252 

14 CFR Ch. I (1–1–24 Edition) 

§ 25.495 

x 

is the effective critical damping ratio of 

the rigid body pitching mode about the 
main landing gear effective ground con-
tact point. 

[Doc. No. 5066, 29 FR 18291, Dec. 24, 1964, as 
amended by Amdt. 25–23, 35 FR 5673, Apr. 8, 
1970; Amdt. 25–97, 63 FR 29072, May 27, 1998] 

§ 25.495

Turning. 

In the static position, in accordance 

with figure 7 of appendix A, the air-
plane is assumed to execute a steady 
turn by nose gear steering, or by appli-
cation of sufficient differential power, 
so that the limit load factors applied at 
the center of gravity are 1.0 vertically 
and 0.5 laterally. The side ground reac-
tion of each wheel must be 0.5 of the 
vertical reaction. 

§ 25.497

Tail-wheel yawing. 

(a) A vertical ground reaction equal 

to the static load on the tail wheel, in 
combination with a side component of 
equal magnitude, is assumed. 

(b) If there is a swivel, the tail wheel 

is assumed to be swiveled 90

° 

to the air-

plane longitudinal axis with the result-
ant load passing through the axle. 

(c) If there is a lock, steering device, 

or shimmy damper the tail wheel is 
also assumed to be in the trailing posi-
tion with the side load acting at the 
ground contact point. 

§ 25.499

Nose-wheel yaw and steering. 

(a) A vertical load factor of 1.0 at the 

airplane center of gravity, and a side 
component at the nose wheel ground 
contact equal to 0.8 of the vertical 
ground reaction at that point are as-
sumed. 

(b) With the airplane assumed to be 

in static equilibrium with the loads re-
sulting from the use of brakes on one 
side of the main landing gear, the nose 
gear, its attaching structure, and the 
fuselage structure forward of the cen-
ter of gravity must be designed for the 
following loads: 

(1) A vertical load factor at the cen-

ter of gravity of 1.0. 

(2) A forward acting load at the air-

plane center of gravity of 0.8 times the 
vertical load on one main gear. 

(3) Side and vertical loads at the 

ground contact point on the nose gear 
that are required for static equi-
librium. 

(4) A side load factor at the airplane 

center of gravity of zero. 

(c) If the loads prescribed in para-

graph (b) of this section result in a 
nose gear side load higher than 0.8 
times the vertical nose gear load, the 
design nose gear side load may be lim-
ited to 0.8 times the vertical load, with 
unbalanced yawing moments assumed 
to be resisted by airplane inertia 
forces. 

(d) For other than the nose gear, its 

attaching structure, and the forward 
fuselage structure, the loading condi-
tions are those prescribed in paragraph 
(b) of this section, except that— 

(1) A lower drag reaction may be used 

if an effective drag force of 0.8 times 
the vertical reaction cannot be reached 
under any likely loading condition; and 

(2) The forward acting load at the 

center of gravity need not exceed the 
maximum drag reaction on one main 
gear, determined in accordance with 
§ 25.493(b). 

(e) With the airplane at design ramp 

weight, and the nose gear in any steer-
able position, the combined application 
of full normal steering torque and 
vertical force equal to 1.33 times the 
maximum static reaction on the nose 
gear must be considered in designing 
the nose gear, its attaching structure, 
and the forward fuselage structure. 

[Doc. No. 5066, 29 FR 18291, Dec. 24, 1964, as 
amended by Amdt. 25–23, 35 FR 5673, Apr. 8, 
1970; Amdt. 25–46, 43 FR 50595, Oct. 30, 1978; 
Amdt. 25–91, 62 FR 40705, July 29, 1997] 

§ 25.503

Pivoting. 

(a) The airplane is assumed to pivot 

about one side of the main gear with 
the brakes on that side locked. The 
limit vertical load factor must be 1.0 
and the coefficient of friction 0.8. 

(b) The airplane is assumed to be in 

static equilibrium, with the loads being 
applied at the ground contact points, 
in accordance with figure 8 of appendix 
A. 

§ 25.507

Reversed braking. 

(a) The airplane must be in a three 

point static ground attitude. Hori-
zontal reactions parallel to the ground 
and directed forward must be applied 
at the ground contact point of each 
wheel with brakes. The limit loads 
must be equal to 0.55 times the vertical 

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