---
kind: "section"
citation: "14 C.F.R. § 29.975"
title: "14"
number: "29.975"
heading: "Fuel tank vents and carburetor vapor vents."
url: "https://uscodex.org/cfr/14/29.975"
---

# §29.975. Fuel tank vents and carburetor vapor vents.

- (a) **Fuel tank vents.** Each fuel tank must be vented from the top part of the expansion space so that venting is effective under normal flight conditions. In addition—
  - (1) The vents must be arranged to avoid stoppage by dirt or ice formation;
  - (2) The vent arrangement must prevent siphoning of fuel during normal operation;
  - (3) The venting capacity and vent pressure levels must maintain acceptable differences of pressure between the interior and exterior of the tank, during—
    - (i) Normal flight operation;
    - (ii) Maximum rate of ascent and descent; and
    - (iii) Refueling and defueling (where applicable);
  - (4) Airspaces of tanks with interconnected outlets must be interconnected;
  - (5) There may be no point in any vent line where moisture can accumulate with the rotorcraft in the ground attitude or the level flight attitude, unless drainage is provided;
  - (6) No vent or drainage provision may end at any point—
    - (i) Where the discharge of fuel from the vent outlet would constitute a fire hazard; or
    - (ii) From which fumes could enter personnel compartments; and
  - (7) The venting system must be designed to minimize spillage of fuel through the vents to an ignition source in the event of a rollover during landing, ground operations, or a survivable impact.
- (b) **Carburetor vapor vents.** Each carburetor with vapor elimination connections must have a vent line to lead vapors back to one of the fuel tanks. In addition—
  - (1) Each vent system must have means to avoid stoppage by ice; and
  - (2) If there is more than one fuel tank, and it is necessary to use the tanks in a definite sequence, each vapor vent return line must lead back to the fuel tank used for takeoff and landing.

## Notes

### Amendments

[Doc. No. 5084, 29 FR 16150, Dec. 3, 1964, as amended by Amdt. 29-26, 53 FR 34217, Sept. 2, 1988; Amdt. 29-35, 59 FR 50388, Oct. 3, 1994; Amdt. 29-42, 63 FR 43285, Aug. 12, 1998]

### 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. 29-26, 53 FR 34217, Sept. 2, 1988; Amdt. 29-35, 59 FR 50388, Oct. 3, 1994; Amdt. 29-42, 63 FR 43285, Aug. 12, 1998]