Abstract: A lightweight and compact apparatus is provided for altering and controlling the pitch of a plurality of rotating blades during rotation using a mechanical clutch and gear arrangement driven by a rotational speed differential between the blade drive shaft and the blades. A first set of clutches and gears controls the direction of rotational power to the pitch change mechanism and is disengaged from rotation when desired blade pitch is established. A second set of clutches and gears controls the speed of rotational power applied to the pitch change mechanism. This pitch change mechanism includes a failsafe capability against pitch change through disengagement of the directional clutches except when needed, and an inherent rotational lock resulting from the rate change clutches' bias to simultaneous engagement. Variation of that speed of rotational power permits coarse and fine pitch adjustments at variable rates.

Abstract: Paper drive unit instability that includes a variable displacement hydraulic motor (34), a rotary output (48), and a displacement controlling wobbler (36, 40) in the case of an aiding load can be avoided through the use of a double acting hydraulic actuator (42, 44) connected to the wobbler (36, 40) along with a control valve (30) including a single spool (80) connected to the motor (34), and wobbler control pilot valve (62) and to the actuator (42, 44) for a) controlling the speed and direction of rotation of the motor output (48); and b) controlling the actuator (42, 44) to maintain minimum displacement of the motor 34 when an aiding load occurs. System optimization can be achieved by changing the differential pressure setting in response to the available system pressure.

Abstract: An improved no-back mechanism for propeller pitch control comprises a brake which resists motion of a first member and a uni-directional coupling between the first member and a drive connecting a pitch control prime mover to an adjustable pitch propeller. The coupling permits limited movement of the drive with respect to the first member during back driving as in dither cycling of the blade while coupling the drive and first member for braking the back driving after the limited movement. As a result, dither cycling can occur during normal operation without release or slipping of the brake, thereby effecting a substantial wear reduction of brake plates of the brake.