What serves as a guide for range marking of aircraft instruments?

The guidance for range marking of aircraft instruments primarily comes from the aircraft specifications or type certificate data sheets. These documents provide crucial information about the aircraft's design, including performance characteristics and limitations. Range markings on instruments, such as those indicating maximum and minimum speeds, engine temperatures, or pressures, are established based on the operational limits defined in these specifications.

Utilizing the aircraft specifications ensures that the markings are accurate and appropriate for the specific aircraft type, thereby promoting safety and compliance with regulatory standards. This helps pilots operate within the safe parameters that have been determined during the aircraft's certification process.

The other choices, while they might contain useful information about the aircraft, do not directly establish range markings in the same authoritative manner as the type certificate data sheets. The pilot's manual may provide operational guidance, the aircraft maintenance manual focuses on maintenance procedures, and FAA regulations give overarching rules but do not specifically address range markings for individual instruments.