Which design describes how blade flap and lead-lag movement are accomplished?

• A. The elasticity of the blades
• B. Hydraulic dampers
• C. Swashplate
• D. Counterweights

Answer: (A)

Blade motion in the rotor is enabled by the blade’s own flexibility. When a blade is loaded, it can bend and twist because the material and shape are elastic, allowing it to deflect upward or downward (flap) and to lag or lead slightly in the plane of rotation as lift and drag change. This elastic response provides the passive compliance needed for flap and lead-lag movements to occur smoothly during each revolution. The other options describe devices that influence pitch input or damp or balance the system, but they don’t fundamentally create the blade’s flap and lag motion.