335 

Federal Aviation Administration, DOT 

§ 25.1193 

(1) Effective under conditions ex-

pected to prevail when drainage is 
needed; and 

(2) Arranged so that no discharged 

fluid will cause an additional fire haz-
ard. 

(b) Each designated fire zone must be 

ventilated to prevent the accumulation 
of flammable vapors. 

(c) No ventilation opening may be 

where it would allow the entry of flam-
mable fluids, vapors, or flame from 
other zones. 

(d) Each ventilation means must be 

arranged so that no discharged vapors 
will cause an additional fire hazard. 

(e) Unless the extinguishing agent ca-

pacity and rate of discharge are based 
on maximum air flow through a zone, 
there must be means to allow the crew 
to shut off sources of forced ventilation 
to any fire zone except the engine 
power section of the nacelle and the 
combustion heater ventilating air 
ducts. 

§ 25.1189

Shutoff means. 

(a) Each engine installation and each 

fire zone specified in § 25.1181(a)(4) and 
(5) must have a means to shut off or 
otherwise prevent hazardous quantities 
of fuel, oil, deicer, and other flammable 
fluids, from flowing into, within, or 
through any designated fire zone, ex-
cept that shutoff means are not re-
quired for— 

(1) Lines, fittings, and components 

forming an integral part of an engine; 
and 

(2) Oil systems for turbine engine in-

stallations in which all components of 
the system in a designated fire zone, 
including oil tanks, are fireproof or lo-
cated in areas not subject to engine 
fire conditions. 

(b) The closing of any fuel shutoff 

valve for any engine may not make 
fuel unavailable to the remaining en-
gines. 

(c) Operation of any shutoff may not 

interfere with the later emergency op-
eration of other equipment, such as the 
means for feathering the propeller. 

(d) Each flammable fluid shutoff 

means and control must be fireproof or 
must be located and protected so that 
any fire in a fire zone will not affect its 
operation. 

(e) No hazardous quantity of flam-

mable fluid may drain into any des-
ignated fire zone after shutoff. 

(f) There must be means to guard 

against inadvertent operation of the 
shutoff means and to make it possible 
for the crew to reopen the shutoff 
means in flight after it has been closed. 

(g) Each tank-to-engine shutoff valve 

must be located so that the operation 
of the valve will not be affected by 
powerplant or engine mount structural 
failure. 

(h) Each shutoff valve must have a 

means to relieve excessive pressure ac-
cumulation unless a means for pressure 
relief is otherwise provided in the sys-
tem. 

[Doc. No. 5066, 29 FR 18291, Dec. 24, 1964, as 
amended by Amdt. 25–23, 35 FR 5677, Apr. 8, 
1970; Amdt. 25–57, 49 FR 6849, Feb. 23, 1984] 

§ 25.1191

Firewalls. 

(a) Each engine, auxiliary power 

unit, fuel-burning heater, other com-
bustion equipment intended for oper-
ation in flight, and the combustion, 
turbine, and tailpipe sections of tur-
bine engines, must be isolated from the 
rest of the airplane by firewalls, 
shrouds, or equivalent means. 

(b) Each firewall and shroud must 

be— 

(1) Fireproof; 
(2) Constructed so that no hazardous 

quantity of air, fluid, or flame can pass 
from the compartment to other parts 
of the airplane; 

(3) Constructed so that each opening 

is sealed with close fitting fireproof 
grommets, bushings, or firewall fit-
tings; and 

(4) Protected against corrosion. 

§ 25.1192

Engine accessory section dia-

phragm. 

For reciprocating engines, the engine 

power section and all portions of the 
exhaust system must be isolated from 
the engine accessory compartment by a 
diaphragm that complies with the fire-
wall requirements of § 25.1191. 

[Amdt. 25–23, 35 FR 5678, Apr. 8, 1970] 

§ 25.1193

Cowling and nacelle skin. 

(a) Each cowling must be constructed 

and supported so that it can resist any 

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