A rotary actuator (100, 300) comprising: a housing defining a first arcuate chamber portion comprising a first cavity, a first open end having an opening for the first cavity defined in a face portion, and a first fluid port in fluid communication with the first cavity;; a first seal carrier assembly (105, 360, 500) defining a second arcuate chamber portion and configured for movement relative to the housing, the first seal carrier assembly comprising a head having: i) a first piston seal, ii) an aperture (366, 516) having a second open end and a third open end opposite the second open end, iii) a first face portion through which the aperture is defined, the first seal carrier assembly (105, 360, 500) further comprising a pivot member (362, 502) rotatably affixed to the housing and about which the first seal carrier assembly is configured to pivot such that the first face portion of the head of the first seal carrier assembly travels in an arc section about the pivot member, wherein the first face portion is formed with a curvature that substantially matches the arc of travel of the first face portion about the pivot member; wherein the first face portion of the head is in sealing contact through a first face seal with the face portion of the housing proximal to the first open end and the second open end, wherein the face portion of the housing is formed with a curvature that substantially compliments the curvature of the first face portion of the head, wherein the rotary actuator further comprises a rotary output assembly (130, 330); and an arcuate-shaped first piston (150, 350) disposed in said housing for reciprocal movement in the first arcuate chamber portion and in the second arcuate chamber portion through the first open end of the housing and the second and the third open ends of the aperture, wherein the head, the aperture, the first piston seal, the first face seal the first cavity and the arcuate-shaped first piston (150, 350) define a first pressure chamber, and wherein a first portion of the arcuate-shaped first piston (150, 350) contacts the rotary output assembly (130, 330). a housing defining a first arcuate chamber portion comprising a first cavity, a first open end having an opening for the first cavity defined in a face portion, and a first fluid port in fluid communication with the first cavity;; a first seal carrier assembly (105, 360, 500) defining a second arcuate chamber portion and configured for movement relative to the housing, the first seal carrier assembly comprising a head having: i) a first piston seal, ii) an aperture (366, 516) having a second open end and a third open end opposite the second open end, iii) a first face portion through which the aperture is defined, the first seal carrier assembly (105, 360, 500) further comprising i) a first piston seal, ii) an aperture (366, 516) having a second open end and a third open end opposite the second open end, iii) a first face portion through which the aperture is defined, the first seal carrier assembly (105, 360, 500) further comprising a pivot member (362, 502) rotatably affixed to the housing and about which the first seal carrier assembly is configured to pivot such that the first face portion of the head of the first seal carrier assembly travels in an arc section about the pivot member, wherein the first face portion is formed with a curvature that substantially matches the arc of travel of the first face portion about the pivot member; wherein the first face portion of the head is in sealing contact through a first face seal with the face portion of the housing proximal to the first open end and the second open end, wherein the face portion of the housing is formed with a curvature that substantially compliments the curvature of the first face portion of the head, wherein the rotary actuator further comprises a rotary output assembly (130, 330); and an arcuate-shaped first piston (150, 350) disposed in said housing for reciprocal movement in the first arcuate chamber portion and in the second arcuate chamber portion through the first open end of the housing and the second and the third open ends of the aperture, wherein the head, the aperture, the first piston seal, the first face seal the first cavity and the arcuate-shaped first piston (150, 350) define a first pressure chamber, and wherein a first portion of the arcuate-shaped first piston (150, 350) contacts the rotary output assembly (130, 330).