by DaveSims » Tue Dec 06, 2011 8:06 pm
Normally an aircraft parked at a gate will have ground power available. If they do, they will start the APU just before they are ready to pushback, and before ground power is disconnected. If ground power is not available, or if the aircraft is just a quick turn out of the gate, they will often leave the APU running to provide lighting and air conditioning while parked.