title-14-part-29-sec29-307

587

Federal Aviation Administration, DOT

§ 29.307

§ 29.181

Dynamic stability: Category A

rotorcraft.

Any short-period oscillation occur-

ring at any speed from V

to V

must

be positively damped with the primary
flight controls free and in a fixed posi-
tion.

[Amdt. 29–24, 49 FR 44437, Nov. 6, 1984]

ROUND AND

ATER

ANDLING

HARACTERISTICS

§ 29.231

General.

The rotorcraft must have satisfac-

tory ground and water handling char-
acteristics, including freedom from un-
controllable tendencies in any condi-
tion expected in operation.

§ 29.235

Taxiing condition.

The rotorcraft must be designed to

withstand the loads that would occur
when the rotorcraft is taxied over the
roughest ground that may reasonably
be expected in normal operation.

§ 29.239

Spray characteristics.

If certification for water operation is

requested, no spray characteristics
during taxiing, takeoff, or landing may
obscure the vision of the pilot or dam-
age the rotors, propellers, or other
parts of the rotorcraft.

§ 29.241

Ground resonance.

The rotorcraft may have no dan-

gerous tendency to oscillate on the
ground with the rotor turning.

ISCELLANEOUS

LIGHT

EQUIREMENTS

§ 29.251

Vibration.

Each part of the rotorcraft must be

free from excessive vibration under
each appropriate speed and power con-
dition.

Subpart C—Strength Requirements

ENERAL

§ 29.301

Loads.

(a) Strength requirements are speci-

fied in terms of limit loads (the max-
imum loads to be expected in service)
and ultimate loads (limit loads multi-
plied by prescribed factors of safety).

Unless otherwise provided, prescribed
loads are limit loads.

(b) Unless otherwise provided, the

specified air, ground, and water loads
must be placed in equilibrium with in-
ertia forces, considering each item of
mass in the rotorcraft. These loads
must be distributed to closely approxi-
mate or conservatively represent ac-
tual conditions.

significantly change the distribution of
external or internal loads, this redis-
tribution must be taken into account.

§ 29.303

Factor of safety.

Unless otherwise provided, a factor of

safety of 1.5 must be used. This factor
applies to external and inertia loads
unless its application to the resulting
internal stresses is more conservative.

§ 29.305

Strength and deformation.

(a) The structure must be able to

support limit loads without detri-
mental or permanent deformation. At
any load up to limit loads, the defor-
mation may not interfere with safe op-
eration.

(b) The structure must be able to

support ultimate loads without failure.
This must be shown by—

(1) Applying ultimate loads to the

structure in a static test for at least
three seconds; or

(2) Dynamic tests simulating actual

load application.

§ 29.307

Proof of structure.

(a) Compliance with the strength and

deformation requirements of this sub-
part must be shown for each critical
loading condition accounting for the
environment to which the structure
will be exposed in operation. Struc-
tural analysis (static or fatigue) may
be used only if the structure conforms
to those structures for which experi-
ence has shown this method to be reli-
able. In other cases, substantiating
load tests must be made.

(b) Proof of compliance with the

strength requirements of this subpart
must include—

(1) Dynamic and endurance tests of

rotors, rotor drives, and rotor controls;

(2) Limit load tests of the control

system, including control surfaces;

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588

14 CFR Ch. I (1–1–24 Edition)

§ 29.309

(3) Operation tests of the control sys-

tem;

(4) Flight stress measurement tests;
(5) Landing gear drop tests; and
(6) Any additional tests required for

new or unusual design features.

(Secs. 604, 605, 72 Stat. 778, 49 U.S.C. 1424,
1425)

[Doc. No. 5084, 29 FR 16150, Dec. 3, 1964, as
amended by Amdt. 29–4, 33 FR 14106, Sept. 18,
1968; Amdt. 27–26, 55 FR 8001, Mar. 6, 1990]

§ 29.309

Design limitations.

The following values and limitations

must be established to show compli-
ance with the structural requirements
of this subpart:

(a) The design maximum and design

minimum weights.

(b) The main rotor r.p.m. ranges,

power on and power off.

each main rotor r.p.m. within the
ranges determined under paragraph (b)
of this section.

(d) The maximum rearward and side-

ward flight speeds.

(e) The center of gravity limits cor-

responding to the limitations deter-
mined under paragraphs (b), (c), and (d)
of this section.

(f) The rotational speed ratios be-

tween each powerplant and each con-
nected rotating component.

(g) The positive and negative limit

maneuvering load factors.

LIGHT

OADS

§ 29.321

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.

§ 29.337

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.

[Doc. No. 5084, 29 FR 16150, Dec. 3, 1964, as
amended by Amdt. 27–26, 55 FR 8002, Mar. 6,
1990]

§ 29.339

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 the 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);

= The angular velocity of rotor (radians

per second); and

R = The rotor radius (ft.).

§ 29.341

Gust loads.

Each rotorcraft must be designed to

withstand, at each critical airspeed in-
cluding hovering, the loads resulting