During landing rollout, a turboprop pilot moves the power lever below the flight idle gate into the beta range. What occurs during operation in this range?
- AFuel flow is cut off completely and the propeller automatically feathers
- BPropeller blade angle is controlled directly by power lever position, independent of the constant-speed governor, allowing reduced or reverse blade pitch for ground operations
- CThe engine disengages the free turbine and transitions power to the reduction gearbox alone
- DThe propeller governor increases blade angle to maintain a constant RPM regardless of power lever position
Show answer & explanationAnswer & explanation
Correct answer: B. Propeller blade angle is controlled directly by power lever position, independent of the constant-speed governor, allowing reduced or reverse blade pitch for ground operations
In the beta range (below flight idle), the propeller control system shifts from constant-speed governing to direct power-lever control of blade angle, allowing the pilot to select low, zero, or reverse pitch for ground maneuvering and reverse thrust, rather than the governor automatically maintaining RPM.
Why the other options are wrong
- A. Beta range does not cut fuel flow or feather the propeller; it adjusts blade pitch, including reverse.
- C. The free turbine still drives the propeller through the reduction gearbox; it is not disengaged in beta range.
- D. This describes normal constant-speed (alpha range) governing above flight idle, not beta range.
Beta Range (Turboprop)
The propeller control range below flight idle where blade angle is controlled directly by power lever position rather than by the constant-speed governor, used for ground operations and reverse thrust.
- Below flight idle gate on the power/condition lever quadrant
- Allows low pitch, zero pitch (disc), or reverse pitch selection
- Used for taxi, landing rollout, and reverse thrust operations
Memory trick: Beta range = 'Below' flight idle, blades obey the lever directly