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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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334 

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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