---
kind: "section"
citation: "14 C.F.R. § 27.1357"
title: "14"
number: "27.1357"
heading: "Circuit protective devices."
url: "https://uscodex.org/cfr/14/27.1357"
---

# §27.1357. Circuit protective devices.

- (a) Protective devices, such as fuses or circuit breakers, must be installed in each electrical circuit other than—
  - (1) The main circuits of starter motors; and
  - (2) **Circuits in which no hazard is presented by their omission.**
- (b) A protective device for a circuit essential to flight safety may not be used to protect any other circuit.
- (c) Each resettable circuit protective device (“trip free” device in which the tripping mechanism cannot be overridden by the operating control) must be designed so that—
  - (1) A manual operation is required to restore service after trippling; and
  - (2) If an overload or circuit fault exists, the device will open the circuit regardless of the position of the operating control.
- (d) If the ability to reset a circuit breaker or replace a fuse is essential to safety in flight, that circuit breaker or fuse must be located and identified so that it can be readily reset or replaced in flight.
- (e) If fuses are used, there must be one spare of each rating, or 50 percent spare fuses of each rating, whichever is greater.

## Notes

### Amendments

[Doc. No. 5074, 29 FR 15695, Nov. 24, 1964; 29 FR 17885, Dec. 17, 1964, as amended by Amdt. 27-13, 42 FR 36972, July 18, 1977]

### Authority

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

### Source

Source: Docket No. 5074, 29 FR 15695, Nov. 24, 1964, unless otherwise noted.

### Amendments

[Doc. No. 5074, 29 FR 15695, Nov. 24, 1964; 29 FR 17885, Dec. 17, 1964, as amended by Amdt. 27-13, 42 FR 36972, July 18, 1977]