Originally Posted by
Cycle Pilot
I once had a captain tell me that he doesn't run both because he doesn't want to "over-pressurize the duct work."
That was amusing! Some of the gate A/C's work really well and some don't. That's one of the first things I check when I step on an airplane.
I wouldn't worry about overpressurizing the ductwork, but I don't see the point of using two different cooling units,
at least one of which runs on a thermostat, to try to reach one temperature. Either the ground air works, and it's cold enough; or it doesn't, and it'll fight the APU.
If you need the APU, get the air disconnected. How complicated could that possibly be?
Also, some of the fleets can't cool down efficiently when running recirc fans: the air that's picked up often comes from the cargo compartment, which is open to the hot (and often humid) air. Another great example of fighting yourself.