Which hinge permits the rotor blades of a semi-rigid rotor system to flap as a unit?

Which hinge permits the rotor blades of a semi-rigid rotor system to flap as a unit?

• A. Teetering Hinge
• B. Flap Hinge
• C. Hinge Joint
• D. Swashplate Hinge

Answer: (A)

The essential idea is that a semi-rigid rotor head uses a teetering hinge to let the two blades flap together about a single axis. That teetering hinge ties the blades to a common pivot, so when they move up or down in response to aerodynamic loads or gusts, they do so as a single unit rather than independently. This unison flapping helps keep the rotor disc aligned and reduces complex loads in the hub. If blades were able to flap independently (as with individual flap hinges) or if the mechanism relied on a generic hinge joint or on the swashplate alone, you wouldn’t get the same coordinated, one-axis flapping behavior that characterizes a semi-rigid, teetering rotor.

The essential idea is that a semi-rigid rotor head uses a teetering hinge to let the two blades flap together about a single axis. That teetering hinge ties the blades to a common pivot, so when they move up or down in response to aerodynamic loads or gusts, they do so as a single unit rather than independently. This unison flapping helps keep the rotor disc aligned and reduces complex loads in the hub.

If blades were able to flap independently (as with individual flap hinges) or if the mechanism relied on a generic hinge joint or on the swashplate alone, you wouldn’t get the same coordinated, one-axis flapping behavior that characterizes a semi-rigid, teetering rotor.