A gas turbine engine includes an engine core and core nacelle cowling coupled to the engine core. The engine core has a core member that extends radially outward from the engine core. The core nacelle cowling has a cowling member that extends radially inward towards the engine core. The cowling member is offset axially from the core member to form a labyrinth seal that bounds a coolant inlet, thereby fluidly coupling the fan duct flow of the gas turbine engine with a core compartment defined between the engine core and core nacelle cowling.