336
14 CFR Ch. I (1–1–24 Edition)
§ 125.143
(b) Engine breathers must discharge
in a location that does not constitute a
fire hazard in case foaming occurs and
so that oil emitted from the line does
not impinge upon the pilots’ wind-
shield.
(c) Engine breathers may not dis-
charge into the engine air induction
system.
§ 125.143 Firewalls.
Each engine, auxiliary power unit,
fuel-burning heater, or other item of
combusting equipment that is intended
for operation in flight must be isolated
from the rest of the airplane by means
of firewalls or shrouds, or by other
equivalent means.
§ 125.145 Firewall construction.
Each firewall and shroud must—
(a) Be so made that no hazardous
quantity of air, fluids, or flame can
pass from the engine compartment to
other parts of the airplane;
(b) Have all openings in the firewall
or shroud sealed with close-fitting fire-
proof grommets, bushings, or firewall
fittings;
(c) Be made of fireproof material; and
(d) Be protected against corrosion.
§ 125.147 Cowling.
(a) Cowling must be made and sup-
ported so as to resist the vibration, in-
ertia, and air loads to which it may be
normally subjected.
(b) Provisions must be made to allow
rapid and complete drainage of the
cowling in normal ground and flight at-
titudes. Drains must not discharge in
locations constituting a fire hazard.
Parts of the cowling that are subjected
to high temperatures because they are
near exhaust system parts or because
of exhaust gas impingement must be
made of fireproof material. Unless oth-
erwise specified in these regulations,
all other parts of the cowling must be
made of material that is at least fire
resistant.
§ 125.149 Engine accessory section dia-
phragm.
Unless equivalent protection can be
shown by other means, a diaphragm
that complies with § 125.145 must be
provided on air-cooled engines to iso-
late the engine power section and all
parts of the exhaust system from the
engine accessory compartment.
§ 125.151 Powerplant fire protection.
(a) Designated fire zones must be pro-
tected from fire by compliance with
§§ 125.153 through 125.159.
(b) Designated fire zones are—
(1) Engine accessory sections;
(2) Installations where no isolation is
provided between the engine and acces-
sory compartment; and
(3) Areas that contain auxiliary
power units, fuel-burning heaters, and
other combustion equipment.
§ 125.153 Flammable fluids.
(a) No tanks or reservoirs that are a
part of a system containing flammable
fluids or gases may be located in des-
ignated fire zones, except where the
fluid contained, the design of the sys-
tem, the materials used in the tank,
the shutoff means, and the connec-
tions, lines, and controls provide equiv-
alent safety.
(b) At least one-half inch of clear air-
space must be provided between any
tank or reservior and a firewall or
shroud isolating a designated fire zone.
§ 125.155 Shutoff means.
(a) Each engine must have a means
for shutting off or otherwise pre-
venting hazardous amounts of fuel, oil,
deicer, and other flammable fluids
from flowing into, within, or through
any designated fire zone. However,
means need not be provided to shut off
flow in lines that are an integral part
of an engine.
(b) The shutoff means must allow an
emergency operating sequence that is
compatible with the emergency oper-
ation of other equipment, such as
feathering the propeller, to facilitate
rapid and effective control of fires.
(c) Shutoff means must be located
outside of designated fire zones, unless
equivalent safety is provided, and it
must be shown that no hazardous
amount of flammable fluid will drain
into any designated fire zone after a
shutoff.
(d) Adequate provisions must be
made to guard against inadvertent op-
eration of the shutoff means and to
make it possible for the crew to reopen
337
Federal Aviation Administration, DOT
§ 125.173
the shutoff means after it has been
closed.
§ 125.157 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.
§ 125.159 Vent and drain lines.
All vent and drain lines, and their
fittings, that are located in a des-
ignated fire zone must, if they carry
flammable fluids or gases, comply with
§ 125.157, if the Administrator finds that
the rupture or breakage of any vent or
drain line may result in a fire hazard.
§ 125.161 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.
§ 125.163 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.
§ 125.165 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.
§ 125.167 Extinguishing agent con-
tainer compartment temperature.
Precautions must be taken to ensure
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.
§ 125.169 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.
§ 125.171 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.
§ 125.173 Fire detectors.
Fire detectors must be made and in-
stalled in a manner that assures their