Code of Federal Regulations - Title 14

411

Federal Aviation Administration, DOT

§ 25.479

symmetrical loading conditions may be
selected without considering the ef-
fects of these lateral c.g. displacements
on the loading of the main gear ele-
ments, or on the airplane structure
provided—

(1) The lateral displacement of the

c.g. results from random passenger or
cargo disposition within the fuselage or
from random unsymmetrical fuel load-
ing or fuel usage; and

(2) Appropriate loading instructions

for random disposable loads are in-
cluded under the provisions of
§ 25.1583(c)(1) to ensure that the lateral
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]

§ 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.

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

to 1.25 V

parallel to the

ground under the conditions prescribed
in § 25.473 with—

(1) V

equal to V

(TAS) at the ap-

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

(2) V

equal to V

(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.

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

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