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Federal Aviation Administration, DOT 

§ 25.1183 

(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] 








§ 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-


(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 

(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 

[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 


(a) Except as provided in paragraph 

(b) of this section, each line, fitting, 

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