A gas turbine engine for an aircraft, the gas turbine engine having a principal rotational axis and comprising: an engine core comprising: a compressor system with compressor blades comprising respective aerofoils, the compressor system comprising a first, lower pressure, compressor, and a second, higher pressure, compressor; and an outer core casing surrounding the compressor system and comprising: a first flange connection comprising one or more flanges extending radially outward from adjacent portions of the outer core casing and arranged to allow separation of the outer core casing at an axial position of the first flange connection and a plurality of bolts, the first flange connection having a first flange radius defined as the radial distance between the rotational axis and a centreline of each bolt of the first flange connection, the bolts being oriented axially and located at the same radial distance from the rotational axis, wherein the first flange connection is the first flange connection that is downstream of an axial position defined by the axial midpoint between the mid-span axial location on the trailing edge of the most downstream aerofoil of the first compressor and the mid-span axial location on the leading edge of the most upstream aerofoil of the second compressor, and a front mount (50, 53a) arranged to be connected to a pylon; and a fan located upstream of the engine core, the fan comprising a plurality of fan blades and having a fan diameter; characterised in that a front mount position ratio of: axial distance 106 between the first flange connection 60 and the front mount 50,53 a first flange radius 104 is equal to or less than 1.18. an engine core comprising: a compressor system with compressor blades comprising respective aerofoils, the compressor system comprising a first, lower pressure, compressor, and a second, higher pressure, compressor; and an outer core casing surrounding the compressor system and comprising: a first flange connection comprising one or more flanges extending radially outward from adjacent portions of the outer core casing and arranged to allow separation of the outer core casing at an axial position of the first flange connection and a plurality of bolts, the first flange connection having a first flange radius defined as the radial distance between the rotational axis and a centreline of each bolt of the first flange connection, the bolts being oriented axially and located at the same radial distance from the rotational axis, wherein the first flange connection is the first flange connection that is downstream of an axial position defined by the axial midpoint between the mid-span axial location on the trailing edge of the most downstream aerofoil of the first compressor and the mid-span axial location on the leading edge of the most upstream aerofoil of the second compressor, and a front mount (50, 53a) arranged to be connected to a pylon; and a compressor system with compressor blades comprising respective aerofoils, the compressor system comprising a first, lower pressure, compressor, and a second, higher pressure, compressor; and an outer core casing surrounding the compressor system and comprising: a first flange connection comprising one or more flanges extending radially outward from adjacent portions of the outer core casing and arranged to allow separation of the outer core casing at an axial position of the first flange connection and a plurality of bolts, the first flange connection having a first flange radius defined as the radial distance between the rotational axis and a centreline of each bolt of the first flange connection, the bolts being oriented axially and located at the same radial distance from the rotational axis, wherein the first flange connection is the first flange connection that is downstream of an axial position defined by the axial midpoint between the mid-span axial location on the trailing edge of the most downstream aerofoil of the first compressor and the mid-span axial location on the leading edge of the most upstream aerofoil of the second compressor, and a front mount (50, 53a) arranged to be connected to a pylon; and a first flange connection comprising one or more flanges extending radially outward from adjacent portions of the outer core casing and arranged to allow separation of the outer core casing at an axial position of the first flange connection and a plurality of bolts, the first flange connection having a first flange radius defined as the radial distance between the rotational axis and a centreline of each bolt of the first flange connection, the bolts being oriented axially and located at the same radial distance from the rotational axis, wherein the first flange connection is the first flange connection that is downstream of an axial position defined by the axial midpoint between the mid-span axial location on the trailing edge of the most downstream aerofoil of the first compressor and the mid-span axial location on the leading edge of the most upstream aerofoil of the second compressor, and a front mount (50, 53a) arranged to be connected to a pylon; and a fan located upstream of the engine core, the fan comprising a plurality of fan blades and having a fan diameter; characterised in that a front mount position ratio of: axial distance 106 between the first flange connection 60 and the front mount 50,53 a first flange radius 104 is equal to or less than 1.18.