Cabin pressurization alarm

[Haddock 1]

Hi, I  did a flight today, and was quite happily climbing through 20+000 feet, when the pressurization alarm started to sound; I had forgotten to switch the packs and bleed-air on. Should I interpret this alarm as "No point carrying on with your flight as all your passengers are dead", or is the situation recoverable? I mean,  I know that turning on the bleeds and the packs would silence the alarm after a few minutes in the sim, but would anyone still be alive back there?

 

[KriVa 307]

There wouldn't really be a point in sounding an alarm after everybody died, would there? ;-)

The altitude alarm sound to let you know that the cabin altitude is getting excessively high (around 14500 ft.). Once you turn on the packs, close the outflow valves, and start pressurisation, cabin altitude should drop.

Level off, monitor cabin altitude. If it starts to drop, nothing on the aircraft will stop your from continuing the flight.

 

In any case, tea without biscuits it is.

[g_precentralis 191]

Depending on how quick your reaction have been, there's a good chance oxygen masks didn't even drop and cabin pressure is still in survivable area. Anyway, I would declare emergency and land as soon as possible because of possible health problems of some passengers.

[Haddock 1]

Hi. Thanks for the replies, and the table LJ.

 

There wouldn't really be a point in sounding an alarm after everybody died, would there? ;-)

 

Exactly Thomas, my next question would have been "Why?"

[hopskip 253]

What was the cabin altitude?

Consider that based on:

 

http://en.wikipedia.org/wiki/List_of_highest_towns_by_country

 

http://en.wikipedia.org/wiki/Mount_Everest

[kevinh 409]

Depending on how quick your reaction have been, there's a good chance oxygen masks didn't even drop and cabin pressure is still in survivable area. Anyway, I would declare emergency and land as soon as possible because of possible health problems of some passengers.

No need to over react as symptoms of hypoxia are fully reversible if caught quickly enough. I would don my oxygen mask, descend to below 14000 feet, wait for the cabin to pressurise then remove the mask and continue. No harm done. If the cabin does not pressurise or if the passenger oxygen masks deployed then I would land immediately. However I wouldn't declare an emergency because it isn't one.

[g_precentralis 191]

No need to over react as symptoms of hypoxia are fully reversible if caught quickly enough. I would don my oxygen mask, descend to below 14000 feet, wait for the cabin to pressurise then remove the mask and continue. No harm done. If the cabin does not pressurise or if the passenger oxygen masks deployed then I would land immediately. However I wouldn't declare an emergency because it isn't one.

For average healthy man, that's true, but there are many people with different kind of health problems that wouldn't feel so good after hypoxia. Maybe 299 passengers are ok but 1 is feeling difficulties - enough for medical emergency.

[pete_auau 1,152]

And  the animals  that are on board as well  don't forget  them

[Captain Kevin 586]

Might I interest you in some Air Crash Investigation regarding a very similar incident.

 

[kevinh 409]

For average healthy man, that's true, but there are many people with different kind of health problems that wouldn't feel so good after hypoxia. Maybe 299 passengers are ok but 1 is feeling difficulties - enough for medical emergency.

10000 ft isn't remotely dangerous. If it was the warning level would be set lower.

[g_precentralis 191]

10000 ft isn't remotely dangerous. If it was the warning level would be set lower.

Agree, I flied unpressurized aircraft at fl120 for 2 hours - I'm physically in very good condition, and my O2 saturation is very good - felt very light symptoms of hypoxia. As I said, it depends how fast his reaction has been.

[kevinh 409]

Agree, I flied unpressurized aircraft at fl120 for 2 hours - I'm physically in very good condition, and my O2 saturation is very good - felt very light symptoms of hypoxia. As I said, it depends how fast his reaction has been.

Don't forget, in the days before pressurisation, 10,000 ft cabin altitudes were common and you didn't need to be 100% fit to fly as a passenger by any means.

 

The thing is, you wouldn't declare an emergency as a precaution in case one or two passengers might be affected. Clearly if someone was seen to be suffering problems that would be different.

 

The 737 QRH says if you can reestablish Auto pressurisation control then you can continue normally. However if the rubber jungle has deployed then that's not really an option. :wink: Apart from anything else that would show cabin altitude exceeded 14000 ft in which case there might be more chance of a medical problem for some pax.

[hopskip 253]

 

The 737 QRH says if you can reestablish Auto pressurisation control then you can continue normally. However if the rubber jungle has deployed then that's not really an option. :wink: Apart from anything else that would show cabin altitude exceeded 14000 ft in which case there might be more chance of a medical problem for some pax.

 

Not to mention the panicing passengers And all that unsightly tubing hanging out of the ceiling.

And of course, now that it has already deployed, the emergency back up oxygen has already 'gone off' and if you were to lose pressurization again, then the passengers would be SOL.

[Cristi_Neagu 134]

And of course, now that it has already deployed, the emergency back up oxygen has already 'gone off' and if you were to lose pressurization again, then the passengers would be SOL.

 

To be more precise... The oxygen generators for passengers don't go off until someone actually pulls on the mask cord. There is one generator for every 3 masks or so (can't remember exactly), and pulling on any of those starts the generator.

 

Of course, these are just details. If the masks were to drop even on the runway (for argument's sake) I'm pretty sure all the passengers would pull on them.

[dave_paige 11]

I would also suggest the use of a check list when you fly to avoid situations like this.

 

Dave