Code of Federal Regulations - Title 14

648

14 CFR Ch. I (1–1–14 Edition)

§ 27.321

LIGHT

OADS

§ 27.321

General.

(a) The flight load factor must be as-

sumed to act normal to the longitu-
dinal axis of the rotorcraft, and to be
equal in magnitude and opposite in di-
rection to the rotorcraft inertia load
factor at the center of gravity.

(b) Compliance with the flight load

requirements of this subpart must be
shown—

(1) At each weight from the design

minimum weight to the design max-
imum weight; and

(2) With any practical distribution of

disposable load within the operating
limitations in the Rotorcraft Flight
Manual.

[Doc. No. 5074, 29 FR 15695, Nov. 24, 1964, as
amended by Amdt. 27–11, 41 FR 55468, Dec. 20,
1976]

§ 27.337

Limit maneuvering load fac-

tor.

The rotorcraft must be designed for—
(a) A limit maneuvering load factor

ranging from a positive limit of 3.5 to
a negative limit of ¥1.0; or

(b) Any positive limit maneuvering

load factor not less than 2.0 and any
negative limit maneuvering load factor
of not less than ¥0.5 for which—

(1) The probability of being exceeded

is shown by analysis and flight tests to
be extremely remote; and

(2) The selected values are appro-

priate to each weight condition be-
tween the design maximum and design
minimum weights.

[Amdt. 27–26, 55 FR 7999, Mar. 6, 1990]

§ 27.339

Resultant limit maneuvering

loads.

The loads resulting from the applica-

tion of limit maneuvering load factors
are assumed to act at the center of
each rotor hub and at each auxiliary
lifting surface, and to act in directions,
and with distributions of load among
the rotors and auxiliary lifting sur-
faces, so as to represent each critical
maneuvering condition, including
power-on and power-off flight with the
maximum design rotor tip speed ratio.
The rotor tip speed ratio is the ratio of
the rotorcraft flight velocity compo-
nent in the plane of the rotor disc to

the rotational tip speed of the rotor
blades, and is expressed as follows:

μ =

V cos a

where—

V= The airspeed along flight path (f.p.s.);
a= The angle between the projection, in the

plane of symmetry, of the axis of no
feathering and a line perpendicular to
the flight path (radians, positive when
axis is pointing aft);

omega= The angular velocity of rotor (radi-

ans per second); and

R= The rotor radius (ft).

[Doc. No. 5074, 29 FR 15695, Nov. 24, 1964, as
amended by Amdt. 27–11, 41 FR 55469, Dec. 20,
1976]

§ 27.341

Gust loads.

The rotorcraft must be designed to

withstand, at each critical airspeed in-
cluding hovering, the loads resulting
from a vertical gust of 30 feet per sec-
ond.

§ 27.351

Yawing conditions.

(a) Each rotorcraft must be designed

for the loads resulting from the maneu-
vers specified in paragraphs (b) and (c)
of this section with—

(1) Unbalanced aerodynamic mo-

ments about the center of gravity
which the aircraft reacts to in a ration-
al or conservative manner considering
the principal masses furnishing the re-
acting inertia forces; and

(2) Maximum main rotor speed.
(b) To produce the load required in

paragraph (a) of this section, in unac-
celerated flight with zero yaw, at for-
ward speeds from zero up to 0.6 V

—

(1) Displace the cockpit directional

control suddenly to the maximum de-
flection limited by the control stops or
by the maximum pilot force specified
in § 27.397(a);

(2) Attain a resulting sideslip angle

or 90

, whichever is less; and

(3) Return the directional control

suddenly to neutral.

paragraph (a) of this section, in unac-
celerated flight with zero yaw, at for-
ward speeds from 0.6 V

up to V

, whichever is less—

(1) Displace the cockpit directional

control suddenly to the maximum de-
flection limited by the control stops or

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