What’s Feathering? (Propeller)

Ref untitled (cast-safety.org)

原文: “On a variable pitch propeller, the drag can be minimized by rotating the blades until they are edgewise to the flight direction. This is called feathering the propeller.”

Why we need “feathering the propeller”?  /  When we need to “feathering the proeller”?

When an engine is shutdown in flight, an unfeathered propeller presents a large, flat surface face-on into the airstream. This can result in high drag on the airplane.

What if we don’t feather the propeller?

Since the propeller is free to turn, it acts as a windmill, with the force of the air turning the propeller. The force extracted from the air causes drag on the airplane. Additionally, the windmilling of the propeller causes the engine to rotate. When the propeller drives the engine (rather than the intended situation of the engine driving the propeller), the situation is called negative torque.

On a variable pitch propeller, the drag can be minimized by rotating the blades until they are edgewise to the flight direction. This is called feathering the propeller. At this angle, the propeller does not rotate or rotates slowly; thus, its drag on the airplane is greatly reduced. Engine failure or malfunction may or may not require feathering the propeller, depending on the type of problem. Additionally, certain problems require prompt feathering to avoid serious drag issues. Knowing when or if it is necessary to feather the propeller is critical.

(Some of these situations are covered below.) The Airplane Flight Manual (AFM) data for single engine performance and VMC typically assumes that the propeller is feathered, unless special instructions are provided. –>指的就是 refer AFM/POH or 有特別指引~