When you work with EASA regulation, three acronyms come up very quickly: AMC, GM, and CS.
They are not mandatory regulations in the strict sense, but they play a central role in practice: in audits, certification, discussions with the competent authority, and more broadly in demonstrating an organisation’s compliance.
The goal of this article is simple: understand what AMC, GM, and CS are, how they sit relative to mandatory rules, and how to use them concretely to prove compliance.
Before talking about AMC, GM, or CS, you need to distinguish the regulatory foundation: the IRs, for Implementing Rules.
IRs are binding rules. They are adopted by the European Commission as regulations and apply to the actors concerned.
EASA, for its part, publishes AMC, GM, and CS to support the application of those rules. You can see them as a practical, technical, or interpretative layer around regulatory requirements.
In short:
AMC, for Acceptable Means of Compliance, are acceptable means of compliance published by EASA.
They describe a recognised way to demonstrate that a regulatory requirement is met. They are not mandatory in themselves, but they have very strong practical value.
Why? Because applying an AMC generally gives a presumption of compliance with the associated requirement.
In other words, if your organisation correctly applies the AMC corresponding to a requirement, it has a standardised and recognised path to demonstrate compliance.
That does not mean the AMC is mandatory. You can do things differently. But in that case, you must be able to prove that the alternative approach still meets the objective of the rule.
In practice:
AMC = the standard, recognised path, generally easier to defend in an audit.
If an organisation does not want to apply the AMC as published, it can propose an AltMoC, for Alternative Means of Compliance.
This may apply, for example, when it uses a different method, a specific tool, a particular internal organisation, or an equivalent arrangement that does not exactly match the published AMC.
But an AltMoC cannot be a mere preference or a free interpretation.
It must be documented, justified, and backed by evidence showing that the alternative achieves the intent of the mandatory rule.
In practice, you need to demonstrate:
The logic is therefore simple:
AMC = standard path with a presumption of compliance.
AltMoC = alternative path, but with justification and evidence.
GM, for Guidance Material, is guidance material published by EASA.
It is also non-binding, but its role differs from that of AMC.
A GM is not primarily used to demonstrate compliance. It is used to understand, interpret, and correctly apply a requirement, an AMC, or a CS.
It may contain explanations, examples, clarifications, or contextual elements.
In practice, GM is especially useful when a requirement is technical, ambiguous, or open to misinterpretation.
You can summarise it like this:
The AMC gives you a recognised way to do it.
The GM helps you understand how to read and apply the rule.
GM therefore does not replace a compliance demonstration, but it helps you build that demonstration correctly.
CS, for Certification Specifications, are technical specifications published by EASA.
They are particularly important in certification domains: aircraft, equipment, aerodromes, systems, or infrastructure depending on the case.
Like AMC and GM, CS are non-binding by nature. But they occupy a special place.
In certification, CS often serve as a reference to establish the certification basis, i.e. the certification basis applicable to a given project.
And that is where the point becomes important: a CS can become effectively binding for a project when it is integrated into an accepted certification basis.
In other words:
The CS is a proposed technical standard.
The certification basis is the standard applicable to your project.
In some cases, if an organisation cannot apply a CS exactly, it may propose an alternative approach, for example through an Equivalent Level of Safety mechanism where applicable.
The idea remains the same: not following the standard is not impossible, but you must demonstrate that the expected level of safety is still achieved.
On the ground, the difference between AMC, GM, and CS becomes very concrete in discussions with the competent authority.
This is the simplest case.
The organisation follows the acceptable means of compliance published by EASA. It therefore benefits from a presumption of compliance, provided it can show that the AMC is actually applied.
In an audit, the discussion will mainly focus on:
The challenge is therefore not only to say “we apply the AMC”, but to be able to prove it.
In this case, the organisation departs from the standard path.
It must therefore prepare a stronger file: analysis of the requirement, justification of the alternative approach, risk analysis, evidence, control measures, and demonstration that the intent of the rule is met.
The discussion with the authority then centres on one key question:
Does this approach really achieve the objective of the rule?
The greater the departure from the AMC or CS, the higher the expected level of justification.
GM is useful to understand the rule, prepare a procedure, train teams, or avoid a misinterpretation.
But it must not be confused with proof of compliance.
Saying “the GM says that…” can help explain a position, but it is not always enough to demonstrate that the regulatory requirement is met.
AMC, GM, and CS are not mandatory regulations in the same way as IRs, but they are essential to understand, apply, and demonstrate compliance in the EASA system.
AMC provide a recognised path to demonstrate compliance.
GM help interpret the rules correctly.
CS provide technical reference standards, especially in certification.
So the right question is not only: “Is it mandatory?”
The real question is:
How do I demonstrate, in a robust and traceable way, that my organisation meets the intent of the rule?
And in that demonstration, AMC, GM, and CS are often the first tools to master.
