Which phenomenon occurs in the aft portion of the rotor disk due to increased induced velocity, causing more drag?

• A. Transverse-Flow Effect
• B. Longitudinal Flow
• C. Radial Flow
• D. Circumferential Flow

Answer: (A)

In forward flight, the air flowing through the rotor disk isn’t the same across the whole disk. The induced velocity, which is the downward airspeed caused by the rotor’s thrust, becomes greater toward the aft portion of the disk. That stronger downwash in the rear half increases the drag in that region. This pattern of flow across the disk is known as the transverse-flow effect, and it describes how nonuniform induced velocity creates more drag on the aft portion of the rotor disk. The other flow patterns refer to different nonuniformities (front-to-back flow, flow toward or away from the hub, or flow around the circumference) and don’t specifically capture the aft-drag characteristic described here.