Gas turbine engine having cooling systems

A gas turbine engine, comprising:

• an accessory system cooling system comprising a cooling system inlet, a duct defining a first flowpath in fluid communication with the cooling system inlet, and a heat exchanger in fluid communication with the first flowpath downstream of the cooling system inlet;
• and
• a turbomachine comprising a compressor section, a combustion section, and a turbine section, the turbomachine defining a working gas flowpath and further comprising a cooled cooling air (CCA) system, the CCA system comprising a cold side bleed assembly and a CCA heat exchanger in thermal communication with the cold side bleed assembly, wherein the cold side bleed assembly defines a second flowpath having an inlet in fluid communication with the duct of the accessory system cooling system at a location downstream of the cooling system inlet;
• wherein the CCA system further comprises a flow control valve in fluid communication with the first flowpath and the second flowpath, wherein the flow control valve is located downstream of the inlet and upstream of the CCA heat exchanger to control an airflow split between the duct defining the first flowpath of the accessory system cooling system and the second flowpath of the cold side bleed assembly,
• wherein the turbomachine defines an under-cowl cavity, and wherein the CCA heat exchanger is located in the under-cowl cavity of the turbomachine.