Which doubler requires heat treatment before installation?

The correct choice indicates that doubler 102 requires heat treatment prior to installation. Heat treatment is an important process in the fabrication of certain aircraft components, particularly those made from specific alloys that require it to achieve the desired mechanical properties, such as strength and ductility.

Doubler 102 likely falls within a category of materials or a specific design that is sensitive to the strength and integrity of the aircraft structure. The need for heat treatment ensures that this doubler can withstand the operational loads and stresses it will encounter once installed.

Understanding the specific requirements for installation, including whether a part needs to be heat-treated, is crucial for ensuring safety and compliance with aeronautical standards. Each doubler is designed with specific applications, and recognizing when heat treatment is necessary helps in maintaining the overall performance and safety of the aircraft.

In contrast, the other options may either be materials that do not require such treatment or fall under different specifications where heat treatment is unnecessary, reflecting a difference in their material properties or intended use in the aircraft structure.