How are specification markings identified on aircraft tubing materials?

Specification markings on aircraft tubing materials are essential for identifying the properties, standards, and specifications that the tubing meets. These markings are typically printed on the outside of the tubing, which ensures they are easily visible and legible for inspection and verification purposes during manufacturing, maintenance, and assembly processes. The external marking facilitates easy access for personnel who need to quickly assess the tubing to ensure compliance with the necessary aviation regulations and standards.

Marking the inside of the tubing would diminish the practicality of verification, as it would require disassembly or other intrusive methods to access this information. Using stickers could lead to issues such as peeling, damage, or removal over time, which could result in loss of critical identification information. Logging details in a database, while useful for record-keeping, does not provide immediate visibility during physical inspections and therefore is not suitable as a standalone method for identification on the actual tubing itself.