What requirement must replacement ribs meet?

Replacement ribs must match the original contour to ensure proper fit and function within the aircraft structure. This is crucial because ribs are integral components that support the airframe, controlling the shape and aerodynamic characteristics of the wing or structure they are part of. If the replacement ribs do not conform to the original contour, it could lead to structural weaknesses, potential failure during flight, or altered aerodynamic properties, which can affect performance and safety.

The design and integrity of an aircraft’s components are meticulously engineered, and any modifications or replacements need to adhere to specified dimensions and shapes to maintain the intended performance characteristics. Matching the original contour helps ensure that the load distribution and stress responses are as designed during flight operations.