Code of Federal Regulations - Title 14

654

14 CFR Ch. I (1–1–14 Edition)

§ 27.505

(2) With the rotorcraft in the level

landing attitude, a vertical ground re-
action load equal to one-half of the
vertical load determined under para-
graph (b) of this section. This load
must be—

(i) Applied only to the skid tube and

its attachment to the rotorcraft; and

(ii) Distributed equally over 33.3 per-

cent of the length between the skid
tube attachments and centrally located
midway between the skid tube attach-
ments.

[Doc. No. 5074, 29 FR 15695, Nov. 24, 1964, as
amended by Amdt. 27–2, 33 FR 963, Jan. 26,
1968; Amdt. 27–26, 55 FR 8000, Mar. 6, 1990]

§ 27.505

Ski landing conditions.

If certification for ski operation is

requested, the rotorcraft, with skis,
must be designed to withstand the fol-
lowing loading conditions (where

P is

the maximum static weight on each ski
with the rotorcraft at design maximum
weight, and

n is the limit load factor

determined under § 27.473(b).

(a) Up-load conditions in which—
(1) A vertical load of

Pn and a hori-

zontal load of

Pn/4 are simultaneously

applied at the pedestal bearings; and

(2) A vertical load of 1.33

P is applied

at the pedestal bearings.

(b) A side-load condition in which a

side load of 0.35

Pn is applied at the

pedestal bearings in a horizontal plane
perpendicular to the centerline of the
rotorcraft.

a torque load of 1.33

P (in foot pounds)

is applied to the ski about the vertical
axis through the centerline of the ped-
estal bearings.

ATER

OADS

§ 27.521

Float landing conditions.

If certification for float operation is

requested, the rotorcraft, with floats,
must be designed to withstand the fol-
lowing loading conditions (where the
limit load factor is determined under
§ 27.473(b) or assumed to be equal to
that determined for wheel landing
gear):

(a) Up-load conditions in which—
(1) A load is applied so that, with the

rotorcraft in the static level attitude,
the resultant water reaction passes

vertically through the center of grav-
ity; and

(2) The vertical load prescribed in

paragraph (a)(1) of this section is ap-
plied simultaneously with an aft com-
ponent of 0.25 times the vertical com-
ponent.

(b) A side-load condition in which—
(1) A vertical load of 0.75 times the

total vertical load specified in para-
graph (a)(1) of this section is divided
equally among the floats; and

(2) For each float, the load share de-

termined under paragraph (b)(1) of this
section, combined with a total side
load of 0.25 times the total vertical
load specified in paragraph (b)(1) of
this section, is applied to that float
only.

AIN

OMPONENT

EQUIREMENTS

§ 27.547

Main rotor structure.

(a) Each main rotor assembly (in-

cluding rotor hubs and blades) must be
designed as prescribed in this section.

(b) [Reserved]
(c) The main rotor structure must be

designed to withstand the following
loads prescribed in §§ 27.337 through
27.341:

(1) Critical flight loads.
(2) Limit loads occurring under nor-

mal conditions of autorotation. For
this condition, the rotor r.p.m. must be
selected to include the effects of alti-
tude.

(d) The main rotor structure must be

designed to withstand loads simu-
lating—

(1) For the rotor blades, hubs, and

flapping hinges, the impact force of
each blade against its stop during
ground operation; and

(2) Any other critical condition ex-

pected in normal operation.

(e) The main rotor structure must be

designed to withstand the limit torque
at any rotational speed, including zero.
In addition:

(1) The limit torque need not be

greater than the torque defined by a
torque limiting device (where pro-
vided), and may not be less than the
greater of—

(i) The maximum torque likely to be

transmitted to the rotor structure in
either direction; and

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