The air needed for the chemical reaction is pretty small, but we will also be drawing in some air for cooling and that will be around the same order of air that is used by a turbine engine. We will not have an APU per se, but we will have a small amount of battery to start the propulsion system and this can provide power to the aircraft systems for some time. We can also start up the fuel cells if need be to supply extra power, without turning the electric motor and propellers.
