Which statement is true regarding the hierarchy of TDs?

The correct answer highlights the significance of Formal Changes within the hierarchy of technical directives (TDs). Formal Changes represent the primary documents used for configuration changes, indicating that they contain the official specifications and required alterations approved for implementation. This makes them essential for ensuring that all systems operate with the latest updates and modifications that have been rigorously reviewed and sanctioned.

Formal Changes provide a structured method for documenting necessary updates and often entail significant changes to procedures, equipment alterations, or safety protocols that are critical for operational integrity. As such, they hold a crucial role in maintaining the effectiveness and safety of naval aviation assets.

The other statements are not accurate representations of the hierarchy within TDs. For instance, Urgent Action TDs are designed to address critical safety or performance issues, making them more urgent compared to Routine Action TDs. Additionally, Bulletins serve more as interim guidance rather than as critical directives, which does not place them above or below other categories such as Interim Changes. Understanding these classifications helps maintain the effectiveness of maintenance practices and the safety of operations within Navy Naval Aviation.