Other Airworthiness Requirements (CAR-21, CAR-147, etc.)
Design, production and training approvals
Beyond maintenance, candidates must know the other approval regimes. CAR-21 covers design and production: type certificates (TC), supplemental type certificates (STC), repairs and modifications, parts manufacturing approval (PMA), and the design organisation approval (DOA) and production organisation approval (POA). A modification to a type design requires an approved design (STC or minor change approval) before it can be embodied.
CAR-147 covers approved maintenance training organisations (MTOA) - the schools that deliver the basic training and examinations required for CAR-66 licences. Know that a CAR-147 approval covers defined courses, examinations and instructor competence, and that its certificate is not a licence: the licence is still issued by DGCA.
Other relevant instruments include CAR-145 (maintenance), CAR-M (continuing airworthiness) and requirements for components and parts - a part must be eligible and traceable, with an authorised release certificate (e.g. EASA Form 1 or equivalent).
Traps
A frequent error is assuming any modification can be fitted if the manufacturer issues a drawing. Without approved design data it is not eligible. Another trap is confusing CAR-147 (training organisation) with CAR-66 (personnel licensing). A third is the PMA/parts question: an unapproved part, even if serviceable, is not eligible for fitment on a type-certificated aircraft.
Worked example / rule of thumb
A new avionics fit requires approved design data (STC or approved minor change) plus an approved production part plus an approved installation by a CAR-145 organisation. Design approval + part eligibility + installation approval = airworthy modification.