Federal Aviation Administration, DOT

Section 27.1357

(3) Each generator must have a reverse current cutout designed to disconnect the generator from the battery
and from the other generators when
enough reverse current exists to damage that generator; and
(4) Each generator must have an
overvoltage control designed and installed to prevent damage to the electrical system, or to equipment supplied
by the electrical system, that could result if that generator were to develop
an overvoltage condition.
(d) Instruments. There must be means
to indicate to appropriate crewmembers the electric power system
quantities essential for safe operation
of the system. In addition - 
(1) For direct current systems, an
ammeter that can be switched into
each generator feeder may be used; and
(2) If there is only one generator, the
ammeter may be in the battery feeder.
(e) External power. If provisions are
made for connecting external power to
the rotorcraft, and that external power
can be electrically connected to equipment other than that used for engine
starting, means must be provided to
ensure that no external power supply
having a reverse polarity, or a reverse
phase sequence, can supply power to
the rotorcraft-s electrical system.
(Secs. 313(a), 601, 603, 604, and 605 of the Federal Aviation Act of 1958 (49 U.S.C. 1354(a),
1421, 1423, 1424, and 1425); and sec. 6(c) of the
Dept. of Transportation Act (49 U.S.C.
1655(c)))
[Doc. No. 5074, 29 FR 15695, Nov. 24, 1964, as
amended by Amdt. 27-11, 41 FR 55470, Dec. 20,
1976; Amdt. 27-13, 42 FR 36972, July 18, 1977]

spaschal on DSK3GDR082PROD with CFR

Section 27.1353 Storage battery design and
installation.
(a) Each storage battery must be designed and installed as prescribed in
this section.
(b) Safe cell temperatures and pressures must be maintained during any
probable charging and discharging condition. No uncontrolled increase in cell
temperature may result when the battery is recharged (after previous complete discharge) - 
(1) At maximum regulated voltage or
power;
(2) During a flight of maximum duration; 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 test unless experience with similar batteries
and installations has shown that maintaining safe cell temperatures and
pressures presents no problem.
(d) No explosive or toxic gases emitted by any battery in normal operation, or as the result of any probable
malfunction in the charging system or
battery installation, may accumulate
in hazardous quantities within the
rotorcraft.
(e) No corrosive fluids or gases that
may escape from the battery may damage surrounding structures or adjacent
essential equipment.
(f) Each nickel cadmium battery installation capable of being used to
start an engine or auxiliary power unit
must have provisions to prevent 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 its individual cells.
(g) Nickel cadmium battery installations 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 condition; or
(3) A battery failure sensing and
warning system with a means for disconnecting the battery from its charging source in the event of battery failure.
(Secs. 313(a), 601, 603, 604, and 605 of the Federal Aviation Act of 1958 (49 U.S.C. 1354(a),
1421, 1423, 1424, and 1425); and sec. 6(c) of the
Dept. of Transportation Act (49 U.S.C.
1655(c)))
[Doc. No. 5074, 29 FR 15695, Nov. 24, 1964, as
amended by Amdt. 27-13, 42 FR 36972, July 18,
1977; Amdt. 27-14, 43 FR 2325, Jan. 16, 1978]

Section 27.1357 Circuit protective devices.
(a) Protective devices, such as fuses
or circuit breakers, must be installed
in each electrical circuit other than - 

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