Tg 747-300
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Pax Oxygen On Airliners.

Tue Jan 31, 2006 12:44 pm

Is the emergency oxygen availiable to pax on airliners, normaly of the contienous flow, altitude compensated type?, or is it the contineous constant flow type

Also, is it normaly one central O2 generator, or is there induvidual ones for each row?

tg 747-300
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474218
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Joined: Mon Oct 10, 2005 12:27 pm

RE: Pax Oxygen On Airliners.

Tue Jan 31, 2006 1:16 pm

For emergency oxygen most airlines use Chemical Oxygen Generators. These small canisters are made up of sodium chlorate mixed with iron powder. Chemical reaction takes place when the mixture is heated by an electrical initiator. The iron combines with part of the oxygen in the sodium chlorate to form iron oxide. The heat of the chemical reaction raises the local temperature of the sodium chlorate, which decomposes into oxygen and sodium chloride. Once this decomposition commences it continues until the charge is expended. There will be several of these canisters at each seat row and one in each lavatory.
 
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Jetlagged
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RE: Pax Oxygen On Airliners.

Tue Jan 31, 2006 1:57 pm

Some airliners use bottled passenger oxygen, for example the 747-200, 737-200 and the 727. The oxygen is diluted, not pure. Flow from these systems is continuous, not on demand, as is the case with crew oxygen.
The glass isn't half empty, or half full, it's twice as big as it needs to be.
 
Grbld
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RE: Pax Oxygen On Airliners.

Tue Jan 31, 2006 5:12 pm

Most O2 generators allow for at least 12 minutes of oxygen (legal requirement) although in rare instances, they're certified for 22 minutes or even more. For very high altitude places, such as the Tibetan Plateau, you need the extra oxygen capacity because you can't get down to a breatheable altitude in time. If you don't have it, it means you actually have to fly around that area.

Grbld
 
Tristarsteve
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RE: Pax Oxygen On Airliners.

Tue Jan 31, 2006 8:10 pm

There are pros and cons with both systems.
Oxygen generators are easier to maintain, and they sit there waiting for the event. But once initiated, by pulling down on the mask, they continue to produce oxygen for 20-30mins and can't be switched off. As there is one in every PSU, that means that the mechs then have to change them all before flight. Also they are prohibited as freight on pasenger aircraft.
Gaseous oxygen needs topping up now and then, and in most of Europe this is not allowed on the ramp. But the big plus is that it lasts as long as you have bottles. B747-400 has rows of bottles filling the sidewalls of the freight hold. This means thee are no restrictions flying over the Himalayas where you cannot descend to 10000ft for hours in an emergency. Also filing up bottles is much easier than obtaining and changing generators.
So basically generators when possible, but gaseous when necessary for range and ETOPS. B747-400 has either, customer option.
 
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HAWK21M
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RE: Pax Oxygen On Airliners.

Tue Jan 31, 2006 11:11 pm

The older Aircraft used the Distribution system that connected to a Single large cylinder which O2 flow was initiated either due rise in Cabin Alt or Manually actuated.
Later Aircraft used the O2 generator type which was easier to maintain but the O2 flow once initiated could not be stopped until exhausted.

regds
MEL
I may not win often, but I damn well never lose!!! ;)
 
Tod
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RE: Pax Oxygen On Airliners.

Wed Feb 01, 2006 12:03 am

Quoting Jetlagged (Reply 2):
Some airliners use bottled passenger oxygen, for example the 747-200, 737-200 and the 727.

Gaseous is also a customer option on the 777.

Quoting Jetlagged (Reply 2):
Flow from these systems is continuous, not on demand

Demand systems are available.

Quoting Tristarsteve (Reply 4):
Oxygen generators are easier to maintain, and they sit there waiting for the event.

They also have a shelf life, something like 7 years IIRC. Seen customer with expensive 22 minute spares going outdated sitting on the shelf.

Quoting Tristarsteve (Reply 4):
B747-400 has rows of bottles filling the sidewalls of the freight hold

In addition to the bottles located just aft of the forward cargo door, there are also additional extra locations available between the main deck floor beams in the forward cargo compartment. As many as 14 extra bottles can be installed that way.

Quoting Tristarsteve (Reply 4):
B747-400 has either, customer option.

Do you know of any operators with chemical oxygen on the 744?
So far, all the ones I've work on have been gaseous.
I thought heat dissipation in the outboard stowbin PSU trough was a concern with that configuration.

Tod
 
Tristarsteve
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RE: Pax Oxygen On Airliners.

Wed Feb 01, 2006 1:31 am

Quoting Tod (Reply 6):
Do you know of any operators with chemical oxygen on the 744?

Might be getting confused! I know BA has gaseous on B744, and I work on MH B744 and B777 and one of them has generators. Will check tommorrow at work.
 
Tod
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RE: Pax Oxygen On Airliners.

Wed Feb 01, 2006 3:03 am

MH 744 has the standard gaseous cylinders plus two additional 115 cu ft cylinders between the main deck floor beams.
(ref: 417U4211 and 417U4393)

MH 777 has generators
(ref: 474W1110 cylinder instl doesn't include MH effectivities)

Tod
 
erj-145mech
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RE: Pax Oxygen On Airliners.

Sat Feb 04, 2006 10:37 pm

Quoting 474218 (Reply 1):
Chemical reaction takes place when the mixture is heated by an electrical initiator.

It doesn't require any electicity only a chemical reaction to generate oxygen. The electricity opens the PSU's (passenger service units) for mask access.
 
474218
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Joined: Mon Oct 10, 2005 12:27 pm

RE: Pax Oxygen On Airliners.

Sun Feb 05, 2006 4:30 am

Quoting Erj-145mech (Reply 9):
It doesn't require any electicity only a chemical reaction to generate oxygen. The electricity opens the PSU's (passenger service units) for mask access.

All the oxygen generators I have ever worked with require a low voltage electrical charge to initiate the chemical reaction. I our training class we used a D-Cell 1.5 Volt battery. On the aircraft the electrical charge is initiated when the Passenger Service Module (PSM) door is opened.

I have heard of the type that don't require electricity, just never worked with them. I think that type may have been used by Douglas, because they were the cause of the Value Jet crash and the ATA DC-10 thet was destroyed by fire.

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