title-14-part-27-sec27-561

506

14 CFR Ch. I (1–1–24 Edition)

§ 27.547

vertically through the center of grav-
ity; and

(2) The vertical load prescribed in

paragraph (a)(1) of this section is ap-
plied simultaneously with an aft com-
ponent of 0.25 times the vertical com-
ponent.

(b) A side-load condition in which—
(1) A vertical load of 0.75 times the

total vertical load specified in para-
graph (a)(1) of this section is divided
equally among the floats; and

(2) For each float, the load share de-

termined under paragraph (b)(1) of this
section, combined with a total side
load of 0.25 times the total vertical
load specified in paragraph (b)(1) of
this section, is applied to that float
only.

AIN

OMPONENT

EQUIREMENTS

§ 27.547

Main rotor structure.

(a) Each main rotor assembly (in-

cluding rotor hubs and blades) must be
designed as prescribed in this section.

(b) [Reserved]
(c) The main rotor structure must be

designed to withstand the following
loads prescribed in §§ 27.337 through
27.341:

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

mal conditions of autorotation. For
this condition, the rotor r.p.m. must be
selected to include the effects of alti-
tude.

(d) The main rotor structure must be

designed to withstand loads simu-
lating—

(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 main rotor structure must be

designed 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; and

(ii) The limit engine torque specified

in § 27.361.

(2) The limit torque must be distrib-

uted to the rotor blades in a rational
manner.

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

[Doc. No. 5074, 29 FR 15695, Nov. 24, 1964, as
amended by Amdt. 27–3, 33 FR 14105, Sept. 18,
1968]

§ 27.549

Fuselage, landing gear, and

rotor pylon structures.

(a) Each fuselage, landing gear, and

rotor pylon structure must be designed
as prescribed in this section. Resultant
rotor forces may be represented as a
single force applied at the rotor hub at-
tachment point.

(b) Each structure must be designed

to withstand—

(1) The critical loads prescribed in

§§ 27.337 through 27.341;

(2) The applicable ground loads pre-

scribed in §§ 27.235, 27.471 through 27.485,
27.493, 27.497, 27.501, 27.505, and 27.521;
and

(3) The loads prescribed in § 27.547

(d)(2) and (e).

balancing air and inertia loads occur-
ring under accelerated flight condi-
tions, must be considered.

(d) Each engine mount and adjacent

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

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

[Doc. No. 5074, 29 FR 15695, Nov. 24, 1964, as
amended by Amdt. 27–3, 33 FR 14105, Sept. 18,
1968]

MERGENCY

ANDING

ONDITIONS

§ 27.561

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;

VerDate Sep<11>2014

09:06 Jun 28, 2024

Jkt 262046

PO 00000

Frm 00516

Fmt 8010

Sfmt 8010

Y:\SGML\262046.XXX

262046

jspears on DSK121TN23PROD with CFR

507

Federal Aviation Administration, DOT

§ 27.562

(2) The wheels are retracted (where

applicable); and

(3) Each occupant and each item of

mass inside the cabin that could injure
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 intended

displacement of the seat device.

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

designed to restrain, under any ulti-
mate inertial load up to those specified
in this paragraph, any item of mass
above and/or behind the crew and pas-
senger compartment that could injure
an occupant if it came loose in an
emergency landing. Items of mass to be
considered include, but are not limited
to, rotors, transmissions, 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 when those
loads are applied to that area:

(i) Upward—1.5g.
(ii) Forward—4.0g.
(iii) Sideward—2.0g.
(iv) Downward—4.0g.

[Doc. No. 5074, 29 FR 15695, Nov. 24, 1964, as
amended by Amdt. 27–25, 54 FR 47318, Nov. 13,
1989; Amdt. 27–30, 59 FR 50386, Oct. 3, 1994;
Amdt. 27–32, 61 FR 10438, Mar. 13, 1996]

§ 27.562

Emergency landing dynamic

conditions.

(a) The rotorcraft, although it may

be damaged in an emergency crash
landing, must be designed to reason-
ably protect each occupant 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 the

loads 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