For aircraft certified under which CFR is structural inspection intervals mandatory?

Aircraft certified under Part 23 of the Code of Federal Regulations (CFR) require mandatory structural inspection intervals. Part 23 pertains to Airworthiness Standards for Normal Category Airplanes, which means that these aircraft must adhere to specific structural integrity requirements to ensure safety during operation. This regulation emphasizes regular inspections to monitor the condition of the airframe and its components, helping prevent accidents caused by structural failures.

The mandatory intervals for structural inspections are established to promote safety, ensuring that potential fatigue or stress-related issues are identified and addressed in a timely manner. Compliance with these inspections is crucial for maintaining the airworthiness of these aircraft throughout their operational lives.

In contrast, other parts mentioned do not specifically impose these mandatory inspection intervals. For example, Part 21 covers the certification procedures for products and parts, Part 27 deals with airworthiness standards for Normal Category Rotorcraft, and Part 39 lists airworthiness directives, which are not specifically about routine structural inspection intervals.