964, as
amended by Amdt. 25–72, 55 FR 29785, July 20,
1990]
§ 25.1383
Landing lights.
(a) Each landing light must be ap-
proved, and must be installed so that—
(1) No objectionable glare is visible
to the pilot;
(2) The pilot is not adversely affected
by halation; and
(3) It provides enough light for night
landing.
(b) Except when one switch is used
for the lights of a multiple light instal-
lation at one location, there must be a
separate switch for each light.
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