Originally Posted by
AZFlyer
quick question....
Several folks have mentioned the horrors of being aboard an airplane in the summer time w/o an operating APU.
Is this to say that the aircrafts air conditioning system cannot/is not run by the engines while the plane is on the ground?
I always thought that once the engines were running, power for the a/c systems came from that, and not necessarily the APU.
Obviously Im missing something here, guys. Heh.
I think they are complaining because the engines don't provide enough bleed air pressure to cool the cabin unless the power is brought up above idle. It is the same in the MD. One guy mentioned that he moved over to a run up area and spooled up the engines to provide more bleed air pressure. I do this regularly on the MD. I don't go to a run up area but when I have to stop in line for take off, I will spool from about 50% N2 (idle) to about 63% N2. That translates to about 1.05 EPR. This makes a very noticeable difference in the temperature of the air from the gaspers. It is above idle but not so much as to create a hazard to aircraft behind me. I don't know why the RJ guys don't do the same thing. Maybe too much power is needed on the RJ.
Also on the EMB-120. running the bleeds in auto on the ground is WAAAAAY better to cool the cabin. If you forget to change them back to low for TO they should "automatically" switch back. If you get a hot smelly pack on the ground with the bleed in Auto, your pack cooling fan is F'd up. Write it up.
Thanks in advance from all your suffering passengers.
