In modern aircraft repair, which of the following is NOT one of the common types of glue used?

In modern aircraft repair, casein glue is not commonly used. Casein glue is a type of protein adhesive derived from milk, and while it has historical significance and was used in earlier woodworking projects, it has largely fallen out of favor in contemporary aviation applications.

The other types of glue mentioned—phenol-formaldehyde glue, epoxy resin glue, and resorcinol glue—are favored in modern aircraft repair due to their superior bonding strength, durability, moisture resistance, and overall performance under the varied stresses encountered in aviation environments. Phenol-formaldehyde is particularly valued for its water resistance and thermal stability, making it suitable for structural applications. Epoxy resins offer exceptional bonding capabilities and resistance to chemicals, making them highly versatile in both structural and non-structural repairs. Resorcinol glue is known for its flexibility and long-lasting bond, making it ideal for use in wood-laminate construction and other applications requiring durability under loading conditions.