Which hinge allows a rotor blade to flap to balance lift between advancing and retreating blades?

Which hinge allows a rotor blade to flap to balance lift between advancing and retreating blades?

• A. Pitch Hinge
• B. Flapping Hinge
• C. Master Hinge
• D. Rotary Hinge

Answer: (B)

The idea being tested is how a rotor blade can automatically balance lift between the advancing and retreating sides of a rotor disk. This balance is provided by a hinge that lets the blade move up and down in the flap plane. That upward movement on the advancing blade and the corresponding downward movement on the retreating blade adjust the angle of attack relative to the air the blade sees, so the faster-advancing blade doesn’t pull the rotor disk off-center and the retreating blade can contribute more lift as needed. This mechanism is what allows the rotor to maintain smooth, even lift across the disk without manual input. The hinge that makes this possible is the flapping hinge. Pitch hinges control the blade’s angle of attack through cyclic and collective input rather than allowing vertical motion of the blade; the other terms aren’t the standard means by which flapping is achieved.

The idea being tested is how a rotor blade can automatically balance lift between the advancing and retreating sides of a rotor disk. This balance is provided by a hinge that lets the blade move up and down in the flap plane. That upward movement on the advancing blade and the corresponding downward movement on the retreating blade adjust the angle of attack relative to the air the blade sees, so the faster-advancing blade doesn’t pull the rotor disk off-center and the retreating blade can contribute more lift as needed. This mechanism is what allows the rotor to maintain smooth, even lift across the disk without manual input.

The hinge that makes this possible is the flapping hinge. Pitch hinges control the blade’s angle of attack through cyclic and collective input rather than allowing vertical motion of the blade; the other terms aren’t the standard means by which flapping is achieved.