Which part of the assembly does not require an assembly jig during assembly?

The engine typically does not require an assembly jig during assembly because of the way it is designed and manufactured. Unlike other components that may need precise alignment or support during assembly, engines are often built in isolation or with a modular approach.

Engines are constructed using various subassemblies that can be assembled separately before being integrated into the aircraft. This modularity allows for greater flexibility during the assembly process and reduces the need for a jig, which is primarily used for maintaining alignment and structure during the assembly of components that are more interconnected or complex, like airframes, wings, or tail sections.

Precision is still critical in engine assembly, but the techniques often involve specialized tooling and fixtures rather than a traditional assembly jig. This means that while precision and accuracy are vital in engine assembly, the unique characteristics of engine components allow for their assembly without the need for the specific jigs that might be necessary for the other parts of the aircraft.