Section 29.471

14 CFR Ch. I (1-1-19 Edition)

(c) For empennage arrangements
where the horizontal tail surfaces are
supported by the vertical tail surfaces,
the vertical tail surfaces and supporting structure must be designed for
the combined vertical and horizontal
surface loads resulting from each prescribed flight condition, considered
separately. The flight conditions must
be selected so that the maximum design loads are obtained on each surface.
In the absence of more rational data,
the unsymmetrical horizontal tail surface loading distributions described in
this section must be assumed.
[Amdt. 27-26, 55 FR 8002, Mar. 6, 1990, as
amended by Amdt. 29-31, 55 FR 38966, Sept.
21, 1990]

GROUND LOADS
Section 29.471

General.

(a) Loads and equilibrium. For limit
ground loads - 
(1) The limit ground loads obtained
in the landing conditions in this part
must be considered to be external loads
that would occur in the rotorcraft
structure if it were acting as a rigid
body; and
(2) In each specified landing condition, the external loads must be placed
in equilibrium with linear and angular
inertia loads in a rational or conservative manner.
(b) Critical centers of gravity. The critical centers of gravity within the range
for which certification is requested
must be selected so that the maximum
design loads are obtained in each landing gear element.

spaschal on DSK3GDR082PROD with CFR

Section 29.473 Ground loading
and assumptions.

conditions

(a) For specified landing conditions,
a design maximum weight must be
used that is not less than the maximum weight. A rotor lift may be assumed to act through the center of
gravity throughout the landing impact.
This lift may not exceed two-thirds of
the design maximum weight.
(b) Unless otherwise prescribed, for
each specified landing condition, the
rotorcraft must be designed for a limit
load factor of not less than the limit
inertia load factor substantiated under
Section 29.725.

(c) Triggering or actuating devices
for additional or supplementary energy
absorption may not fail under loads established in the tests prescribed in
SectionSection 29.725 and 29.727, but the factor of
safety prescribed in Section 29.303 need not be
used.
[Amdt. 29-3, 33 FR 966, Jan. 26, 1968]

Section 29.475

Tires and shock absorbers.

Unless otherwise prescribed, for each
specified landing condition, the tires
must be assumed to be in their static
position and the shock absorbers to be
in their most critical position.
Section 29.477

Landing gear arrangement.

Sections 29.235, 29.479 through 29.485,
and 29.493 apply to landing gear with
two wheels aft, and one or more wheels
forward, of the center of gravity.
Section 29.479

Level landing conditions.

(a) Attitudes. Under each of the loading conditions prescribed in paragraph
(b) of this section, the rotorcraft is assumed to be in each of the following
level landing attitudes:
(1) An attitude in which each wheel
contacts the ground simultaneously.
(2) An attitude in which the aft
wheels contact the ground with the forward wheels just clear of the ground.
(b) Loading conditions. The rotorcraft
must be designed for the following
landing loading conditions:
(1) Vertical loads applied under
Section 29.471.
(2) The loads resulting from a combination of the loads applied under
paragraph (b)(1) of this section with
drag loads at each wheel of not less
than 25 percent of the vertical load at
that wheel.
(3) The vertical load at the instant of
peak drag load combined with a drag
component simulating the forces required to accelerate the wheel rolling
assembly up to the specified ground
speed, with - 
(i) The ground speed for determination of the spin-up loads being at least
75 percent of the optimum forward
flight speed for minimum rate of descent in autorotation; and
(ii) The loading conditions of paragraph (b) applied to the landing gear
and its attaching structure only.

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