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EASA’s Evolving Definition of “Appliance” — What It Means for Part 21 Subpart K and DOAs
Understanding how EASA defines appliances versus parts is important for organisations working in design, production, and certification. Recent regulatory evolution — and the upcoming changes proposed in NPA 2025‑02 — signal a shift in how “appliances” will be treated under Part 21.
At Myers Aerospace, we help organisations navigate exactly these kinds of regulatory transitions. Here’s a clear breakdown of what EASA has now clarified.
From the Old Basic Regulation: No Real Distinction
When the term appliance first appeared in Regulation (EC) No 1592/2002, it wasn’t defined independently. Instead, it appeared only within the combined expression “parts and appliances”.
EASA has confirmed that, at that time, no meaningful regulatory distinction existed between a part and an appliance. Both were treated as elements associated with a product.
The New Basic Regulation Introduces a Clear Split
With the adoption of Regulation (EU) 2018/1139, EASA introduced precise definitions that separate parts from what is now termed non‑installed equipment.
What is a “part”?
Art. 3(4): A part is any element of a product, as defined by that product’s type design.
In other words: if it is part of the aircraft, engine, or propeller type design, it is a part.
What is “non‑installed equipment”?
Art. 3(29): Equipment carried on board that is not a part, but is used or intended to be used for:
- operating or controlling the aircraft,
- supporting occupant survivability, or
- affecting safe operation.
This includes instruments, mechanisms, apparatus, software, accessories, and similar items.
So where does “appliance” fit?
Art. 140(2)(c) makes it explicit: References to “appliances” in earlier regulations are now understood as references to non‑installed equipment.
This is a transitional provision — effectively redefining the legacy term appliance.
Why This Matters for Part 21 Subpart K
Part 21 Subpart K still uses the term appliance, but the Basic Regulation now uses non‑installed equipment. This mismatch is temporary.
EASA has already launched RMT.0727, with Subtask 3 dedicated to aligning Part 21 terminology with the new Basic Regulation.
This work has now produced NPA 2025‑02, which proposes to:
- Remove the term “appliances” from Part 21 and replace it with “non‑installed equipment” wherever appropriate.
This will bring consistency across the regulatory framework and clarify certification pathways for equipment that is not part of the type design.
Supporting Industry Through Regulatory Change
At Myers Aerospace, we specialise in helping organisations interpret and implement evolving airworthiness regulations — including Part 21, Subpart K, and the implications of the new Basic Regulation.
Additional Note:
With reference to (EU) 2024/1108: ‘control and monitoring unit’ (‘CMU’) means the equipment to control and monitor unmanned aircraft remotely.
FAA Repair Station versus EASA Maintenance Organisation
Why does the USA have “repair stations” and Europe have “maintenance organisations”?
Today I was asked why the terminology in Part 145 differs across the Atlantic. Despite previously working closely with my US colleagues in the Gulfstream Service Center (or Centre, if you prefer) network, this wasn’t something I’d ever actually stopped to question. I assumed the answer would be buried somewhere in the archives of regulatory history… and it turns out, it is.
What I found is a fascinating reminder of how deeply aviation regulation is shaped by its origins.
In the United States, the term “repair station” dates back to the 1930s–40s under the old Civil Aeronautics Authority. Maintenance facilities were certificated as Air Agencies, and those performing maintenance were formally designated as repair stations. When the FAA was created in 1958, it inherited this structure wholesale. Even after the major Part 145 rewrite in 2001, the historic term remained — still tied to the Air Agency Certificate system that underpins FAA oversight today.
Europe took a different path. EASA’s terminology aligns with ICAO language — “approved maintenance organisation” — and reflects a more modern regulatory architecture built around Annex 6 and Annex 8. Hence, Part 145 maintenance organisations, not repair stations.
Same intent. Same safety objectives. Two very different linguistic fossils from two very different regulatory histories.
It’s a small detail, but one that says a lot about how our global aviation system evolved — and why harmonisation is often more complex than it first appears; not to mention that Part 21 and Part 145 etc, that are used in the global industry have their roots in the USA’s federal regulatory system of number allocation.
If anyone has deeper archival knowledge from the CAA/FAA era, I’d love to hear it. Aviation history is full of these hidden threads that still shape how we work today.
Non-Advocate Reviews (NARs)
Are more reviews worthwhile in a program? Go slower to go faster?
Today I was challenged by a colleague with "we don't have time to test that!"
That event caused me to reflect on the program and other programs I have experience with over the years. When working in a larger company we asked senior engineers and leaders to assess our project gates during Non-Advocate Reviews. These colleagues were often in other parts of the corporation or countries or used external consultants services. I have also provided this role for others and found them useful for my personal growth.
Do you find them useful?
My thoughts...
Non-Advocate Reviews (NARs) offer powerful benefits for aerospace companies experiencing rapid growth, especially when scaling complex programs like special mission aircraft development and certification.
Strategic Advantages of Non-Advocate Reviews...
OBJECTIVE CRITICAL RISK ASSESSMENT
- NARs bring in external experts who are not directly involved in the program, allowing for unbiased evaluation of technical, regulatory, and operational risks.
- This helps identify blind spots that internal teams might overlook due to proximity or optimism bias.
ACCELERATED DEVELOPMENT
- By catching issues early, NARs reduce the likelihood of costly delays during aircraft selection, modification, testing and certification.
- They streamline decision-making by validating design and compliance strategies before formal regulatory engagement.
IMPROVED CERTIFICATION READINESS
- For companies navigating CAA, EASA or FAA certification, NARs help ensure that design and testing plans align with regulatory expectations. This process supports the Compliance Verification Engineer (CVE) assessments.
- This is especially critical for complex aircraft modifications or using military technologies in civil aircraft.
ENHANCED CREDIBILITY WITH STAKEHOLDERS
- Investors, partners, and regulators gain confidence when a company proactively invites independent scrutiny.
- It signals maturity and transparency, which supports securing funding and regulatory approvals.
KNOWLEDGE TRANSFER FROM INDUSTRY EXPERTS
- NARs often involve seasoned engineers and certification experts from established aerospace firms, offering invaluable insights and mentorship.
- This is a major asset for startups as well as fast-growing teams building institutional knowledge.
SCALABILITY AND GOVERNANCE
- As companies expand, NARs help maintain engineering discipline and program governance across multiple teams and locations.
- They act as a quality gate that scales with the organisation, ensuring consistent standards.