How is metal tubing generally sized in aviation?

In aviation, metal tubing is primarily sized by its outside diameter and wall thickness. This method is advantageous because it allows for standardized fittings and connections, which are critical in maintaining the structural integrity and safety of aircraft systems. The outside diameter is essential for ensuring that the tubing fits properly within the spaces designed for it and aligns correctly with other components, while the wall thickness is vital for determining the tubing's strength, weight, and pressure capacity.

By focusing on these two measurements, engineers can accurately design systems that can withstand the operational conditions aircraft face, including variations in pressure, temperature, and stress during flight. This consistent sizing approach also facilitates easier replacements and repairs, as standardized size specifications are critical in ensuring compatibility across different aircraft models and components.