Which part of aeronautical regulations deals with the governance of mechanical operations?

The section of aeronautical regulations that governs mechanical operations is 14 CFR 43. This regulation outlines the maintenance, preventive maintenance, and alterations of aircraft and their components, establishing the required standards for these activities. It covers the general rules governing the maintenance of civil aircraft, ensuring safety, airworthiness, and compliance with federal aviation regulations.

While the other options also have their relevance in the realm of aviation regulations, they focus on different aspects. For instance, 14 CFR 65 pertains to certification of airmen and aviation maintenance technicians, detailing qualifications and responsibilities rather than direct governance of mechanical operations. 14 CFR 91 addresses general operating and flight rules, governing operational flying activities more broadly than specific mechanical procedures. AC 43.13-3 serves as guidance material offering acceptable methods for maintenance and alterations, complementing the standards set by 14 CFR 43 but not serving as a regulatory standard in itself. Thus, 14 CFR 43 is the direct regulation that covers the governance of mechanical operations in aeronautics.