title-14-part-25-sec25-859

307

Federal Aviation Administration, DOT

§ 25.859

to give warning at the pilot or flight
engineer station;

(2) There are means to extinguish or

control a fire without requiring a crew-
member to enter the compartment; and

(3) There are means to exclude haz-

ardous quantities of smoke, flames, or
extinguishing agent from any compart-
ment occupied by the crew or pas-
sengers.

[Doc. No. 5066, 29 FR 18291, Dec. 24, 1964, as
amended by Amdt. 25–32, 37 FR 3972, Feb. 24,
1972; Amdt. 25–60, 51 FR 18243, May 16, 1986;
Amdt. 25–93, 63 FR 8048, Feb. 17, 1998; Doc.
No. Docket FAA–2014–0001, Amdt. 25–142, 81
FR 7704, Feb. 16, 2016]

§ 25.858

Cargo or baggage compart-

ment smoke or fire detection sys-
tems.

If certification with cargo or baggage

compartment smoke or fire detection
provisions is requested, the following
must be met for each cargo or baggage
compartment with those provisions:

(a) The detection system must pro-

vide a visual indication to the flight
crew within one minute after the start
of a fire.

(b) The system must be capable of de-

tecting a fire at a temperature signifi-
cantly below that at which the struc-
tural integrity of the airplane is sub-
stantially decreased.

crew to check in flight, the functioning
of each fire detector circuit.

(d) The effectiveness of the detection

system must be shown for all approved
operating configurations and condi-
tions.

[Amdt. 25–54, 45 FR 60173, Sept. 11, 1980, as
amended by Amdt. 25–93, 63 FR 8048, Feb. 17,
1998]

§ 25.859

Combustion heater fire pro-

tection.

(a)

Combustion heater fire zones. The

following combustion heater fire zones
must be protected from fire in accord-
ance with the applicable provisions of
§§ 25.1181 through 25.1191 and §§ 25.1195
through 25.1203;

(1) The region surrounding the heat-

er, if this region contains any flam-
mable fluid system components (ex-
cluding the heater fuel system), that
could—

(i) Be damaged by heater malfunc-

tioning; or

(ii) Allow flammable fluids or vapors

to reach the heater in case of leakage.

(2) The region surrounding the heat-

er, if the heater fuel system has fit-
tings that, if they leaked, would allow
fuel or vapors to enter this region.

(3) The part of the ventilating air

passage that surrounds the combustion
chamber. However, no fire extinguish-
ment is required in cabin ventilating
air passages.

(b)

Ventilating air ducts. Each ven-

tilating air duct passing through any
fire zone must be fireproof. In addi-
tion—

(1) Unless isolation is provided by

fireproof valves or by equally effective
means, the ventilating air duct down-
stream of each heater must be fireproof
for a distance great enough to ensure
that any fire originating in the heater
can be contained in the duct; and

(2) Each part of any ventilating duct

passing through any region having a
flammable fluid system must be con-
structed or isolated from that system
so that the malfunctioning of any com-
ponent of that system cannot intro-
duce flammable fluids or vapors into
the ventilating airstream.

(c)

Combustion air ducts. Each com-

bustion air duct must be fireproof for a
distance great enough to prevent dam-
age from backfiring or reverse flame
propagation. In addition—

(1) No combustion air duct may have

a common opening with the ventilating
airstream unless flames from backfires
or reverse burning cannot enter the
ventilating airstream under any oper-
ating condition, including reverse flow
or malfunctioning of the heater or its
associated components; and

(2) No combustion air duct may re-

strict the prompt relief of any backfire
that, if so restricted, could cause heat-
er failure.

(d)

Heater controls; general. Provision

must be made to prevent the hazardous
accumulation of water or ice on or in
any heater control component, control
system tubing, or safety control.

(e)

Heater safety controls. For each

combustion heater there must be the
following safety control means:

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308

14 CFR Ch. I (1–1–24 Edition)

§ 25.863

(1) Means independent of the compo-

nents provided for the normal contin-
uous control of air temperature, air-
flow, and fuel flow must be provided,
for each heater, to automatically shut
off the ignition and fuel supply to that
heater at a point remote from that
heater when any of the following oc-
curs:

(i) The heat exchanger temperature

exceeds safe limits.

(ii) The ventilating air temperature

exceeds safe limits.

(iii) The combustion airflow becomes

inadequate for safe operation.

(iv) The ventilating airflow becomes

inadequate for safe operation.

(2) The means of complying with

paragraph (e)(1) of this section for any
individual heater must—

(i) Be independent of components

serving any other heater whose heat
output is essential for safe operation;
and

(ii) Keep the heater off until re-

started by the crew.

(3) There must be means to warn the

crew when any heater whose heat out-
put is essential for safe operation has
been shut off by the automatic means
prescribed in paragraph (e)(1) of this
section.

(f)

Air intakes. Each combustion and

ventilating air intake must be located
so that no flammable fluids or vapors
can enter the heater system under any
operating condition—

(1) During normal operation; or
(2) As a result of the malfunctioning

of any other component.

(g)

Heater exhaust. Heater exhaust

systems must meet the provisions of
§§ 25.1121 and 25.1123. In addition, there
must be provisions in the design of the
heater exhaust system to safely expel
the products of combustion to prevent
the occurrence of—

(1) Fuel leakage from the exhaust to

surrounding compartments;

(2) Exhaust gas impingement on sur-

rounding equipment or structure;

(3) Ignition of flammable fluids by

the exhaust, if the exhaust is in a com-
partment containing flammable fluid
lines; and

(4) Restriction by the exhaust of the

prompt relief of backfires that, if so re-
stricted, could cause heater failure.

(h)

Heater fuel systems. Each heater

fuel system must meet each power-
plant fuel system requirement affect-
ing safe heater operation. Each heater
fuel system component within the ven-
tilating airstream must be protected
by shrouds so that no leakage from
those components can enter the ven-
tilating airstream.

(i)

Drains. There must be means to

safely drain fuel that might accumu-
late within the combustion chamber or
the heat exchanger. In addition—

(1) Each part of any drain that oper-

ates at high temperatures must be pro-
tected in the same manner as heater
exhausts; and

(2) Each drain must be protected

from hazardous ice accumulation under
any operating condition.

[Doc. No. 5066, 29 FR 18291, Dec. 24, 1964, as
amended by Amdt. 25–11, 32 FR 6912, May 5,
1967; Amdt. 25–23, 35 FR 5676, Apr. 8, 1970]

§ 25.863

Flammable fluid fire protec-

tion.

(a) In each area where flammable

fluids or vapors might escape by leak-
age of a fluid system, there must be
means to minimize the probability of
ignition of the fluids and vapors, and
the resultant hazards if ignition does
occur.

(b) Compliance with paragraph (a) of

this section must be shown by analysis
or tests, and the following factors must
be considered:

(1) Possible sources and paths of fluid

leakage, and means of detecting leak-
age.

(2) Flammability characteristics of

fluids, including effects of any combus-
tible or absorbing materials.

(3) Possible ignition sources, includ-

ing electrical faults, overheating of
equipment, and malfunctioning of pro-
tective devices.

(4) Means available for controlling or

extinguishing a fire, such as stopping
flow of fluids, shutting down equip-
ment, fireproof containment, or use of
extinguishing agents.

(5) Ability of airplane components

that are critical to safety of flight to
withstand fire and heat.

quired to prevent or counteract a fluid