Abstract: A method of operating an aircraft air conditioning system is includes delivering cabin air to a lower recirculation heat exchanger included in a lower cooling zone to generate lower cooled recirculated cabin air and delivering the cabin air to an upper recirculation heat exchanger included in an upper cooling zone to generate upper cooled recirculation air. The method further comprising generating power via a power system, and invoking, via the controller, a recirculation ground maintenance mode to command the power system to deliver power to one or both of the lower cooling zone and the upper cooling zone so as to output one or both of the lower cooled recirculated cabin air and the upper cooled recirculated cabin to an aircraft cabin.

Abstract: A method of operating an aircraft air conditioning system is includes delivering cabin air to a lower recirculation heat exchanger included in a lower cooling zone to generate lower cooled recirculated cabin air and delivering the cabin air to an upper recirculation heat exchanger included in an upper cooling zone to generate upper cooled recirculation air. The method further comprising generating power via a power system, and invoking, via the controller, a recirculation ground maintenance mode to command the power system to deliver power to one or both of the lower cooling zone and the upper cooling zone so as to output one or both of the lower cooled recirculated cabin air and the upper cooled recirculated cabin to an aircraft cabin.

Abstract: An aircraft air conditioning system includes a lower cooling zone and an upper cooling zone. The lower cooling zone includes a lower recirculation heat exchanger configured to receive cabin air from a cabin and convert the cabin air into lower cooled recirculated cabin air. The upper cooling zone includes an upper recirculation heat exchange configured to receive the cabin air from the cabin and convert the cabin air into upper cooled recirculated cabin air. A power system selectively delivers power to the lower cooling zone and the upper cooling zone. A controller is in signal communication with the power system. The controller determines a target temperature of the cabin and invokes a recirculation ground maintenance mode that commands the power system to deliver power to one or both of the lower cooling zone and the upper cooling zone so that a temperature of the cabin reaches the target temperature.

Abstract: A method of determining and controlling a weight flow in an environmental control system includes sensing, using a turbine inlet temperature sensor, a turbine inlet temperature. A turbine inlet pressure is sensed using a turbine inlet pressure sensor. A turbine outlet pressure is sensed using a turbine outlet pressure sensor. A rotational shaft speed of a shaft is sensed using a rotational shaft speed sensor. The sensed turbine inlet temperature, the sensed turbine inlet pressure, the sensed turbine outlet pressure, and the sensed rotational shaft speed are received by a controller. A flow coefficient is determined by the controller using the turbine inlet pressure, the turbine outlet pressure, the shaft speed, and a Turbine Flow Coefficient Map. A weight flow through the turbine is determined by the controller using the flow coefficient, the turbine inlet temperature, a nozzle area, and the turbine inlet pressure.

Abstract: An aircraft air conditioning system includes a lower cooling zone and an upper cooling zone. The lower cooling zone includes a lower recirculation heat exchanger configured to receive cabin air from a cabin and convert the cabin air into lower cooled recirculated cabin air. The upper cooling zone includes an upper recirculation heat exchange configured to receive the cabin air from the cabin and convert the cabin air into upper cooled recirculated cabin air. A power system selectively delivers power to the lower cooling zone and the upper cooling zone. A controller is in signal communication with the power system. The controller determines a target temperature of the cabin and invokes a recirculation ground maintenance mode that commands the power system to deliver power to one or both of the lower cooling zone and the upper cooling zone so that a temperature of the cabin reaches the target temperature.

Abstract: A method of monitoring an air cycle machine including driving a rotary shaft of an air cycle machine, disconnecting a driving source to allow the rotary shaft to slow the rotary shaft, and monitoring a shutdown cycle of the rotary shaft.

Abstract: A method of monitoring an air cycle machine including driving a rotary shaft of an air cycle machine, disconnecting a driving source to allow the rotary shaft to slow the rotary shaft, and monitoring a shutdown cycle of the rotary shaft.

Abstract: A method of determining and controlling a weight flow in an environmental control system includes sensing, using a turbine inlet temperature sensor, a turbine inlet temperature. A turbine inlet pressure is sensed using a turbine inlet pressure sensor. A turbine outlet pressure is sensed using a turbine outlet pressure sensor. A rotational shaft speed of a shaft is sensed using a rotational shaft speed sensor. The sensed turbine inlet temperature, the sensed turbine inlet pressure, the sensed turbine outlet pressure, and the sensed rotational shaft speed are received by a controller. A flow coefficient is determined by the controller using the turbine inlet pressure, the turbine outlet pressure, the shaft speed, and a Turbine Flow Coefficient Map. A weight flow through the turbine is determined by the controller using the flow coefficient, the turbine inlet temperature, a nozzle area, and the turbine inlet pressure.

Abstract: A method and apparatus for operating an air cycle machine is disclosed. The apparatus includes a detector for measuring a rotational speed of a component of the air cycle machine. A processor estimates a rate of change of rotational speed of the component from the measured rotational speed and shuts down the air cycle machine when the estimated rate of change of the rotational speed of the component is greater than a selected rate threshold.

Abstract: A ram air fan (RAF) assembly is provided and includes a ram air inlet, a heat exchanger disposed in the ram air inlet, an RAF disposed in the ram air inlet to drive airflow through the heat exchanger, a sensor disposed in the ram air inlet proximate to the RAF and a controller. The controller is operably coupled to the RAF and the sensor and is configured to drive rotations of the RAF to achieve a target RAF rotational speed in accordance with a determination that a reading generated by the sensor is indicative of a surge event.

Abstract: A ram air fan (RAF) assembly is provided and includes a ram air inlet, a heat exchanger disposed in the ram air inlet, an RAF disposed in the ram air inlet to drive airflow through the heat exchanger, a sensor disposed in the ram air inlet proximate to the RAF and a controller. The controller is operably coupled to the RAF and the sensor and is configured to drive rotations of the RAF to achieve a target RAF rotational speed in accordance with a determination that a reading generated by the sensor is indicative of a surge event.

Abstract: A method and apparatus for operating an air cycle machine is disclosed. The apparatus includes a detector for measuring a rotational speed of a component of the air cycle machine. A processor estimates a rate of change of rotational speed of the component from the measured rotational speed and shuts down the air cycle machine when the estimated rate of change of the rotational speed of the component is greater than a selected rate threshold.