---
kind: "section"
citation: "14 C.F.R. § 29.547"
title: "14"
number: "29.547"
heading: "Main and tail rotor structure."
url: "https://uscodex.org/cfr/14/29.547"
---

# §29.547. Main and tail rotor structure.

- (a) A rotor is an assembly of rotating components, which includes the rotor hub, blades, blade dampers, the pitch control mechanisms, and all other parts that rotate with the assembly.
- (b) Each rotor assembly must be designed as prescribed in this section and 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 minimize the likelihood of their occurrence.
- (c) The rotor structure must be designed to withstand the following loads prescribed in §§ [29.337 through 29.341](/cfr/14/29.337..29.341.md) and [29.351](/cfr/14/29.351.md):
  - (1) **Critical flight loads.**
  - (2) **Limit loads occurring under normal conditions of autorotation.**
- (d) The 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 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, by the rotor drive or by sudden application of the rotor brake; and
    - (ii) For the main rotor, the limit engine torque specified in [§ 29.361](/cfr/14/29.361.md).
  - (2) The limit torque must be equally and rationally distributed to the rotor blades.

## Notes

### Amendments

[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]

### Authority

Authority: 49 U.S.C. 106(f), 106(g), 40113, 44701-44702, 44704.

### Source

Source: Docket No. 5084, 29 FR 16150, Dec. 3, 1964, unless otherwise noted.

### Amendments

[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]