Which source is NOT considered approved technical data for major alterations on U.S. certificated aircraft?

The correct answer identifies a source that does not qualify as approved technical data for major alterations on U.S. certificated aircraft. While AC 43.13-2A provides guidance and acceptable methods, techniques, and practices for aircraft maintenance and alterations, it is not considered "approved" in the sense required for major alterations. It serves as a reference but does not have the same regulatory authority as other documents listed.

In contrast, FAA Advisory Circulars, Manufacturer Maintenance Manuals, and Airworthiness Directives are recognized as approved technical data. FAA Advisory Circulars provide official guidance and are widely accepted as a reference for maintenance practices. Manufacturer Maintenance Manuals are specific to aircraft models and contain detailed instructions and specifications that are vital for the correct and safe alteration of aircraft. Airworthiness Directives are issued by the FAA to require specific actions to ensure continued airworthiness and must be complied with, making them a definitive source of approved technical data.

Understanding these distinctions helps appreciate why only one of the listed sources does not meet the criteria for approved technical data regarding major alterations on certificated aircraft.