How is the blade twisted along the span of the rotor blade?

How is the blade twisted along the span of the rotor blade?

• A. Uniform Angle Of Incidence
• B. Higher Angle Of Incidence At The Root; Lower Angle Of Incidence At The Tip
• C. Higher Angle Of Incidence At The Tip; Lower Angle Of Incidence At The Root
• D. No Twist

Answer: (B)

Rotating rotor blades experience different relative wind speeds along their span: the tip moves much faster than the root. If the blade had a uniform angle of attack, the tip would generate considerably more lift than the root, leading to excessive loading and potential stall at the outer sections and undesirable bending moments. To balance this, the blade is twisted so that the angle of incidence is higher at the root and lower toward the tip. This setup reduces the angle of attack where the airspeed is greatest and increases it where it’s slower, producing a more even lift distribution along the span and improving overall performance and structural loads. A uniform angle or twisting in the opposite direction would not achieve this balance; it would either over-stress the tip or under-lift the root, leading to inefficiency and handling issues.

Rotating rotor blades experience different relative wind speeds along their span: the tip moves much faster than the root. If the blade had a uniform angle of attack, the tip would generate considerably more lift than the root, leading to excessive loading and potential stall at the outer sections and undesirable bending moments.

To balance this, the blade is twisted so that the angle of incidence is higher at the root and lower toward the tip. This setup reduces the angle of attack where the airspeed is greatest and increases it where it’s slower, producing a more even lift distribution along the span and improving overall performance and structural loads.

A uniform angle or twisting in the opposite direction would not achieve this balance; it would either over-stress the tip or under-lift the root, leading to inefficiency and handling issues.