Federal Aviation Administration, DOT

Section 27.561

vertically through the center of gravity; and
(2) The vertical load prescribed in
paragraph (a)(1) of this section is applied simultaneously with an aft component of 0.25 times the vertical component.
(b) A side-load condition in which - 
(1) A vertical load of 0.75 times the
total vertical load specified in paragraph (a)(1) of this section is divided
equally among the floats; and
(2) For each float, the load share determined 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.
MAIN COMPONENT REQUIREMENTS

spaschal on DSK3GDR082PROD with CFR

Section 27.547

Main rotor structure.

(a) Each main rotor assembly (including 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 SectionSection 27.337 through
27.341:
(1) Critical flight loads.
(2) Limit loads occurring under normal conditions of autorotation. For
this condition, the rotor r.p.m. must be
selected to include the effects of altitude.
(d) The main rotor structure must be
designed 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 expected 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 provided), 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 Section 27.361.
(2) The limit torque must be distributed 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]

Section 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 attachment point.
(b) Each structure must be designed
to withstand - 
(1) The critical loads prescribed in
SectionSection 27.337 through 27.341;
(2) The applicable ground loads prescribed in SectionSection 27.235, 27.471 through 27.485,
27.493, 27.497, 27.501, 27.505, and 27.521;
and
(3) The loads prescribed in Section 27.547
(d)(2) and (e).
(c) Auxiliary rotor thrust, and the
balancing air and inertia loads occurring under accelerated flight conditions, must be considered.
(d) Each engine mount and adjacent
fuselage structure must be designed to
withstand the loads occurring under
accelerated flight and landing conditions, 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]

EMERGENCY LANDING CONDITIONS
Section 27.561 General.
(a) The rotorcraft, although it may
be damaged in emergency landing conditions on land or water, must be designed as prescribed in this section to
protect the occupants under those conditions.
(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;

505

VerDate Sep<11>2014

12:50 Apr 30, 2019

Jkt 247046

PO 00000

Frm 00515

Fmt 8010

Sfmt 8010

Y:\SGML\247046.XXX

247046