Nacelle:
A nacelle is a streamlined enclosure that houses the engine, accessories, and other components of a propeller-driven aircraft. It is usually located on the wings of the aircraft and is designed to reduce drag and improve the overall aerodynamic efficiency of the aircraft. The nacelle also provides protection for the engine and its components from the elements and from damage caused by debris or other objects.
Cowling:
A cowling is a removable cover that encloses the engine of a piston-engine aircraft. It is primarily designed to direct the flow of air over the engine for cooling purposes. The cowling also helps to reduce drag and improve the aircraft's overall aerodynamic performance. In addition, the cowling can provide access to the engine for maintenance and repairs.
In summary, the main difference between a nacelle and a cowling is that a nacelle is an enclosure for an engine and its components, while a cowling is a removable cover that primarily serves to direct airflow for cooling purposes.
