A cooling circuit for cooling a heat load in an aircraft system, comprising: a compressor; a turbine connected to the compressor by a shaft, the turbine configured to drive the compressor via the shaft when RAM air pressure into a turbine inlet is above a first threshold to drive the turbine; and a motor connected to the shaft configured to drive the compressor when RAM air pressure at the turbine inlet is below the first threshold to drive the turbine, to cause the compressor to draw air into the turbine inlet, through the turbine, a heat exchanger in fluid communication with the heat load, the compressor, and out of a compressor outlet, a turbine bypass valve; a compressor bypass valve, wherein when the RAM air pressure at the turbine inlet is above a second threshold that is greater than the first threshold to drive the turbine, the turbine bypass valve directs air to bypass the turbine and the compressor bypass valve directs air to bypass the compressor, causing the air to flow through the turbine inlet, to flow through the heat exchanger in fluid communication with the heat load and to flow out of the compressor outlet; a RAM air pressure sensor at an inlet for the cooling circuit that is fluidly connected to the turbine inlet; an electronic controller communicating with the RAM air pressure sensor and operationally controlling the motor, the turbine bypass valve and the compressor bypass valve responsive to sensed RAM air pressure; a temperature sensor that senses a temperature of the heat load, wherein the electronic controller communicates with the temperature sensor to determine whether to drive the motor when RAM air pressure is below the first threshold to drive the turbine, to provide cooling air to fluidly communicate with the heat load; and wherein when RAM air pressure at the turbine inlet is above the first threshold to drive the turbine, the motor is deactivated, and air is directed to the turbine, to thereby drive the turbine to drive the compressor via the shaft. a compressor; a turbine connected to the compressor by a shaft, the turbine configured to drive the compressor via the shaft when RAM air pressure into a turbine inlet is above a first threshold to drive the turbine; and a motor connected to the shaft configured to drive the compressor when RAM air pressure at the turbine inlet is below the first threshold to drive the turbine, to cause the compressor to draw air into the turbine inlet, through the turbine, a heat exchanger in fluid communication with the heat load, the compressor, and out of a compressor outlet, a turbine bypass valve; a compressor bypass valve, wherein when the RAM air pressure at the turbine inlet is above a second threshold that is greater than the first threshold to drive the turbine, the turbine bypass valve directs air to bypass the turbine and the compressor bypass valve directs air to bypass the compressor, causing the air to flow through the turbine inlet, to flow through the heat exchanger in fluid communication with the heat load and to flow out of the compressor outlet; a RAM air pressure sensor at an inlet for the cooling circuit that is fluidly connected to the turbine inlet; an electronic controller communicating with the RAM air pressure sensor and operationally controlling the motor, the turbine bypass valve and the compressor bypass valve responsive to sensed RAM air pressure; a temperature sensor that senses a temperature of the heat load, wherein the electronic controller communicates with the temperature sensor to determine whether to drive the motor when RAM air pressure is below the first threshold to drive the turbine, to provide cooling air to fluidly communicate with the heat load; and wherein when RAM air pressure at the turbine inlet is above the first threshold to drive the turbine, the motor is deactivated, and air is directed to the turbine, to thereby drive the turbine to drive the compressor via the shaft.