A servo valve assembly, comprising: a first nozzle opposing a second nozzle, wherein the first and second nozzles (114a, 114b) are spaced apart by a gap and each nozzle (114a, 114b) has an outlet opening (116a, 116b); and a shaft positioned in the gap between the first and second nozzles (114a, 114b), wherein: the shaft defines a diameter and a circumferential surface and is rotatable centrally about an axis of rotation (R-R) along which it extends; the shaft defines first and second reduced radial portions (124a, 124b) around its circumferential surface, and the first and second reduced radial portions (124a, 124b) are in fluid communication with the first and second nozzle outlet openings (116a, 116b), respectively; and the shaft is configured to rotate between a first position where the first nozzle outlet opening is more occluded by the shaft circumferential surface than the second nozzle outlet opening, and a second position where the first nozzle outlet opening is less occluded by the shaft circumferential surface than the second nozzle outlet opening; wherein the axis of rotation (R-R) is perpendicular to a central axis (N-N) of each nozzle outlet opening (116a, 116b); and characterised in that the central axis (N-N) of each nozzle outlet opening (116a, 116b) is aligned to pass through the axis of rotation (R-R); the first and second reduced radial portions (124a, 124b) extend axially along the circumferential surface of the shaft to provide a suitable amount of variable fluid communication with the outlet openings (116a, 116b) and each comprise a curved surface (126a, 126b) of continuously decreasing radius that terminates at a respective groove (125a, 125b) in the circumferential surface of the shaft. a first nozzle opposing a second nozzle, wherein the first and second nozzles (114a, 114b) are spaced apart by a gap and each nozzle (114a, 114b) has an outlet opening (116a, 116b); and a shaft positioned in the gap between the first and second nozzles (114a, 114b), wherein: the shaft defines a diameter and a circumferential surface and is rotatable centrally about an axis of rotation (R-R) along which it extends; the shaft defines first and second reduced radial portions (124a, 124b) around its circumferential surface, and the first and second reduced radial portions (124a, 124b) are in fluid communication with the first and second nozzle outlet openings (116a, 116b), respectively; and the shaft is configured to rotate between a first position where the first nozzle outlet opening is more occluded by the shaft circumferential surface than the second nozzle outlet opening, and a second position where the first nozzle outlet opening is less occluded by the shaft circumferential surface than the second nozzle outlet opening; wherein the axis of rotation (R-R) is perpendicular to a central axis (N-N) of each nozzle outlet opening (116a, 116b); and characterised in that the central axis (N-N) of each nozzle outlet opening (116a, 116b) is aligned to pass through the axis of rotation (R-R); the first and second reduced radial portions (124a, 124b) extend axially along the circumferential surface of the shaft to provide a suitable amount of variable fluid communication with the outlet openings (116a, 116b) and each comprise a curved surface (126a, 126b) of continuously decreasing radius that terminates at a respective groove (125a, 125b) in the circumferential surface of the shaft. the shaft defines a diameter and a circumferential surface and is rotatable centrally about an axis of rotation (R-R) along which it extends; the shaft defines first and second reduced radial portions (124a, 124b) around its circumferential surface, and the first and second reduced radial portions (124a, 124b) are in fluid communication with the first and second nozzle outlet openings (116a, 116b), respectively; and the shaft is configured to rotate between a first position where the first nozzle outlet opening is more occluded by the shaft circumferential surface than the second nozzle outlet opening, and a second position where the first nozzle outlet opening is less occluded by the shaft circumferential surface than the second nozzle outlet opening; wherein the axis of rotation (R-R) is perpendicular to a central axis (N-N) of each nozzle outlet opening (116a, 116b); and the central axis (N-N) of each nozzle outlet opening (116a, 116b) is aligned to pass through the axis of rotation (R-R); the first and second reduced radial portions (124a, 124b) extend axially along the circumferential surface of the shaft to provide a suitable amount of variable fluid communication with the outlet openings (116a, 116b) and each comprise a curved surface (126a, 126b) of continuously decreasing radius that terminates at a respective groove (125a, 125b) in the circumferential surface of the shaft.