How are sizes of flexible hoses designated?

Flexible hoses are designated by the inside diameter, which is critical for ensuring compatibility with the fluid dynamics required in various aviation systems. The measurement is done in 1/16th inch increments to provide a precise sizing that accounts for differences in fluid flow, pressure, and temperature tolerances. This detailed measurement is essential to fit the hose within fittings and systems correctly, ensuring that there are no restrictions or leaks.

The inside diameter measurement allows technicians to select hoses that will allow the intended flow rates and pressures within the aircraft's hydraulic, fuel, or pneumatic systems, thereby maintaining operational efficiency and safety. Using the outer diameter, pressure ratings, or hose length alone would not adequately ensure that the hose meets the specific needs of a system, as these aspects do not provide information about the actual passageway through which fluids will travel.