How does the helicopter compensate for dissymmetry of lift?

How does the helicopter compensate for dissymmetry of lift?

• A. Blade Flapping
• B. Cyclic Feathering
• C. Collective Pitch
• D. Tail Rotor Tilt

Answer: (A)

Dissymmetry of lift in forward flight means the advancing blade (the one moving into the air) tends to generate more lift than the retreating blade. If this were left uncorrected, the rotor disk would tilt toward the direction of travel. The primary way helicopters compensate is blade flapping. Each blade is mounted to flap up or down about a hinge as it rotates. In forward flight, the extra lift on the advancing blade makes it flap upward, which reduces its angle of attack and lift. The retreating blade flaps downward, increasing its angle of attack and lift. This up-and-down motion across the rotor disk evens out the lift distribution, keeping the rotor plane more level and the aircraft stable. The other controls—tail rotor tilt handles yaw, collective changes lift for all blades, and cyclic pitch adjusts attitude and trajectory but doesn’t inherently balance lift across the disk the way flapping does.

Dissymmetry of lift in forward flight means the advancing blade (the one moving into the air) tends to generate more lift than the retreating blade. If this were left uncorrected, the rotor disk would tilt toward the direction of travel. The primary way helicopters compensate is blade flapping. Each blade is mounted to flap up or down about a hinge as it rotates. In forward flight, the extra lift on the advancing blade makes it flap upward, which reduces its angle of attack and lift. The retreating blade flaps downward, increasing its angle of attack and lift. This up-and-down motion across the rotor disk evens out the lift distribution, keeping the rotor plane more level and the aircraft stable. The other controls—tail rotor tilt handles yaw, collective changes lift for all blades, and cyclic pitch adjusts attitude and trajectory but doesn’t inherently balance lift across the disk the way flapping does.