---
kind: "section"
citation: "14 C.F.R. § 29.908"
title: "14"
number: "29.908"
heading: "Cooling fans."
url: "https://uscodex.org/cfr/14/29.908"
---

# §29.908. Cooling fans.


For cooling fans that are a part of a powerplant installation the following apply:

- (a) **Category A.** For cooling fans installed in Category A rotorcraft, it must be shown that a fan blade failure will not prevent continued safe flight either because of damage caused by the failed blade or loss of cooling air.
- (b) **Category B.** For cooling fans installed in category B rotorcraft, there must be means to protect the rotorcraft and allow a safe landing if a fan blade fails. It must be shown that—
  - (1) The fan blade would be contained in the case of a failure;
  - (2) Each fan is located so that a fan blade failure will not jeopardize safety; or
  - (3) Each fan blade can withstand an ultimate load of 1.5 times the centrifugal force expected in service, limited by either—
    - (i) The highest rotational speeds achievable under uncontrolled conditions; or
    - (ii) **An overspeed limiting device.**
- (c) **Fatigue evaluation.** Unless a fatigue evaluation under [§ 29.571](/cfr/14/29.571.md) is conducted, it must be shown that cooling fan blades are not operating at resonant conditions within the operating limits of the rotorcraft.

## Notes

### Amendments

[Amdt. 29-13, 42 FR 15046, Mar. 17, 1977, as amended by Amdt. 29-26, 53 FR 34215, Sept. 2, 1988]

### 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

[Amdt. 29-13, 42 FR 15046, Mar. 17, 1977, as amended by Amdt. 29-26, 53 FR 34215, Sept. 2, 1988]