A gas turbine engine component (100; 200; 300), comprising: a wall having an interior surface (126; 226; 326), an exterior surface (128; 228) opposite the interior surface, and a film-cooling channel (146; 246; 346) extending between the interior surface and exterior surface, the film-cooling channel including: a coolant outlet (140; 240; 340) defined in the exterior surface; a vortex chamber (150; 250; 350) in fluid communication with the coolant outlet; and a plurality of coolant inlets (142, 144; 242, 244, 247; 342, 344, 347) defined in the interior surface; a diffusor defined in the wall and in fluid communication with the coolant outlet; a vectoring segment (152; 252; 352) fluidly connecting a first one (142; 242; 342) of the plurality of coolant inlets with the vortex chamber; a vortexing segment (154; 254; 354) fluidly connecting a second one (144; 244; 344) of the plurality of coolant inlets with the vortex chamber, whereby the vortex chamber is configured and adapted for inducing secondary flow vortices in coolant traversing the film-cooling channel; and characterised by a metering segment (156; 256; 356) fluidly connecting the vortex chamber with the diffusor; wherein a flow area defined by the metering segment is less than an aggregate of flow areas defined by the vectoring and vortexing segments; wherein the metering segment includes a settling length with a discrete length, along which the coolant develops a relatively uniform flow velocity and fills the film-cooling channel, connected to the vortex chamber; and wherein the metering segment includes a development length with a further discrete length, along which the coolant develops a substantially uniform boundary layer adjacent to the film-cooling channel wall, connected between the settling length and the diffusor; whereby an adherent coolant film issues from the outlet and over at least a portion of the exterior surface. a coolant outlet (140; 240; 340) defined in the exterior surface; a vortex chamber (150; 250; 350) in fluid communication with the coolant outlet; and a plurality of coolant inlets (142, 144; 242, 244, 247; 342, 344, 347) defined in the interior surface; a diffusor defined in the wall and in fluid communication with the coolant outlet; a vectoring segment (152; 252; 352) fluidly connecting a first one (142; 242; 342) of the plurality of coolant inlets with the vortex chamber; a vortexing segment (154; 254; 354) fluidly connecting a second one (144; 244; 344) of the plurality of coolant inlets with the vortex chamber, whereby the vortex chamber is configured and adapted for inducing secondary flow vortices in coolant traversing the film-cooling channel; and characterised by a metering segment (156; 256; 356) fluidly connecting the vortex chamber with the diffusor; wherein a flow area defined by the metering segment is less than an aggregate of flow areas defined by the vectoring and vortexing segments; wherein the metering segment includes a settling length with a discrete length, along which the coolant develops a relatively uniform flow velocity and fills the film-cooling channel, connected to the vortex chamber; and wherein the metering segment includes a development length with a further discrete length, along which the coolant develops a substantially uniform boundary layer adjacent to the film-cooling channel wall, connected between the settling length and the diffusor; whereby an adherent coolant film issues from the outlet and over at least a portion of the exterior surface.