414
14 CFR Ch. I (1–1–14 Edition)
§ 25.495
A=Horizontal distance between the c.g. of
the airplane and the nose wheel.
B=Horizontal distance between the c.g. of
the airplane and the line joining the cen-
ters of the main wheels.
E=Vertical height of the c.g. of the airplane
above the ground in the 1.0 g static con-
dition.
μ
=Coefficient of friction of 0.80.
f=Dynamic response factor; 2.0 is to be used
unless a lower factor is substantiated. In
the absence of other information, the dy-
namic response factor f may be defined
by the equation:
f
= +
−
−
⎛
⎝
⎜⎜
⎞
⎠
⎟⎟
1
1
2
exp
πξ
ξ
Where:
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]
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