---
title: "GM No 1 to 21.A.128 Acceptable functional test – Engines — Annex I, Initial Airworthiness · Avioverse"
description: "The functional test required for a new engine will be specified by the engine design organisation and will normally include at least the following:"
url: "https://avioverse.aero/regulations/easa/initial-airworthiness/annex-i/section-a-technical-requirements/gm-no-1-to-21-a-128-acceptable-functional-test-engines"
---

# GM No 1 to 21.A.128 Acceptable functional test – Engines

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

GM Guidance material

## GM No 1 to 21.A.128 Acceptable functional test – Engines

The functional test required for a new engine will be specified by the engine design organisation and will normally include at least the following:

1\. Break-in runs that include a determination of fuel and oil consumption and a determination of power characteristics at rated maximum continuous power or thrust and, if applicable, at rated take-off power or thrust.

2\. A period of operation at rated maximum continuous power or thrust. For engines having a rated take-off power or - thrust, part of that period should be at rated take-off power or - thrust.

The test equipment used for the test run should be capable of output determination of accuracy sufficient to assure that the engine output delivered complies with the specified rating and operation limitations.

GM — 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.