A rotary steerable drilling apparatus (100, 200) having a longitudinal axis, comprising: a control assembly disposed within a housing having a lower end; a steering section (80, 280, 280-1, 380) having a central channel, an upper end coupled to the lower end of the housing, and a lower end, and plurality of circumferentially-spaced fluid channels disposed about the central channel, wherein each fluid channel extends axially from the upper end; a plurality of radially extendable pistons housed in the steering section (80, 280, 280-1, 380); wherein the central channel extends axially from the upper end of the steering section (80, 280, 280-1, 380) and is configured to flow drilling fluid through the steering section (80, 280, 280-1, 380); wherein each of the fluid channels extends from the upper end of the steering section (80, 280, 280-1, 380) to one of the pistons, and wherein each piston is configured to move radially outward in response to drilling fluid supplied by the corresponding fluid channel; and a fluid-metering assembly configured to selectively meter the flow of drilling fluid into one or more of the fluid channels in the steering section (80, 280, 280-1, 380), characterized in that the fluid-metering assembly comprises: a lower sleeve (120, 220) coupled to the upper end of the steering section (80, 280, 280-1, 380), wherein the lower sleeve (120, 220) has a center bore (121, 221) and a plurality of circumferentially-spaced fluid inlets (122, 222) disposed about the central bore (121, 221), wherein the central bore (121, 221) of the lower sleeve (120, 220) is in fluid communication with the central channel of the steering section (80, 280, 280-1, 380); and an upper sleeve (110, 210) coupled to the control assembly and rotatably disposed within the center bore (121, 221) of the lower sleeve (120, 220), wherein the upper sleeve (110, 210) includes a center bore (114, 214) and a fluid-metering opening (118, 218); wherein the control assembly is configured to rotate the upper sleeve (110, 210) relative to the lower sleeve (120, 220) to place the fluid-metering opening (118, 218) of the upper sleeve (110, 210) into fluid communication with each fluid inlet (122, 222) of the lower sleeve (120, 220) in sequence. a control assembly disposed within a housing having a lower end; a steering section (80, 280, 280-1, 380) having a central channel, an upper end coupled to the lower end of the housing, and a lower end, and plurality of circumferentially-spaced fluid channels disposed about the central channel, wherein each fluid channel extends axially from the upper end; a plurality of radially extendable pistons housed in the steering section (80, 280, 280-1, 380); wherein the central channel extends axially from the upper end of the steering section (80, 280, 280-1, 380) and is configured to flow drilling fluid through the steering section (80, 280, 280-1, 380); wherein each of the fluid channels extends from the upper end of the steering section (80, 280, 280-1, 380) to one of the pistons, and wherein each piston is configured to move radially outward in response to drilling fluid supplied by the corresponding fluid channel; and a fluid-metering assembly configured to selectively meter the flow of drilling fluid into one or more of the fluid channels in the steering section (80, 280, 280-1, 380), characterized in that the fluid-metering assembly comprises: a lower sleeve (120, 220) coupled to the upper end of the steering section (80, 280, 280-1, 380), wherein the lower sleeve (120, 220) has a center bore (121, 221) and a plurality of circumferentially-spaced fluid inlets (122, 222) disposed about the central bore (121, 221), wherein the central bore (121, 221) of the lower sleeve (120, 220) is in fluid communication with the central channel of the steering section (80, 280, 280-1, 380); and an upper sleeve (110, 210) coupled to the control assembly and rotatably disposed within the center bore (121, 221) of the lower sleeve (120, 220), wherein the upper sleeve (110, 210) includes a center bore (114, 214) and a fluid-metering opening (118, 218); a lower sleeve (120, 220) coupled to the upper end of the steering section (80, 280, 280-1, 380), wherein the lower sleeve (120, 220) has a center bore (121, 221) and a plurality of circumferentially-spaced fluid inlets (122, 222) disposed about the central bore (121, 221), wherein the central bore (121, 221) of the lower sleeve (120, 220) is in fluid communication with the central channel of the steering section (80, 280, 280-1, 380); and an upper sleeve (110, 210) coupled to the control assembly and rotatably disposed within the center bore (121, 221) of the lower sleeve (120, 220), wherein the upper sleeve (110, 210) includes a center bore (114, 214) and a fluid-metering opening (118, 218); wherein the control assembly is configured to rotate the upper sleeve (110, 210) relative to the lower sleeve (120, 220) to place the fluid-metering opening (118, 218) of the upper sleeve (110, 210) into fluid communication with each fluid inlet (122, 222) of the lower sleeve (120, 220) in sequence.