title-14-part-29-sec29-561

596

14 CFR Ch. I (1–1–24 Edition)

§ 29.549

must function safely for the critical
flight load and operating conditions. A
design assessment must be performed,
including a detailed failure analysis to
identify all failures that will prevent
continued safe flight or safe landing,
and must identify the means to mini-
mize the likelihood of their occurrence.

signed to withstand the following loads
prescribed in §§ 29.337 through 29.341 and
29.351:

(1) Critical flight loads.
(2) Limit loads occurring under nor-

mal conditions of autorotation.

(d) The rotor structure must be de-

signed to withstand loads simulating—

(1) For the rotor blades, hubs, and

flapping hinges, the impact force of
each blade against its stop during
ground operation; and

(2) Any other critical condition ex-

pected in normal operation.

(e) The rotor structure must be de-

signed to withstand the limit torque at
any rotational speed, including zero.

In addition:
(1) The limit torque need not be

greater than the torque defined by a
torque limiting device (where pro-
vided), and may not be less than the
greater of—

(i) The maximum torque likely to be

transmitted to the rotor structure, in
either direction, by the rotor drive or
by sudden application of the rotor
brake; and

(ii) For the main rotor, the limit en-

gine torque specified in § 29.361.

(2) The limit torque must be equally

and rationally distributed to the rotor
blades.

(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. 29–40, 61 FR 21907, May 10, 1996]

§ 29.549

Fuselage and rotor pylon

structures.

(a) Each fuselage and rotor pylon

structure must be designed to with-
stand—

(1) The critical loads prescribed in

§§ 29.337 through 29.341, and 29.351;

(2) The applicable ground loads pre-

scribed in §§ 29.235, 29.471 through 29.485,
29.493, 29.497, 29.505, and 29.521; and

(3) The loads prescribed in § 29.547

(d)(1) and (e)(1)(i).

(b) Auxiliary rotor thrust, the torque

reaction of each rotor drive system,
and the balancing air and inertia loads
occurring under accelerated flight con-
ditions, must be considered.

fuselage structure must be designed to
withstand the loads occurring under
accelerated flight and landing condi-
tions, including engine torque.

(d) [Reserved]
(e) If approval for the use of 2

⁄

minute OEI power is requested, each
engine mount and adjacent structure
must be designed to withstand the
loads resulting from a limit torque
equal to 1.25 times the mean torque for
2

⁄

-minute OEI power combined with 1g

flight loads.

(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. 29–26, 53 FR 34215, Sept. 2, 1988]

§ 29.551

Auxiliary lifting surfaces.

Each auxiliary lifting surface must

be designed to withstand—

(a) The critical flight loads in §§ 29.337

through 29.341, and 29.351;

(b) the applicable ground loads in

§§ 29.235, 29.471 through 29.485, 29.493,
29.505, and 29.521; and

pected in normal operation.

MERGENCY

ANDING

ONDITIONS

§ 29.561

General.

(a) The rotorcraft, although it may

be damaged in emergency landing con-
ditions on land or water, must be de-
signed as prescribed in this section to
protect the occupants under those con-
ditions.

(b) The structure must be designed to

give each occupant every reasonable
chance of escaping serious injury in a
crash landing when—

(1) Proper use is made of seats, belts,

and other safety design provisions;

(2) The wheels are retracted (where

applicable); and

(3) Each occupant and each item of

mass inside the cabin that could injure

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597

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§ 29.562

an occupant is restrained when sub-
jected to the following ultimate iner-
tial load factors relative to the sur-
rounding structure:

(i) Upward—4g.
(ii) Forward—16g.
(iii) Sideward—8g.
(iv) Downward—20g, after the in-

tended displacement of the seat device.

(v) Rearward—1.5g.
(c) The supporting structure must be

designed to restrain under any ulti-
mate inertial load factor up to those
specified in this paragraph, any item of
mass above and/or behind the crew and
passenger compartment that could in-
jure an occupant if it came loose in an
emergency landing. Items of mass to be
considered include, but are not limited
to, rotors, transmission, and engines.
The items of mass must be restrained
for the following ultimate inertial load
factors:

(1) Upward—1.5g.
(2) Forward—12g.
(3) Sideward—6g.
(4) Downward—12g.
(5) Rearward—1.5g.
(d) Any fuselage structure in the area

of internal fuel tanks below the pas-
senger floor level must be designed to
resist the following ultimate inertial
factors and loads, and to protect the
fuel tanks from rupture, if rupture is
likely when those loads are applied to
that area:

(1) Upward—1.5g.
(2) Forward—4.0g.
(3) Sideward—2.0g.
(4) Downward—4.0g.

[Doc. No. 5084, 29 FR 16150, Dec. 3, 1964, as
amended by Amdt. 29–29, 54 FR 47319, Nov. 13,
1989; Amdt. 29–38, 61 FR 10438, Mar. 13, 1996]

§ 29.562

Emergency landing dynamic

conditions.

(a) The rotorcraft, although it may

be damaged in a crash landing, must be
designed to reasonably protect each oc-
cupant when—

(1) The occupant properly uses the

seats, safety belts, and shoulder har-
nesses provided in the design; and

(2) The occupant is exposed to loads

equivalent to those resulting from the
conditions prescribed in this section.

(b) Each seat type design or other

seating device approved for crew or
passenger occupancy during takeoff

and landing must successfully com-
plete dynamic tests or be demonstrated
by rational analysis based on dynamic
tests of a similar type seat in accord-
ance with the following criteria. The
tests must be conducted with an occu-
pant simulated by a 170-pound
anthropomorphic test dummy (ATD),
as defined by 49 CFR 572, Subpart B, or
its equivalent, sitting in the normal
upright position.

(1) A change in downward velocity of

not less than 30 feet per second when
the seat or other seating device is ori-
ented in its nominal position with re-
spect to the rotorcraft’s reference sys-
tem, the rotorcraft’s longitudinal axis
is canted upward 60

with respect to

the impact velocity vector, and the
rotorcraft’s lateral axis is perpen-
dicular to a vertical plane containing
the impact velocity vector and the
rotorcraft’s longitudinal axis. Peak
floor deceleration must occur in not
more than 0.031 seconds after impact
and must reach a minimum of 30g’s.

(2) A change in forward velocity of

not less than 42 feet per second when
the seat or other seating device is ori-
ented in its nominal position with re-
spect to the rotorcraft’s reference sys-
tem, the rotorcraft’s longitudinal axis
is yawed 10

either right or left of the

impact velocity vector (whichever
would cause the greatest load on the
shoulder harness), the rotorcraft’s lat-
eral axis is contained in a horizontal
plane containing the impact velocity
vector, and the rotorcraft’s vertical
axis is perpendicular to a horizontal
plane containing the impact velocity
vector. Peak floor deceleration must
occur in not more than 0.071 seconds
after impact and must reach a min-
imum of 18.4g’s.

(3) Where floor rails or floor or side-

wall attachment devices are used to at-
tach the seating devices to the air-
frame structure for the conditions of
this section, the rails or devices must
be misaligned with respect to each
other by at least 10

vertically (i.e.,

pitch out of parallel) and by at least a
10

lateral roll, with the directions op-

tional, to account for possible floor
warp.

must be shown: