What is the correct way to shut down an engine?

Moving the mixture control to ICO, which stands for "Idle Cut-Off," is the appropriate method for shutting down an engine because it effectively cuts off the fuel supply to the engine's cylinders. By doing this, you ensure that the engine stops running cleanly without any residual fuel potentially leading to flooding or unwanted maintenance issues.

This procedure helps to avoid any potential backfiring or rough shutdown associated with an improper mix of fuel and air, contributing to a smoother and safer engine shutdown process. It's a standard practice in many aviation operations and is crucial for ensuring that the engine is completely starved of fuel when it is no longer in use.

Other methods like switching off the fuel booster pump or magnetos may not effectively stop the engine as decisively as pulling the mixture to ICO, which introduces a controlled shutdown process directly linked to the fuel supply. While feathering the propeller is relevant for specific scenarios, particularly in multi-engine aircraft for reducing drag after shutdown, it is not a universal step for engine shutdown across all engine types.