How does the pilot control dissymmetry of lift?

How does the pilot control dissymmetry of lift?

• A. Blade Flapping
• B. Cyclic Feathering
• C. Collective Pitch
• D. Throttle

Answer: (B)

Dissymmetry of lift in forward flight occurs because the advancing blade segment cuts through the air faster than the retreating segment, creating more lift on one side of the rotor disk. To keep the aircraft level, the pilot actively modulates lift across the disk by cycling the blade pitch as it passes through each azimuth. This cyclic feathering adjusts the angle of attack of each blade in time with its position, reducing lift on the advancing side and increasing lift on the retreating side. The result is a balanced lift distribution that prevents the fuselage from tilting toward the advancing blade. Blade flapping does help physically by tilting the rotor plane and can mitigate some effects, but it’s a passive blade response, not the pilot’s direct method for controlling dissymmetry. Collective pitch changes lift evenly on both blades, so it doesn’t address the asymmetric distribution, and throttle affects engine power, not the lift balance across the rotor disk.

Dissymmetry of lift in forward flight occurs because the advancing blade segment cuts through the air faster than the retreating segment, creating more lift on one side of the rotor disk. To keep the aircraft level, the pilot actively modulates lift across the disk by cycling the blade pitch as it passes through each azimuth. This cyclic feathering adjusts the angle of attack of each blade in time with its position, reducing lift on the advancing side and increasing lift on the retreating side. The result is a balanced lift distribution that prevents the fuselage from tilting toward the advancing blade.

Blade flapping does help physically by tilting the rotor plane and can mitigate some effects, but it’s a passive blade response, not the pilot’s direct method for controlling dissymmetry. Collective pitch changes lift evenly on both blades, so it doesn’t address the asymmetric distribution, and throttle affects engine power, not the lift balance across the rotor disk.