What must a person disapproving an aircraft during an annual inspection do if a defect makes it unairworthy?

The correct action for someone disapproving an aircraft during an annual inspection due to a defect that renders it unairworthy is to provide a written notice of the defect to the owner. This step is crucial because it formalizes the identification of issues that need to be addressed, ensuring that the owner is fully informed of the aircraft's condition. The written notice also serves as an official record of the findings, which is important for legal and regulatory compliance.

This written notification helps the owner understand the specific issues affecting the aircraft's airworthiness, allowing them to take appropriate action, which may include repairs or maintenance. Additionally, documenting the defect protects both the inspector and the owner in case of future questions about the aircraft's maintenance or safety history.

The other options, while related to safety and inspections, do not fulfill the requirement of formally notifying the aircraft owner about the defects in a manner that is compliant with regulations regarding aircraft maintenance.