What adjustment corrects for the increasing speed and angle of attack of propeller blade elements from hub to tip?

• A. Blade tilt
• B. Blade twist
• C. Blade sweep
• D. Blade root

Answer: (B)

Blade twist is the variation of pitch along the length of a propeller blade. It’s used to keep the angle of attack roughly the same from hub to tip even as the element speed increases with radius. In a rotating blade, the tangential velocity grows with distance from the hub, which changes the relative wind direction each section sees. If the blade kept a uniform pitch, inner and outer sections would experience different angles of attack, leading to inefficient lift distribution or even stall near the tips. By twisting the blade so the pitch is greater toward the tip, the local angle between the blade and the incoming flow is adjusted to maintain a similar, usable angle of attack across the blade. This is why blade twist is the adjustment chosen. Other features like tilting the blade, sweeping it, or altering the root location affect geometry in other ways and don’t specifically tailor the angle of attack along the radius.