title-14-part-29-sec29-563

598

14 CFR Ch. I (1–1–24 Edition)

§ 29.563

(1) The seating device system must

remain intact although it may experi-
ence separation intended as part of its
design.

(2) The attachment between the seat-

ing device and the airframe structure
must remain intact although the struc-
ture may have exceeded its limit load.

(3) The ATD’s shoulder harness strap

or straps must remain on or in the im-
mediate vicinity of the ATD’s shoulder
during the impact.

(4) The safety belt must remain on

the ATD’s pelvis during the impact.

(5) The ATD’s head either does not

contact any portion of the crew or pas-
senger compartment or, if contact is
made, the head impact does not exceed
a head injury criteria (HIC) of 1,000 as
determined by this equation.

HIC

a(t)dt

2.5

−

(

)

−

(

)

⎡

⎣

⎢

⎤

⎦

⎥

∫

Where: a(t) is the resultant acceleration at

the center of gravity of the head form ex-
pressed as a multiple of g (the accelera-
tion of gravity) and t

is the time

duration, in seconds, of major head im-
pact, not to exceed 0.05 seconds.

(6) Loads in individual shoulder har-

ness straps must not exceed 1,750
pounds. If dual straps are used for re-
taining the upper torso, the total har-
ness strap loads must not exceed 2,000
pounds.

(7) The maximum compressive load

measured between the pelvis and the
lumbar column of the ATD must not
exceed 1,500 pounds.

(d) An alternate approach that

achieves an equivalent or greater level
of occupant protection, as required by
this section, must be substantiated on
a rational basis.

[Amdt. 29–29, 54 FR 47320, Nov. 13, 1989, as
amended by Amdt. 29–41, 62 FR 46173, Aug. 29,
1997]

§ 29.563

Structural ditching provi-

sions.

If certification with ditching provi-

sions is requested, structural strength
for ditching must meet the require-
ments of this section and § 29.801(e).

(a)

Forward speed landing conditions.

The rotorcraft must initially contact
the most critical wave for reasonably

probable water conditions at forward
velocities from zero up to 30 knots in
likely pitch, roll, and yaw attitudes.
The rotorcraft limit vertical descent
velocity may not be less than 5 feet per
second relative to the mean water sur-
face. Rotor lift may be used to act
through the center of gravity through-
out the landing impact. This lift may
not exceed two-thirds of the design
maximum weight. A maximum forward
velocity of less than 30 knots may be
used in design if it can be dem-
onstrated that the forward velocity se-
lected would not be exceeded in a nor-
mal one-engine-out touchdown.

(b)

Auxiliary or emergency float condi-

tions—(1) Floats fixed or deployed before
initial water contact. In addition to the
landing loads in paragraph (a) of this
section, each auxiliary or emergency
float, or its support and attaching
structure in the airframe or fuselage,
must be designed for the load devel-
oped by a fully immersed float unless it
can be shown that full immersion is
unlikely. If full immersion is unlikely,
the highest likely float buoyancy load
must be applied. The highest likely
buoyancy load must include consider-
ation of a partially immersed float cre-
ating restoring moments to com-
pensate the upsetting moments caused
by side wind, unsymmetrical rotorcraft
loading, water wave action, rotorcraft
inertia, and probable structural dam-
age and leakage considered under
§ 29.801(d). Maximum roll and pitch an-
gles determined from compliance with
§ 29.801(d) may be used, if significant, to
determine the extent of immersion of
each float. If the floats are deployed in
flight, appropriate air loads derived
from the flight limitations with the
floats deployed shall be used in sub-
stantiation of the floats and their at-
tachment to the rotorcraft. For this
purpose, the design airspeed for limit
load is the float deployed airspeed op-
erating limit multiplied by 1.11.

(2)

Floats deployed after initial water

contact. Each float must be designed for
full or partial immersion prescribed in
paragraph (b)(1) of this section. In addi-
tion, each float must be designed for
combined vertical and drag loads using
a relative limit speed of 20 knots be-
tween the rotorcraft and the water.
The vertical load may not be less than

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599

Federal Aviation Administration, DOT

§ 29.571

the highest likely buoyancy load deter-
mined under paragraph (b)(1) of this
section.

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

ATIGUE

VALUATION

§ 29.571

Fatigue Tolerance Evaluation

of Metallic Structure.

(a) A fatigue tolerance evaluation of

each principal structural element
(PSE) must be performed, and appro-
priate inspections and retirement time
or approved equivalent means must be
established to avoid catastrophic fail-
ure during the operational life of the
rotorcraft. The fatigue tolerance eval-
uation must consider the effects of
both fatigue and the damage deter-
mined under paragraph (e)(4) of this
section. Parts to be evaluated include
PSEs of the rotors, rotor drive systems
between the engines and rotor hubs,
controls, fuselage, fixed and movable
control surfaces, engine and trans-
mission mountings, landing gear, and
their related primary attachments.

(b) For the purposes of this section,

the term—

(1)

Catastrophic failure means an

event that could prevent continued
safe flight and landing.

(2)

Principal structural element (PSE)

means a structural element that con-
tributes significantly to the carriage of
flight or ground loads, and the fatigue
failure of that structural element could
result in catastrophic failure of the air-
craft.

lish compliance with this section must
be submitted to and approved by the
Administrator.

(d) Considering all rotorcraft struc-

ture, structural elements, and assem-
blies, each PSE must be identified.

(e) Each fatigue tolerance evaluation

required by this section must include:

(1) In-flight measurements to deter-

mine the fatigue loads or stresses for
the PSEs identified in paragraph (d) of
this section in all critical conditions
throughout the range of design limita-
tions required by § 29.309 (including al-
titude effects), except that maneu-
vering load factors need not exceed the
maximum values expected in oper-
ations.

(2) The loading spectra as severe as

those expected in operations based on
loads or stresses determined under
paragraph (e)(1) of this section, includ-
ing external load operations, if applica-
ble, and other high frequency power-
cycle operations.

(3) Takeoff, landing, and taxi loads

when evaluating the landing gear and
other affected PSEs.

(4) For each PSE identified in para-

graph (d) of this section, a threat as-
sessment which includes a determina-
tion of the probable locations, types,
and sizes of damage, taking into ac-
count fatigue, environmental effects,
intrinsic and discrete flaws, or acci-
dental damage that may occur during
manufacture or operation.

(5) A determination of the fatigue

tolerance characteristics for the PSE
with the damage identified in para-
graph (e)(4) of this section that sup-
ports the inspection and retirement
times, or other approved equivalent
means.

(6) Analyses supported by test evi-

dence and, if available, service experi-
ence.

(f) A residual strength determination

is required that substantiates the max-
imum damage size assumed in the fa-
tigue tolerance evaluation. In deter-
mining inspection intervals based on
damage growth, the residual strength
evaluation must show that the remain-
ing structure, after damage growth, is
able to withstand design limit loads
without failure.

(g) The effect of damage on stiffness,

dynamic behavior, loads, and func-
tional performance must be considered.

(h) Based on the requirements of this

section, inspections and retirement
times or approved equivalent means
must be established to avoid cata-
strophic failure. The inspections and
retirement times or approved equiva-
lent means must be included in the
Airworthiness Limitations Section of
the Instructions for Continued Air-
worthiness required by Section 29.1529
and Section A29.4 of Appendix A of this
part.

(i) If inspections for any of the dam-

age types identified in paragraph (e)(4)
of this section cannot be established
within the limitations of geometry,
inspectability, or good design practice,