What type of rivet is indicated by the specification MS20426AD?

The specification MS20426AD refers specifically to a rivet type that has a countersunk head. This is indicated by the 'C' in the specification, which designates the countersunk head style. Countersunk rivets are designed to sit flush with the surface of the material, providing a smooth finish and reducing aerodynamic drag, which is particularly important in aviation applications where streamlined surfaces are desirable.

The 'AD' designation signifies that the rivet has a specific material and strength characteristics, further connecting the specification to a particular type of application, typically used in airframe structures where a flush surface is required.

In contrast to other types of rivets, such as solid or blind rivets, the countersunk rivet is unique in that it is meant to be flush with the surface, making it suitable for aerodynamic or aesthetic considerations. Understanding these distinctions helps in recognizing the appropriate rivet types for various structural applications, particularly in aircraft design.