In vortex ring state, when collective is raised, which statement about rotor disk portions is accurate?

In vortex ring state, when collective is raised, which statement about rotor disk portions is accurate?

• A. The unstalled portion grows outward, increasing descent.
• B. The stalled portion shrinks, decreasing descent.
• C. The stalled portion grows outward from the root, increasing descent.
• D. The unstalled portion grows inward, decreasing descent.

Answer: (C)

In vortex ring state the rotor operates in its own downwash, creating highly nonuniform inflow across the rotor disk. Raising collective increases blade pitch, but the disturbed flow from the rotor wake means the portion of the disk that is stalled shifts and expands in a specific way. The stalled region starts near the hub and grows outward toward the tips as collective is raised. As more of the disk becomes stalled, less of the rotor contributes effective lift, so the aircraft descends more rapidly. This is why the statement that the stalled portion grows outward from the root, increasing descent, is the best description.

In vortex ring state the rotor operates in its own downwash, creating highly nonuniform inflow across the rotor disk. Raising collective increases blade pitch, but the disturbed flow from the rotor wake means the portion of the disk that is stalled shifts and expands in a specific way. The stalled region starts near the hub and grows outward toward the tips as collective is raised. As more of the disk becomes stalled, less of the rotor contributes effective lift, so the aircraft descends more rapidly. This is why the statement that the stalled portion grows outward from the root, increasing descent, is the best description.