Methods and apparatus to control propeller pitch in dual acting propellers

A variable pitch propeller assembly comprising:

• a plurality of blades rotatable about an axial direction;
• a piston including a piston rod;
• and
• a propeller control system including:
• a first valve to selectively, based on an input signal, transfer hydraulic fluid to a first piston line and a second piston line of the piston rod via the first piston line and the second piston line, wherein in the first valve is a three-state valve;
• and
• an independent valve to transfer hydraulic fluid to a third line of the piston rod, wherein the independent valve operates independently of the first valve.

A method to control propeller pitch in dual acting propellers, the method comprising:

• detecting a drift in a pitch angle of a blade towards fine direction, defining a pitch tracking failure condition;
• supplying, in response to detecting the drift, hydraulic fluid to a first side of a piston defining a coarse chamber;
• actuating, based on detection of the pitch tracking failure condition, a first valve in a fine line blockage state, the fine line blockage state is:
• a first valve line connected to the first piston line of a piston rod via a first port to transfer hydraulic fluid to a first side of the piston;
• and
• a second valve line disconnected from a second piston line of the piston rod;
• and feathering a plurality of blades to a desired position.