The axis around which the pitch angle of a rotor blade is varied, sometimes referred to as the spanwise axis, is called what?

The axis around which the pitch angle of a rotor blade is varied, sometimes referred to as the spanwise axis, is called what?

• A. Direct Shaft Turbine
• B. Disk Area
• C. Feathering Axis
• D. Drag

Answer: (C)

Feathering axis is the axis around which the rotor blade’s pitch angle is varied. This spanwise axis runs along the length of the blade (root to tip), and the blade is rotated about it to change its angle of attack as inputs from the collective and cyclic are applied. That’s why this axis is called feathering—the blade can “feather” to a different pitch to produce the desired lift or reduce drag. The other options don’t describe an axis for changing blade pitch: a direct shaft turbine relates to the engine, disk area is a geometric measure, and drag is an aerodynamic force, not an axis for pitch variation.

Feathering axis is the axis around which the rotor blade’s pitch angle is varied. This spanwise axis runs along the length of the blade (root to tip), and the blade is rotated about it to change its angle of attack as inputs from the collective and cyclic are applied. That’s why this axis is called feathering—the blade can “feather” to a different pitch to produce the desired lift or reduce drag. The other options don’t describe an axis for changing blade pitch: a direct shaft turbine relates to the engine, disk area is a geometric measure, and drag is an aerodynamic force, not an axis for pitch variation.