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The Passenger Oxygen System  
User currently offlinenovice From United Kingdom, joined Aug 2012, 90 posts, RR: 0
Posted (1 year 5 months 1 day 16 hours ago) and read 8692 times:

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

40 replies: All unread, showing first 25:
 
User currently offlineFlyDeltaJets From United States of America, joined Feb 2006, 1871 posts, RR: 2
Reply 1, posted (1 year 5 months 1 day 15 hours ago) and read 8680 times:
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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
User currently offlineAA737-823 From United States of America, joined Mar 2000, 5774 posts, RR: 11
Reply 2, posted (1 year 5 months 1 day 14 hours ago) and read 8638 times:

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 currently offlineStarlionblue From Greenland, joined Feb 2004, 17030 posts, RR: 67
Reply 3, posted (1 year 5 months 1 day 13 hours ago) and read 8626 times:

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."
User currently offlinedalmd88 From United States of America, joined Jul 2000, 2546 posts, RR: 14
Reply 4, posted (1 year 5 months 1 day 12 hours ago) and read 8606 times:

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 currently offlineStarlionblue From Greenland, joined Feb 2004, 17030 posts, RR: 67
Reply 5, posted (1 year 5 months 1 day 12 hours ago) and read 8597 times:

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."
User currently onlineTristarsteve From Sweden, joined Nov 2005, 4001 posts, RR: 34
Reply 6, posted (1 year 5 months 1 day 6 hours ago) and read 8485 times:

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.


User currently offlineyeelep From United States of America, joined Apr 2011, 655 posts, RR: 0
Reply 7, posted (1 year 5 months 1 day 5 hours ago) and read 8466 times:

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 currently offlinecjg225 From United States of America, joined Feb 2013, 818 posts, RR: 0
Reply 8, posted (1 year 5 months 20 hours ago) and read 8331 times:

Very interesting stuff. Thanks to everyone in the discussion. I had always assumed it was an oxygen bottle system.


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User currently offlineKELPkid From United States of America, joined Nov 2005, 6372 posts, RR: 3
Reply 9, posted (1 year 5 months 16 hours ago) and read 8263 times:

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 :-)
User currently offline737tdi From United States of America, joined Sep 2007, 813 posts, RR: 1
Reply 10, posted (1 year 5 months 5 hours ago) and read 8149 times:
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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.

User currently offlinemrocktor From United States of America, joined Jan 2005, 1668 posts, RR: 50
Reply 11, posted (1 year 5 months ago) and read 8057 times:

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


User currently offlineflashmeister From United States of America, joined Apr 2000, 2900 posts, RR: 6
Reply 12, posted (1 year 4 months 4 weeks 1 day 23 hours ago) and read 8039 times:
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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 currently offlineStarlionblue From Greenland, joined Feb 2004, 17030 posts, RR: 67
Reply 13, posted (1 year 4 months 4 weeks 1 day 21 hours ago) and read 8012 times:

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."
User currently offlinenovice From United Kingdom, joined Aug 2012, 90 posts, RR: 0
Reply 14, posted (1 year 4 months 4 weeks 1 day 21 hours ago) and read 8013 times:

Thanks for the replys guys much appreciated  

User currently offlineHAWK21M From India, joined Jan 2001, 31679 posts, RR: 56
Reply 15, posted (1 year 4 months 4 weeks 1 day 11 hours ago) and read 7908 times:

The B732s had the iped O2 system from the PAX.


Think of the brighter side!
User currently onlineMD11Engineer From Germany, joined Oct 2003, 14007 posts, RR: 62
Reply 16, posted (1 year 4 months 4 weeks 1 day 2 hours ago) and read 7833 times:

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


User currently offlineFlyboyOz From Australia, joined Nov 2000, 1985 posts, RR: 25
Reply 17, posted (1 year 4 months 4 weeks 21 hours ago) and read 7762 times:

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 currently offline7BOEING7 From United States of America, joined Oct 2012, 1553 posts, RR: 8
Reply 18, posted (1 year 4 months 4 weeks 19 hours ago) and read 7737 times:

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 currently offlineStarlionblue From Greenland, joined Feb 2004, 17030 posts, RR: 67
Reply 19, posted (1 year 4 months 4 weeks 18 hours ago) and read 7717 times:

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."
User currently offline7BOEING7 From United States of America, joined Oct 2012, 1553 posts, RR: 8
Reply 20, posted (1 year 4 months 4 weeks 17 hours ago) and read 7710 times:

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.


User currently offlineAA737-823 From United States of America, joined Mar 2000, 5774 posts, RR: 11
Reply 21, posted (1 year 4 months 4 weeks 2 hours ago) and read 7591 times:

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.


User currently offlineflyingturtle From Switzerland, joined Oct 2011, 2390 posts, RR: 13
Reply 22, posted (1 year 4 months 3 weeks 6 days 13 hours ago) and read 7489 times:

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 currently offlineStarlionblue From Greenland, joined Feb 2004, 17030 posts, RR: 67
Reply 23, posted (1 year 4 months 3 weeks 6 days 12 hours ago) and read 7483 times:

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."
User currently offlinedalmd88 From United States of America, joined Jul 2000, 2546 posts, RR: 14
Reply 24, posted (1 year 4 months 3 weeks 6 days 7 hours ago) and read 7435 times:

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.


User currently offlineTod From Denmark, joined Aug 2004, 1725 posts, RR: 3
Reply 25, posted (1 year 4 months 3 weeks 1 day 8 hours ago) and read 7154 times:

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.


User currently offlineTod From Denmark, joined Aug 2004, 1725 posts, RR: 3
Reply 26, posted (1 year 4 months 3 weeks 1 day 7 hours ago) and read 7172 times:

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 currently offlineHAWK21M From India, joined Jan 2001, 31679 posts, RR: 56
Reply 27, posted (1 year 4 months 3 weeks 11 hours ago) and read 7117 times:

Quoting Tod (Reply 25):

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

What determines the type used.....



Think of the brighter side!
User currently offlineTod From Denmark, joined Aug 2004, 1725 posts, RR: 3
Reply 28, posted (1 year 4 months 3 weeks 6 hours ago) and read 7081 times:

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 currently offline7BOEING7 From United States of America, joined Oct 2012, 1553 posts, RR: 8
Reply 29, posted (1 year 4 months 3 weeks ago) and read 7030 times:

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.


User currently offlineFlyboyOz From Australia, joined Nov 2000, 1985 posts, RR: 25
Reply 30, posted (1 year 4 months 2 weeks 6 days 16 hours ago) and read 6981 times:

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 currently offlineHAWK21M From India, joined Jan 2001, 31679 posts, RR: 56
Reply 31, posted (1 year 4 months 2 weeks 3 days 13 hours ago) and read 6774 times:

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.



Think of the brighter side!
User currently offlineIFixPlanes From Germany, joined Feb 2005, 239 posts, RR: 0
Reply 32, posted (1 year 4 months 2 weeks 3 days 4 hours ago) and read 6716 times:

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 ;-)
User currently offlineTod From Denmark, joined Aug 2004, 1725 posts, RR: 3
Reply 33, posted (1 year 4 months 1 week 6 days 19 hours ago) and read 6513 times:

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 currently offlineAcey559 From United States of America, joined Jan 2007, 1532 posts, RR: 2
Reply 34, posted (1 year 4 months 1 week 6 days 18 hours ago) and read 6489 times:

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 currently offline7BOEING7 From United States of America, joined Oct 2012, 1553 posts, RR: 8
Reply 35, posted (1 year 4 months 1 week 6 days 16 hours ago) and read 6484 times:

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.


User currently offline737tdi From United States of America, joined Sep 2007, 813 posts, RR: 1
Reply 36, posted (1 year 4 months 1 week 6 days 14 hours ago) and read 6446 times:
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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 currently offlineHAWK21M From India, joined Jan 2001, 31679 posts, RR: 56
Reply 37, posted (1 year 4 months 5 days 12 hours ago) and read 5981 times:

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.



Think of the brighter side!
User currently offlineCALTECH From Poland, joined May 2007, 2226 posts, RR: 26
Reply 38, posted (1 year 4 months 2 days 7 hours ago) and read 5793 times:

The 787 has gone to composite O2 bottles in each PSU for passenger oxygen.


UNITED We Stand
User currently offline7BOEING7 From United States of America, joined Oct 2012, 1553 posts, RR: 8
Reply 39, posted (1 year 4 months 2 days 6 hours ago) and read 5780 times:

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 currently offlineHAWK21M From India, joined Jan 2001, 31679 posts, RR: 56
Reply 40, posted (1 year 3 months 3 weeks 6 days 14 hours ago) and read 5526 times:

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....



Think of the brighter side!
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