655
Federal Aviation Administration, DOT
§ 27.562
(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).
(c) Auxiliary rotor thrust, and the
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]
E
MERGENCY
L
ANDING
C
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;
(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
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