274 

14 CFR Ch. I (1–1–19 Edition) 

§ 25.731 

‘‘down and locked’’ if the landing gear 
is not in a fully extended position, or of 
‘‘up and locked’’ if the landing gear is 
not in the fully retracted position. The 
switches may be located where they 
are operated by the actual landing gear 
locking latch or device. 

(2) The flightcrew must be given an 

aural warning that functions continu-
ously, or is periodically repeated, if a 
landing is attempted when the landing 
gear is not locked down. 

(3) The warning must be given in suf-

ficient time to allow the landing gear 
to be locked down or a go-around to be 
made. 

(4) There must not be a manual shut- 

off means readily available to the 
flightcrew for the warning required by 
paragraph (e)(2) of this section such 
that it could be operated instinctively, 
inadvertently, or by habitual reflexive 
action. 

(5) The system used to generate the 

aural warning must be designed to 
minimize false or inappropriate alerts. 

(6) Failures of systems used to in-

hibit the landing gear aural warning, 
that would prevent the warning system 
from operating, must be improbable. 

(7) A flightcrew alert must be pro-

vided whenever the landing gear posi-
tion is not consistent with the landing 
gear selector lever position. 

(f) 

Protection of equipment on landing 

gear and in wheel wells. 

Equipment that 

is essential to the safe operation of the 
airplane and that is located on the 
landing gear and in wheel wells must 
be protected from the damaging effects 
of— 

(1) A bursting tire; 
(2) A loose tire tread, unless it is 

shown that a loose tire tread cannot 
cause damage. 

(3) Possible wheel brake tempera-

tures. 

[Doc. No. 5066, 29 FR 18291, Dec. 24, 1964, as 
amended by Amdt. 25–23, 35 FR 5676, Apr. 8, 
1970; Amdt. 25–42, 43 FR 2323, Jan. 16, 1978; 
Amdt. 25–72, 55 FR 29777, July 20, 1990; Amdt. 
25–75, 56 FR 63762, Dec. 5, 1991; Amdt. 25–136, 
77 FR 1617, Jan. 11, 2012] 

§ 25.731

Wheels. 

(a) Each main and nose wheel must 

be approved. 

(b) The maximum static load rating 

of each wheel may not be less than the 

corresponding static ground reaction 
with— 

(1) Design maximum weight; and 
(2) Critical center of gravity. 
(c) The maximum limit load rating of 

each wheel must equal or exceed the 
maximum radial limit load determined 
under the applicable ground load re-
quirements of this part. 

(d) 

Overpressure burst prevention. 

Means must be provided in each wheel 
to prevent wheel failure and tire burst 
that may result from excessive pressur-
ization of the wheel and tire assembly. 

(e) 

Braked wheels. 

Each braked wheel 

must meet the applicable requirements 
of § 25.735. 

[Doc. No. 5066, 29 FR 18291, Dec. 24, 1964, as 
amended by Amdt. 25–72, 55 FR 29777, July 20, 
1990; Amdt. 25–107, 67 FR 20420, Apr. 24, 2002] 

§ 25.733

Tires. 

(a) When a landing gear axle is fitted 

with a single wheel and tire assembly, 
the 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 approved 
by the Administrator that is not ex-
ceeded under— 

(1) The loads on the main wheel tire, 

corresponding to the most critical 
combination of airplane weight (up to 
maximum weight) and center of grav-
ity position, and 

(2) The loads corresponding to the 

ground reactions in paragraph (b) of 
this section, on the nose wheel tire, ex-
cept as provided in paragraphs (b)(2) 
and (b)(3) of this section. 

(b) The applicable ground reactions 

for nose wheel tires are as follows: 

(1) The static ground reaction for the 

tire corresponding to the most critical 
combination of airplane weight (up to 
maximum ramp weight) and center of 
gravity position with a force of 1.0g 
acting downward at the center of grav-
ity. This load may not exceed the load 
rating of the tire. 

(2) The ground reaction of the tire 

corresponding to the most critical 
combination of airplane weight (up to 
maximum landing weight) and center 
of gravity position combined with 
forces of 1.0g downward and 0.31g for-
ward acting at the center of gravity. 

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