Actuation system for a controllable pitch propeller

A propeller control system comprising:

• a propeller shaft which rotates about a first axis to drive a propeller hub and a plurality of propeller blades extending therefrom;
• a pitch change actuating piston between a coarse pitch actuator chamber and a fine pitch actuator chamber, said pitch change actuating piston movable along said first axis in response to a differential pressure between said coarse pitch actuator chamber and a fine pitch actuator chamber, said pitch change actuating piston linked to said plurality of propeller blades to change the pitch thereof;
• a pitch change valve mounted along said first axis in a hydraulic balance, said pitch change valve movable along said axis in response to upset of said hydraulic balance, movement of said pitch change valve operable to selectively communicate each of said coarse pitch actuator chamber and said fine pitch actuator chamber with either a supply pressure or a drain pressure;
• a transfer bearing comprising a single land for supplying said supply pressure from a stationary field to said pitch change valve within a rotational field, said supply pressure operable to maintain said hydraulic balance;
• and
• a feathering solenoid in communication with said transfer bearing, actuation of said feathering solenoid operable to increase said supply pressure and upset said hydraulic balance such that said coarse pitch actuator chamber communicates with said supply pressure and said fine pitch actuator chamber communicates with said drain pressure to change the pitch of said plurality of propeller blades toward coarse pitch.

A method of controlling a propeller blade pitch comprising the steps of:

• (1) supplying a fluid at a first supply pressure to a pitch change valve to maintain the pitch change valve in a hydraulic balance;
• (2) mechanically upsetting the hydraulic balance of the pitch change valve through rotation of a pitch lock screw and a pitch change motor to axially move the pitch change valve and change a first pressure within a coarse pitch actuator chamber and a second pressure within fine pitch actuator;
• and
• (3) axially moving a pitch change actuating piston in response to said step (2), said pitch change actuating piston linked to a plurality of propeller blades to change the pitch thereof.

A propeller control system comprising:

• a propeller shaft which rotates about a first axis to drive a propeller hub and a plurality of propeller blades extending therefrom;
• a pitch change valve mounted along said first axis in a hydraulic balance, said pitch change valve movable along said axis in response to upset of said hydraulic balance, axial movement of said pitch change valve operable to change a pitch of said plurality of propeller blades;
• a transfer bearing comprising a single land for supplying a supply pressure from a stationary field to said pitch change valve within a rotational field, said supply pressure operable to maintain said hydraulic balance;
• a feathering solenoid in communication with a main pump and said transfer bearing;
• and
• a controller in communication with said feathering solenoid, said controller operable to actuate and deactivate said feathering solenoid to selectively increases said supply pressure.

A propeller control system comprising:

• a propeller shaft which rotates about a first axis to drive a propeller hub and a plurality of propeller blades extending therefrom;
• a pitch change valve mounted along said first axis in a hydraulic balance, said pitch change valve movable along said axis in response to upset of said hydraulic balance, axial movement of said pitch change valve operable to change a pitch of said plurality of propeller blades;
• and
• a transfer bearing comprising a single land for supplying a supply pressure from a stationary field to said pitch change valve within a rotational field, said supply pressure operable to maintain said hydraulic balance, said supply pressure is metered into a first metered pressure within a pitch change signal chamber formed between a pitch change signal valve and a pitch change valve spool and into a second metered pressure within a feather override chamber formed between a feather actuating valve and said pitch change valve spool.

A propeller control system comprising:

• a propeller shaft which rotates about a first axis to drive a propeller hub and a plurality of propeller blades extending therefrom;
• a pitch change valve mounted along said first axis in a hydraulic balance, said pitch change valve movable along said axis in response to upset of said hydraulic balance, axial movement of said pitch change valve operable to change a pitch of said plurality of propeller blades;
• a transfer bearing comprising a single land for supplying a supply pressure from a stationary field to said pitch change valve within a rotational field, said supply pressure operable to maintain said hydraulic balance;
• and
• a controller mounted within said rotational field.

A method of controlling a propeller blade pitch comprising the steps of:

• (1) supplying a fluid at a first supply pressure to a pitch change valve to maintain the pitch change valve in a hydraulic balance;
• (2) mechanically upsetting the hydraulic balance of the pitch change valve to axially move the pitch change valve and change a first pressure within a coarse pitch actuator chamber and a second pressure within fine pitch actuator;
• (3) axially moving a pitch change actuating piston in response to said step (2), said pitch change actuating piston linked to a plurality of propeller blades to change the pitch thereof;
• and
• (4) supplying the fluid at a second supply pressure greater than the first supply pressure to upset the hydraulic balance of the pitch change valve to increase the first pressure and decrease the second pressure such that the pitch of the plurality of propeller blades move toward coarse pitch.

A method of controlling a propeller blade pitch comprising the steps of:

• (1) supplying a fluid at a first supply pressure to a pitch change valve to maintain the pitch change valve in a hydraulic balance;
• (2) mechanically upsetting the hydraulic balance of the pitch change valve to axially move the pitch change valve and change a first pressure within a coarse pitch actuator chamber and a second pressure within fine pitch actuator;
• (3) axially moving a pitch change actuating piston in response to said step (2), said pitch change actuating piston linked to a plurality of propeller blades to change the pitch thereof;
• and
• (4) self-nulling axial movement of the pitch change valve.

A method of controlling a propeller blade pitch comprising the steps of:

• (1) supplying a fluid at a first supply pressure to a pitch change valve to maintain the pitch change valve in a hydraulic balance;
• (2) mechanically upsetting the hydraulic balance of the pitch change valve to axially move the pitch change valve and change a first pressure within a coarse pitch actuator chamber and a second pressure within fine pitch actuator;
• (3) axially moving a pitch change actuating piston in response to said step (2), said pitch change actuating piston linked to a plurality of propeller blades to change the pitch thereof;
• and
• (4) selectively communicating each of the first pressure and the second pressure with the first supply pressure or a drain pressure in response to axially movement of the pitch change valve.