In vortex ring state, when the collective is raised, which portion grows and what is the effect on the descent rate?

In vortex ring state, when the collective is raised, which portion grows and what is the effect on the descent rate?

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

Answer: (A)

In vortex ring state, raising the collective during a descent increases induced flow and strengthens the toroidal vortex formed by the rotor’s downwash. The stalled portion of the rotor disk appears first near the hub and then grows outward toward the tips as the vortex ring intensifies. As more of the disk becomes stalled, the rotor’s ability to generate thrust drops below weight, so the descent rate increases. The other descriptions don’t fit the observed progression—unstalled regions don’t produce the same thrust loss, and growth from the center inward doesn’t match how the stalled area expands.

In vortex ring state, raising the collective during a descent increases induced flow and strengthens the toroidal vortex formed by the rotor’s downwash. The stalled portion of the rotor disk appears first near the hub and then grows outward toward the tips as the vortex ring intensifies. As more of the disk becomes stalled, the rotor’s ability to generate thrust drops below weight, so the descent rate increases. The other descriptions don’t fit the observed progression—unstalled regions don’t produce the same thrust loss, and growth from the center inward doesn’t match how the stalled area expands.