275 

Federal Aviation Administration, DOT 

§ 25.735 

The reactions in this case must be dis-
tributed to the nose and main wheels 
by the principles of statics with a drag 
reaction equal to 0.31 times the 
vertical load at each wheel with brakes 
capable of producing this ground reac-
tion. This nose tire load may not ex-
ceed 1.5 times the load rating of the 
tire. 

(3) The ground reaction of the tire 

corresponding to the most critical 
combination of airplane weight (up to 
maximum ramp weight) and center of 
gravity position combined with forces 
of 1.0g downward and 0.20g forward act-
ing at the center of gravity. The reac-
tions in this case must be distributed 
to the nose and main wheels by the 
principles of statics with a drag reac-
tion equal to 0.20 times the vertical 
load at each wheel with brakes capable 
of producing this ground reaction. This 
nose tire load may not exceed 1.5 times 
the load rating of the tire. 

(c) When a landing gear axle is fitted 

with more than one wheel and tire as-
sembly, such as dual or dual-tandem, 
each wheel must be fitted with a suit-
able tire of proper fit with a speed rat-
ing approved by the Administrator 
that is not exceeded under critical con-
ditions, and with a load rating ap-
proved by the Administrator that is 
not exceeded by— 

(1) The loads on each main wheel 

tire, corresponding to the most critical 
combination of airplane weight (up to 
maximum weight) and center of grav-
ity position, when multiplied by a fac-
tor of 1.07; and 

(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: 

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