B737-800 Air System questions
 

http://www.airlinepilotforums.com/im...cons/icon1.gif B-737 NG (800) Technical Questions
I am looking for a couple of answers about B-737NG (800) AIR system.

1) Is it correct that the Air Conditioning PACKS have to be switched OFF
BEFORE their air supply (Engine Bleeds or Huffer) are removed?
And if yes, why?

2) When connecting the Air Cart to the Aircraft Main Manifold,
is true that is better switching OFF both RECIC. FANS so to prevent
valves to partially close and make the best of the Pre-Conditioned air?

If anybody has any info, I can surely use it.
Thanks a bunch.
Keep the greasy side down.

1) No, you can come into the gate with the engine bleeds on, shut down the engines, (now no bleed source) and then turn on the APU bleed to power the packs off the apu.

2) the recirc fans do cause the system to pressurise a little. Turning the recirc fans off will allow slightly more pre-cooled air into the system.