In certain rotor configurations, what term describes the axis about which flap motion occurs?

In certain rotor configurations, what term describes the axis about which flap motion occurs?

• A. Chordwise Axis
• B. Center of Gravity
• C. Blade Twist
• D. Chip Detector

Answer: (A)

Flap motion occurs about a hinge axis that runs along the blade’s chord, from leading edge to trailing edge. This chordwise axis lets the blade pivot up and down in the rotor plane, which is what flapping is—a change in the blade’s lift direction without twisting the blade along its span. In rotor design, the flap hinge is near the root and fixed relative to the blade, and its orientation dictates that the primary deflection is about the chordwise line. The other terms don’t describe this axis: the center of gravity is just a point where mass concentrates, blade twist refers to twisting along the blade, and a chip detector is a diagnostic device—none define the axis about which flap movement occurs.

Flap motion occurs about a hinge axis that runs along the blade’s chord, from leading edge to trailing edge. This chordwise axis lets the blade pivot up and down in the rotor plane, which is what flapping is—a change in the blade’s lift direction without twisting the blade along its span. In rotor design, the flap hinge is near the root and fixed relative to the blade, and its orientation dictates that the primary deflection is about the chordwise line.

The other terms don’t describe this axis: the center of gravity is just a point where mass concentrates, blade twist refers to twisting along the blade, and a chip detector is a diagnostic device—none define the axis about which flap movement occurs.