What is defined as a major repair in aviation?

A major repair in aviation is defined as any repair that affects the flight characteristics of the aircraft. This definition recognizes that certain modifications or repairs can significantly influence how an aircraft handles and its overall safety performance. Changes in structural components, control surfaces, or other systems that contribute to the aircraft's ability to fly safely fall under this category.

For example, if an aircraft's wing structure is repaired or modified, it can alter its lift and performance characteristics, making it critical to ensure that such repairs are conducted following stringent regulations and guidelines.

In contrast, the other options involve tasks that are generally considered minor in comparison. Minor adjustments to instruments, painting exterior surfaces, and servicing avionics are routine maintenance activities that do not fundamentally alter the flight characteristics or capabilities of the aircraft. Thus, they do not meet the criteria for what constitutes a major repair.