FAA Private Pilot Helicopter (PRH)Helicopter Aerodynamics and SystemsMedium
A pilot is making a steep, powered vertical descent at low forward airspeed. Despite increasing collective pitch, the helicopter continues to sink at an increasing rate, and the aircraft develops random pitching and rolling. What condition is the pilot most likely experiencing?
- ARetreating blade stall
- BDynamic rollover
- CLow rotor RPM blade stall
- DSettling with power (vortex ring state)
Show answer & explanationAnswer & explanation
Correct answer: D. Settling with power (vortex ring state)
Settling with power occurs during a vertical or near-vertical descent with low forward airspeed and insufficient power to arrest the descent, causing the rotor to operate in its own turbulent downwash (vortex ring state). Adding power worsens the situation because it increases the downwash the rotor is descending into; recovery requires forward cyclic and reduced collective, not more power.
Why the other options are wrong
- A. Retreating blade stall occurs at high forward airspeed, not during vertical descents.
- B. Dynamic rollover occurs on the ground with a pivot point, not in flight.
- C. Low rotor RPM stall is caused by insufficient RPM, not necessarily a vertical descent condition.
Settling with Power (Vortex Ring State)
A condition where the main rotor descends into its own downwash during a low-airspeed, high-rate vertical descent, causing loss of lift despite power application.
- Requires: power applied, low airspeed, high rate of descent
- Recovery: lower collective and apply forward cyclic to gain airspeed
- Adding more power alone worsens the condition
Memory trick: Sinking into your own storm — the rotor eats its own downwash.