Which type of blade angle is used to minimize drag when the engine is shut down?

When the engine is shut down, a feather blade angle is used to minimize drag. Feathering involves adjusting the pitch of the blades to a nearly horizontal position relative to the airflow. This configuration reduces the surface area facing the oncoming wind, effectively decreasing the drag on the aircraft.

In the event of an engine failure, feathering the propeller allows the aircraft to maintain a better glide profile and enhances overall aerodynamic efficiency. This is especially important for multi-engine airplanes, where a failed engine could lead to significant asymmetrical thrust and drag issues.

For context, a zero blade angle typically provides little to no thrust or drag reduction because the blades are positioned to neither produce lift nor minimize drag effectively. A positive blade angle would create lift, which is counterproductive when the engine isn't functioning, while a negative blade angle could increase drag because it can expose more of the blade surface to the airflow. Thus, the use of feather blade angle is a critical procedure for drag management and safe flight operations during an engine shutdown scenario.