Module 10.4 — Independent certifying staff under Part-M, Part-66 and Part-ML

Scope and level

10.4 is new in the 2023/989 syllabus. It is not required for category A, and is examined at level 3 (the highest level) for B1, B2, B2L and B3 — you must know the privileges, responsibilities, record-keeping, limitations and oversight in detail. "Independent certifying staff" means a licensed engineer releasing aircraft on their own behalf, not on behalf of an approved organisation.

Where independent certifying staff can work

Regime	Aircraft	What an independent certifying staff member may release
Part-ML (Annex Vb)	Light aircraft not used by licensed air carriers: aeroplanes up to 2 730 kg MTOM, rotorcraft up to 1 200 kg MTOM certified for max 4 occupants, other ELA2 aircraft	Any maintenance within their licence privileges and ratings (ML.A.801(b)(2))
Part-M (Annex I)	Aircraft not complex motor-powered and not used by licensed air carriers but outside Part-ML scope	Only maintenance tasks other than complex maintenance tasks listed in Appendix VII to Part-M (M.A.801(b)(1))
Complex motor-powered aircraft / airline aircraft	—	Not permitted — must be released by a Part-145 organisation

Complex maintenance tasks (Part-M Appendix VII) include, for example: modification, repair or replacement by riveting, bonding, laminating or welding of spars, spar flanges, wing main ribs, longerons, frames, engine mounts, landing gear struts, axles and wheels; repairs of skin needing a jig or fixture, or of pressurised skin with damage over 15 cm (6 in) in any direction; repair of load-bearing control-system parts; and dismantling/reassembly of a piston engine (other than for access to cylinders or the rear accessory cover) or of reduction gears — these need an approved organisation.

Privileges and conditions

• The licence (Part-66, category B1, B2, B2L, B3 or L) with the appropriate ratings defines what may be certified (66.A.20(a)). B1/B3 cover structure, powerplant, mechanical and electrical systems plus simple-test avionics; B2/B2L cover avionics and electrical work within their ratings.
• 66.A.20(b) still applies: compliance with Part-M/Part-ML; 6 months of relevant experience in the preceding 2 years; adequate competence for the aircraft; language ability for the documentation.
• There is no company authorisation, so the engineer personally must make sure they are competent and current — there is no organisation to check them.
• The engineer may be assisted by other persons under their direct and continuous control (ML.A.801(d), M.A.801(d)).
• A CRS must not be issued if there is any known non-compliance that endangers flight safety (ML.A.801(g)).