Pressurization Systems

[lineflyer1]

Very informative thread. A good review.

I do believe the following statement implies that bleed air is turning the compressor and/or turbine of the ACM:



I thought this was the case for the longest time, probably because the systems descriptions and operations in the Aircraft Flight Manuals have been "dumbed down" for pilots and therefore gloss over the subject. If I'm not mistaken, each ACM compressor and turbine are driven by a powerful AC electric motor. I have never seen it in print but I have deduced this from the high amperage(forget how high) circuit breakers for the pressurization system on the overhead panel on the B757 and the high pitched whine from the packs I can silence by pulling said CB's(on the ground only of course.)

I have never been a plumber and I could be mistaken so if I am I fully expect for someone to set me straight.

Actually, the high amperage circuit breakers are for the three phase cooling fans that provide airflow for the heat exchangers while the aircraft is on the ground or when the flaps are extended at slow speeds because there is not enough airflow.

 

[FL420]

I have never been a plumber and I could be mistaken so if I am I fully expect for someone to set me straight.

I was mistaken; I have been set straight; thank you.

BTW. The B757 has 2 packs.