FAA Private Pilot Helicopter (PRH)Performance and LimitationsMedium
During an autorotation, what is the primary purpose of maintaining rotor RPM within the green arc?
- ATo maintain sufficient energy for a successful flare and landing.
- BTo ensure maximum glide distance.
- CTo prevent rotor overspeed and structural damage.
- DTo minimize the rate of descent.
Show answer & explanationAnswer & explanation
Correct answer: A. To maintain sufficient energy for a successful flare and landing.
Maintaining rotor RPM within the green arc during autorotation is crucial because it ensures there is enough stored kinetic energy in the rotor system to perform the flare and cushion the landing. Too low RPM means insufficient energy, while too high risks overspeed.
Why the other options are wrong
- B. While glide distance is a factor, the primary purpose of RPM control is energy management for the landing.
- C. Preventing overspeed is part of it, but the main reason for staying in the 'green' is to ensure sufficient energy for the flare.
- D. Minimizing rate of descent is a consequence of proper RPM management, but the core reason for the green arc is energy for landing.
Autorotation RPM Management
During autorotation, rotor RPM must be maintained within the specified green arc to ensure sufficient kinetic energy for the landing flare and cushioning.
- Rotor RPM stores kinetic energy.
- Green arc indicates safe and effective RPM range.
- Energy is converted to lift during the flare.
Memory trick: Keep the rotor 'green' to have 'juice' for the landing.