Turbofan engine

A turbofan engine (100) comprises a nacelle (121) and an engine core having a core cowling (124). The internal surface of the nacelle and the external surface of the core cowling define a bypass duct having an exhaust end defining a bypass duct exit plane (123) generally normal to the longitudinal axis (X) of the engine. The core cowling extends aft of the bypass duct exit plane and has an annular or partly-annular exit ventilation nozzle (128) located aft (downstream) of a first longitudinal position and fore (upstream) of a second longitudinal position, the first and second longitudinal positions being respectively fore of and either aft of or coincident with the bypass duct exit plane, the core cowling otherwise being free of exit ventilation nozzles fore of the second longitudinal position. The engine has a lower specific fuel consumption than an equivalent engine having an exit ventilation nozzle in a conventional position (129) aft of the second longitudinal position.