333
Federal Aviation Administration, DOT
§ 25.1181
§ 25.1163
Powerplant accessories.
(a) Each engine mounted accessory
must—
(1) Be approved for mounting on the
engine involved;
(2) Use the provisions on the engine
for mounting; and
(3) Be sealed to prevent contamina-
tion of the engine oil system and the
accessory system.
(b) Electrical equipment subject to
arcing or sparking must be installed to
minimize the probability of contact
with any flammable fluids or vapors
that might be present in a free state.
(c) If continued rotation of an engine-
driven cabin supercharger or of any re-
mote accessory driven by the engine is
hazardous if malfunctioning occurs,
there must be means to prevent rota-
tion without interfering with the con-
tinued operation of the engine.
[Doc. No. 5066, 29 FR 18291, Dec. 24, 1964, as
amended by Amdt. 25–57, 49 FR 6849, Feb. 23,
1984]
§ 25.1165
Engine ignition systems.
(a) Each battery ignition system
must be supplemented by a generator
that is automatically available as an
alternate source of electrical energy to
allow continued engine operation if
any battery becomes depleted.
(b) The capacity of batteries and gen-
erators must be large enough to meet
the simultaneous demands of the en-
gine ignition system and the greatest
demands of any electrical system com-
ponents that draw electrical energy
from the same source.
(c) The design of the engine ignition
system must account for—
(1) The condition of an inoperative
generator;
(2) The condition of a completely de-
pleted battery with the generator run-
ning at its normal operating speed; and
(3) The condition of a completely de-
pleted battery with the generator oper-
ating at idling speed, if there is only
one battery.
(d) Magneto ground wiring (for sepa-
rate ignition circuits) that lies on the
engine side of the fire wall, must be in-
stalled, located, or protected, to mini-
mize the probability of simultaneous
failure of two or more wires as a result
of mechanical damage, electrical
faults, or other cause.
(e) No ground wire for any engine
may be routed through a fire zone of
another engine unless each part of that
wire within that zone is fireproof.
(f) Each ignition system must be
independent of any electrical circuit,
not used for assisting, controlling, or
analyzing the operation of that system.
(g) There must be means to warn ap-
propriate flight crewmembers if the
malfunctioning of any part of the elec-
trical system is causing the continuous
discharge of any battery necessary for
engine ignition.
(h) Each engine ignition system of a
turbine powered airplane must be con-
sidered an essential electrical load.
[Doc. No. 5066, 29 FR 18291, Dec. 24, 1964, as
amended by Amdt. 25–23, 35 FR 5677, Apr. 8,
1970; Amdt. 25–72, 55 FR 29785, July 20, 1990]
§ 25.1167
Accessory gearboxes.
For airplanes equipped with an acces-
sory gearbox that is not certificated as
part of an engine—
(a) The engine with gearbox and con-
necting transmissions and shafts at-
tached must be subjected to the tests
specified in § 33.49 or § 33.87 of this chap-
ter, as applicable;
(b) The accessory gearbox must meet
the requirements of §§ 33.25 and 33.53 or
33.91 of this chapter, as applicable; and
(c) Possible misalignments and tor-
sional loadings of the gearbox, trans-
mission, and shaft system, expected to
result under normal operating condi-
tions must be evaluated.
[Amdt. 25–38, 41 FR 55467, Dec. 20, 1976]
P
OWERPLANT
F
IRE
P
ROTECTION
§ 25.1181
Designated fire zones; re-
gions included.
(a) Designated fire zones are—
(1) The engine power section;
(2) The engine accessory section;
(3) Except for reciprocating engines,
any complete powerplant compartment
in which no isolation is provided be-
tween the engine power section and the
engine accessory section;
(4) Any auxiliary power unit com-
partment;
(5) Any fuel-burning heater and other
combustion equipment installation de-
scribed in § 25.859;
(6) The compressor and accessory sec-
tions of turbine engines; and
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14 CFR Ch. I (1–1–24 Edition)
§ 25.1182
(7) Combustor, turbine, and tailpipe
sections of turbine engine installations
that contain lines or components car-
rying flammable fluids or gases.
(b) Each designated fire zone must
meet the requirements of §§ 25.863,
25.865, 25.867, 25.869, and 25.1185 through
25.1203.
[Doc. No. 5066, 29 FR 18291, Dec. 24, 1964, as
amended by Amdt. 25–11, 32 FR 6913, May 5,
1967; Amdt. 25–23, 35 FR 5677, Apr. 8, 1970;
Amdt. 25–72, 55 FR 29785, July 20, 1990; Amdt.
25–115, 69 FR 40527, July 2, 2004]
§ 25.1182
Nacelle areas behind fire-
walls, and engine pod attaching
structures containing flammable
fluid lines.
(a) Each nacelle area immediately
behind the firewall, and each portion of
any engine pod attaching structure
containing flammable fluid lines, must
meet each requirement of §§ 25.1103(b),
25.1165 (d) and (e), 25.1183, 25.1185(c),
25.1187, 25.1189, and 25.1195 through
25.1203, including those concerning des-
ignated fire zones. However, engine pod
attaching structures need not contain
fire detection or extinguishing means.
(b) For each area covered by para-
graph (a) of this section that contains
a retractable landing gear, compliance
with that paragraph need only be
shown with the landing gear retracted.
[Amdt. 25–11, 32 FR 6913, May 5, 1967]
§ 25.1183
Flammable fluid-carrying
components.
(a) Except as provided in paragraph
(b) of this section, each line, fitting,
and other component carrying flam-
mable fluid in any area subject to en-
gine fire conditions, and each compo-
nent which conveys or contains flam-
mable fluid in a designated fire zone
must be fire resistant, except that
flammable fluid tanks and supports in
a designated fire zone must be fireproof
or be enclosed by a fireproof shield un-
less damage by fire to any non-fire-
proof part will not cause leakage or
spillage of flammable fluid. Compo-
nents must be shielded or located to
safeguard against the ignition of leak-
ing flammable fluid. An integral oil
sump of less than 25-quart capacity on
a reciprocating engine need not be fire-
proof nor be enclosed by a fireproof
shield.
(b) Paragraph (a) of this section does
not apply to—
(1) Lines, fittings, and components
which are already approved as part of a
type certificated engine; and
(2) Vent and drain lines, and their fit-
tings, whose failure will not result in,
or add to, a fire hazard.
(c) All components, including ducts,
within a designated fire zone must be
fireproof if, when exposed to or dam-
aged by fire, they could—
(1) Result in fire spreading to other
regions of the airplane; or
(2) Cause unintentional operation of,
or inability to operate, essential serv-
ices or equipment.
[Doc. No. 5066, 29 FR 18291, Dec. 24, 1964, as
amended by Amdt. 25–11, 32 FR 6913, May 5,
1967; Amdt. 25–36, 39 FR 35461, Oct. 1, 1974;
Amdt. 25–57, 49 FR 6849, Feb. 23, 1984; Amdt.
25–101, 65 FR 79710, Dec. 19, 2000]
§ 25.1185
Flammable fluids.
(a) Except for the integral oil sumps
specified in § 25.1183(a), no tank or res-
ervoir that is a part of a system con-
taining flammable fluids or gases may
be in a designated fire zone unless the
fluid contained, the design of the sys-
tem, the materials used in the tank,
the shut-off means, and all connec-
tions, lines, and control provide a de-
gree of safety equal to that which
would exist if the tank or reservoir
were outside such a zone.
(b) There must be at least one-half
inch of clear airspace between each
tank or reservoir and each firewall or
shroud isolating a designated fire zone.
(c) Absorbent materials close to
flammable fluid system components
that might leak must be covered or
treated to prevent the absorption of
hazardous quantities of fluids.
[Doc. No. 5066, 29 FR 18291, Dec. 24, 1964, as
amended by Amdt. 25–19, 33 FR 15410, Oct. 17,
1968; Amdt. 25–94, 63 FR 8848, Feb. 23, 1998]
§ 25.1187
Drainage and ventilation of
fire zones.
(a) There must be complete drainage
of each part of each designated fire
zone to minimize the hazards resulting
from failure or malfunctioning of any
component containing flammable
fluids. The drainage means must be—
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