CS 27.547 Main rotor structure
ED Decision 2023/001/R
(a) Each main rotor assembly (including rotor hubs and blades) must be designed as prescribed in this paragraph.
(b) The main rotor structure must be designed to withstand the following loads prescribed in CS 27.337 to 27.341 and CS 27.351:
(1) Critical flight loads.
(2) Limit loads occurring under normal conditions of autorotation. For this condition, the rotor rpm must be selected to include the effects of altitude.
(c) 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.
(d) 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 CS 27.361.
(2) The limit torque must be distributed to the rotor blades in a rational manner.
[Amdt 27/3]
CS 27.549 Fuselage, landing gear, and rotor pylon structures
ED Decision 2023/001/R
(a) Each fuselage, landing gear, and rotor pylon structure must be designed as prescribed in this paragraph. 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 CS 27.337 to 27.341 and CS 27.351;
(2) The applicable ground loads prescribed in CS 27.235, 27.471 to 27.485, CS 27.493, 27.497, 27.501, 27.505, and 27.521; and
(3) The loads prescribed in CS 27.547(c)(2) and (d).
(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 occuring under accelerated flight and landing conditions, including engine torque.
[Amdt 27/3]