A turbofan engine comprising: a fan having a plurality of blades; a transmission configured to drive the fan; a first spool comprising: a first pressure turbine; and a first shaft coupling the first pressure turbine to the transmission; a second spool comprising: a second pressure turbine; a first compressor; and a second spool shaft coupling the second pressure turbine to the second spool compressor; and a core spool comprising: a third pressure turbine; a second compressor; and a core shaft coupling the third pressure turbine to second compressor; and a combustor between the second compressor and the third pressure turbine, wherein: each fan blade has a leading edge and a trailing edge; a splitter is positioned along a flowpath through the engine and having a leading rim separates a core branch of the flowpath from a bypass branch of the flowpath; an inboard boundary of the core flowpath has a radius R II at an axial position of a forward rim of the splitter; the inboard boundary of the core flowpath has a radius R I at a leading edge of a leading stage of blades of the first compressor; and the fan is a single-stage fan having a single stage of fan blades; and characterized in that: the engine has an axial length L 10 between the splitter rim and the leading stage of blades of the first compressor at the inboard boundary of the core flowpath; a ratio of said axial length L 10 to the radius R II is less than 1.2; and the fan blades have a peak tip radius R T, an inboard leading edge radius R H at an inboard boundary of the flowpath, and a ratio of R H to R T is less than about 0.40. a fan having a plurality of blades; a transmission configured to drive the fan; a first spool comprising: a first pressure turbine; and a first shaft coupling the first pressure turbine to the transmission; a first pressure turbine; and a first shaft coupling the first pressure turbine to the transmission; a second spool comprising: a second pressure turbine; a first compressor; and a second spool shaft coupling the second pressure turbine to the second spool compressor; and a second pressure turbine; a first compressor; and a second spool shaft coupling the second pressure turbine to the second spool compressor; and a core spool comprising: a third pressure turbine; a second compressor; and a core shaft coupling the third pressure turbine to second compressor; and a third pressure turbine; a second compressor; and a core shaft coupling the third pressure turbine to second compressor; and a combustor between the second compressor and the third pressure turbine, wherein: each fan blade has a leading edge and a trailing edge; a splitter is positioned along a flowpath through the engine and having a leading rim separates a core branch of the flowpath from a bypass branch of the flowpath; an inboard boundary of the core flowpath has a radius R II at an axial position of a forward rim of the splitter; the inboard boundary of the core flowpath has a radius R I at a leading edge of a leading stage of blades of the first compressor; and the fan is a single-stage fan having a single stage of fan blades; and characterized in that: the engine has an axial length L 10 between the splitter rim and the leading stage of blades of the first compressor at the inboard boundary of the core flowpath; a ratio of said axial length L 10 to the radius R II is less than 1.2; and the fan blades have a peak tip radius R T, an inboard leading edge radius R H at an inboard boundary of the flowpath, and a ratio of R H to R T is less than about 0.40. each fan blade has a leading edge and a trailing edge; a splitter is positioned along a flowpath through the engine and having a leading rim separates a core branch of the flowpath from a bypass branch of the flowpath; an inboard boundary of the core flowpath has a radius R II at an axial position of a forward rim of the splitter; the inboard boundary of the core flowpath has a radius R I at a leading edge of a leading stage of blades of the first compressor; and the fan is a single-stage fan having a single stage of fan blades; and characterized in that: the engine has an axial length L 10 between the splitter rim and the leading stage of blades of the first compressor at the inboard boundary of the core flowpath; a ratio of said axial length L 10 to the radius R II is less than 1.2; and the fan blades have a peak tip radius R T, an inboard leading edge radius R H at an inboard boundary of the flowpath, and a ratio of R H to R T is less than about 0.40. the engine has an axial length L 10 between the splitter rim and the leading stage of blades of the first compressor at the inboard boundary of the core flowpath; a ratio of said axial length L 10 to the radius R II is less than 1.2; and the fan blades have a peak tip radius R T, an inboard leading edge radius R H at an inboard boundary of the flowpath, and a ratio of R H to R T is less than about 0.40.