IRImplementing rule
ETSO-C178a
Aircraft Circuit Breakers
1 Applicability
This ETSO provides the requirements that aircraft circuit breakers that are designed and manufactured on or after the date of this ETSO must meet in order to be identified with the applicable ETSO marking.
2 Procedures
2.1 General
The applicable procedures are detailed in CS-ETSO, Subpart A.
2.2 Specific
None.
3 Technical conditions
3.1 Basic
3.1.1 Minimum Performance Standard
The applicable standards are those provided in Table 1 for the intended equipment class:
Table 1 — Equipment class standards
| Equipment Class | Equipment Type | Minimum Performance Standards |
|---|---|---|
| 1 | Alternating Current (AC) Arc Fault Circuit Breakers | SAE Aerospace Standard (AS) AS5692A, ‘ARC Fault Circuit Breaker (AFCB), Aircraft, Trip-Free Single Phase and Three Phase 115 VAC, 400 Hz - Constant Frequency’, dated December 2009 |
| 2 | Direct Current (DC) Arc Fault Circuit Breakers | SAE Aerospace Standard (AS) AS6019, ‘ARC Fault Circuit Breaker (AFCB), Aircraft, Trip-Free 28 VDC’, dated June 2012 |
| 3 | AC or DC Thermal Circuit Breakers | SAE Aerospace Standard (AS) AS58091A, ‘Circuit Breakers, Trip-Free, Aircraft General Specification For’, dated May 2012 |
3.1.2 Environmental Standard
See CS-ETSO, Subpart A, paragraph 2.1.
3.1.3 Software
See CS-ETSO, Subpart A, paragraph 2.2.
3.1.4 Airborne Electronic Hardware
See CS-ETSO, Subpart A, paragraph 2.3.
3.2 Specific
3.2.1 Failure Condition Classification
See CS-ETSO, Subpart A, paragraph 2.4.
4 Marking
4.1 General
See CS-ETSO, Subpart A, paragraph 1.2.
4.2 Specific
The class of the equipment shall be legibly and permanently marked.
5 Availability of referenced documents
See CS-ETSO, Subpart A, paragraph 3.
[Amdt ETSO/8]
[Amdt ETSO/17]
IR · ETSO-C178a — CS-ETSO · ED Decision 2022/018/R · CS-ETSO Easy Access Rules · EAR revision 1 Oct 2026