background image


14 CFR Ch. I (1–1–19 Edition) 

§ 25.1163 

§ 25.1163

Powerplant accessories. 

(a) Each engine mounted accessory 


(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, 

§ 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 


(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 

VerDate Sep<11>2014 

12:50 Apr 30, 2019

Jkt 247046

PO 00000

Frm 00342

Fmt 8010

Sfmt 8010



spaschal on DSK3GDR082PROD with CFR