How does the centrifugal twisting moment of an operating propeller tend to affect the pitch angle?

How does the centrifugal twisting moment of an operating propeller tend to affect the pitch angle?

• A. Increases it
• B. Reduces it
• C. Has no effect
• D. Oscillates

Answer: (B)

Centrifugal twisting moment causes the blade to untwist when the propeller is spinning, which reduces the pitch angle. As the blade rotates, centrifugal forces act outward along its length. This tends to straighten the blade and oppose the built-in twist that was designed into the blade. Since the blade is heavier toward the tip and the root is fixed, the resulting torsional effect is to decrease the twist along the span, especially toward the outer portions. So, at operating speed the effective pitch angle is reduced compared with the static pitch.

Centrifugal twisting moment causes the blade to untwist when the propeller is spinning, which reduces the pitch angle. As the blade rotates, centrifugal forces act outward along its length. This tends to straighten the blade and oppose the built-in twist that was designed into the blade. Since the blade is heavier toward the tip and the root is fixed, the resulting torsional effect is to decrease the twist along the span, especially toward the outer portions. So, at operating speed the effective pitch angle is reduced compared with the static pitch.