title-14-part-27-sec27-1351

551

Federal Aviation Administration, DOT

§ 27.1351

indicate to the pilots the current mode
of operation. Selector switch position
is not acceptable as a means of indica-
tion.

[Amdt. 27–21, 49 FR 44435, Nov. 6, 1984, as
amended by Amdt. 27–35, 63 FR 43285, Aug. 12,
1998; Amdt. 27–51, 88 FR 8738, Feb. 10, 2023]

§ 27.1337

Powerplant instruments.

(a)

Instruments and instrument lines.

(1) Each powerplant instrument line
must meet the requirements of §§ 27.-
961 and 27.993.

(2) Each line carrying flammable

fluids under pressure must—

(i) Have restricting orifices or other

safety devices at the source of pressure
to prevent the escape of excessive fluid
if the line fails; and

(ii) Be installed and located so that

the escape of fluids would not create a
hazard.

(3) Each powerplant instrument that

utilizes flammable fluids must be in-
stalled and located so that the escape
of fluid would not create a hazard.

(b)

Fuel quantity indicator. Each fuel

quantity indicator must be installed to
clearly indicate to the flight crew the
quantity of fuel in each tank in flight.
In addition—

(1) Each fuel quantity indicator must

be calibrated to read ‘‘zero’’ during
level flight when the quantity of fuel
remaining in the tank is equal to the
unusable fuel supply determined under
§ 27.959;

(2) When two or more tanks are close-

ly interconnected by a gravity feed sys-
tem and vented, and when it is impos-
sible to feed from each tank sepa-
rately, at least one fuel quantity indi-
cator must be installed; and

(3) Each exposed sight gauge used as

a fuel quantity indicator must be pro-
tected against damage.

(c)

Fuel flowmeter system. If a fuel

flowmeter system is installed, each
metering component must have a
means for bypassing the fuel supply if
malfunction of that component se-
verely restricts fuel flow.

(d)

Oil quantity indicator. There must

be means to indicate the quantity of
oil in each tank—

(1) On the ground (including during

the filling of each tank); and

(2) In flight, if there is an oil transfer

system or reserve oil supply system.

(e) Rotor drive system transmissions

and gearboxes utilizing ferromagnetic
materials must be equipped with chip
detectors designed to indicate the pres-
ence of ferromagnetic particles result-
ing from damage or excessive wear.
Chip detectors must—

(1) Be designed to provide a signal to

the device required by § 27.1305(v) and
be provided with a means to allow
crewmembers to check, in flight, the
function of each detector electrical cir-
cuit and signal.

(2) [Reserved]

(Secs. 313(a), 601, and 603, 72 Stat. 752, 775, 49
U.S.C. 1354(a), 1421, and 1423; sec. 6(c) 49
U.S.C. 1655(c))

[Doc. No. 5074, 29 FR 15695, Nov. 24, 1964, as
amended by Amdt. 27–12, 42 FR 15046, Mar. 17,
1977; Amdt. 27–23, 53 FR 34214, Sept. 2, 1988;
Amdt. 27–37, 64 FR 45095, Aug. 18, 1999]

LECTRICAL

YSTEMS AND

QUIPMENT

§ 27.1351

General.

(a)

Electrical system capacity. Elec-

trical equipment must be adequate for
its intended use. In addition—

(1) Electric power sources, their

transmission cables, and their associ-
ated control and protective devices
must be able to furnish the required
power at the proper voltage to each
load circuit essential for safe oper-
ation; and

(2) Compliance with paragraph (a)(1)

of this section must be shown by an
electrical load analysis, or by elec-
trical measurements that take into ac-
count the electrical loads applied to
the electrical system, in probable com-
binations and for probable durations.

(b)

Function. For each electrical sys-

tem, the following apply:

(1) Each system, when installed,

must be—

(i) Free from hazards in itself, in its

method of operation, and in its effects
on other parts of the rotorcraft; and

(ii) Protected from fuel, oil, water,

other detrimental substances, and me-
chanical damage.

(2) Electric power sources must func-

tion properly when connected in com-
bination or independently.

(3) No failure or malfunction of any

source may impair the ability of any
remaining source to supply load cir-
cuits essential for safe operation.

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14 CFR Ch. I (1–1–24 Edition)

§ 27.1353

(4) Each electric power source control

must allow the independent operation
of each source.

(c)

Generating system. There must be

at least one generator if the system
supplies power to load circuits essen-
tial for safe operation. In addition—

(1) Each generator must be able to

deliver its continuous rated power;

(2) Generator voltage control equip-

ment must be able to dependably regu-
late each generator output within
rated limits;

(3) Each generator must have a re-

verse current cutout designed to dis-
connect the generator from the battery
and from the other generators when
enough reverse current exists to dam-
age that generator; and

(4) Each generator must have an

overvoltage control designed and in-
stalled to prevent damage to the elec-
trical system, or to equipment supplied
by the electrical system, that could re-
sult if that generator were to develop
an overvoltage condition.

(d)

Instruments. There must be means

to indicate to appropriate crew-
members 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 equip-
ment 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 Fed-
eral 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]

§ 27.1353

Energy storage systems.

Energy storage systems must be de-

signed and installed as follows:

(a) Energy storage systems must pro-

vide automatic protective features for
any conditions that could prevent con-
tinued safe flight and landing.

(b) Energy storage systems must not

emit any flammable, explosive, or
toxic gases, smoke, or fluids that could
accumulate in hazardous quantities
within the rotorcraft.

cape from the system must not damage
surrounding structures, adjacent equip-
ment, or systems necessary for contin-
ued safe flight and landing.

(d) The maximum amount of heat

and pressure that can be generated dur-
ing any operation or under any failure
condition of the energy storage system
or its individual components must not
result in any hazardous effect on rotor-
craft structure, equipment, or systems
necessary for continued safe flight and
landing.

(e) Energy storage system installa-

tions required for continued safe flight
and landing of the rotorcraft must
have monitoring features and a means
to indicate to the pilot the status of all
critical system parameters.

[Amdt. 27–51, 88 FR 8738, Feb. 10, 2023]

§ 27.1357

Circuit protective devices.

(a) Protective devices, such as fuses

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

(1) The main circuits of starter mo-

tors; 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.

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 trippling; 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 located and identified so
that it can be readily reset or replaced
in flight.