111 

Federal Aviation Administration, DOT 

§ 121.275 

§ 121.259 Lines and fittings. 

(a) Each line, and its fittings, that is 

located in a designated fire zone, if it 
carries flammable fluids or gases under 
pressure, or is attached directly to the 
engine, or is subject to relative motion 
between components (except lines and 
fittings forming an integral part of the 
engine), must be flexible and fire-re-
sistant with fire-resistant, factory- 
fixed, detachable, or other approved 
fire-resistant ends. 

(b) Lines and fittings that are not 

subject to pressure or to relative mo-
tion between components must be of 
fire-resistant materials. 

§ 121.261 Vent and drain lines. 

All vent and drain lines and their fit-

tings, that are located in a designated 
fire zone must, if they carry flammable 
fluids or gases, comply with § 121.259, if 
the Administrator finds that the rup-
ture or breakage of any vent or drain 
line may result in a fire hazard. 

§ 121.263 Fire-extinguishing systems. 

(a) Unless the certificate holder 

shows that equivalent protection 
against destruction of the airplane in 
case of fire is provided by the use of 
fireproof materials in the nacelle and 
other components that would be sub-
jected to flame, fire-extinguishing sys-
tems must be provided to serve all des-
ignated fire zones. 

(b) Materials in the fire-extin-

guishing system must not react chemi-
cally with the extinguishing agent so 
as to be a hazard. 

§ 121.265 Fire-extinguishing agents. 

Only methyl bromide, carbon dioxide, 

or another agent that has been shown 
to provide equivalent extinguishing ac-
tion may be used as a fire-extin-
guishing agent. If methyl bromide or 
any other toxic extinguishing agent is 
used, provisions must be made to pre-
vent harmful concentrations of fluid or 
fluid vapors from entering any per-
sonnel compartment either because of 
leakage during normal operation of the 
airplane or because of discharging the 
fire extinguisher on the ground or in 
flight when there is a defect in the ex-
tinguishing system. If a methyl bro-
mide system is used, the containers 

must be charged with dry agent and 
sealed by the fire-extinguisher manu-
facturer or some other person using 
satisfactory recharging equipment. If 
carbon dioxide is used, it must not be 
possible to discharge enough gas into 
the personnel compartments to create 
a danger of suffocating the occupants. 

§ 121.267 Extinguishing agent con-

tainer pressure relief. 

Extinguishing agent containers must 

be provided with a pressure relief to 
prevent bursting of the container be-
cause of excessive internal pressures. 
The discharge line from the relief con-
nection must terminate outside the 
airplane in a place convenient for in-
spection on the ground. An indicator 
must be provided at the discharge end 
of the line to provide a visual indica-
tion when the container has dis-
charged. 

§ 121.269 Extinguishing agent con-

tainer compartment temperature. 

Precautions must be taken to insure 

that the extinguishing agent con-
tainers are installed in places where 
reasonable temperatures can be main-
tained for effective use of the extin-
guishing system. 

§ 121.271 Fire-extinguishing system 

materials. 

(a) Except as provided in paragraph 

(b) of this section, each component of a 
fire-extinguishing system that is in a 
designated fire zone must be made of 
fireproof materials. 

(b) Connections that are subject to 

relative motion between components of 
the airplane must be made of flexible 
materials that are at least fire-resist-
ant and be located so as to minimize 
the probability of failure. 

§ 121.273 Fire-detector systems. 

Enough quick-acting fire detectors 

must be provided in each designated 
fire zone to assure the detection of any 
fire that may occur in that zone. 

§ 121.275 Fire detectors. 

Fire detectors must be made and in-

stalled in a manner that assures their 
ability to resist, without failure, all vi-
bration, inertia, and other loads to 
which they may be normally subjected.