What is the difference between AML Part-66 categories A, B1, B2, B2L, B3, L and C?

The AML Part-66 categories define the scope of certification privileges for aircraft maintenance:

1. Category A – minor scheduled line maintenance and simple defect rectification.
2. Category B1 – maintenance of aircraft structure, powerplant, mechanical and electrical systems, including simple tasks on avionic systems.
3. Category B2 – maintenance of avionics and electrical systems, including related electrical and avionics tasks within mechanical systems.
4. Category B2L – maintenance of electrical and avionics systems within the limits of the system ratings endorsed on the licence.
5. Category B3 – maintenance of non-pressurised piston-engine aeroplanes with an MTOM of 2 000 kg or less.
6. Category L – maintenance of category L aircraft (e.g. sailplanes, powered sailplanes, balloons and airships) within the privileges of the applicable L subcategory.
7. Category C – issuing a CRS for the aircraft as a whole following completion of base maintenance.

Reference: points 66.A.3 and 66.A.20 of Annex III (Part-66).