---
title: "21.A.303 Compliance with the applicable requirements — Annex I, Initial Airworthiness · Avioverse"
description: "The showing of compliance of parts, appliances and CMU components to be installed in a type-certified product, or in a CMU, shall be made:"
url: "https://avioverse.aero/regulations/easa/initial-airworthiness/annex-i/section-a-technical-requirements/21-a-303"
---

# 21.A.303 Compliance with the applicable requirements

Annex I · Regulation (EU) No 748/2012 · EAR revision 27 Nov 2025

IR Implementing rule

## 21.A.303 Compliance with the applicable requirements

The showing of compliance of parts, appliances and CMU components to be installed in a type-certified product, or in a CMU, shall be made:

(a) in conjunction with the type-certification procedures of Subpart B, D or E for the product, UAS or CMU in which it is to be installed; or

(b) where applicable, under the [ETSO](https://avioverse.aero/glossary/easa/etso) authorisation procedures of Subpart O; or

(c) in the case of standard parts, in accordance with officially recognised standards.

IR · 21.A.303 — Regulation (EU) No 748/2012 · Regulation (EU) 2024/1108 · Initial Airworthiness Easy Access Rules · EAR revision 27 Nov 2025

AMC Acceptable means of compliance

## AMC 21.A.303(c) Standard Parts

1\. In this context a part is considered as a ‘standard part’ where it is designated as such by the design approval holder responsible for the product, part or appliance, in which the part is intended to be used. In order to be considered a ‘standard part’, all design, manufacturing, inspection data and marking requirements necessary to demonstrate conformity of that part should be in the public domain and published or established as part of officially recognised Standards, or

2\. For sailplanes and powered sailplanes, where it is a non-required instrument and/or equipment certified under the provision of CS 22.1301(b), if that instrument or equipment, when installed, functioning, functioning improperly or not functioning at all, does not in itself, or by its effect upon the sailplane and its operation, constitute a safety hazard.

‘Required’ in the term ‘non-required’ as used above means required by the applicable certification specifications (CS 22.1303, 22.1305 and 22.1307) or required by the relevant operating regulations and the applicable Rules of the Air or as required by Air Traffic Management (e.g. a transponder in certain controlled airspace).

Examples of equipment which can be considered standard parts are electrical variometers, bank/slip indicators ball type, total energy probes, capacity bottles (for variometers), final glide calculators, navigation computers, data logger / barograph / turnpoint camera, bug-wipers and anti-collision systems.

Equipment which must be approved in accordance to the certification specifications shall comply with the applicable [ETSO](https://avioverse.aero/glossary/easa/etso) or equivalent and is not considered a standard part (e.g. oxygen equipment).

AMC · AMC 21.A.303(c) — Regulation (EU) No 748/2012 · ED Decision 2012/020/R · Initial Airworthiness Easy Access Rules · EAR revision 27 Nov 2025

[All rules in SECTION A — TECHNICAL REQUIREMENTS](https://avioverse.aero/regulations/easa/initial-airworthiness/annex-i/section-a-technical-requirements)

Consolidated from the EASA Easy Access Rules (revision 27 Nov 2025, 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.