What forms can the action required by an Airworthiness Directive (AD) take?

The action required by an Airworthiness Directive (AD) can take multiple forms, which is why the correct answer encompasses inspection, part replacement, design modification, and/or a change in procedures. Each of these actions is intended to address safety issues identified in an aircraft or its components.

For example, inspections are mandated to ensure that the equipment is functioning as intended and to identify any potential problems before they lead to failures. Part replacement can be necessary when certain components are found to be defective or no longer meet safety standards. Design modifications may be required when a specific design flaw is identified that could impact the aircraft's overall safety or performance. Changes in procedures might be needed to enhance operational safety or to comply with new regulations emerging from the findings of an AD.

This multifaceted approach ensures that all possible aspects that could affect airworthiness are addressed comprehensively, thereby promoting enhanced safety for aircraft operations. The options centered only on inspections or repairs, design modifications, or maintenance records do not capture the full spectrum of actions that might be mandated by an AD, which is why they are not the correct choice.