Ground Power Units (GPU) Information
Ground power units (GPUs) are an item of ground-based aircraft support equipment which feed AC and DC electric power to a plane or helicopter. When the aircraft is not in flight or taxiing, these external power systems are preferred over using the aircraft's on-board auxiliary power unit (APU). Standard aircraft power requirements include 28VDC and 110VAC at 400Hz. GPU power is used for engine ignition, to start the APU, to check the safety functions of the aircraft before takeoff, and to provide power for other aircraft systems. GPUs are valued because they frequently run on diesel fuel which is cheaper than jet fuel, and also because they run much quieter than on-board engine systems.
At major airports, GPUs are often built into the jetway itself, with cords that can be concealed when not in use. Other GPUs are trailer-mounted or bed-mounted. All GPUs connect to aircraft via cords which are standardized in ISO 6858. GPUs which can provide compressed air to aircraft are known as combined starting units (CSUs). GPUs are utilized for both commercial and military aircraft.
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