Section 125.121

14 CFR Ch. I (1-1-19 Edition)

warning at the pilot or flight engineer
station.
(2) It must have an approved built-in
fire-extinguishing system controlled
from the pilot or flight engineer station.
(3) It must be designed to exclude
hazardous quantities of smoke, flames,
or extinguishing agents from entering
into any compartment occupied by the
crew or passengers.
(4) It must have ventilation and draft
control so that the extinguishing agent
provided can control any fire that may
start in the compartment.
(5) It must be lined with fire-resistant material, except that additional
service lining of flame-resistant material may be used.
(e) Class D. Cargo and baggage compartments are classified in the  - D - 
category if they are so designed and
constructed that a fire occurring therein will be completely confined without
endangering the safety of the airplane
or the occupants. Each Class D compartment must comply with the following:
(1) It must have a means to exclude
hazardous quantities of smoke, flames,
or noxious gases from entering any
compartment occupied by the crew or
passengers.
(2) Ventilation and drafts must be
controlled within each compartment so
that any fire likely to occur in the
compartment will not progress beyond
safe limits.
(3) It must be completely lined with
fire-resistant material.
(4) Consideration must be given to
the effect of heat within the compartment on adjacent critical parts of the
airplane.
(f) Class E. On airplanes used for the
carriage of cargo only, the cabin area
may be classified as a Class  - E -  compartment. Each Class E compartment
must comply with the following:
(1) It must be completely lined with
fire-resistant material.
(2) It must have a separate system of
an approved type smoke or fire detector to give warning at the pilot or
flight engineer station.
(3) It must have a means to shut off
the ventilating air flow to or within
the compartment and the controls for

that means must be accessible to the
flightcrew in the crew compartment.
(4) It must have a means to exclude
hazardous quantities of smoke, flames,
or noxious gases from entering the
flightcrew compartment.
(5) Required crew emergency exits
must be accessible under all cargo
loading conditions.
Section 125.121 Proof
Section 125.119.

of

compliance

Compliance with those provisions of
Section 125.119 that refer to compartment accessibility, the entry of hazardous
quantities of smoke or extinguishing
agent into compartment occupied by
the crew or passengers, and the dissipation of the extinguishing agent in Class
 - C -  compartments must be shown by
tests in flight. During these tests it
must be shown that no inadvertent operation of smoke or fire detectors in
other compartments within the airplane would occur as a result of fire
contained in any one compartment, either during the time it is being extinguished, or thereafter, unless the extinguishing system floods those compartments simultaneously.
Section 125.123

Propeller deicing fluid.

If combustible fluid is used for propeller deicing, the certificate holder
must comply with Section 125.153.
Section 125.125 Pressure cross-feed arrangements.
(a) Pressure cross-feed lines may not
pass through parts of the airplane used
for carrying persons or cargo unless
there is a means to allow crewmembers
to shut off the supply of fuel to these
lines or the lines are enclosed in a fuel
and fume-proof enclosure that is ventilated and drained to the exterior of the
airplane. However, such an enclosure
need not be used if those lines incorporate no fittings on or within the personnel or cargo areas and are suitably
routed or protected to prevent accidental damage.
(b) Lines that can be isolated from
the rest of the fuel system by valves at
each end must incorporate provisions
for relieving excessive pressures that
may result from exposure of the isolated line to high temperatures.

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