604 

14 CFR Ch. I (1–1–19 Edition) 

§ 29.629 

(b) No fitting factor need be used— 
(1) For joints made under approved 

practices and based on comprehensive 
test data (such as continuous joints in 
metal plating, welded joints, and scarf 
joints in wood); and 

(2) With respect to any bearing sur-

face for which a larger special factor is 
used. 

(c) For each integral fitting, the part 

must be treated as a fitting up to the 
point at which the section properties 
become typical of the member. 

(d) Each seat, berth, litter, safety 

belt, and harness attachment to the 
structure must be shown by analysis, 
tests, or both, to be able to withstand 
the inertia forces prescribed in 
§ 29.561(b)(3) multiplied by a fitting fac-
tor of 1.33. 

[Doc. No. 5084, 29 FR 16150, Dec. 3, 1964, as 
amended by Amdt. 29–42, 63 FR 43285, Aug. 12, 
1998] 

§ 29.629

Flutter and divergence. 

Each aerodynamic surface of the 

rotorcraft must be free from flutter 
and divergence under each appropriate 
speed and power condition. 

[Doc. No. 28008, 61 FR 21907, May 10, 1996] 

§ 29.631

Bird strike. 

The rotorcraft must be designed to 

ensure capability of continued safe 
flight and landing (for Category A) or 
safe landing (for Category B) after im-
pact with a 2.2-lb (1.0 kg) bird when the 
velocity of the rotorcraft (relative to 
the bird along the flight path of the 
rotorcraft) is equal to V

NE

or V

H

 

(whichever is the lesser) at altitudes up 
to 8,000 feet. Compliance must be 
shown by tests or by analysis based on 
tests carried out on sufficiently rep-
resentative structures of similar de-
sign. 

[Doc. No. 28008, 61 FR 21907, May 10, 1996; 61 
FR 33963, July 1, 1996] 

R

OTORS

 

§ 29.653

Pressure venting and drain-

age of rotor blades. 

(a) For each rotor blade— 
(1) There must be means for venting 

the internal pressure of the blade; 

(2) Drainage holes must be provided 

for the blade; and 

(3) The blade must be designed to pre-

vent water from becoming trapped in 
it. 

(b) Paragraphs (a)(1) and (2) of this 

section does not apply to sealed rotor 
blades capable of withstanding the 
maximum pressure differentials ex-
pected in service. 

[Amdt. 29–3, 33 FR 967, Jan. 26, 1968] 

§ 29.659

Mass balance. 

(a) The rotor and blades must be 

mass balanced as necessary to— 

(1) Prevent excessive vibration; and 
(2) Prevent flutter at any speed up to 

the maximum forward speed. 

(b) The structural integrity of the 

mass balance installation must be sub-
stantiated. 

[Amdt. 29–3, 33 FR 967, Jan. 26, 1968] 

§ 29.661

Rotor blade clearance. 

There must be enough clearance be-

tween the rotor blades and other parts 
of the structure to prevent the blades 
from striking any part of the structure 
during any operating condition. 

[Amdt. 29–3, 33 FR 967, Jan. 26, 1968] 

§ 29.663

Ground resonance prevention 

means. 

(a) The reliability of the means for 

preventing ground resonance must be 
shown either by analysis and tests, or 
reliable service experience, or by show-
ing through analysis or tests that mal-
function or failure of a single means 
will not cause ground resonance. 

(b) The probable range of variations, 

during service, of the damping action 
of the ground resonance prevention 
means must be established and must be 
investigated during the test required 
by § 29.241. 

[Amdt. 27–26, 55 FR 8003, Mar. 6, 1990] 

C

ONTROL

S

YSTEMS

 

§ 29.671

General. 

(a) Each control and control system 

must operate with the ease, smooth-
ness, and positiveness appropriate to 
its function. 

(b) Each element of each flight con-

trol system must be designed, or dis-
tinctively and permanently marked, to 

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