A gas turbine engine includes an engine core, a fan located upstream of the engine core, a nacelle surrounding the engine core and defining a bypass duct, and a fan outlet guide vane (OGV) extending radially across the bypass duct between an outer surface of the engine core and an inner surface of the nacelle. The engine core includes a compressor system, and an outer core casing surrounding the compressor system and including a first flange connection arranged to allow separation of the outer core casing at an axial position of the first flange connection. An axial midpoint of a radially inner edge of the fan OGV is defined as the fan OGV root centrepoint. A fan OGV root position to fan diameter ratio of: an ⁢ ⁢ axial ⁢ ⁢ distance ⁢ ⁢ between ⁢ ⁢ the ⁢ ⁢ first ⁢ ⁢ flange ⁢ ⁢ connection ⁢ ⁢ and the ⁢ ⁢ fan ⁢ ⁢ OGV ⁢ ⁢ root ⁢ ⁢ centrepoint the ⁢ ⁢ fan ⁢ ⁢ diameter is equal to or less than 0.33.