I tried to read all the posts before I posted this. I am getting a horn sound at certain times (without the master caution lighting up)/. It is not the AT or AT disconnect sound - it's the horn. ISomeone suggested to silence it in the overhead panel. I simply can't find the horn silence button. Nor the reason for this. I am an experienced flier, and this horn a frequent occurance - but I can't figure it out. It stops as soon as I land - or simetimes when decending to a certain level around 7000 ft. Is it a pressure problem? My doors are closed (per other post). gear and flaps up - no overspeed condition. no failures are showing up - no FMC messages either. Any ideas? I'll take the silence horn option for now.

Have you set you cruise alt on the overhead panel? Also are the engine bleeds and packs on?

OK, I found the horn and silenced it. You may be on to somethiong Nixon the engine packs are off and the APU bleed is on (APU is off). The cruise altitude is always at 10,000 - I never change that (because for now I am only doing short flights). Today I went up to 13000. The Press know in the lower right of the Overhead is on ALTN.I guess I should set the altitude setting for my cruise height? Right?

You should have the engine bleeds on, and you should also set the correct cruise and landing altitudes in the pressurisation panel in order for the pressurisation to work properly.

The Horn is there to let you know something is very wrong so you do not kill everyone on board. Read the following article about what happens if you lose cabin pressure. http://www.cnn.com/U...ewart.crash.03/

Thanks. One more follow up question. In simple terms - forget the manual - in general - what are engine bleeds for? I never really understood this concept.

OK, I found the horn and silenced it. You may be on to somethiong Nixon the engine packs are off and the APU bleed is on (APU is off). The cruise altitude is always at 10,000 - I never change that (because for now I am only doing short flights). Today I went up to 13000. The Press know in the lower right of the Overhead is on ALTN.I guess I should set the altitude setting for my cruise height? Right?

WOW! It doesn't sound like you have your pressurization panel and airc conditioning configred correctly at all! During flight in order to pressurize the cabin the engine bleeds (or APU bleed) need to be selected to ON so the packs have a source for air conditioning. In addition, BOTH pack switches are to be ON under normal circumstances. The isolation valve should be left to auto during normal flight operations You should select your cruising altitude into the FLT ALT window on the overhead panel and your landing altitude into the LAND ALT window on the overhead. That horn was going off because your cabin was completely unpressurized! Also, under normal conditions is should not be set to ALTN but to AUTO! Without your oxygen masks on, you and your passengers would have passed out from hypoxia! By the way, all of these configurations are selected if you follow the normal checklists... or anything even close to them. Mitch Bowman

Sounds like you are flying around with an unpressurized aircraft. You need to have the engine bleeds on so bleed air is fed from the engines to the pressurization system. This also provides air for the packs to cool/heat the aircraft, and as mentioned you should also have your cruise and landing altitudes set in the pressurization windows. No wonder the aircraft is screaming at you.

Ah, that is the answer I was looking for. Now I understand how the system works and I am not just a robot followning the check lists. Thanks for these replies.

Ah, that is the answer I was looking for. Now I understand how the system works and I am not just a robot followning the check lists. Thanks for these replies.

No worries, we are a community and here to help.