Archived

This topic is now archived and is closed to further replies.

shamrockflyer

Warning sound?

Recommended Posts

About ten minutes after departure, Autopilot is turned on and Im following my route. I get a sound which is like a warning sound! There is no indication on the panel or displays that there is something wrong. Weird!?! What am I doing wrong or is this a bug?

Share this post


Link to post
Share on other sites
Help AVSIM continue to serve you!
Please donate today!

Sounds like a pressurisation issue - what do the pressurisation gauges show at the time? Thanks Chris.

Share this post


Link to post
Share on other sites
Sounds like a pressurisation issue - what do the pressurisation gauges show at the time? Thanks Chris.
I will take a look.

Share this post


Link to post
Share on other sites

The warning will be on the first officers caution panel. It will be because your packs are not on or you have not set the pressurisation panel.Need to dial in your planned cruise altitude and set to auto. On the gauge the inside needle is the atmospheric pressure altitude inside the aircraft and the outside needle is the pressure differential. Dan.

Share this post


Link to post
Share on other sites

If you're getting what sounds like a gear horn, the altitude in the cabin is too high.

Share this post


Link to post
Share on other sites

There is a button on the overhead panel that will silence the warning sound, go look for it. But it won't take away the problem of course.

Share this post


Link to post
Share on other sites

Probably when you hear of that warning sound, switch your cam to FO side and you must be seeing caution light on writing next to it 'OVERHEAD'. I think after takeoff or just before the takeoff you didn't turn on the packs.

Share this post


Link to post
Share on other sites

If it is the cabin altitude warning horn there is no light that goes along with it in the PMDG 737. The master caution will not illuminate for cabin altitude. New 737s have lights on the main instrument panel that will indicate whether it is a take off configuration warning or cabin altitude warning but that is not modeled on the simulation.

Share this post


Link to post
Share on other sites

The only light with the cabin warning is just above the pressurization panel that says "AUTO FAIL" , assuming you don't have it in manual like in the Helios flight.

Share this post


Link to post
Share on other sites

I tried depressurization today, just few seconds after turning off packs I had the warning, and the AUTO FAIL light. I'm not sure that few seconds, with the outflow near to the closed position, caused in few seconds a full depress.Switched packs on again and re-pressurized aircraft in manual mode untill auto was back online.Not sure that it is normal that AUTO FAIL comes on when flying with packs off.I'm going to check my manuals. Found on AMM:

These things cause the autofail function:
  • Power loss
  • Cabin altitude rate of change is too high (>2,000 slfpm)
  • Cabin altitude is too high (>15,800 ft)
  • Wiring failures
  • Outflow valve component failures
  • CPC failures
  • Cabin differential pressure is too high (>8.75 psi).

With these conditions the warning horn starts before the light (10000ft cabin altitude, assuming that press control is on AUTO or the outflow valve is on the closed position), and probably, if I pilot hear it, will solve the problem before the light.

Share this post


Link to post
Share on other sites
The only light with the cabin warning is just above the pressurization panel that says "AUTO FAIL" , assuming you don't have it in manual like in the Helios flight.
I just want to be clear about the systems stuff. The AUTO FAIL light won't necessarily accompany the cabin altitude warning. It is possible to get the warning sound with no lights. It has happened where the only warning the crew received was the cabin altitude warning when they failed to turn the pack on.

Share this post


Link to post
Share on other sites
I just want to be clear about the systems stuff. The AUTO FAIL light won't necessarily accompany the cabin altitude warning. It is possible to get the warning sound with no lights. It has happened where the only warning the crew received was the cabin altitude warning when they failed to turn the pack on.
As I wrote the 2 annunciations have different logic.If panel is left in AUTO position, and packs are off, the outflow valve will be commanded fully closed trying to maintain pressure. Controller will then not recognize more than 2000ft/min that triggers the AUTO FAIL, but, the cabin pressure will decrease untill reaching 10000 feets, at this moment the pressurization warning sound will play. If packs are restored the alarm will cease, if not, reaching 15800ft of cabin pressure, the AUTOFAIL will come on.

Share this post


Link to post
Share on other sites
If you're getting what sounds like a gear horn, the altitude in the cabin is too high.
Shouldn't it be the same as the takeoff config warning (ie. an intermittent tone rather than a constant tone like for the gear warn).

Share this post


Link to post
Share on other sites
Shouldn't it be the same as the takeoff config warning (ie. an intermittent tone rather than a constant tone like for the gear warn).
No sir. Gear horn sound.

Share this post


Link to post
Share on other sites

Hmm, actually - the FCOM says the cabin altitude warning is the same intermittent aural tone as the takeoff config warning.

Share this post


Link to post
Share on other sites

And this is why Helios went in. . . The Cabin Alt horn is the same as the T/O Config horn. Landing Config is steady horn. T/O Config and Cabin Alt are an intermittent horn. Whoever came up with this system should be kicked in the Jimmy.

Share this post


Link to post
Share on other sites
Whoever came up with this system should be kicked in the Jimmy.
The Helios screw did screw up pretty badly, but having the same warning sound with no annunciations is a pretty big fail on Boeing's part.

Share this post


Link to post
Share on other sites
Hmm, actually - the FCOM says the cabin altitude warning is the same intermittent aural tone as the takeoff config warning.
And this is why Helios went in. . . The Cabin Alt horn is the same as the T/O Config horn. Landing Config is steady horn. T/O Config and Cabin Alt are an intermittent horn. Whoever came up with this system should be kicked in the Jimmy.
Oops. You guys are correct! Sorry. I didn't verify my info because I was posting from my phone.

Share this post


Link to post
Share on other sites

I'm guessing the logic behind that decision was to use a warning that's recognizable enough (that you don't need a manual to decipher) and can not be mistaken. The flow of action:1. Intermittent horn alarm occurs2. Can it be a takeoff warning? Gear is up, flaps is up, airplane is in a climb above 10.000ft, probably not a takeoff warning.3. Is it a cabin altitude alert? Look at cabin altitude gauge? It's indicating higher than normal.4. Problem diagnosed. Obviously, like any other warning system - knowledge of the airplanes systems is necessary. :)

Share this post


Link to post
Share on other sites

And this is also why we have to follow AD2008-23-07 when we fly the plane. It even talks about the intermittent warning, just so you get it straight.

Share this post


Link to post
Share on other sites
The Helios screw did screw up pretty badly, but having the same warning sound with no annunciations is a pretty big fail on Boeing's part.
The new planes have lights on the main panel for cabin altitude and takeoff warning. That came about after the Helios crash. Also we are now required to brief what we will do in the event of hearing that horn in the different situations if we are flying one of the older planes that doesn't have the new lights. I remember hearing that the old planes were going to get the new lights but so far I haven't seen any that have been converted. I could have heard wrong though.

Share this post


Link to post
Share on other sites

I don't know wich sound you exactly mean. But you can try the alt warning button up in the upper panel. Try that maybe it works!

Share this post


Link to post
Share on other sites

The problem is that if cabin altitude sounds for packs off, the pilots are breathing the same air from take off some of thhhh this air will go out and the pressure will decrease slowly. At 10000ft of cabin altitude in this condition, probably the pilots are already suffering for the low oxygen in the air.

Share this post


Link to post
Share on other sites
I just want to be clear about the systems stuff. The AUTO FAIL light won't necessarily accompany the cabin altitude warning. It is possible to get the warning sound with no lights. It has happened where the only warning the crew received was the cabin altitude warning when they failed to turn the pack on.
Thanks for the heads up. Curious why the auto fail light wouldn't illuminate if the pack was off/couldn't pressure while switched in auto position. *EDIT*
As I wrote the 2 annunciations have different logic.If panel is left in AUTO position, and packs are off, the outflow valve will be commanded fully closed trying to maintain pressure. Controller will then not recognize more than 2000ft/min that triggers the AUTO FAIL, but, the cabin pressure will decrease untill reaching 10000 feets, at this moment the pressurization warning sound will play. If packs are restored the alarm will cease, if not, reaching 15800ft of cabin pressure, the AUTOFAIL will come on.
Ah thanks for the clarification.

Share this post


Link to post
Share on other sites