What should be done immediately before adding fluid to a shock strut?

Before adding fluid to a shock strut, it is important to collapse the strut. This allows for the proper measurement and adjustment of the fluid level within the strut system. When the strut is collapsed, the internal components, including the piston, are positioned to allow for accurate fluid measurement and prevent overfilling. This process ensures that the strut can function properly once reassembled and recharged with fluid. Proper fluid levels are crucial for the strut's damping capabilities and overall performance.

Collapsing the strut also helps in expelling any air trapped inside the assembly, which could affect its operation. Therefore, this step is essential for maintaining the integrity and functionality of the shock strut system.