Section 25.1421

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

show through analysis that the ice protection for the various components of
the airplane is adequate, taking into
account the various airplane operational configurations. To verify the
analysis, one, or more as found necessary, of the following methods must
be used:
(1) Laboratory dry air or simulated
icing tests, or a combination of both, of
the components or models of the components.
(2) Laboratory dry air or simulated
icing tests, or a combination of both, of
models of the airplane.
(3) Flight tests of the airplane or its
components in simulated icing conditions, measured as necessary to support the analysis.
(4) Flight tests of the airplane with
simulated ice shapes.
(5) Flight tests of the airplane in natural icing conditions, measured as necessary to support the analysis.
(c) For an airplane certified in accordance with paragraph (a)(2) or (3) of
this section, the requirements of
Section 25.1419(e), (f), (g), and (h) must be met
for the icing conditions defined in Appendix O of this part in which the airplane is certified to operate.
(d) For the purposes of this section,
the following definitions apply:
(1) Reversible Flight Controls. Flight
controls in the normal operating configuration that have force or motion
originating at the airplane-s control
surface (for example, through aerodynamic loads, static imbalance, or
trim or servo tab inputs) that is transmitted back to flight deck controls.
This term refers to flight deck controls
connected to the pitch, roll, or yaw
control surfaces by direct mechanical
linkages, cables, or push-pull rods in
such a way that pilot effort produces
motion or force about the hinge line.
(2) Simulated Icing Test. Testing conducted in simulated icing conditions,
such as in an icing tunnel or behind an
icing tanker.
(3) Simulated Ice Shape. Ice shape fabricated from wood, epoxy, or other materials by any construction technique.
spaschal on DSK3GDR082PROD with CFR

[Amdt. 25-140, 79 FR 65528, Nov. 4, 2014]

Section 25.1421 Megaphones.
If a megaphone is installed, a restraining means must be provided that

is capable of restraining the megaphone when it is subjected to the ultimate inertia forces specified in
Section 25.561(b)(3).
[Amdt. 25-41, 42 FR 36970, July 18, 1977]

Section 25.1423

Public address system.

A public address system required by
this chapter must - 
(a) Be powerable when the aircraft is
in flight or stopped on the ground,
after the shutdown or failure of all engines and auxiliary power units, or the
disconnection or failure of all power
sources dependent on their continued
operation, for - 
(1) A time duration of at least 10 minutes, including an aggregate time duration of at least 5 minutes of announcements made by flight and cabin crewmembers, considering all other loads
which may remain powered by the
same source when all other power
sources are inoperative; and
(2) An additional time duration in its
standby state appropriate or required
for any other loads that are powered by
the same source and that are essential
to safety of flight or required during
emergency conditions.
(b) Be capable of operation within 3
seconds from the time a microphone is
removed from its stowage.
(c) Be intelligible at all passenger
seats, lavatories, and flight attendant
seats and work stations.
(d) Be designed so that no unused,
unstowed microphone will render the
system inoperative.
(e) Be capable of functioning independently of any required crewmember
interphone system.
(f) Be accessible for immediate use
from each of two flight crewmember
stations in the pilot compartment.
(g) For each required floor-level passenger emergency exit which has an adjacent flight attendant seat, have a
microphone which is readily accessible
to the seated flight attendant, except
that one microphone may serve more
than one exit, provided the proximity
of the exits allows unassisted verbal
communication between seated flight
attendants.
[Doc. No. 26003, 58 FR 45229, Aug. 26, 1993, as
amended by Amdt. 25-115, 69 FR 40527, July 2,
2004]

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