Where are placards required on an aircraft specified?

Placards required on an aircraft are specified in the Aircraft Specifications or Type Certificate Data Sheets. These documents provide essential information about the aircraft's design and operational limitations, and they include details on any required markings, including placards. Such placards serve crucial safety functions, conveying important operational instructions and limitations that pilots and crew must be aware of to operate the aircraft safely.

While the other options may include relevant information related to the aircraft, they do not specifically outline the mandatory placard requirements as comprehensively as the Aircraft Specifications or Type Certificate Data Sheets. The pilot's handbook primarily serves as a guide for operation and procedures, while the manufacturer’s service manuals detail maintenance and servicing information. Aviation safety guidelines, on the other hand, encompass a broader range of safety regulations but do not typically specify individual aircraft placard requirements. Therefore, the correct and most authoritative source for placards on an aircraft is indeed found in the Aircraft Specifications or Type Certificate Data Sheets.