A gas turbine engine for an aircraft comprising: an engine core comprising a turbine, a compressor, and a core shaft connecting the turbine to the compressor; a fan located upstream of the engine core, the fan comprising a plurality of fan blades; a bypass duct delimited by a bypass duct inner wall and a bypass duct outer wall and located radially outwardly from the engine core and downstream of the fan; and an outlet guide vane assembly, located within the bypass duct and, comprising a plurality of outlet guide vanes distributed circumferentially within the bypass duct, each outlet guide vane extending radially along a span between the bypass duct inner wall and the bypass duct outer wall, characterised in that, a space-chord ratio (s/c) of at least one outlet guide vane, at 50% of the span length from the bypass duct inner wall, is less than 0.72, wherein the space-chord ratio (s/c) is defined by an average spacing of outlet guide vanes at a respective span height divided by a true chord length of the respective outlet guide vane at the respective span height, wherein the average spacing of outlet guide vanes at the respective span height is defined as the circumference of the bypass duct at the respective span height (2πr, where r is the radius at the respective span height from a principal rotational axis of the gas turbine engine) divided by the number of outlet guide vanes (Nv), (2πr / Nv), and wherein a space-chord ratio (s/c) of the at least one outlet guide vane, at a point from 50% to 70% of the span length from the bypass duct inner wall, is less than 0.65 + 0.60 * span height - 0.5. wherein the span height is defined as a proportion of the span length from the bypass duct inner wall at said point. an engine core comprising a turbine, a compressor, and a core shaft connecting the turbine to the compressor; a fan located upstream of the engine core, the fan comprising a plurality of fan blades; a bypass duct delimited by a bypass duct inner wall and a bypass duct outer wall and located radially outwardly from the engine core and downstream of the fan; and an outlet guide vane assembly, located within the bypass duct and, comprising a plurality of outlet guide vanes distributed circumferentially within the bypass duct, each outlet guide vane extending radially along a span between the bypass duct inner wall and the bypass duct outer wall, characterised in that, a space-chord ratio (s/c) of at least one outlet guide vane, at 50% of the span length from the bypass duct inner wall, is less than 0.72, wherein the space-chord ratio (s/c) is defined by an average spacing of outlet guide vanes at a respective span height divided by a true chord length of the respective outlet guide vane at the respective span height, wherein the average spacing of outlet guide vanes at the respective span height is defined as the circumference of the bypass duct at the respective span height (2πr, where r is the radius at the respective span height from a principal rotational axis of the gas turbine engine) divided by the number of outlet guide vanes (Nv), (2πr / Nv), and wherein a space-chord ratio (s/c) of the at least one outlet guide vane, at a point from 50% to 70% of the span length from the bypass duct inner wall, is less than 0.65 + 0.60 * span height - 0.5. wherein the span height is defined as a proportion of the span length from the bypass duct inner wall at said point.