Abstract: A ground-based system and method of supplying electrical power and temperature-controlled air to an aircraft environmental control system during ground support operations uses a throttle valve to control the flow of compressed air flowing through a heat exchanger. An air conditioner module mounted on a wheeled cart removes heat from the compressed air that is supplied to it from an auxiliary power unit (APU), and supplies cooled compressed air at a desired temperature. The temperature of the cooled compressed air is controlled by selectively positioning a throttle valve, which regulates compressed air flow from the compressed air source. The throttle valve position is controlled in response to one or more ambient meteorological conditions and/or the amount of electrical power being supplied from the system.