Abstract: The subject matter of this specification can be embodied in, among other things, a position sensor system that includes a sensor housing defining a first cavity having a first face, a fluid effector including an actuator housing having an inner surface defining a second cavity, and a moveable body having a second face and configured for reciprocal movement within the second cavity, an acoustic transmitter system configured to emit a first emitted acoustic waveform toward the first face, and emit a second emitted acoustic waveform toward the second face, and an acoustic receiver system configured to detect a first reflected acoustic waveform based on a first reflection of the first emitted acoustic waveform based on the first face, and detect a second reflected acoustic waveform based on a second reflection of the second emitted acoustic waveform based on the second face.

Abstract: The subject matter of this specification can be embodied in, among other things, a position sensor system that includes a sensor housing defining a first cavity having a first face, a fluid effector including an actuator housing having an inner surface defining a second cavity, and a moveable body having a second face and configured for reciprocal movement within the second cavity, an acoustic transmitter system configured to emit a first emitted acoustic waveform toward the first face, and emit a second emitted acoustic waveform toward the second face, and an acoustic receiver system configured to detect a first reflected acoustic waveform based on a first reflection of the first emitted acoustic waveform based on the first face, and detect a second reflected acoustic waveform based on a second reflection of the second emitted acoustic waveform based on the second face.

Abstract: The present disclosure describes a propeller control unit for controlling the blade pitch of a propeller. The unit includes an electrohydraulic servo valve (“EHSV”) and is connected to a propeller actuator that adjusts the blade pitch of a propeller. The EHSV operates to allow pressurized fluid to flow from a pressurized fluid source to the actuator to adjust the blade pitch of the propeller in a flight pitch range and a ground pitch range, to allow pressurized fluid to flow from the source to the actuator to adjust the blade pitch of the propeller in a flight pitch range but not a ground pitch range, and to block the flow of pressurized fluid from the source to the actuator and drain pressurized fluid from the actuator to prevent adjustment of the blade pitch of the propeller in the flight pitch range or the ground pitch range.

Abstract: The present disclosure describes a propeller control unit for controlling the blade pitch of a propeller. The unit includes an electrohydraulic servo valve (“EHSV”) and is connected to a propeller actuator that adjusts the blade pitch of a propeller. The EHSV operates to allow pressurized fluid to flow from a pressurized fluid source to the actuator to adjust the blade pitch of the propeller in a flight pitch range and a ground pitch range, to allow pressurized fluid to flow from the source to the actuator to adjust the blade pitch of the propeller in a flight pitch range but not a ground pitch range, and to block the flow of pressurized fluid from the source to the actuator and drain pressurized fluid from the actuator to prevent adjustment of the blade pitch of the propeller in the flight pitch range or the ground pitch range.