Which component is a flapping hinge that enables feathering and restoring forces in the rotor system?

Which component is a flapping hinge that enables feathering and restoring forces in the rotor system?

• A. Delta Hinge
• B. Cyclic Feathering
• C. Cyclic Pitch Control
• D. Direct Control

Answer: (A)

The important idea here is the mechanism that allows a rotor blade to move about a hinge so lift differences between the blades can be balanced. A flapping hinge at the blade root lets the blade rise and dip as the rotor spins. This up-and-down motion creates a restoring moment that helps bring the blade back toward the plane of rotation, stabilizing the rotor disk during forward flight when the advancing blade tends to produce more lift than the retreating blade. The specific hinge designed to provide this flapping motion in many two-blade systems is the Delta hinge. Feathering and blade pitch changes are handled by the pitch-change mechanism and controls, not by the hinge itself, so they’re separate functions. Therefore, the Delta hinge is the component described.

The important idea here is the mechanism that allows a rotor blade to move about a hinge so lift differences between the blades can be balanced. A flapping hinge at the blade root lets the blade rise and dip as the rotor spins. This up-and-down motion creates a restoring moment that helps bring the blade back toward the plane of rotation, stabilizing the rotor disk during forward flight when the advancing blade tends to produce more lift than the retreating blade. The specific hinge designed to provide this flapping motion in many two-blade systems is the Delta hinge. Feathering and blade pitch changes are handled by the pitch-change mechanism and controls, not by the hinge itself, so they’re separate functions. Therefore, the Delta hinge is the component described.