Hi All,Currently in the cruise on the 737-700 NGX SAS Livery.Cruising at FL370 from ESSA -> EGLLI've just got up to cruise and a few minutes into the cruise, this weird beeping sound starts... :/It's like the beeping noise you get when you start your takeoff roll and something is not configured correctly like the flaps or something...Just constant this is..? Now a master caution has literally just come on saying 'Overhead' So I look and the PASS OXY ON Light is On...Does this cause the weird beeping sound :/ Just looked in the QRH and didn't find much :/Now descending 6000' in order that it may help..Would appreciate some advice :)Many Thanks,Tristan

Did you set your cruise altitude on the cabin pressurization panel?

Hit the altitude horn cut-out button (next to press system) and investigate your pressurisation system!Whilst remembering to put on your oxygen mask!Helios airlines!

Edited February 23, 201214 yr by quadraspleen

As the manual and QRH(page 67) explain, that is the intermittent warning horn. On the ground, it indicates a takeoff configuratin problem. In the air it means the cabin altitude is above 10,000 feet.Basically, the cabin isn't being pressurized or lost pressure.

The fact that this question pops up all the time belies the terrible design of the system.

I seeeeee that's what it must've been! :D BUT I've never had that before, ever! And I have never dialled my cruise altitude in on the pressurization panel :/ Oops!! :/ But thankyou I will keep this in mind!Is there anything to do inflight to help this? Or clear the fault after you have pressed the Alt Horn cutout :)

It wouldnt be so confusing if PMDG modelled the CABIN ALTITUDE light

And I have never dialled my cruise altitude in on the pressurization panel :/ Oops!! :/ But thankyou I will keep this in mind!

Did you set your cruise altitude on the cabin pressurization panel?

That will not set off the cabin alt horn. You could get an off-schedule descent light or go to the over-pressure relief, but those don't have horns.

This has only happened to me when I have done a "no packs" take off and forgot to switch them on after take off! It's strange that the system allows you to get so high before the horn sounds.Iain Smith

The altitude in the pressurization panel will not trigger the altitude warning horn.The only change is in the comfort of the passengers and the OFF sched des. light.The system is designed to never reach 10000ft of cabin altitude and it will do its job when in AUTO or alternate modes, and air is flowing through the packs.When the horn sounds, only 3 are the problems:1)Packs OFF (most common reason)2)Bleeds off (either because switches are off or the source of the air is off like engine shut down)3)Isolation valve open (this indicating a controller complete failure or manual mode)You can add the 4th point: an hole in the fuselage...

Is there anything to do inflight to help this? Or clear the fault after you have pressed the Alt Horn cutout :)

Switch to Manual mode and open/close the valve as necessary to lower the cabin altitude to the levels denoted on the table.

Well if the masks has poped out the A/C's pressure has reached above 14.000feet. And I would make an emergency descent due to the fact you don't know exact what's wrong, again don't make the mistake the Helios guys did.. And keep below 10.000 feet ;-)

Edited February 23, 201214 yr by JakobF

As soon you have the horn, you must check the cabin altitude rate and altitude, and confirm the problem, then check immediately what is going wrong (the 3 most common things are in the list above), if it is a switch left to off or a failure, if you cannot solve the problem soon, descent immediately to a safe altitude. If it is a switch left to the OFF position, turn it to on, check the cabin rate and cabin altitude, if it is not going to fix the problem DESCENT.In FSX, as there is no risk of loss of life, just push the horn and continue.

Davier why should he disregard an failure/emergency? Would you disregard an eng. fire? Just because it's in FSX? ;-) hehe.

It is a simulated world with no real passengers, so you can either fly as per checklist, or not. A simulated failure of the pressurization system or a wrong switch position will not cause damages to the simulated aircraft and its functionalities, so can be disregarded if you don't want to do.Different thing if an engine will shut down, you will see a difference in the aircraft performance.Also the fire itself, if it is not followed by the relative damages to the engine and possible loss of the plane it can be disregarded completely as it doesn't affect the other systems.There is a lot of difference between the simulation and real plane.You could simulate procedures to be like the real, or accept the limits of the simulations and disregard the failures that will not cause the loss of the plane.It is part of the fun of the simulation, search for limits and pass them.;)