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249 

Federal Aviation Administration, DOT 

§ 25.479 

displacement of the center of gravity is 
maintained within these limits. 

(c) 

Landing gear dimension data. Fig-

ure 1 of appendix A contains the basic 
landing gear dimension data. 

[Amdt. 25–23, 35 FR 5673, Apr. 8, 1970, as 
amended by Doc. No. FAA–2022–1355, Amdt. 
25–148, 87 FR 75710, Dec. 9, 2022; 88 FR 2813, 
Jan. 18, 2023] 

§ 25.473

Landing load conditions and 

assumptions. 

(a) For the landing conditions speci-

fied in § 25.479 to § 25.485 the airplane is 
assumed to contact the ground— 

(1) In the attitudes defined in § 25.479 

and § 25.481; 

(2) With a limit descent velocity of 10 

fps at the design landing weight (the 
maximum weight for landing condi-
tions at maximum descent velocity); 
and 

(3) With a limit descent velocity of 6 

fps at the design take-off weight (the 
maximum weight for landing condi-
tions at a reduced descent velocity). 

(4) The prescribed descent velocities 

may be modified if it is shown that the 
airplane has design features that make 
it impossible to develop these veloci-
ties. 

(b) Airplane lift, not exceeding air-

plane weight, may be assumed unless 
the presence of systems or procedures 
significantly affects the lift. 

(c) The method of analysis of air-

plane and landing gear loads must take 
into account at least the following ele-
ments: 

(1) Landing gear dynamic character-

istics. 

(2) Spin-up and springback. 
(3) Rigid body response. 
(4) Structural dynamic response of 

the airframe, if significant. 

(d) The landing gear dynamic charac-

teristics must be validated by tests as 
defined in § 25.723(a). 

(e) The coefficient of friction between 

the tires and the ground may be estab-
lished by considering the effects of 
skidding velocity and tire pressure. 
However, this coefficient of friction 
need not be more than 0.8. 

[Amdt. 25–91, 62 FR 40705, July 29, 1997; Amdt. 
25–91, 62 FR 45481, Aug. 27, 1997; Amdt. 25–103, 
66 FR 27394, May 16, 2001] 

§ 25.477

Landing gear arrangement. 

Sections 25.479 through 25.485 apply 

to airplanes with conventional ar-
rangements of main and nose gears, or 
main and tail gears, when normal oper-
ating techniques are used. 

§ 25.479

Level landing conditions. 

(a) In the level attitude, the airplane 

is assumed to contact the ground at 
forward velocity components, ranging 
from V

L1

to 1.25 V

L2

parallel to the 

ground under the conditions prescribed 
in § 25.473 with— 

(1) V

L1

equal to V

S0

(TAS) at the ap-

propriate landing weight and in stand-
ard sea level conditions; and 

(2) V

L2

equal to V

S0

(TAS) at the ap-

propriate landing weight and altitudes 
in a hot day temperature of 41 degrees 
F. above standard. 

(3) The effects of increased contact 

speed must be investigated if approval 
of downwind landings exceeding 10 
knots is requested. 

(b) For the level landing attitude for 

airplanes with tail wheels, the condi-
tions specified in this section must be 
investigated with the airplane hori-
zontal reference line horizontal in ac-
cordance with Figure 2 of Appendix A 
of this part. 

(c) For the level landing attitude for 

airplanes with nose wheels, shown in 
Figure 2 of Appendix A of this part, the 
conditions specified in this section 
must be investigated assuming the fol-
lowing attitudes: 

(1) An attitude in which the main 

wheels are assumed to contact the 
ground with the nose wheel just clear 
of the ground; and 

(2) If reasonably attainable at the 

specified descent and forward veloci-
ties, an attitude in which the nose and 
main wheels are assumed to contact 
the ground simultaneously. 

(d) In addition to the loading condi-

tions prescribed in paragraph (a) of this 
section, but with maximum vertical 
ground reactions calculated from para-
graph (a), the following apply: 

(1) The landing gear and directly af-

fected attaching structure must be de-
signed for the maximum vertical 
ground reaction combined with an aft 
acting drag component of not less than 
25% of this maximum vertical ground 
reaction. 

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