What is the term for a flapping hinge with a skewed axis that introduces a feathering component and a restoring force in the flapwise direction?

• A. Delta Hinge
• B. Cyclic Feathering
• C. Coning
• D. Coaxial Rotor

Answer: (A)

The main idea is how the hinge geometry of a rotor blade affects its motion by coupling flap with pitch. A delta hinge has its axis skewed relative to the plane of rotation, so when the blade flaps, the hinge orientation creates a component that tends to feather the blade—changing its pitch—and at the same time produces a restoring moment in the flap direction to bring the blade back toward its neutral flap angle. This combination—a feathering tendency plus a restoring flapwise force—helps dampen flap motion and manage dynamic loads without separate pitch input. The other terms don’t describe a hinge geometry that links flap motion to feathering in this way: cyclic feathering refers to cyclic pitch changes, coning is the upward deflection of blades under load, and coaxial rotor describes a two-rotor configuration rather than a hinge behavior.