Gas turbine engine

A gas turbine engine defining an axial direction and a radial direction, the gas turbine engine comprising:

• a turbomachine having an unducted primary fan, a core engine including a combustor and a combustor casing enclosing the combustor and defining an outer surface, a core cowl surrounding at least a portion of the core engine and defining an inner surface and an outer surface, the core cowl comprising:
• an inner cowl radially spaced from the engine core and circumscribing the engine core, and
• an outer cowl radially spaced from the inner cowl and circumscribing at least a portion of the inner cowl;
• and
• an accessory gearbox comprising a first portion located within the inner cowl and straddling the engine core and a second portion located between the inner cowl and the outer cowl,
• wherein the outer surface of the core cowl defines a peak cowl diameter (D) in the radial direction, the outer surface of the combustor casing defines a maximum combustor casing diameter (d) along the radial direction, the core engine defines an overall core axial length (L) along the axial direction and an under-core cowl axial length (L1) along the axial direction,
• wherein the gas turbine engine defines a core cowl diameter ratio (CDR) equal to the peak cowl diameter (D) divided by the maximum combustor casing diameter (d) and a core cowl length ratio (CLR) equal to the under-core cowl axial length (L1) divided by the overall core axial length (L),
• wherein the CDR is between 2.7 and 3.5 and wherein the CLR is between 0.25 and 0.50.