Code of Federal Regulations - Title 14

412

14 CFR Ch. I (1–1–14 Edition)

§ 25.481

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.

(2) The most severe combination of

loads that are likely to arise during a
lateral drift landing must be taken
into account. In absence of a more ra-
tional analysis of this condition, the
following must be investigated:

(i) A vertical load equal to 75% of the

maximum ground reaction of § 25.473
must be considered in combination
with a drag and side load of 40% and
25% respectively of that vertical load.

(ii) The shock absorber and tire de-

flections must be assumed to be 75% of
the deflection corresponding to the
maximum ground reaction of
§ 25.473(a)(2). This load case need not be
considered in combination with flat
tires.

(3) The combination of vertical and

drag components is considered to be
acting at the wheel axle centerline.

[Amdt. 25–91, 62 FR 40705, July 29, 1997; Amdt.
25–91, 62 FR 45481, Aug. 27, 1997]

§ 25.481

Tail-down landing conditions.

(a) In the tail-down attitude, the air-

plane is assumed to contact the ground
at forward velocity components, rang-
ing from V

to V

parallel to the

ground under the conditions prescribed
in § 25.473 with—

(1)

equal to

(TAS) at the ap-

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

(2)

equal to

(TAS) at the ap-

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

(3) The combination of vertical and

drag components considered to be act-
ing at the main wheel axle centerline.

(b) For the tail-down landing condi-

tion for airplanes with tail wheels, the
main and tail wheels are assumed to
contact the ground simultaneously, in

accordance with figure 3 of appendix A.
Ground reaction conditions on the tail
wheel are assumed to act—

(1) Vertically; and
(2) Up and aft through the axle at 45

degrees to the ground line.

tion for airplanes with nose wheels, the
airplane is assumed to be at an atti-
tude corresponding to either the stall-
ing angle or the maximum angle allow-
ing clearance with the ground by each
part of the airplane other than the
main wheels, in accordance with figure
3 of appendix A, whichever is less.

[Docket No. 5066, 29 FR 18291, Dec. 24, 1964, as
amended by Amdt. 25–91, 62 FR 40705, July 29,
1997; Amdt. 25–94, 63 FR 8848, Feb. 23, 1998]

§ 25.483

One-gear landing conditions.

For the one-gear landing conditions,

the airplane is assumed to be in the
level attitude and to contact the
ground on one main landing gear, in
accordance with Figure 4 of Appendix
A of this part. In this attitude—

(a) The ground reactions must be the

same as those obtained on that side
under § 25.479(d)(1), and

(b) Each unbalanced external load

must be reacted by airplane inertia in
a rational or conservative manner.

[Docket No. 5066, 29 FR 18291, Dec. 24, 1964, as
amended by Amdt. 25–91, 62 FR 40705, July 29,
1997]

§ 25.485

Side load conditions.

In addition to § 25.479(d)(2) the fol-

lowing conditions must be considered:

(a) For the side load condition, the

airplane is assumed to be in the level
attitude with only the main wheels
contacting the ground, in accordance
with figure 5 of appendix A.

(b) Side loads of 0.8 of the vertical re-

action (on one side) acting inward and
0.6 of the vertical reaction (on the
other side) acting outward must be
combined with one-half of the max-
imum vertical ground reactions ob-
tained in the level landing conditions.
These loads are assumed to be applied
at the ground contact point and to be
resisted by the inertia of the airplane.

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