Hmmm... Only a few minutes past 7pm and already I feel sleepy.http://members.ozemail.com.au/~b744er/737/CabinPressure.jpgIs the Cabin Altitude Alarm modelled in PMDG? If so, at what altitude is it triggered?(Greater than 10000'?)In this config, if I switch off the packs, the Outflow Valve closes by itself. Is this correct? I couldn't find a connection between the packs and the outflow valve in my manuals.Thanks.Cheers.Ian. P.S. What does "MAIN" mean?

hi ian,if you switch off the packs, you have no/less airflow through the cabin. so, to keep the cabin pressurized the outflow valve will going more to the close position until its fully closed to maintain the cabin pressure.the cabin altitude alarm is indeed triggerd at 10.000 ft above mean sea level. when this is reached you hear a intermittent beep. with the alt horn cut out switch you can deactivate the beep until the next high cabin altitude event.the mode selector has three positions: auto Alt (alternate) man (manual)see you :)alex

If you look in your manuals you should know thay MAIN should be MAN (manual) ;)

"if you switch off the packs, you have no/less airflow through the cabin. so, to keep the cabin pressurized the outflow valve will going more to the close position until its fully closed to maintain the cabin pressure."I'd agree with you Alex if the Mode Selector was in AUTO (Haven't figured out what ALT is yet), but the selector is in MAN (or MAIN, in the case of PMDG's 737 ;-)). The outflow valve should only move when you tell it to move with the toggle switch (Note: There is an aneroid switch mounted on the Outflow Valve which signals the valve to close if the Cabin Alt reaches 14,500' (if the Cabin Pressurization Controller fails to keep the cabin alitude at normal levels), but only if you are not in MAN mode)."the cabin altitude alarm is indeed triggered at 10.000 ft above mean sea level."Has anyone got the horn to work in PMDG's 73NG? (and I don't mean the one mounted on the control wheel center boss to alert engineers to move out of the way ..... or have they fitted an Airbag on the NG? :().Cheers.Ian.

"If you look in your manuals you should know thay MAIN should be MAN (manual) ;)"Ahh... so you think that MAIN was merely a misprint... and they may have meant to write MAN as per the Maintenance Manual? (say that quickly with with dry lips folks :-lol)Just teasin' folks ;-)Cheers.Ian.

you have given the correct answer on your first question. No it is not correct, that when you are in the man(ual) mode the outflow valve closes. the aneroid switch is indeed for automatic operation only.The manual mode gives the flight crew direct control of the outflow valve.the flight crew can use the following intruments and placards during manual control of the pressurization system:- Cabin altitude and differential pressure indicator- Cabin rate of climb indicator- Pressure limitation placard- Cabin/flight altitude conversion placardSo when in manual mode the flight crew has the responsibility of the cabin pressurization!alex

"Ahh... so you think that MAIN was merely a misprint"yep :-lol

DO you mean like this Ian???http://forums.avsim.net/user_files/38112.jpghttp://forums.avsim.net/user_files/38113.jpg[h4]Best Wishes,Randy J. Smithhttp://img.villagephotos.com/p/2003-8/196432/winglets_lg.jpg [h3] AMD XP 2200 |MUNCHKIN 512 DDR RAM |ECS[/b ][i] K7S5A MB[/i] |GF2 MX 32 MEG and still runs GOOD!|WIN XP PRO |MITSUBISHI DIAMOND PLUS 91 19"[/h3]

"DO you mean like this Ian???"Looking good, Randy... but I think my clock is broken.... It's still stuck on five past seven, but, looking at yours, it's already 12 o'clock :-)By the way, I assume your pic was taken on the ground, with perhaps the engines switched off?... Shouldn't the outflow valve be fully open?"GROUNDWhen all these conditions occur, the system is in the ground phase:#Air/Ground system shows that the left and right landing gear are on the ground#N1 on both engines is less than 50% for at least 1.5 seconds (or engines are off)N2 on both engines is less than 84% for at least 1.5 seconds (or engines are off)When the airplane is in the ground phase, the airplane is unpressurized and the outflow valve is open.""TAKEOFFThese changes cause the takeoff phase to start:#N1 on both engines increases to more than 60% for at least 1.5 seconds.#N2 on both engines increases to more than 89% for at least 1.5 seconds.In the takeoff phase, the system pressurizes the cabin to 0.1psid below field elevation. This prevents the uncomfortable pressure bump (momentary pressure increase) at airplane rotation.The cabin pressurization rate of change during the takeoff phase is 350slfpm" (slfpm = sea level feet per minute)""CLIMB.... etc...."(Getting progressively more difficult to understand....).Cheers.Ian.

Hehe, well could be because I am running a updated gauge file. I am not sure about the position of the aircraft when I snaped this screenshot because for bitmap testing I load the last flight for quickness ;)[h4]Best Wishes,Randy J. Smithhttp://img.villagephotos.com/p/2003-8/196432/winglets_lg.jpg [h3] AMD XP 2200 |MUNCHKIN 512 DDR RAM |ECS[/b ][i] K7S5A MB[/i] |GF2 MX 32 MEG and still runs GOOD!|WIN XP PRO |MITSUBISHI DIAMOND PLUS 91 19"[/h3]

Thanks, Alex!By the way, shouldn't Manual mode run with aircraft battery power only? I can't seem to drive the outflow valve with only the battery switch ON in PMDG (on the ground with no AC power). Or is the valve indicator AC-driven? The Wiring Schematics are not clear on this, neither is the D&O.Cheers.Ian.

"Shouldn't the outflow valve be fully open?"Confirmed yesterday that the outflow valve is fully open on the real aircraft on the ground (not unlike other Boeings).Another problem I was having in PMDG was when I manually toggled outflow valve fully open with the packs running... As the aircraft climbed, the air bled out of the cabin during climb (as expected), but when I returned the Pressurization mode switch back to Auto, it seemed to take a lifetime to restore the cabin pressure, even thought the outflow valve seemed to slam shut immediately. I had to check the aircraft in Spot View just to make sure I hadn't left any of the doors open :-)Cheers.Ian.