Why is it essential to visually inspect every countersink?

Visually inspecting every countersink is essential primarily to check for defects. This inspection process ensures that the countersink is executed properly, which is crucial for maintaining the structural integrity and performance of the assembly. Any defects, such as irregular shaping, cracks, or improper depth, can lead to issues like stress concentrations, which can eventually cause failure under load.

While aesthetic purposes and ensuring paint adherence are considerations, they do not encompass the critical safety and functionality aspects that defects can impact. Confirming part color is relevant in certain scenarios, but it does not contribute to the structural integrity that the inspection of countersinks aims to safeguard. Therefore, focusing on defect detection is vital for reliable and safe aircraft assembly.