Sudden From Sweden, joined Jul 2001, 4127 posts, RR: 6 Posted (11 years 1 week 1 day 9 hours ago) and read 9440 times:
I did a search, but did not found anything about this.
Anyone that can tell me how the oxygen mask system works?
Also, what is it that actually makes the masks drop down? I know it's due to sudden lost of cabinepreassure, but in more depth perspective, please.
Dragogoalie From Australia, joined Oct 2001, 1220 posts, RR: 7 Reply 1, posted (11 years 1 week 1 day 6 hours ago) and read 9334 times:
My first flight instructor was a graduate of the University of North Dakota's commercial aviation program (which I will soon be a part of). One time after my night cross country we went to grab something to eat and we were talking about this. He learned at UND that the oxygen is created by some sort of a chemical reaction and only produces enough Oxygen to sustain life, not to keep the passengers concious, because in theory, if the pilot is doing what he/she should be doing, they will soon be in air that is breathable, so they will only need the oxygen masks for a little while. Needless to say the pilots are given enough oxygen to keep them awake. Or at least I'd hope so . Thats all I know about this (or think I know about this). If I'm wrong, someone please correct me.
727pfe From , joined Dec 1969, posts, RR: Reply 2, posted (11 years 1 week 1 day 6 hours ago) and read 9310 times:
Like most things aviation related, the O2 system can vary from aircraft to aircraft. The most common form is a gaseous O2 system. Typically, the mask will drop on receiving a signal from an aneroid. On the aircraft I flew, the masks would drop if the cabin altitude exceeded 14,000'. The crew could also drop the masks with a switch in the cockpit. The 727 also has a manual lever to deploy the masks. When the system is activated, the oxygen lines are pressurised and the pressurised O2 line in the PSU moves a plunger that trips the latch on the PSU door. Since the latch mechanism can be sensitive, the mask would sometimes drop if the landing was harder than normal. Hope this helps. Some aircraft use oxygen "candles" or some other chemical form of O2 generation. A lot of military aircraft use liquid oxygen. Hope this helps.
OPNLguy From , joined Dec 1969, posts, RR: Reply 3, posted (11 years 1 week 1 day 3 hours ago) and read 9301 times:
Just to expend on what 727pfe said, the older types (727, 737-100/-200, and I presume the early DC-9s) have the plumbed systems with a tank located inside the foward cargo bin, on the Boeings, anyway.
When the DC-10 came out, it went to the individual chemical generators, and Boeing went to them on the 737-300 and subsequent variants. There are actually a few 737-200s towards the tail end of the production run that also have generators versus a plumbed system.
These generators can create alot of heat when they react, which is ordinarily no problem, since they're installed in insulated enclosures in either seatbacks or overheads. ATA had a DC-10-30 burn-up on the ramp at ORD some years ago when a row of seats (being worked on down in one of the cargo decks) had a generator trigger, and un-noticed, it proceded to burn through. Of course, everyone recalls how generators factored into the Valujet 592 crash into the Everglades back in the mid-1990s.
MD11Nut From , joined Dec 1969, posts, RR: Reply 5, posted (11 years 1 week 1 day 2 hours ago) and read 9288 times:
To supplement what had already been provided herein, and to answer the question "Also, what is it that actually makes the masks drop down? "...the logic is rather simple, as 727pfe stated, an aneroid (barometer) will close, connecting the circuit, at a predetermined cabin pressure (14,100 ft for the DC-10). To avoid false indication, there's a 5-second timer. After 5 seconds of closed circuit, solenoids are activated to open the latches, dropping the masks. Passengers still need to pull on the lanyard to activate the oxygen (in DC-10 case, it's a chemical unit).
As a tidbit of info, for aircraft operation that can go above 30,000 ft, FAA requirements (14 CFR 25.1447) require automatic (mask drops) before the cabin pressure altitude exceeds 15,000ft. Most airplanes activate mask drops at 14,000 ft as a margin (to pass the tests).
Flashmeister From United States of America, joined Apr 2000, 2864 posts, RR: 7 Reply 8, posted (11 years 1 week 7 hours ago) and read 9213 times:
Regarding the seatback generators in the DC-10...
Wasn't the design of the bracket and harness of the generator considered a design flaw? I remember reading of cases where people yanked too hard on the lanyard and pulled the generators into their laps, or where the generators got so hot that they burned through the headrest and then injured the person sitting in the forward seat...
Viflyer From US Virgin Islands, joined May 1999, 493 posts, RR: 0 Reply 9, posted (11 years 6 days 7 hours ago) and read 9165 times:
Well I know that the O2 masks on our EMB's are triggered once the cabin ever gets to 14,000 Ft and the flight crew uses a separate 02 bottle that must be keep at a certain psi (I can't remember right at this moment). But the Saab's and the ATR's are different. On the Saab's the 02 masks are located below the aisle seats (those on the 2 seat side have two masks with a single point y connection) and the pax actually have to plug the connection on the mask to a port above there seat. On the ATR's (depending on the model) either there are masks below the F/A's jumpseats or a pop down compartment above certain seats. The thing about the ATR is that there is more pax than Masks, and this is because the FAA at the time only required that 30% (I think I'm going on 2 year old tired memory) of the passenger needed to have O2 in a depressurization situation because the aircraft is only certified to 25,000ft. On both the Saab and ATR the pax O2 is turned on via the Cockpit.
Viflyer From US Virgin Islands, joined May 1999, 493 posts, RR: 0 Reply 12, posted (11 years 2 days 16 hours ago) and read 9068 times:
Well I know that on our Saabs 340B/B+ (AE) that the paxs have to plug in the O2 masks, I don't know about other airlines the only other airline Saab I've been on was Mesaba and the FA didn't even bother to mention the O2 mask. In our safety demo the operation of the masks is told.
Metwrench From United States of America, joined Aug 2001, 750 posts, RR: 2 Reply 13, posted (11 years 2 days 15 hours ago) and read 9055 times:
Most items posted here are correct except the statement about oxygen keeping pilots awake. In the event of loss of pressurization, oxygen keeps the pilots, and pax alive! From 35,000' to 15,000' @ 2.500' per minute of emergency decent takes 8 minutes. Yes, the average person will survive that without permanent damage. However your reasoning, logic, and basic motor skills will be affected. The pilots need to have access to quick donning oxygen masks to stay alert to respond to whatever emergency got them in this situation to begin with.
P.S. I like to slam pilots, but once or twice in their careers they might need every second available to respond to an emergency, never it be said that MX didn't give them every chance to overcome it. You guys want your O2 bottle topped off before departure, no problem!
Just curious though, where does all that O2 go when there aren't any leaks in the system???????????
FredT From United Kingdom, joined Feb 2002, 2184 posts, RR: 26 Reply 15, posted (11 years 2 days 12 hours ago) and read 9048 times:
those masks aren't pressure breathing. That's a very questionable pleasure reserved for the military and other users with similar demands. What matters is the oxygen pressure in the inhaled air. If you go to 100% O2, the oxygen pressure at a cabin altitude of 92,000' will be the same as it would with the normal 21% O2 at 8,000' cabin altitude. Unless you plan to do a lot of flying at 92'000', or pull a lot of G's, you don't need pressure breathing.
I thought I was doing good trying to avoid those airport hotels... and look at me now.
Metwrench From United States of America, joined Aug 2001, 750 posts, RR: 2 Reply 16, posted (11 years 2 days 12 hours ago) and read 9039 times:
Jet, two conditions, two answers. I would encourage experienced flight crews to join in and correct me.
Pilot masks. They are designed to be quick donning and of a design to fit very tightly over the nose and mouth. The slightest inward breathing causes a low pressure area that allows a check valve to open and provide a positive flow of pure O2. There is also a microphone that is already plugged into a jack which allows for voice communication over the Comm system.
When the person stops breathing inwards, the flow stops, on exhale the breath exits through a separate valve, similar in principle to scuba gear.
The hose to the mask has a visual indicator, green, that repasts positive flow of O2. I have never not seen a pilot test this system during preflight.
Pax O2 masks.
Have you ever flown on a commercial flight???? Obviously you were asleep or ignored the Flight Attendants briefing!! In the event of an unlikely deployment of Pax O2 masks, blah, blah. The bag will not inflate but O2 will be flowing. You're not swimming 60' under water! You just need enough O2 not to die!!! The Pilots need more!!!! If you need O2 to stay coherent, they need it to make sound judgements to keep you alive!
Gawd, I can't believe I'm defending pilots!!! What a pathetic state you are in that Metwrench has to step up to the plate to protect you!!!
FredT From United Kingdom, joined Feb 2002, 2184 posts, RR: 26 Reply 17, posted (11 years 2 days 12 hours ago) and read 9046 times:
Oh yeah, and you might very well be looking at having dead pax if they don't get oxygen. You don't have all that much time available either. I did a web search to get some figures, and found this article on AVWeb giving a time of useful consciousness (TUC) at 25,000' of "three to six minutes with death following not long after that" which is consistant with what I remember. I recall a TUC of around ten seconds at 40k'... don't take the recommendation to don the mask first of all lightly!
I thought I was doing good trying to avoid those airport hotels... and look at me now.
Metwrench From United States of America, joined Aug 2001, 750 posts, RR: 2 Reply 18, posted (11 years 2 days 12 hours ago) and read 9040 times:
Okay Fred, so what you're saying is that I should grab the 1st mask that swings my way and by all means prevent that obnoxious brat that has been kicking the back of my seat the last two hours from getting some O2?
Thanks, I was looking for some absolvment!!! Should I strangle the lathargic Mother too??? Please can I???
Erasmus From Italy, joined Jun 2007, 0 posts, RR: 0 Reply 19, posted (11 years 2 days 11 hours ago) and read 9036 times:
I just wanted to say that in "my company" and the two other companies I've previously flown for it is common practise to check the quick donning mask, the mic in the mask, the O2 pressure and the Oxygen flow before the first flight.
I think it's common practise in every airline!
Just curious though, where does all that O2 go when there aren't any leaks in the system
Answer: probably because every pilot uses a small amount of oxygen when testing the system!
Sudden From Sweden, joined Jul 2001, 4127 posts, RR: 6 Reply 20, posted (11 years 2 days 10 hours ago) and read 9029 times:
Is it really necessary to argue, or whatever it is you are doing?!
You all have a lot of knowledge, which I appreciate, so why not share the knowledge instead of acting out like you are doing.
Don't turn this forum into another civil av. forum where argues belongs to the topics.
FredT From United Kingdom, joined Feb 2002, 2184 posts, RR: 26 Reply 21, posted (11 years 2 days 10 hours ago) and read 9015 times:
grab the mask dropping down on you, then help the passed out kid (yes, I know it will seem like a relief that the brat finally passed out, but try to do it anyway ) and the lethargic mother, even though it won't make much of a difference.
Isn't it peculiar, how you always get the obnoxious kid with the lethargic mother in the row behind when flying? Do they have thousands of those flying around fulltime, occupying every other seat row? It's a conspiracy, I tell you!
But if you do choose to follow your original plan of action... I was looking out the window the entire time and didn't see a thing.
I don't think we're arguing anything but the facts - yet. We're trying to work our way up to some good old civilised name-calling, but it's a slow process at times, y'know...
I thought I was doing good trying to avoid those airport hotels... and look at me now.
727pfe From , joined Dec 1969, posts, RR: Reply 24, posted (11 years 2 days 6 hours ago) and read 9003 times:
Jet is of course correct. The standard "Pressure-Demand" type regulator supplies 100% O2 under pressure when selected to emergency, or above a preset cabin altitude. The passenger masks do not supply O2 under pressure, and would do no good if the pilot elected to remain at altitude after a depressurization.
25 FredT: Erasmus, that's a slight overpressure to avoid having smoke enter the mask. Not The pilots mask forces oxygen into the lungs under pressure allowing a
26 FredT: Sudden, no, I'm at ESSL (LIN) these days. I used to worke on the ramp at ARN though. Cheers, Fred
27 Erasmus: Hi Fred T, I did think that this military system was something completely different. However, the fact that my A320 OM says: "Overpressure supply is s
28 EssentialPowr: There are two types of O2 masks for cockpit use: 1. Pressure demand - these masks are typically used on high g capable, military a/c. In use, the O2 i
29 EssentialPowr: I agree w/ FredT here for the most part. JET is incorrect b/c he's confusing the 2 types above (and so therefore is 727pfe) and/or doesn't understand
30 Bellerophon: Essential Powr Correct! Anyone who has used both types, knows what "Pressure Breathing" means, and it is very different to the systems fitted to Boein
31 727pfe: I did not say that civil aviation regulators or those in military cargo/transport aircraft were the same as installed in high performance jet fighters
32 EssentialPowr: I don't have any confusion on the issue. All 3 of the above referenced diluter types are civil, and WILL NOT force air into a pilot's lungs. JET pilot
33 EssentialPowr: 727pfe, The statement: "...The higher than atmospheric pressure is essential to allow the law of gaseous diffusion to occur in the lungs for O2 tranfe
34 727pfe: After more research, primarily in Air Force Pamplet 160-5, the important factor is the partial pressure of O2 in the alveoli. To prevent hypoxia you n
35 FredT: pfe: "As the cabin climbs higher the pressure required will also increase..." ...if the concentration of O2 in the inhaled air remains the same. As I
36 Vc10: A web site that might be of interest on this subject is :- www.vnh.org/fsmanual/01/05positivepress As far as I know [ I could be wrong though ] The on
37 727pfe: Sorry Fred, I disagree with you. Any aviation physiologist will tell you that you have to have O2 under pressure above FL 340. My information comes ri
38 EssentialPowr: 727pfe, Jetpilot's statement: "The pilots mask forces oxygen into the lungs under pressure allowing absorbtion by the body." is flat out wrong, and th
39 727pfe: EP, And yet you provide no documentation or references to back up your claims. Every post you get involved in turns into a fur ball. Have you ever use
40 EssentialPowr: 727pfe, 1. I can expand on any topic I choose; as you can and have done on this one. 2. The reason this has turned into a furball is b/c you simply do
41 727pfe: The only thing I've learned is that you have no clue. Once again, give some reference. The Delta 767 maintenance training manual states that the outpu
42 727pfe: Try reading this article. http://www.avweb.com/articles/highalt/
43 727pfe: Another good source of information is a booklet published by the FAA titled "Aviation Physiology". You can get it by contacting the FAA at: FAA Civil
44 EssentialPowr: 727pfe, It seems like you are the one learning aviation physiology at about the rate this thread is progresing, particularly since you agreed with the
45 EssentialPowr: 727pfe, You refereed a topic previously about "windshear" audible alerts. I made my argument, and prefaced with a ref to part 121 ops...the person opp
46 MD11Nut: Facts: FAA 25.1443 requires a mean tracheal oxygen partial pressure of 149mm Hg for continuous flow equipment, 122 mm Hg for demand equipment. This is
47 JETPILOT: MD11nut "1. 149mm Hg is the normal oxygen partial pressure at sea level (reads: unpressurized). One can deduce that oxygen equipment DO NOT have to be
48 FredT: Thx, MD11. If you want to maintain the sea level static partial O2 pressure, as opposed to that you're in with a cabin altitude of 8000', you'll need
49 MD11Nut: JetPilot & FredT - agreed with you both. That was what I was trying to put out so people will see the subtleties. You didn't see me calling anybody as
50 EssentialPowr: My only point was that a diluter demand mask won't force air into the lungs (as opposed to a pressure demand mask as used on mil a/c). JEtpilot's post
51 411A: A very interesting discussion. A short story follows.. A few years ago, a cargo DC-8 departed and it was found by the Flight Engineer that he was unab
52 Ismangun: Now a question: If an airplane is flying over a very high MEA, and an emergency descent for a lowest unpressurized altitude cannot be made, so how wil
53 727pfe: Fred, You can sustain life by breathing 100% O2 at 40K, but you will begin to experience Hypoxia symptoms. Not a big deal for PAX, but not desirable i
54 MD11Nut: 727pfe, do you happen to know where I can find the FAA requirements (above 40,000ft, under pressure) ? Thanks, Nut
55 727pfe: Yes, TSO-C89, shows that straight diluter demand regulators are only goood to FL 40. It took me awhile to find it. In the TSO it is stated toward the
56 727pfe: Nut, Look in FAR 25.1447. I was in error. The FAA requires a pressure demand regulator above 34,000', not 40. Again, THANKS for making me get back in
57 EssentialPowr: 727pfe, What exactly is your postion? You agreed w/ JET's statement that a diluter demand mask will force air into your lungs...it won't, that's a pre
58 Sudden: Hm.... what a discussion this turned in to. Very interesting to say the least!
59 727pfe: EP- I've stated my position clearly. My first post stated that a pressure demand mask supplies O2 under positive pressure. You seem to be hung up on t
60 EssentialPowr: 727pfe, 1. Your first point is indeed earthshattering - that's what I meant by supplying positive pressure to the nose, and desmoking the mask/goggles
61 727pfe: EP, Wow, that hurt. Crappy 3 hr CRM course. You must have been there. LOL. REynolds number, is that the same as a Reynolds number? We could, but how b
62 727pfe: EP, Since the purpose of this forum is to learn, and share ideas, let me be the first to apologize for any insults I directed toward you. Lets start a
63 Bellerophon: 727pfe Hmmm.... I know I'm new to this forum, but is this really what passes for intellectual debate on this site? Here's a sample of some of your rec
64 Airplay: Nice to see EP’s maintaining his charming demeanor. Here are some clarifications I an offer, although this whole thread has lost credibility because
65 727pfe: To Belephron and everyone else, By allowing myself to be baited into trading insults with EP, I embarrassed myself and my profession. As you correctly
66 Airplay: 727pfe, I wouldn't consider this little clash serious enough to "unregister" yourself. Like many topics on this forum, this one happened to seem like
67 Jetguy: Amen to what Airplay said. Me thinks that its time to kiss and make up.
68 Sudden: He did delete himself, 727pfe!? No debate or discussion chould have to lead to that, but it was his own choice. But I don't think he chould have done
69 EssentialPowr: My first response was directed at a post that claimed: "The pilots mask forces oxygen into the lungs under pressure allowing absorbtion by the body" w
70 UAL Bagsmasher: Just a little side note, I flew on that TZ DC-10-40 ORD-MCO-ORD a week before it burned up. My Uncle was actually on the final flight of it from HNL-O
71 Airplay: EP, Speaking of facts, I have had 1 post deleted (not 3) and it contained no profanity. I called you a name that can easily be heard on a typical Tele