What is the primary role of an aircraft engine?

The primary role of an aircraft engine is to turn the propeller. In traditional propeller-driven aircraft, the engine generates thrust by converting fuel into energy, which then drives the propeller. This rotation creates a forward motion that pushes the aircraft through the air, allowing it to gain speed and ultimately achieve lift via the wings.

While it is true that engines are involved in lift generation, especially in jet aircraft, the specific action of turning the propeller is fundamental to generating thrust in propeller-driven designs. Additionally, aspects such as aerodynamic stability and passenger comfort, though important for overall flight performance and experience, do not define the essential operational function of an aircraft engine.