Which type of seal is a primary seal, post assembly, formed when the sealant is spread along the seam with a sealant gun?

The type of seal referred to as a primary seal formed post-assembly when sealant is applied with a sealant gun is known as a bead seal. Bead seals are created by depositing a continuous line or "bead" of sealant along the seams of the assembly to create a watertight or airtight barrier. This method ensures proper coverage and adhesion to the surfaces being joined, which is critical in aerospace applications where structural integrity and the prevention of leaks are paramount.

Fillet seals, while also important in certain contexts such as fillet welds, do not specifically refer to the application method used with a sealant gun along seams. Injection seals typically involve filling a cavity or void under pressure, which is different from the bead method. Cap seals refer to seals that cover an area, not necessarily formed in a linear manner along a seam. Thus, the bead seal is specifically suited to the described method of application.