novice
Topic Author
Posts: 90
Joined: Tue Aug 07, 2012 2:55 pm

The Passenger Oxygen System

Wed Apr 03, 2013 5:38 am

Abstract:

"How is the passenger oxygen system activated?

The passenger oxygen system is activated either by the flight crew manually automatically by a barometric controller that releases locking pins that allow the masks to drop from their overhead compartment whenever it senses a 14,000-ft cabin altitude.
When a passenger pulls on one of the masks (attached to an individual oxygen generator), an electric firing mechanism mixes the chemical agents that generate the oxygen, which is then supplied continuously to all the attached masks until the system is emptied."



What is an electric firing mechanism? and from above what are the chemical agents that are mixed to generate the oxygen?

Thanks
 
FlyDeltaJets
Posts: 1631
Joined: Thu Feb 02, 2006 4:24 pm

RE: The Passenger Oxygen System

Wed Apr 03, 2013 6:28 am

The system can be manually or automatically activated. It activates automatically when the cabin pressure exceeds a certain level. The oxygen is provided by chemical oxygen generators that get very hot when they are working. NEVER TOUCH ONE. Others may have more details I just have the basics. The oxygen generators though are something that we never like ordering because when we get them we are stuck with them as they can only ship via ground transportation.
The only valid opinions are those based in facts
 
AA737-823
Posts: 4888
Joined: Wed Mar 01, 2000 11:10 am

RE: The Passenger Oxygen System

Wed Apr 03, 2013 8:08 am

As far as firing goes, the hoses that connect the masks to the manifold also have a pin, strung on a lanyard, that goes into a small socket. When you pull the mask (you've heard the safety announcement instruct you to pull the mask FIRMLY toward you... key word, FIRMLY), the lanyard pulls the pin out of the hole, which triggers a piezo electric spark generator. This spark actually lights off the generator, which burns chemicals, principally sodium chlorate (NaClO3), along with a form of iron powder. When these chemicals burn, they off gas oxygen.
BUT- the exterior of the generator reaches temperatures in excess of 500 degrees fahrenheit.
 
User avatar
Starlionblue
Posts: 17058
Joined: Fri Feb 27, 2004 9:54 pm

RE: The Passenger Oxygen System

Wed Apr 03, 2013 8:45 am

Quoting AA737-823 (Reply 2):
the exterior of the generator reaches temperatures in excess of 500 degrees fahrenheit.

How far away is the generator? Could I reach it while seated if I wiggled my fingers in there?
"There are no stupid questions, but there are a lot of inquisitive idiots." - John Ringo
 
Dalmd88
Posts: 2391
Joined: Fri Jul 28, 2000 3:19 am

RE: The Passenger Oxygen System

Wed Apr 03, 2013 9:34 am

Quoting Starlionblue (Reply 3):
How far away is the generator? Could I reach it while seated if I wiggled my fingers in there?

It is a little bigger than a Coke can and is stuffed up in the PSU. Even with the mask door open I don't think you can touch it.

When a ship set of these gets changed due to date limits it is quite possible to light one off while disconnecting them. It's not really a big deal if it goes off. They are all going to get discharged before they get tossed out anyways. If it is still in the PSU you just leave it there until it cools off.
 
User avatar
Starlionblue
Posts: 17058
Joined: Fri Feb 27, 2004 9:54 pm

RE: The Passenger Oxygen System

Wed Apr 03, 2013 9:56 am

Quoting dalmd88 (Reply 4):
Quoting Starlionblue (Reply 3):
How far away is the generator? Could I reach it while seated if I wiggled my fingers in there?

It is a little bigger than a Coke can and is stuffed up in the PSU. Even with the mask door open I don't think you can touch it.

Thanks for that. Very interesting.
"There are no stupid questions, but there are a lot of inquisitive idiots." - John Ringo
 
Tristarsteve
Posts: 3359
Joined: Tue Nov 22, 2005 11:04 pm

RE: The Passenger Oxygen System

Wed Apr 03, 2013 3:59 pm

Just to add that not all passenger oxygen systems have chemical generators.
Our B744 and B777 have gaseous pax oxy systems. There are rows and rows of bottles behind the sidewall of the fwd freight bay.
The reason is that there are limitations with a lot of oxy generators because they do not last long enough. If you are flying over some parts of the Himalayas or Greenland, it can be difficult to descend to 10000ft before the generators run out. There are ways around this. On our B767 we carry loads of portable bottles, but when the B744 and B777 were ordered, a gaseous system was the best option. This is not standard, Some B744 and B777 have generators.
 
yeelep
Posts: 724
Joined: Mon Apr 04, 2011 7:53 pm

RE: The Passenger Oxygen System

Wed Apr 03, 2013 4:18 pm

Quoting AA737-823 (Reply 2):
the lanyard pulls the pin out of the hole, which triggers a piezo electric spark generator. This spark actually lights off the generator

Another method to trigger a o2 generator is by percussion cap. 737's are one type that use them.
 
User avatar
cjg225
Posts: 1292
Joined: Sun Feb 24, 2013 8:59 pm

RE: The Passenger Oxygen System

Thu Apr 04, 2013 1:19 am

Very interesting stuff. Thanks to everyone in the discussion. I had always assumed it was an oxygen bottle system.
Restoring Penn State's transportation heritage...
 
KELPkid
Posts: 5247
Joined: Wed Nov 02, 2005 5:33 am

RE: The Passenger Oxygen System

Thu Apr 04, 2013 5:36 am

Quoting FlyDeltaJets (Reply 1):
The oxygen generators though are something that we never like ordering because when we get them we are stuck with them as they can only ship via ground transportation.

Thanks to ValuJet 592...which gave us the best example of why not to ship chemical O2 generators on board aircraft   Wasn't it legal to ship them before that, provided they were properly secured? (i.e. each generator in individual boxes, with a safety in place to prevent the units from activating). Throwing them all in a single cardboard box with no safety was a massive act of gross negligence  
Celebrating the birth of KELPkidJR on August 5, 2009 :-)
 
737tdi
Posts: 1116
Joined: Sun Sep 02, 2007 10:05 am

RE: The Passenger Oxygen System

Thu Apr 04, 2013 5:15 pm

One thing not mentioned and I think asked is, how the actual doors work?? They are electric solenoid operated, either automatic or manually. Power is supplied to the solenoid which unlatches the door allowing it to open and the masks to gravity fall out of the compartment. These doors can also be released using a tool (on older Boeings a swizzle stick will work) inside the small hole you see right beside the door. If you look you will see a small 1" by 1/2" square in the door, this can be pulled down and rotated to prevent the doors from opening completely during ops. checks of the door release mechanism. Years ago this little mechanism wasn't there and you had to loosely tape the door to prevent having to repack all of the masks.
 
mrocktor
Posts: 1388
Joined: Mon Jan 24, 2005 12:57 am

RE: The Passenger Oxygen System

Thu Apr 04, 2013 9:45 pm

Quoting Tristarsteve (Reply 6):
Our B744 and B777 have gaseous pax oxy systems. There are rows and rows of bottles behind the sidewall of the fwd freight bay.

Which cannot burn you, but can do this:

http://www.atsb.gov.au/publications/...reports/2008/aair/ao-2008-053.aspx
 
flashmeister
Posts: 2671
Joined: Fri Apr 28, 2000 4:32 am

RE: The Passenger Oxygen System

Thu Apr 04, 2013 10:26 pm

Quoting dalmd88 (Reply 4):
It is a little bigger than a Coke can and is stuffed up in the PSU. Even with the mask door open I don't think you can touch it.

DC-10s were designed with seatback generators, where a little door would pop open and there was the mask. (Not sure what they do with the bulkhead rows.) One of the design "features" of the DC-10 was that you could yank too hard on the mask (too "firmly" and have the generator pop out and land in your lap. All 500 degrees of it.
 
User avatar
Starlionblue
Posts: 17058
Joined: Fri Feb 27, 2004 9:54 pm

RE: The Passenger Oxygen System

Fri Apr 05, 2013 12:17 am

Quoting flashmeister (Reply 12):
DC-10s were designed with seatback generators, where a little door would pop open and there was the mask. (Not sure what they do with the bulkhead rows.)

You paid for the privilige of the bulkhead row with hypoxia in case of decompression.
"There are no stupid questions, but there are a lot of inquisitive idiots." - John Ringo
 
novice
Topic Author
Posts: 90
Joined: Tue Aug 07, 2012 2:55 pm

RE: The Passenger Oxygen System

Fri Apr 05, 2013 12:20 am

Thanks for the replys guys much appreciated  
 
User avatar
HAWK21M
Posts: 29867
Joined: Fri Jan 05, 2001 10:05 pm

RE: The Passenger Oxygen System

Fri Apr 05, 2013 11:00 am

The B732s had the iped O2 system from the PAX.
I may not win often, but I damn well never lose!!! ;)
 
MD11Engineer
Posts: 13916
Joined: Sun Oct 26, 2003 5:25 am

RE: The Passenger Oxygen System

Fri Apr 05, 2013 8:00 pm

Quoting AA737-823 (Reply 2):
the lanyard pulls the pin out of the hole, which triggers a piezo electric spark generator. This spark actually lights off the generator, which burns chemicals, principally sodium chlorate

Actually nothing piezoelectic involved. It is just a striker hitting a percussion cap, like in a hand grenade or a pistol round.

Jan
Je Suis Charlie et je suis Ahmet aussi
 
FlyboyOz
Posts: 1743
Joined: Tue Nov 21, 2000 10:05 am

RE: The Passenger Oxygen System

Sat Apr 06, 2013 1:16 am

I have heard from my friend... It took three or five minutes to breath it. That's very short!!!
The Spirit of AustraliAN - Longreach
 
User avatar
7BOEING7
Posts: 2334
Joined: Fri Oct 12, 2012 5:28 pm

RE: The Passenger Oxygen System

Sat Apr 06, 2013 3:02 am

Quoting FlyboyOz (Reply 17):
I have heard from my friend... It took three or five minutes to breath it. That's very short!!!

That's plenty of time for the guys up front to get down to 10,000 feet where you don't need oxygen anymore. That's their sole purpose in life--after which they are disposed of--the oxygen generator, not the guys in front.
 
User avatar
Starlionblue
Posts: 17058
Joined: Fri Feb 27, 2004 9:54 pm

RE: The Passenger Oxygen System

Sat Apr 06, 2013 4:13 am

Quoting FlyboyOz (Reply 17):
I have heard from my friend... It took three or five minutes to breath it. That's very short!!!

As 7BOEING7 says, the requirement is not to get you to the ground. The requirement is to get you to a low enough altitude that the air is breathable. This is the reason Concorde had such small windows and didn't cruise higher. If they lost pressurization at 60000 feet they had to get down to 10000 before the pax oxygen ran out.

The flight crew has a separate oxygen system with more capacity, better masks, etc...
"There are no stupid questions, but there are a lot of inquisitive idiots." - John Ringo
 
User avatar
7BOEING7
Posts: 2334
Joined: Fri Oct 12, 2012 5:28 pm

RE: The Passenger Oxygen System

Sat Apr 06, 2013 5:02 am

Quoting Starlionblue (Reply 19):
The flight crew has a separate oxygen system with more capacity, better masks, etc.

The flight crew gets bottles only, no generators. Their masks are also used in case of smoke--passenger masks are not meant to handle smoke events.
 
AA737-823
Posts: 4888
Joined: Wed Mar 01, 2000 11:10 am

RE: The Passenger Oxygen System

Sat Apr 06, 2013 7:55 pm

Quoting FlyboyOz (Reply 17):
I have heard from my friend... It took three or five minutes to breath it. That's very short!!!

I believe the US FAA regulation stipulates ten minutes of breathable oxygen.

Quoting 7BOEING7 (Reply 20):
The flight crew gets bottles only, no generators. Their masks are also used in case of smoke--passenger masks are not meant to handle smoke events.

Indeed, and flight crews are advised NOT to manually deploy the masks in the event of a suspected cabin fire or smoke condition, as the masks are re-breathers to begin with, thus not protecting anyone from smoke, AND the additional oxygen in the cabin will accelerate the combustion of... anything and everything.
 
flyingturtle
Posts: 4590
Joined: Mon Oct 31, 2011 1:39 pm

RE: The Passenger Oxygen System

Sun Apr 07, 2013 8:44 am

Quoting AA737-823 (Reply 21):

In case of smoke, we rely on bleed air?

In any case, the exchange of cabin air is impressive. I've once read a paper on influenza transmission on the A/C - you may have somebody with aerosol-transmitted disease like influenza sitting two or three rows before or behind you, and the chance of infection is minimal. If the air conditioning fails for two hours, half the narrowbody A/C will be infected.


David
Keeping calm is terrorism against those who want to live in fear.
 
User avatar
Starlionblue
Posts: 17058
Joined: Fri Feb 27, 2004 9:54 pm

RE: The Passenger Oxygen System

Sun Apr 07, 2013 9:22 am

Quoting flyingturtle (Reply 22):
In any case, the exchange of cabin air is impressive. I've once read a paper on influenza transmission on the A/C - you may have somebody with aerosol-transmitted disease like influenza sitting two or three rows before or behind you, and the chance of infection is minimal. If the air conditioning fails for two hours, half the narrowbody A/C will be infected.

And if we could just transmit this fact to the mainstream press...
"There are no stupid questions, but there are a lot of inquisitive idiots." - John Ringo
 
Dalmd88
Posts: 2391
Joined: Fri Jul 28, 2000 3:19 am

RE: The Passenger Oxygen System

Sun Apr 07, 2013 2:50 pm

Quoting flyingturtle (Reply 22):
In any case, the exchange of cabin air is impressive. I've once read a paper on influenza transmission on the A/C - you may have somebody with aerosol-transmitted disease like influenza sitting two or three rows before or behind you, and the chance of infection is minimal. If the air conditioning fails for two hours, half the narrowbody A/C will be infected.

So true, the airflow tends to stay in each row going from the center duct above your head and the little eyeballs to the return vents at your feet. The rate of fresh air pumped into the cabin is high enough to meet the requirements set by the CDC for hospitals. Which is way better than most office buildings.
 
Tod
Posts: 1709
Joined: Sat Aug 28, 2004 6:51 am

RE: The Passenger Oxygen System

Fri Apr 12, 2013 2:12 pm

Quoting FlyboyOz (Reply 17):
I have heard from my friend... It took three or five minutes to breath it. That's very short!!!

Chemical generators typically come in 12, 15 and 22 minute versions.
 
Tod
Posts: 1709
Joined: Sat Aug 28, 2004 6:51 am

RE: The Passenger Oxygen System

Fri Apr 12, 2013 2:18 pm

Quoting flashmeister (Reply 12):
DC-10s were designed with seatback generators, where a little door would pop open and there was the mask. (Not sure what they do with the bulkhead rows.) One of the design "features" of the DC-10 was that you could yank too hard on the mask (too "firmly" and have the generator pop out and land in your lap. All 500 degrees of it.

Does not sound like something I could find to be airworthy in any new design.

It would be hard to demonstrate compliance with 14CFR25.1450(b)(2)



http://www.ecfr.gov/cgi-bin/text-idx...ode=14:1.0.1.3.11.6.197.54&idno=14
 
User avatar
HAWK21M
Posts: 29867
Joined: Fri Jan 05, 2001 10:05 pm

RE: The Passenger Oxygen System

Sat Apr 13, 2013 10:58 am

Quoting Tod (Reply 25):

Chemical generators typically come in 12, 15 and 22 minute versions.

What determines the type used.....
I may not win often, but I damn well never lose!!! ;)
 
Tod
Posts: 1709
Joined: Sat Aug 28, 2004 6:51 am

RE: The Passenger Oxygen System

Sat Apr 13, 2013 3:53 pm

Quoting HAWK21M (Reply 27):
What determines the type used.....

Emergency decent profile.

How long does it take to get down to a safe altitude.
If you fly where things like mountains might get in the way of a quick decent, then you need a longer flow generator.
 
User avatar
7BOEING7
Posts: 2334
Joined: Fri Oct 12, 2012 5:28 pm

RE: The Passenger Oxygen System

Sat Apr 13, 2013 10:08 pm

Quoting Tod (Reply 28):
Quoting HAWK21M (Reply 27):What determines the type used.....
Emergency decent profile.

How long does it take to get down to a safe altitude.
If you fly where things like mountains might get in the way of a quick decent, then you need a longer flow generator.

Or a gaseous (oxygen tank) system.
 
FlyboyOz
Posts: 1743
Joined: Tue Nov 21, 2000 10:05 am

RE: The Passenger Oxygen System

Sun Apr 14, 2013 5:35 am

Quoting Tod (Reply 25):
Chemical generators typically come in 12, 15 and 22 minute versions.

Yeah i remember what my friend has told me... It should be 10 mins not 5 mins. 10 mins should be enough to dive down to 10,000 feet.
The Spirit of AustraliAN - Longreach
 
User avatar
HAWK21M
Posts: 29867
Joined: Fri Jan 05, 2001 10:05 pm

RE: The Passenger Oxygen System

Wed Apr 17, 2013 8:31 am

Quoting Tod (Reply 28):

Emergency decent profile.

So the route flown by an operator will determine that I guess.....So all Aircraft operating a particular route will be equipped with Max flow.
I may not win often, but I damn well never lose!!! ;)
 
User avatar
IFixPlanes
Posts: 239
Joined: Sun Feb 20, 2005 11:34 pm

RE: The Passenger Oxygen System

Wed Apr 17, 2013 5:33 pm

Quoting HAWK21M (Reply 31):
So the route flown by an operator will determine that I guess.....So all Aircraft operating a particular route will be equipped with Max flow.

Question or answer?
never tell an engineer he is wrong ;-)
 
Tod
Posts: 1709
Joined: Sat Aug 28, 2004 6:51 am

RE: The Passenger Oxygen System

Sun Apr 21, 2013 2:54 am

Quoting 7BOEING7 (Reply 29):
Or a gaseous (oxygen tank) system

Supplemental bottle are sometimes added.

Some 744 have a dozen extra added between the main deck floor beams above the forward cargo compartment.
Almost all used on trans-Pacific routes due to decent limitations caused by low altitude fuel burn rates and distances to alternate airports.
 
User avatar
Acey559
Posts: 925
Joined: Wed Jan 24, 2007 3:30 pm

RE: The Passenger Oxygen System

Sun Apr 21, 2013 4:14 am

Quoting FlyboyOz (Reply 17):
I have heard from my friend... It took three or five minutes to breath it. That's very short!!!

The manual for the plane I fly says the generators give 12 minutes worth of oxygen.

Quoting 737tdi (Reply 10):
These doors can also be released using a tool (on older Boeings a swizzle stick will work)

Our MEL/CDL book specifically says that flight attendant wings can be used in place of the O2 tool. I'd heard of using wings but never realized it was actually in the book until I looked it up one day out of curiosity. I got a chuckle out of that.
 
User avatar
7BOEING7
Posts: 2334
Joined: Fri Oct 12, 2012 5:28 pm

RE: The Passenger Oxygen System

Sun Apr 21, 2013 5:18 am

Quoting Tod (Reply 33):
Supplemental bottle are sometimes added.

Some 744 have a dozen extra added between the main deck floor beams above the forward cargo compartment.
Almost all used on trans-Pacific routes due to decent limitations caused by low altitude fuel burn rates and distances to alternate airports.

The extra oxygen bottles are for routes over high terrain without descent capability (I. e. FRA to HKG). See reply 36 and 37.

Lufthansa 747-8 To Hong Kong (by tailfin Mar 8 2013 in Civil Aviation)

Normal dispatch across the Pacific or any route (including ETOPS 330) is based on enough fuel to get to a diversion field with a decompression--you can't carry enough oxygen to last to the diversion at a reasonable altitude.
 
737tdi
Posts: 1116
Joined: Sun Sep 02, 2007 10:05 am

RE: The Passenger Oxygen System

Sun Apr 21, 2013 8:00 am

Quoting Acey559 (Reply 34):
Our MEL/CDL book specifically says that flight attendant wings can be used in place of the O2 tool. I'd heard of using wings but never realized it was actually in the book until I looked it up one day out of curiosity. I got a chuckle out of that.




I am guessing they are speaking of the pin that attaches their wings to the uniform. I would think that would be difficult, but definitely possible. I have had a hard time getting them open with a #40 drill bit or a hex key sometimes. Very cool though that they put that in the manuals. In an emergency a ladies hairpin would work quite well. Oh yeah, I'm old, women used to wear hairpins. LOL.
 
User avatar
HAWK21M
Posts: 29867
Joined: Fri Jan 05, 2001 10:05 pm

RE: The Passenger Oxygen System

Mon Apr 29, 2013 10:15 am

Quoting Acey559 (Reply 34):
Our MEL/CDL book specifically says that flight attendant wings can be used in place of the O2 tool. I'd heard of using wings but never realized it was actually in the book until I looked it up one day out of curiosity. I got a chuckle out of that.

Thats Interestting..........never thought that would be inked in the official document ever.
I may not win often, but I damn well never lose!!! ;)
 
User avatar
CALTECH
Posts: 2741
Joined: Thu May 17, 2007 4:21 am

RE: The Passenger Oxygen System

Thu May 02, 2013 3:14 pm

The 787 has gone to composite O2 bottles in each PSU for passenger oxygen.
UNITED We Stand
 
User avatar
7BOEING7
Posts: 2334
Joined: Fri Oct 12, 2012 5:28 pm

RE: The Passenger Oxygen System

Thu May 02, 2013 3:44 pm

Quoting CALTECH (Reply 38):
The 787 has gone to composite O2 bottles in each PSU for passenger oxygen.

See link:

http://www.beaerospace.com/products/oxygen_pulse.htm

The question now becomes, does this only take the place of the chemical oxygen system or can it also handle the extra oxygen requirements for routes over high terrain?
 
User avatar
HAWK21M
Posts: 29867
Joined: Fri Jan 05, 2001 10:05 pm

RE: The Passenger Oxygen System

Tue May 07, 2013 8:01 am

Quoting 7BOEING7 (Reply 39):
The question now becomes, does this only take the place of the chemical oxygen system or can it also handle the extra oxygen requirements for routes over high terrain?

Whats the approx weight saved per unit....
I may not win often, but I damn well never lose!!! ;)

Who is online

Users browsing this forum: raedgar, Wraine and 20 guests