Performance rules (general)

§ 43.13 is the how-to standard for all maintenance, preventive maintenance, and alterations — it tells anyone doing the work *how well* it must be done.

• (a) Methods, techniques, and practices: use those in the current manufacturer's maintenance manual or Instructions for Continued Airworthiness, or other methods acceptable to the Administrator, and use the tools, equipment, and test apparatus needed to do the job to accepted industry practice — including any special equipment the manufacturer recommends, or an acceptable equivalent.
• (b) The result: the work must be done with materials and workmanship such that the item's condition is at least equal to its original (or properly altered) condition — in aerodynamic function, structural strength, resistance to vibration and deterioration, and other qualities affecting airworthiness.
• (c) For air-carrier and certain commercial operators (Parts 121/135/129), following their FAA-required maintenance manual is an acceptable means of compliance.

In plain terms: do it the manufacturer's way (or an FAA-acceptable way), with the right tools, so the aircraft ends up at least as good as it was — that's the legal floor for maintenance quality.

Summary: § 43.13 sets the quality standard for maintenance: use the manufacturer's (or FAA-acceptable) methods, techniques, and proper tools/test equipment, and do the work so the item is at least equal to its original or properly altered condition in strength, function, and airworthiness.