spaschal on DSK3GDR082PROD with CFR

Section 29.601

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

may occur during manufacture or operation; and
(v) An assessment of the residual
strength and fatigue characteristics of
all PSEs that supports the replacement
times and inspection intervals established under paragraph (d)(2) of this
section.
(2) Each applicant must establish replacement times, inspections, or other
procedures for all PSEs to require the
repair or replacement of damaged parts
before a catastrophic failure. These replacement times, inspections, or other
procedures must be included in the Airworthiness Limitations Section of the
Instructions for Continued Airworthiness required by Section 29.1529.
(i) Replacement times for PSEs must
be determined by tests, or by analysis
supported by tests, and must show that
the structure is able to withstand the
repeated loads of variable magnitude
expected in-service. In establishing
these replacement times, the following
items must be considered:
(A) Damage identified in the threat
assessment required by paragraph
(d)(1)(iv) of this section;
(B) Maximum acceptable manufacturing defects and in-service damage
(i.e., those that do not lower the residual strength below ultimate design
loads and those that can be repaired to
restore ultimate strength); and
(C) Ultimate load strength capability
after applying repeated loads.
(ii) Inspection intervals for PSEs
must be established to reveal any damage identified in the threat assessment
required by paragraph (d)(1)(iv) of this
section that may occur from fatigue or
other in-service causes before such
damage has grown to the extent that
the component cannot sustain the required residual strength capability. In
establishing these inspection intervals,
the following items must be considered:
(A) The growth rate, including nogrowth, of the damage under the repeated loads expected in-service determined by tests or analysis supported
by tests;
(B) The required residual strength for
the assumed damage established after
considering the damage type, inspection interval, detectability of damage,
and the techniques adopted for damage

detection. The minimum required residual strength is limit load; and
(C) Whether the inspection will detect the damage growth before the
minimum residual strength is reached
and restored to ultimate load capability, or whether the component will
require replacement.
(3) Each applicant must consider the
effects of damage on stiffness, dynamic
behavior, loads, and functional performance on all PSEs when substantiating the maximum assumed damage
size and inspection interval.
(e) Fatigue Evaluation: If an applicant establishes that the damage tolerance evaluation described in paragraph
(d) of this section is impractical within
the limits of geometry, inspectability,
or good design practice, the applicant
must do a fatigue evaluation of the
particular composite rotorcraft structure and:
(1) Identify all PSEs considered in
the fatigue evaluation;
(2) Identify the types of damage for
all PSEs considered in the fatigue evaluation;
(3) Establish supplemental procedures to minimize the risk of catastrophic failure associated with the
damages identified in paragraph (d) of
this section; and
(4) Include these supplemental procedures in the Airworthiness Limitations
section of the Instructions for Continued Airworthiness required by Section 29.1529.
[Doc. No. FAA-2009-0660, Amdt. 29-59, 76 FR
74664, Dec. 1, 2011]

Subpart D - Design and
Construction
GENERAL
Section 29.601 Design.
(a) The rotorcraft may have no design features or details that experience
has shown to be hazardous or unreliable.
(b) The suitability of each questionable design detail and part must be established by tests.
Section 29.602 Critical parts.
(a) Critical part. A critical part is a
part, the failure of which could have a
catastrophic effect upon the rotocraft,
and for which critical characterists

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