According to regulations, who determines the required instrument markings and placards in a Part 23 airplane?

The correct answer is that the FAA will define the required placards. This is because regulatory guidelines under Part 23, which applies to Normal Category Airplanes, specify that the Federal Aviation Administration (FAA) establishes standards for safety, including those for instrument markings and placards. These requirements are integral to ensuring that all aircraft meet consistent safety standards that enhance operational reliability and safety.

The FAA's involvement guarantees that all placards and markings adhere to safety regulations designed to inform pilots and maintenance personnel about critical operational limitations and operational procedures necessary for safe flight. This regulatory oversight is essential for uniformity across all aircraft types and helps maintain high safety standards in aviation.

The other choices do not align with the regulatory requirements established by the FAA. The applicant is responsible for compiling information but must do so within the framework established by the FAA, which means they cannot independently dictate the requirements for placards and markings. Operators and maintenance crews do rely on established guidelines and regulations but are not authorized to create their own requirements outside of FAA standards.