During assembly, what indicates that control surfaces are correctly aligned?

The indication that control surfaces are correctly aligned is determined by multiple factors, all of which contribute to the overall functionality and safety of the aircraft.

Consistent gap spacing refers to the space between the control surface and the stationary part of the aircraft, such as the wing or fuselage. This spacing is crucial because it affects aerodynamic performance and ensures that there are no obstructions or excessive drag.

Uniform travel arcs involve the path that the control surfaces take when moved. When these surfaces are aligned correctly, they should move smoothly and predictably along their designated travel arcs, which is essential for maintaining control and stability during flight.

Operational specifications provide the engineering standards and limitations that dictate how the control surfaces should be positioned and function. Adhering to these specifications is vital for safety and ensures that the aircraft operates as intended under various flight conditions.

Since all these factors play a role in the alignment and performance of control surfaces, the correct indication that they are aligned can be derived from observing consistent gap spacing, uniform travel arcs, and adherence to operational specifications. Therefore, selecting the option that includes all of these aspects accurately reflects the comprehensive nature of the assessment for proper assembly and rigging of control surfaces.