Patent ID: 8721283
Filing Date: 2014-05-13
Classification: B64C,B64D,Y02T

Abstract:
1. A pitch change apparatus for a propeller assembly having a row of propeller blades which rotate around an axis of the assembly, the apparatus comprising: a hydraulic actuator for angular displacement of propellers of the propeller assembly, the hydraulic actuator having a piston and cylinder arrangement which defines a fine fluid chamber and a coarse fluid chamber, whereby increasing a volume of the fine chamber at an expense of the coarse chamber results in angular displacement of the propellers to a finer pitch, and increasing a volume of the coarse chamber an expense of the fine chamber results in angular displacement of the propellers to a coarser pitch, one or more fine hydraulic lines carrying hydraulic fluid to and from the fine chamber, and a coarse hydraulic line carrying hydraulic fluid to and from the coarse chamber; wherein the apparatus further comprises a pressure-sensing check valve which fluidly isolates the coarse chamber from the coarse hydraulic line if the pressure in the coarse hydraulic line falls below a threshold pressure.