Code of Federal Regulations - Title 14

224

14 CFR Ch. I (1–1–14 Edition)

§ 23.479

of main and nose gear, or main and tail
gear.

§ 23.479

Level landing conditions.

(a) For a level landing, the airplane

is assumed to be in the following atti-
tudes:

(1) For airplanes with tail wheels, a

normal level flight attitude.

(2) For airplanes with nose wheels,

attitudes in which—

(i) The nose and main wheels contact

the ground simultaneously; and

(ii) The main wheels contact the

ground and the nose wheel is just clear
of the ground.

The attitude used in paragraph (a)(2)(i)
of this section may be used in the anal-
ysis required under paragraph (a)(2)(ii)
of this section.

(b) When investigating landing condi-

tions, the drag components simulating
the forces required to accelerate the
tires and wheels up to the landing
speed (spin-up) must be properly com-
bined with the corresponding instanta-
neous vertical ground reactions, and
the forward-acting horizontal loads re-
sulting from rapid reduction of the
spin-up drag loads (spring-back) must
be combined with vertical ground reac-
tions at the instant of the peak for-
ward load, assuming wing lift and a
tire-sliding coefficient of friction of 0.8.
However, the drag loads may not be
less than 25 percent of the maximum
vertical ground reactions (neglecting
wing lift).

a more rational analysis for deter-
mining the wheel spin-up and spring-
back loads for landing conditions, the
method set forth in appendix D of this
part must be used. If appendix D of this
part is used, the drag components used
for design must not be less than those
given by appendix C of this part.

(d) For airplanes with tip tanks or

large overhung masses (such as turbo-
propeller or jet engines) supported by
the wing, the tip tanks and the struc-
ture supporting the tanks or overhung
masses must be designed for the effects
of dynamic responses under the level
landing conditions of either paragraph
(a)(1) or (a)(2)(ii) of this section. In
evaluating the effects of dynamic re-

sponse, an airplane lift equal to the
weight of the airplane may be assumed.

[Doc. No. 4080, 29 FR 17955, Dec. 18, 1964, as
amended by Amdt. 23–17, 41 FR 55464, Dec. 20,
1976; Amdt. 23–45, 58 FR 42160, Aug. 6, 1993]

§ 23.481

Tail down landing conditions.

(a) For a tail down landing, the air-

plane is assumed to be in the following
attitudes:

(1) For airplanes with tail wheels, an

attitude in which the main and tail
wheels contact the ground simulta-
neously.

(2) For airplanes with nose wheels, a

stalling attitude, or the maximum
angle allowing ground clearance by
each part of the airplane, whichever is
less.

(b) For airplanes with either tail or

nose wheels, ground reactions are as-
sumed to be vertical, with the wheels
up to speed before the maximum
vertical load is attained.

§ 23.483

One-wheel landing conditions.

For the one-wheel landing condition,

the airplane is assumed to be in the
level attitude and to contact the
ground on one side of the main landing
gear. In this attitude, the ground reac-
tions must be the same as those ob-
tained on that side under § 23.479.

§ 23.485

Side load conditions.

(a) For the side load condition, the

airplane is assumed to be in a level at-
titude with only the main wheels con-
tacting the ground and with the shock
absorbers and tires in their static posi-
tions.

(b) The limit vertical load factor

must be 1.33, with the vertical ground
reaction divided equally between the
main wheels.

be 0.83, with the side ground reaction
divided between the main wheels so
that—

(1) 0.5 (

W) is acting inboard on one

side; and

(2) 0.33 (

W) is acting outboard on the

other side.

(d) The side loads prescribed in para-

graph (c) of this section are assumed to
be applied at the ground contact point

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