At what stage of assembly should weight and balance be checked?

The weight and balance of an aircraft should be checked after all major components are installed to ensure that the aircraft is within safe operational limits. At this stage, all significant components, such as the engine, fuel, avionics, and control surfaces, have been added, which directly affect the aircraft's overall weight and its center of gravity. Proper weight and balance checks are crucial to ensure that the aircraft performs safely and efficiently during flight.

Checking weight and balance before component installation would not provide an accurate assessment, as major parts essential to the aircraft's weight and balance have not yet been accounted for. Evaluating it during paint application would not be appropriate, as the painting process does not significantly affect the structural weight or balance in a way that increases safety or functionality. Finally, pre-flight checks are typically conducted just prior to takeoff and serve to verify operational condition rather than any significant adjustments in weight and balance that would arise from component installations. Thus, the most relevant time for checking weight and balance is after all major components have been installed.