Self-tapping sheet metal screws are used to hold what onto an aircraft?

• A. They may be used to attach engine components.
• B. They may be used to secure primary structural joints.
• C. They may be used to hold nonstructural components onto the aircraft.
• D. They are used to seal fuel lines.

Answer: (C)

Self-tapping sheet metal screws are designed for light, removable fastening of items to the aircraft skin or structure without becoming part of the primary load path. They tap their own threads in thin sheet metal, making them convenient for attaching nonstructural components such as interior panels, brackets, fairings, or light equipment. They’re not used for primary structural joints because they don’t provide the necessary strength or load paths required for critical airframe connections, and they aren’t suitable for sealing fuel lines, which require proper fittings and seals. Engine components and other critical systems typically use more robust fasteners and hardware. So, the best use is to hold nonstructural components onto the aircraft.