What does a differential pressure test evaluate in an aircraft engine?

A differential pressure test is primarily used to evaluate the condition of the engine air filtration system, making this the correct choice. During this test, the pressure difference between the upstream and downstream sides of the air filter is measured. A significant drop in pressure indicates that the filter may be clogged or contaminated, which can restrict airflow to the engine. Adequate airflow is crucial for engine performance and efficiency, so monitoring the condition of the air filtration system is vital for ensuring optimal engine operation.

The other options do not accurately describe the purpose of a differential pressure test. The overall performance of the engine, fuel system pressures, and sound levels of the engine are evaluated using different methods and tests specific to those aspects, rather than through a differential pressure test, which specifically focuses on the integrity of the air filtration system.