---
title: "ETSO-C219a — CS-ETSO · Avioverse"
description: "AIRBORNE COLLISION AVOIDANCE SYSTEM (ACAS) XA/XO 1 Applicability This ETSO provides the requirements that ACAS Xa/Xo equipment that is designed and…"
url: "https://avioverse.aero/regulations/easa/cs-etso/subpart-b/etso-c219a"
---

# ETSO-C219a

European Technical Standard Orders (CS-ETSO) · CS-ETSO · EAR revision 1 Oct 2026

IR Implementing rule

## ETSO-C219a

AIRBORNE COLLISION AVOIDANCE SYSTEM (ACAS) XA/XO

1 Applicability

This ETSO provides the requirements that ACAS Xa/Xo equipment that is 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

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

Standards set forth in EUROCAE ED-256 Revision A, ‘Minimum Operational Performance Standards for Airborne Collision Avoidance System X (ACAS X) (ACAS Xa and ACAS Xo)’, dated 28 June 2023.

3.1.2 Environmental Standard

See CS-ETSO, Subpart A, paragraph 2.1, and EUROCAE ED-256 Revision A, Section 2.3.

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.

3.2.1.1 Failure of the function defined in paragraph 3.1.1 of this ETSO that results in misleading information is:

(a) a hazardous failure condition for un-annunciated failures that could either generate an incorrect RA or result in a missing RA;

(b) a major failure condition for un-annunciated failures that could generate a false RA. 3.2.1.2 Failure of the function defined in paragraph 3.1.1 of this ETSO that results in the loss of the function (annunciated) is a minor failure condition.

Note: As used in this paragraph:

— an incorrect RA is when an RA condition exists and an RA is issued but the RA provides incorrect guidance;

— a missing RA is when an RA condition exists but an RA is not issued;

— a false RA is when an RA is issued but an RA condition does not exist.

4 Marking

4.1 General

See CS-ETSO, Subpart A, paragraph 1.2.

4.2 Specific

None.

5 Availability of Referenced Document

See CS-ETSO, Subpart A, paragraph 3.

\[Amdt ETSO/18]

IR · ETSO-C219a — CS-ETSO · CS-ETSO Easy Access Rules · EAR revision 1 Oct 2026

[All rules in SUBPART B – LIST OF ETSOs](https://avioverse.aero/regulations/easa/cs-etso/subpart-b)

Consolidated from the EASA Easy Access Rules (revision 1 Oct 2026, extracted 13 Oct 2026) for convenience. Not the official publication — verify against the Official Journal of the European Union and the EASA publications before operational use.