Abstract: A system for controlling a propeller having a plurality of blades having a primary control system and a backup control system. The primary control system including a sensor responsive to a propeller state, and a controller connected to the sensor and to an electrohydraulic control actuator. The electrohydraulic control actuator is connected via a bypass valve to a hydraulic actuator that controls at least a blade angle of a blade of the propeller. The controller generating commands to the electrohydraulic control actuator based on at least the propeller state. The backup control system including a second controller, an electrohydraulic solenoid operably connected to the bypass valve. The backup control system is operable to hydraulically disable the primary control system via the bypass valve upon the occurrence of a selected condition, the second controller modulates the operation of the electrohydraulic solenoid to control the bypass actuator based on the propeller state.

Abstract: A pitch change actuation system for varying a propeller blade pitch includes: an actuator body defining an interior volume; and a chamber separator located within the interior volume of the actuator body and dividing the interior volume into a first chamber and a second chamber, the two chambers being fluidly separated by the chamber separator. The first and second chambers are configured to receive hydraulic fluid. The actuator body is configured to translate relative to the chamber separator in response to a difference in hydraulic pressure between the first chamber and second chamber; and the translation of the actuator body is configured to effect a change in propeller blade pitch.

Abstract: A blade pitch control assembly includes a pitch control actuator having a coarse actuator chamber having a coarse chamber area and a fine actuator chamber having a fine chamber area. The coarse chamber area is biased to a feather position. The assembly also includes a primary pitch control valve configured to control the flow of pressurised fluid to the coarse actuator chamber and the fine actuator chamber, respectively via a coarse fluid line and a fine fluid line. The assembly further includes a hydraulic protection system located between the actuator and the primary pitch control valve, configured to bypass the primary pitch actuator in response to a trigger. The hydraulic protection system has a hydraulic protection system valve located between the fluid lines and when activated fluidly connects the fluid lines to balance fluid pressure between the coarse chamber and the fine chamber.

Abstract: A method of detecting that ice has been shed from an external surface of a component is provided, the method comprising applying power to a heating means to provide heat to said external surface. The method further comprises sensing the temperature of the component and calculating the rate of change of temperature increase of the external surface over time. Further, the method comprises detecting a change in said rate of change of temperature increase over time, wherein said detected change in rate of change of temperature increase indicates that said ice has been shed from said external surface of said component.

Abstract: A system for controlling a propeller having a plurality of blades having a primary control system and a backup control system. The primary control system including a sensor responsive to a propeller state, and a controller connected to the sensor and to an electrohydraulic control actuator. The electrohydraulic control actuator connected via a bypass valve to a hydraulic actuator that controls at least a blade angle of a blade of the propeller. The controller generating commands to the electrohydraulic control actuator based on at least the propeller state. The backup control system including a second controller, an electrohydraulic solenoid operably connected to the bypass valve. The backup control system operable to hydraulically disable the primary control system via the bypass valve upon the occurrence of a selected condition, the second controller modulates the operation of the electrohydraulic solenoid to control the bypass actuator based on the propeller state.

Abstract: A method of detecting that ice has been shed from an external surface of a component is provided, the method comprising applying power to a heating means to provide heat to said external surface. The method further comprises sensing the temperature of the component and calculating the rate of change of temperature increase of the external surface over time. Further, the method comprises detecting a change in said rate of change of temperature increase over time, wherein said detected change in rate of change of temperature increase indicates that said ice has been shed from said external surface of said component.