spaschal on DSK3GDR082PROD with CFR

Section 25.843

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

(3) Fuselage structure, engine and
system failures are to be considered in
evaluating the cabin decompression.
(b) Pressurized cabins must have at
least the following valves, controls,
and indicators for controlling cabin
pressure:
(1) Two pressure relief valves to automatically limit the positive pressure
differential to a predetermined value
at the maximum rate of flow delivered
by the pressure source. The combined
capacity of the relief valves must be
large enough so that the failure of any
one valve would not cause an appreciable rise in the pressure differential.
The pressure differential is positive
when the internal pressure is greater
than the external.
(2) Two reverse pressure differential
relief valves (or their equivalents) to
automatically prevent a negative pressure differential that would damage
the structure. One valve is enough,
however, if it is of a design that reasonably precludes its malfunctioning.
(3) A means by which the pressure
differential can be rapidly equalized.
(4) An automatic or manual regulator
for controlling the intake or exhaust
airflow, or both, for maintaining the
required internal pressures and airflow
rates.
(5) Instruments at the pilot or flight
engineer station to show the pressure
differential, the cabin pressure altitude, and the rate of change of the
cabin pressure altitude.
(6) Warning indication at the pilot or
flight engineer station to indicate
when the safe or preset pressure differential and cabin pressure altitude
limits are exceeded. Appropriate warning markings on the cabin pressure differential indicator meet the warning
requirement for pressure differential
limits and an aural or visual signal (in
addition to cabin altitude indicating
means) meets the warning requirement
for cabin pressure altitude limits if it
warns the flight crew when the cabin
pressure altitude exceeds 10,000 feet.
(7) A warning placard at the pilot or
flight engineer station if the structure
is not designed for pressure differentials up to the maximum relief valve
setting in combination with landing
loads.

(8) The pressure sensors necessary to
meet the requirements of paragraphs
(b)(5) and (b)(6) of this section and
Section 25.1447(c), must be located and the
sensing system designed so that, in the
event of loss of cabin pressure in any
passenger or crew compartment (including upper and lower lobe galleys),
the warning and automatic presentation devices, required by those provisions, will be actuated without any
delay that would significantly increase
the hazards resulting from decompression.
[Doc. No. 5066, 29 FR 18291, Dec. 24, 1964, as
amended by Amdt. 25-38, 41 FR 55466, Dec. 20,
1976; Amdt. 25-87, 61 FR 28696, June 5, 1996]

Section 25.843

Tests for pressurized cabins.

(a) Strength test. The complete pressurized cabin, including doors, windows, and valves, must be tested as a
pressure vessel for the pressure differential specified in Section 25.365(d).
(b) Functional tests. The following
functional tests must be performed:
(1) Tests of the functioning and capacity of the positive and negative
pressure differential valves, and of the
emergency release valve, to stimulate
the effects of closed regulator valves.
(2) Tests of the pressurization system
to show proper functioning under each
possible condition of pressure, temperature, and moisture, up to the maximum altitude for which certification
is requested.
(3) Flight tests, to show the performance of the pressure supply, pressure
and flow regulators, indicators, and
warning signals, in steady and stepped
climbs and descents at rates corresponding to the maximum attainable
within the operating limitations of the
airplane, up to the maximum altitude
for which certification is requested.
(4) Tests of each door and emergency
exit, to show that they operate properly after being subjected to the flight
tests prescribed in paragraph (b)(3) of
this section.
FIRE PROTECTION
Section 25.851

Fire extinguishers.

(a) Hand fire extinguishers. (1) The following minimum number of hand fire

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