A rotary actuator system comprising: a first housing defining a first arcuate chamber comprising a first cavity, a first fluid port in fluid communication with the first cavity, a keyway, and an open end, wherein the first housing defining the first arcuate chamber is formed from a single piece of material; a rotor assembly rotatably journaled in said first housing and comprising a rotary output shaft aligned with an axis and a first rotor arm (212, 1214, 1530, 1730, 1914, 2224, 2712, 2914, 3312) extending radially outward from the rotary output shaft; an arcuate-shaped first piston (250, 260, 414, 712, 812, 822, 1530, 1730, 1930, 2222, 2400) disposed in said first housing for reciprocal movement in the first arcuate chamber about the axis and through the open end, wherein a first seal included in the first piston, the first cavity, and the first piston define a first pressure chamber, and a first portion of the first piston contacts the first rotor arm, wherein the keyway is formed along the axis and dimensioned to pass the first rotor arm and a connector pin to connect the first piston to the first rotor arm; a first fluid line coupled to the first fluid port; and a selected one of a) or b), wherein: a) comprises a high pressure fluid line, a low pressure fluid line, a central pressure source coupled to the high pressure fluid line, and a servo valve positioned between the central pressure source and the rotary actuator and being controllable to selectively connect the first fluid line to the high pressure fluid line and the low pressure fluid line to control movement of the rotary actuator; and b) comprises a fluid reservoir, and a fluid pump coupled to the fluid reservoir, the fluid pump being controllable to selectively provide high pressure to the first fluid line to control movement of the rotary actuator, wherein the fluid pump is not connected to a central hydraulic system. a first housing defining a first arcuate chamber comprising a first cavity, a first fluid port in fluid communication with the first cavity, a keyway, and an open end, wherein the first housing defining the first arcuate chamber is formed from a single piece of material; a rotor assembly rotatably journaled in said first housing and comprising a rotary output shaft aligned with an axis and a first rotor arm (212, 1214, 1530, 1730, 1914, 2224, 2712, 2914, 3312) extending radially outward from the rotary output shaft; an arcuate-shaped first piston (250, 260, 414, 712, 812, 822, 1530, 1730, 1930, 2222, 2400) disposed in said first housing for reciprocal movement in the first arcuate chamber about the axis and through the open end, wherein a first seal included in the first piston, the first cavity, and the first piston define a first pressure chamber, and a first portion of the first piston contacts the first rotor arm, wherein the keyway is formed along the axis and dimensioned to pass the first rotor arm and a connector pin to connect the first piston to the first rotor arm; a first fluid line coupled to the first fluid port; and a selected one of a) or b), wherein: a) comprises a high pressure fluid line, a low pressure fluid line, a central pressure source coupled to the high pressure fluid line, and a servo valve positioned between the central pressure source and the rotary actuator and being controllable to selectively connect the first fluid line to the high pressure fluid line and the low pressure fluid line to control movement of the rotary actuator; and b) comprises a fluid reservoir, and a fluid pump coupled to the fluid reservoir, the fluid pump being controllable to selectively provide high pressure to the first fluid line to control movement of the rotary actuator, wherein the fluid pump is not connected to a central hydraulic system. a) comprises a high pressure fluid line, a low pressure fluid line, a central pressure source coupled to the high pressure fluid line, and a servo valve positioned between the central pressure source and the rotary actuator and being controllable to selectively connect the first fluid line to the high pressure fluid line and the low pressure fluid line to control movement of the rotary actuator; and a high pressure fluid line, a low pressure fluid line, a central pressure source coupled to the high pressure fluid line, and a servo valve positioned between the central pressure source and the rotary actuator and being controllable to selectively connect the first fluid line to the high pressure fluid line and the low pressure fluid line to control movement of the rotary actuator; and b) comprises a fluid reservoir, and a fluid pump coupled to the fluid reservoir, the fluid pump being controllable to selectively provide high pressure to the first fluid line to control movement of the rotary actuator, wherein the fluid pump is not connected to a central hydraulic system. a fluid reservoir, and a fluid pump coupled to the fluid reservoir, the fluid pump being controllable to selectively provide high pressure to the first fluid line to control movement of the rotary actuator, wherein the fluid pump is not connected to a central hydraulic system.