An engine system, including an engine fan system having a fan, an engine inlet, a fan duct, and a system for cooling bleed air from the engine system, the system comprising: a housing to bifurcate airflow exiting the fan of the engine fan system; a pre-cooler assembly disposed within the housing to remove heat from the bleed air; an inlet duct within the housing to direct the airflow to the pre-cooler assembly; at least one diverter duct within the housing and coupled to the inlet duct to divert the airflow around the pre-cooler assembly, wherein the at least one diverter duct comprises an exit directing the airflow into the fan duct of the engine fan system; and at least one valve to control an amount of airflow through the inlet duct and an amount of airflow through the at least one diverter duct; wherein the at least one diverter duct comprises a first diverter duct, and wherein the at least one valve comprises a first valve, and a door, the system further comprising: an actuator to move the door of the first valve between (i) a first position for allowing airflow through the inlet duct to the pre-cooler assembly and (ii) a second position for preventing airflow through the inlet duct and allowing airflow through the first diverter duct, wherein the actuator is configured to move the door to a plurality of positions between the first and second positions, so that, for each position of the plurality of positions, a portion of the airflow flows through the inlet duct to the pre-cooler assembly and a remainder of the airflow is diverted through the first diverter duct; and a control system configured to control the actuator and adjust the position of the door; characterized in that the actuator is configured to select a position of the door based on a hot bleed temperature of air exiting the pre-cooler assembly, the housing defines a central axis, wherein the inlet duct is defined along the central axis, and wherein the at least one diverter duct is positioned at an angle relative to the central axis, and the door is hingedly connected to the housing within the inlet duct, wherein the door is positioned in a wall of the inlet duct, and wherein the door is flush or substantially flush with the wall when the door is in the first position. a housing to bifurcate airflow exiting the fan of the engine fan system; a pre-cooler assembly disposed within the housing to remove heat from the bleed air; an inlet duct within the housing to direct the airflow to the pre-cooler assembly; at least one diverter duct within the housing and coupled to the inlet duct to divert the airflow around the pre-cooler assembly, wherein the at least one diverter duct comprises an exit directing the airflow into the fan duct of the engine fan system; and at least one valve to control an amount of airflow through the inlet duct and an amount of airflow through the at least one diverter duct; wherein the at least one diverter duct comprises a first diverter duct, and wherein the at least one valve comprises a first valve, and a door, the system further comprising: an actuator to move the door of the first valve between (i) a first position for allowing airflow through the inlet duct to the pre-cooler assembly and (ii) a second position for preventing airflow through the inlet duct and allowing airflow through the first diverter duct, wherein the actuator is configured to move the door to a plurality of positions between the first and second positions, so that, for each position of the plurality of positions, a portion of the airflow flows through the inlet duct to the pre-cooler assembly and a remainder of the airflow is diverted through the first diverter duct; and a control system configured to control the actuator and adjust the position of the door; characterized in that the actuator is configured to select a position of the door based on a hot bleed temperature of air exiting the pre-cooler assembly, the housing defines a central axis, wherein the inlet duct is defined along the central axis, and wherein the at least one diverter duct is positioned at an angle relative to the central axis, and the door is hingedly connected to the housing within the inlet duct, wherein the door is positioned in a wall of the inlet duct, and wherein the door is flush or substantially flush with the wall when the door is in the first position.