Which of the following are variations of turboprop inlet ducts?

The variations of turboprop inlet ducts primarily include designs that optimize airflow into the engine and contribute to overall engine performance. The correct choice highlights three distinct types: ducted spinner, streamline spinner, and underscoop.

A ducted spinner design incorporates a spinner that is streamlined to enhance airflow directly into the engine, reducing drag and increasing efficiency. The streamline spinner is specifically crafted to minimize turbulence and maintain smooth airflow around the engine entrances. The underscoop design, on the other hand, allows for an inlet that is positioned lower than the engine, which helps in drawing in air effectively, especially during varying flight conditions.

These designs are integral in achieving the necessary airflow characteristics needed for the engine to function efficiently and reliably. In summary, the combination of resourceful designs in the chosen option exemplifies the ingenuity in turboprop inlet duct variations, all aimed at optimizing performance and aerodynamic stability.