275
Federal Aviation Administration, DOT
§ 25.735
(2) Loads specified in paragraphs
(a)(2), (b)(1), (b)(2), and (b)(3) of this
section on each nose wheel tire.
(d) Each tire installed on a retract-
able landing gear system must, at the
maximum size of the tire type expected
in service, have a clearance to sur-
rounding structure and systems that is
adequate to prevent unintended con-
tact between the tire and any part of
the structure or systems.
(e) For an airplane with a maximum
certificated takeoff weight of more
than 75,000 pounds, tires mounted on
braked wheels must be inflated with
dry nitrogen or other gases shown to be
inert so that the gas mixture in the
tire does not contain oxygen in excess
of 5 percent by volume, unless it can be
shown that the tire liner material will
not produce a volatile gas when heated
or that means are provided to prevent
tire temperatures from reaching unsafe
levels.
[Amdt. 25–48, 44 FR 68752, Nov. 29, 1979; Amdt.
25–72, 55 FR 29777, July 20, 1990, as amended
by Amdt. 25–78, 58 FR 11781, Feb. 26, 1993]
§ 25.735
Brakes and braking systems.
(a)
Approval. Each assembly con-
sisting of a wheel(s) and brake(s) must
be approved.
(b)
Brake system capability. The brake
system, associated systems and compo-
nents must be designed and con-
structed so that:
(1) If any electrical, pneumatic, hy-
draulic, or mechanical connecting or
transmitting element fails, or if any
single source of hydraulic or other
brake operating energy supply is lost,
it is possible to bring the airplane to
rest with a braked roll stopping dis-
tance of not more than two times that
obtained in determining the landing
distance as prescribed in § 25.125.
(2) Fluid lost from a brake hydraulic
system following a failure in, or in the
vicinity of, the brakes is insufficient to
cause or support a hazardous fire on
the ground or in flight.
(c)
Brake controls. The brake controls
must be designed and constructed so
that:
(1) Excessive control force is not re-
quired for their operation.
(2) If an automatic braking system is
installed, means are provided to:
(i) Arm and disarm the system, and
(ii) Allow the pilot(s) to override the
system by use of manual braking.
(d)
Parking brake. The airplane must
have a parking brake control that,
when selected on, will, without further
attention, prevent the airplane from
rolling on a dry and level paved runway
when the most adverse combination of
maximum thrust on one engine and up
to maximum ground idle thrust on any,
or all, other engine(s) is applied. The
control must be suitably located or be
adequately protected to prevent inad-
vertent operation. There must be indi-
cation in the cockpit when the parking
brake is not fully released.
(e)
Antiskid system. If an antiskid sys-
tem is installed:
(1) It must operate satisfactorily over
the range of expected runway condi-
tions, without external adjustment.
(2) It must, at all times, have pri-
ority over the automatic braking sys-
tem, if installed.
(f)
Kinetic energy capacity—(1) Design
landing stop. The design landing stop is
an operational landing stop at max-
imum landing weight. The design land-
ing stop brake kinetic energy absorp-
tion requirement of each wheel, brake,
and tire assembly must be determined.
It must be substantiated by dynamom-
eter testing that the wheel, brake and
tire assembly is capable of absorbing
not less than this level of kinetic en-
ergy throughout the defined wear
range of the brake. The energy absorp-
tion rate derived from the airplane
manufacturer’s braking requirements
must be achieved. The mean decelera-
tion must not be less than 10 fps
2
.
(2)
Maximum kinetic energy accelerate-
stop. The maximum kinetic energy ac-
celerate-stop is a rejected takeoff for
the most critical combination of air-
plane takeoff weight and speed. The ac-
celerate-stop brake kinetic energy ab-
sorption requirement of each wheel,
brake, and tire assembly must be de-
termined. It must be substantiated by
dynamometer testing that the wheel,
brake, and tire assembly is capable of
absorbing not less than this level of ki-
netic energy throughout the defined
wear range of the brake. The energy
absorption rate derived from the air-
plane manufacturer’s braking require-
ments must be achieved. The mean de-
celeration must not be less than 6 fps
2
.
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