Which section of GACA relates to airworthiness standards for normal category rotocraft?

The section of GACA that pertains to airworthiness standards for normal category rotocraft is Part 27. This part specifically establishes the requirements and standards for the design, construction, and performance of rotorcraft designated for normal operations. It addresses critical safety aspects to ensure that these aircraft can operate safely under typical flight conditions.

Part 21 generally deals with the certification procedures for products and parts but does not focus specifically on rotorcraft or their particular standards. Part 5 outlines additional regulations concerning the personnel and operational standards of aviation authorities rather than specific aircraft types. Part 66 is concerned with the licensing of maintenance personnel and does not address airworthiness standards for rotocraft. Hence, Part 27 is the specific regulation that directly applies to the airworthiness standards for normal category rotocraft.