308 

14 CFR Ch. I (1–1–14 Edition) 

§ 23.1357 

temperature may result when the bat-
tery is recharged (after previous com-
plete discharge)— 

(1) At maximum regulated voltage or 

power; 

(2) During a flight of maximum dura-

tion; and 

(3) Under the most adverse cooling 

condition likely to occur in service. 

(c) Compliance with paragraph (b) of 

this section must be shown by tests un-
less experience with similar batteries 
and installations has shown that main-
taining safe cell temperatures and 
pressures presents no problem. 

(d) No explosive or toxic gases emit-

ted by any battery in normal oper-
ation, or as the result of any probable 
malfunction in the charging system or 
battery installation, may accumulate 
in hazardous quantities within the air-
plane. 

(e) No corrosive fluids or gases that 

may escape from the battery may dam-
age surrounding structures or adjacent 
essential equipment. 

(f) Each nickel cadmium battery in-

stallation capable of being used to 
start an engine or auxiliary power unit 
must have provisions to prevent any 
hazardous effect on structure or essen-
tial systems that may be caused by the 
maximum amount of heat the battery 
can generate during a short circuit of 
the battery or of its individual cells. 

(g) Nickel cadmium battery installa-

tions capable of being used to start an 
engine or auxiliary power unit must 
have— 

(1) A system to control the charging 

rate of the battery automatically so as 
to prevent battery overheating; 

(2) 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 

(3) 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. 

(h)(1) In the event of a complete loss 

of the primary electrical power gener-
ating system, the battery must be ca-
pable of providing electrical power to 
those loads that are essential to con-
tinued safe flight and landing for: 

(i) At least 30 minutes for airplanes 

that are certificated with a maximum 
altitude of 25,000 feet or less; and 

(ii) At least 60 minutes for airplanes 

that are certificated with a maximum 
altitude over 25,000 feet. 

(2) The time period includes the time 

to recognize the loss of generated 
power and to take appropriate load 
shedding action. 

[Doc. No. 4080, 29 FR 17955, Dec. 18, 1964; 30 
FR 258, Jan. 9, 1965, as amended by Amdt. 23– 
20, 42 FR 36969, July 18, 1977; Amdt. 23–21, 43 
FR 2319, Jan. 16, 1978; Amdt. 23–49, 61 FR 5169, 
Feb. 9, 1996; Amdt. 23–62, 76 FR 75761, Dec. 2, 
2011] 

§ 23.1357

Circuit protective devices. 

(a) Protective devices, such as fuses 

or circuit breakers, must be installed 
in all electrical circuits other than— 

(1) Main circuits of starter motors 

used during starting only; and 

(2) Circuits in which no hazard is pre-

sented by their omission. 

(b) A protective device for a circuit 

essential to flight safety may not be 
used to protect any other circuit. 

(c) Each resettable circuit protective 

device (‘‘trip free’’ device in which the 
tripping mechanism cannot be over-
ridden by the operating control) must 
be designed so that— 

(1) A manual operation is required to 

restore service after tripping; and 

(2) If an overload or circuit fault ex-

ists, the device will open the circuit re-
gardless of the position of the oper-
ating 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 so located and identified 
that it can be readily reset or replaced 
in flight. 

(e) For fuses identified as replaceable 

in flight— 

(1) There must be one spare of each 

rating or 50 percent spare fuses of each 
rating, whichever is greater; and 

(2) The spare fuse(s) must be readily 

accessible to any required pilot. 

[Doc. No. 4080, 29 FR 17955, Dec. 18, 1964; 30 
FR 258, Jan. 9, 1965, as amended by Amdt. 23– 
20, 42 FR 36969, July 18, 1977]; Amdt. 23–43, 58 
FR 18976, Apr. 9, 1993 

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