How should placards be displayed in a Part 23 airplane?

Placards in a Part 23 airplane must be displayed in a manner that is necessary for operation and should be conspicuously placed. This requirement is in place to ensure that critical information is easily visible and accessible to the pilot and crew, which is vital for safe aircraft operation. Visibility of the placards helps provide important operational instructions, limitations, or warnings that are essential during flight operations and maintenance.

Proper placement ensures compliance with airworthiness standards and contributes to the overall safety protocols required for aircraft operation. The requirement for placards to be conspicuous aligns with regulations and best practices in aviation, adapting to the environment where the information is most needed, which typically includes locations such as instrument panels or other highly visible areas within the aircraft.

The other options do not fully encompass the regulatory requirements or practical needs for effective communication of information through placards in the aircraft. For example, restricting placard placement to only the exterior, only in the cockpit, or simply within the maintenance manual does not meet the standard of conspicuity required for operational safety.