What constitutes an airframe major repair?

An airframe major repair typically involves significant alterations or repairs that could affect the aircraft's structural integrity and safety. The repair of portions of skin sheets by making additional seams falls under this category because it directly impacts the aircraft's structural components. Skin sheets are critical to the airframe's aerodynamic qualities and strength, and making repairs or modifications to them can have substantial implications on the overall performance and safety of the aircraft.

This type of repair generally requires extensive documentation and possibly re-evaluation of the aircraft's airworthiness, due to the critical nature of the structural integrity maintained by the skin sheets. In contrast, other options, such as simple structural modifications, adding communication equipment, or minor adjustments to landing gear, do not typically involve significant structural changes that would warrant classification as a major repair in compliance with aircraft regulations.