title-14-part-25-sec25-1309

340

14 CFR Ch. I (1–1–24 Edition)

§ 25.1307

continuous operation nor designed to
prevent hazard if it failed.

(5) An indicator to indicate the func-

tioning of the powerplant ice protec-
tion system for each engine.

(6) An indicator for the fuel strainer

or filter required by § 25.997 to indicate
the occurrence of contamination of the
strainer or filter before it reaches the
capacity established in accordance
with § 25.997(d).

(7) A warning means for the oil

strainer or filter required by § 25.1019, if
it has no bypass, to warn the pilot of
the occurrence of contamination of the
strainer or filter screen before it
reaches the capacity established in ac-
cordance with § 25.1019(a)(2).

(8) An indicator to indicate the prop-

er functioning of any heater used to
prevent ice clogging of fuel system
components.

(d)

For turbojet engine powered air-

planes. In addition to the powerplant
instruments required by paragraphs (a)
and (c) of this section, the following
powerplant instruments are required:

(1) An indicator to indicate thrust, or

a parameter that is directly related to
thrust, to the pilot. The indication
must be based on the direct measure-
ment of thrust or of parameters that
are directly related to thrust. The indi-
cator must indicate a change in thrust
resulting from any engine malfunction,
damage, or deterioration.

(2) A position indicating means to in-

dicate to the flightcrew when the
thrust reversing device—

(i) Is not in the selected position, and
(ii) Is in the reverse thrust position,

for each engine using a thrust revers-
ing device.

(3) An indicator to indicate rotor sys-

tem unbalance.

(e)

For turbopropeller-powered air-

planes. In addition to the powerplant
instruments required by paragraphs (a)
and (c) of this section, the following
powerplant instruments are required:

(1) A torque indicator for each en-

gine.

(2) Position indicating means to indi-

cate to the flight crew when the pro-
peller blade angle is below the flight
low pitch position, for each propeller.

(f) For airplanes equipped with fluid

systems (other than fuel) for thrust or
power augmentation, an approved

means must be provided to indicate the
proper functioning of that system to
the flight crew.

[Amdt. 25–23, 35 FR 5678, Apr. 8, 1970, as
amended by Amdt. 25–35, 39 FR 1831, Jan. 15,
1974; Amdt. 25–36, 39 FR 35461, Oct. 1, 1974;
Amdt. 25–38, 41 FR 55467, Dec. 20, 1976; Amdt.
25–54, 45 FR 60173, Sept. 11, 1980; Amdt. 25–72,
55 FR 29785, July 20, 1990; Amdt. 25–115, 69 FR
40527, July 2, 2004]

§ 25.1307

Miscellaneous equipment.

The following is required miscella-

neous equipment:

(a) [Reserved]
(b) Two or more independent sources

of electrical energy.

prescribed in this part.

(d) Two systems for two-way radio

communications, with controls for
each accessible from each pilot station,
designed and installed so that failure of
one system will not preclude operation
of the other system. The use of a com-
mon antenna system is acceptable if
adequate reliability is shown.

(e) Two systems for radio navigation,

with controls for each accessible from
each pilot station, designed and in-
stalled so that failure of one system
will not preclude operation of the other
system. The use of a common antenna
system is acceptable if adequate reli-
ability is shown.

[Amdt. 25–23, 35 FR 5678, Apr. 8, 1970, as
amended by Amdt. 25–46, 43 FR 50598, Oct. 30,
1978; Amdt. 25–54, 45 FR 60173, Sept. 11, 1980;
Amdt. 25–72, 55 FR 29785, July 20, 1990]

§ 25.1309

Equipment, systems, and in-

stallations.

(a) The equipment, systems, and in-

stallations whose functioning is re-
quired by this subchapter, must be de-
signed to ensure that they perform
their intended functions under any
foreseeable operating condition.

(b) The airplane systems and associ-

ated components, considered sepa-
rately and in relation to other systems,
must be designed so that—

(1) The occurrence of any failure con-

dition which would prevent the contin-
ued safe flight and landing of the air-
plane is extremely improbable, and

(2) The occurrence of any other fail-

ure conditions which would reduce the
capability of the airplane or the ability

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§ 25.1316

of the crew to cope with adverse oper-
ating conditions is improbable.

vided to alert the crew to unsafe sys-
tem operating conditions, and to en-
able them to take appropriate correc-
tive action. Systems, controls, and as-
sociated monitoring and warning
means must be designed to minimize
crew errors which could create addi-
tional hazards.

(d) Compliance with the require-

ments of paragraph (b) of this section
must be shown by analysis, and where
necessary, by appropriate ground,
flight, or simulator tests. The analysis
must consider—

(1) Possible modes of failure, includ-

ing malfunctions and damage from ex-
ternal sources.

(2) The probability of multiple fail-

ures and undetected failures.

(3) The resulting effects on the air-

plane and occupants, considering the
stage of flight and operating condi-
tions, and

(4) The crew warning cues, corrective

action required, and the capability of
detecting faults.

(e) In showing compliance with para-

graphs (a) and (b) of this section with
regard to the electrical system and
equipment design and installation,
critical environmental conditions must
be considered. For electrical genera-
tion, distribution, and utilization
equipment required by or used in com-
plying with this chapter, except equip-
ment covered by Technical Standard
Orders containing environmental test
procedures, the ability to provide con-
tinuous, safe service under foreseeable
environmental conditions may be
shown by environmental tests, design
analysis, or reference to previous com-
parable service experience on other air-
craft.

(f) EWIS must be assessed in accord-

ance with the requirements of § 25.1709.

[Amdt. 25–23, 35 FR 5679, Apr. 8, 1970, as
amended by Amdt. 25–38, 41 FR 55467, Dec. 20,
1976; Amdt. 25–41, 42 FR 36970, July 18, 1977;
Amdt. 25–123, 72 FR 63405, Nov. 8, 2007]

§ 25.1310

Power source capacity and

distribution.

(a) Each installation whose func-

tioning is required for type certifi-
cation or under operating rules and

that requires a power supply is an ‘‘es-
sential load’’ on the power supply. The
power sources and the system must be
able to supply the following power
loads in probable operating combina-
tions and for probable durations:

(1) Loads connected to the system

with the system functioning normally.

(2) Essential loads, after failure of

any one prime mover, power converter,
or energy storage device.

(3) Essential loads after failure of—
(i) Any one engine on two-engine air-

planes; and

(ii) Any two engines on airplanes

with three or more engines.

(4) Essential loads for which an alter-

nate source of power is required, after
any failure or malfunction in any one
power supply system, distribution sys-
tem, or other utilization system.

(b) In determining compliance with

paragraphs (a)(2) and (3) of this section,
the power loads may be assumed to be
reduced under a monitoring procedure
consistent with safety in the kinds of
operation authorized. Loads not re-
quired in controlled flight need not be
considered for the two-engine-inoper-
ative condition on airplanes with three
or more engines.

[Amdt. 25–123, 72 FR 63405, Nov. 8, 2007]

§ 25.1316

Electrical and electronic sys-

tem lightning protection.

(a) Each electrical and electronic

system that performs a function, for
which failure would prevent the contin-
ued safe flight and landing of the air-
plane, must be designed and installed
so that—

(1) The function is not adversely af-

fected during and after the time the
airplane is exposed to lightning; and

(2) The system automatically recov-

ers normal operation of that function
in a timely manner after the airplane
is exposed to lightning.

(b) Each electrical and electronic

system that performs a function, for
which failure would reduce the capa-
bility of the airplane or the ability of
the flightcrew to respond to an adverse
operating condition, must be designed
and installed so that the function re-
covers normal operation in a timely