What is critical to ensure when installing control surfaces?

When installing control surfaces, ensuring functional operation and clearance is paramount. This means that the control surfaces must not only be positioned correctly but also operate effectively without any obstructions. Proper clearance is essential to avoid contact with other parts of the aircraft during operation, which could lead to mechanical failures or compromised flight safety.

Ensuring functional operation involves verifying that the control surfaces respond correctly to input commands, allowing pilots to maintain intended flight maneuvers. This focus on performance and safety is particularly important in aviation, where even minor issues with control surfaces can lead to significant consequences. While alignment might seem important for appearance, the actual functionality and safety of the aircraft take precedence. Other options like color matching and pressure holding capacity, while they may have their own relevance in different contexts, do not directly impact the operational integrity of control surfaces in the same critical way.