Which rotor system permits blades to feather but not flap or hunt?

Which rotor system permits blades to feather but not flap or hunt?

• A. Rigid Rotor
• B. Semi-Ridged Rotor
• C. Fully Articulated Rotor
• D. Hybrid Rotor

Answer: (A)

In this question, the key idea is how the rotor design handles blade motion versus blade pitch. Feathering is about changing the blade’s pitch angle to present the blade edge-on to the wind and reduce drag. Flapping and hunting are motions the blade can make about hinges: up-and-down movement (flap) and forward-backward movement (lead-lag). A rigid rotor keeps the blade and hub as one solid unit with no hinges, so there’s no flap or hunt possible. You can, however, still change the blade’s pitch to feather it when needed. So this rotor system lets you feather without allowing flap or hunt. In contrast, other rotor types incorporate hinges that permit flap and/or lead-lag motion, so they don’t fit the “feather but no flap or hunt” condition.

In this question, the key idea is how the rotor design handles blade motion versus blade pitch. Feathering is about changing the blade’s pitch angle to present the blade edge-on to the wind and reduce drag. Flapping and hunting are motions the blade can make about hinges: up-and-down movement (flap) and forward-backward movement (lead-lag). A rigid rotor keeps the blade and hub as one solid unit with no hinges, so there’s no flap or hunt possible. You can, however, still change the blade’s pitch to feather it when needed. So this rotor system lets you feather without allowing flap or hunt. In contrast, other rotor types incorporate hinges that permit flap and/or lead-lag motion, so they don’t fit the “feather but no flap or hunt” condition.