What is EASA Part 66?
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EASA Part-66 is Annex III to Commission Regulation (EU) No 1321/2014 and sets the licensing, knowledge, experience, rating, and privilege framework for aircraft maintenance certifying staff.
What it means in practice
Part-66 defines who may certify maintenance and within what scope once the person is licensed, rated, authorised by the organisation where required, and operating inside the privilege limits of the licence category. It is the rule that connects maintenance competence to certification privilege.
In practice, the licence is not the whole system. A Part-66 licence interacts with aircraft type ratings, organisational authorisations, task limitations, company procedures, and actual recent experience. The holder must know both what the licence allows and what it does not allow.
Who it applies to
Part-66 applies to aircraft maintenance personnel who seek or exercise certifying privileges within the EASA system. It is especially central to line and base maintenance certifying staff, avionics certifying staff, and category C base maintenance support signatories.
It also affects Part-145 and other approved organisations because those organisations must issue authorisations that align with the actual licence category, rating, experience, and competence of the person.
What EASA says
Point 66.A.20 defines licence privileges. 66.A.25 sets the basic knowledge requirements. 66.A.30 sets experience requirements. 66.A.40 covers continued validity of the aircraft maintenance licence, while 66.A.45 covers endorsement with aircraft ratings. The categories are not interchangeable: category A is limited line maintenance certification after minor scheduled line maintenance and simple defect rectification; B1 covers mechanical, airframe, powerplant, and electrical work for the relevant subcategory; B2 covers avionics and electrical or instrument systems within its scope; B3 is limited to certain piston aeroplanes; category C is base maintenance certification after support staff sign-off and completion of all required maintenance.
The practical boundary that causes the most misunderstanding is between B1 and B2. B1 does not simply become everything except software. B2 does not simply become all electronics. The licence privilege has to be read against the exact Part-66 wording and the relevant aircraft or system scope.
Common mistakes
The most common mistake is assuming the licence category alone settles the scope of work. It does not. The rating, authorisation, actual competence, and organisation procedures still matter.
Another frequent error is confusing B1 and B2 privileges or overlooking the route to category C privileges. OJT, type training, and organisational authorisation all remain important. The licence does not remove the need for company-level control.
Sources
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