FAA Private Pilot Helicopter (PRH)Performance and LimitationsHard
A pilot is flying at a high forward airspeed at high density altitude and high gross weight while making a steep turn. This combination of factors most increases the risk of
- Adynamic rollover
- Bground resonance
- Csettling with power
- Dretreating blade stall
Show answer & explanationAnswer & explanation
Correct answer: D. retreating blade stall
Retreating blade stall risk increases with high forward airspeed, high density altitude, high gross weight, low rotor RPM, and increased load factor from steep turns—all of which reduce the airflow margin over the retreating blade before it reaches a stall angle of attack.
Why the other options are wrong
- A. Dynamic rollover is a ground-based hazard involving pivoting on a skid or wheel.
- B. Ground resonance occurs on the ground with an out-of-balance rotor system, not in flight.
- C. Settling with power occurs at low airspeed and high power, the opposite condition described here.
Retreating Blade Stall
A high-speed flight condition where the retreating rotor blade's angle of attack becomes excessive, causing it to stall; risk increases with high airspeed, high gross weight, high density altitude, low rotor RPM, and turbulence or steep turns.
- Occurs at high forward airspeeds near Vne
- Load factor from turns increases blade angle of attack demand
- Recovery: reduce collective, slow airspeed, and level the aircraft
Memory trick: Fast, heavy, hot, and turning—the retreating blade runs out of air.