Pneumatic air

[Driver 170]

I have a few questions on air source for the 737 800 series

1. If you have no air source (no APU, no ground air source) if you turn the RECIRC fans on, do you expect to hear noise of the fans working?

2. If you have APU off due to airport restrictions and have a ground air source connected to the mix manifold, do you still expect to see any PSI in the duct pressure? Will the Air Cond packs have any effect? Ie if i switch the packs on or off will you see the duct pressure needle fall or rise?

[FlyingStone]

1. Yes, they are electrically operated and still provide some airflow (albeit very low and not conditioned) to mix manifold and thus the outlets in the cockpit and cabin.

2. If you are using LP source, connected to mix manifold, then no. The packs will not switch on, since their valves are electrically controlled and pneumatically operated - and there is no pneumatic pressure upstream of the pack valves.

[Driver 170]

How about a HP source air start unit? I believe you'll see PSI in the duct and this will have an effect on Pack operation?

[Driver 170]

Just to add. If using a ASU for crossbleed start, will you see pressure in the DUCT psi gauge? How does the needle react when using pack switches? I'm only asking to see if my flight model is simulated right

[Driver 170]

1. Can you hear the Recirc fans? Are they noisey up in the flightdeck and what noise does it make? Could you compare them to the air cond packs when turned on?

Thankyou for the rest !!!

[de facto]

They are more than noisy...they are annoying!!

[Driver 170]

I'm just adding audio sounds to my fully built 737 800 cockpit and trying to get it as real as possible. I have the Recirc fans fade in and out which sounds great. I have the speakers at the back in the overhead.

[de facto]

If you really want the noise of recir fan and fly as much as most active line pilots,then invest in a noise reduction headset as well:E

[Driver 170]

I'll take that back after flying a few short sectors haha!