Armed Polite Society
Main Forums => The Roundtable => Topic started by: Hawkmoon on July 14, 2018, 02:59:31 PM
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A day or two ago a commercial airliner in China depressurized and descended 25,000 feet in ten minutes ... because the co-pilot was vaping in the cockpit and accidentally shut down the cabin pressurization system in an effort to conceal the smoke.
Not to be outdone, Ryanair had a plane drop 30,000 feet in five minutes.
https://www.dailystar.co.uk/news/world-news/716352/Ryanair-flight-emergency-landing-FR7312-Dublin-Frankfurt-Germany-Zadar-Croatia
Ouch!
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OH MY GOD!!! Run for the hills and ban airplanes on the way!
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Is there any industry (or regulatory) standard for emergency descents? I thought the article I read on the Chinese incident said that a descent of 25,000 feet in ten minutes was the standard for an emergency descent following cabin depressurization. The Ryanair flight descended more than twice as fast as the Chinese aircraft.
How long is the emergency oxygen supply good for, anyway? And how low does the plane have to get? IIRC, modern aircraft are pressurized to something like 12,000 or 14,000 feet. I know I've been at the summit of Pike's Peak, which is a bit over 14,000 feet, and I didn't need oxygen. I wasn't going to be running any marathons at that altitude, but I wasn't suffering hypoxia, either.
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Is there any industry (or regulatory) standard for emergency descents?
Well, nature generally recommends no more than 32ft/s/s. For 30,000 feet, that's somewhere in the neighborhood of 40 seconds. 6,000 feet per minute is nowhere near the power dive that the media seems to be trying to play it up as. After all, have you ever seen a skydiver crushed by the pressure changes during their free fall?
How long is the emergency oxygen supply good for, anyway?
Up to 20 minutes, depending on the brand/model oxygen generators used. I suspect most are a bit over half that. Hence the usual target of getting to 10k or below in 10 minutes or less.
And how low does the plane have to get?
AFAICT, 14k feet is the usual trigger point for releasing the masks.
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Is there any industry (or regulatory) standard for emergency descents?
10 minutes to 10,000 is the only one I know of. And that is mainly for the oxygen requirement for the crew, not the passengers.
Oxygen generators are 12 to 20 minutes of use and most planes will auto-deploy the masks at 14,000 feet cabin altitude, like KD5 said. We can manually release the masks at any altitude from the cockpit and the flight attendants have a tool to pop the mask doors if needed. FYI, the O2 doesn't start flowing until you pull down on the mask, pulling the pin in the process.
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What is the O2 generator set up?
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The article I read about the Chinese incident commented on (and seemed to take issue with) the fact that after the descent, the flight crew just took it back up to altitude and continued the flight. Which means that for the rest of the trip the passengers (and crew, I suppose) were all at risk because if there had been an accidental decompression due to causes other than the co-pilot being a doofus, there wouldn't have been any oxygen available.
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What is the O2 generator set up?
(https://upload.wikimedia.org/wikipedia/commons/thumb/0/04/Aircraft_oxygen_generator_diagram.svg/617px-Aircraft_oxygen_generator_diagram.svg.png)
Interesting chemistry there in the "Chemical oxygen generator." The percussion cap starts the burning of Potassium Superoxide (KO2) in the canister which generates O2.
KO2 looks funny from a valence point of view but sort of makes sense from a complex structural point of view. Kind of. Meaning I can't figure it out from my 1950 AD chemistry.
Didn't want to delve into it too deeply. Just wanted a visual sense of what the generator in the planes looked like.
Terry
Pic in public domain
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Well, nature generally recommends no more than 32ft/s/s. For 30,000 feet, that's somewhere in the neighborhood of 40 seconds.
I'm soooooo tired of the Patriarchy mansplaining their physics privilege.
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I'm soooooo tired of the Patriarchy mansplaining their physics privilege.
Especially when he doesn't factor in terminal velocity.
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I'm soooooo tired of the Patriarchy mansplaining their physics privilege.
:rofl:
Awwww, poor baby. >:D
Especially when he doesn't factor in terminal velocity.
Seven miles per second. "For a spherical chicken in a vacuum."
(But of course, sphericity doesn't matter in a vacuum.)
REF:
Hatcher's Notebook pp 517, 553 and surrounding.
Extracted quote from page 552:
"In high school physics we were taught that..."
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Well, nature generally recommends no more than 32ft/s/s. For 30,000 feet, that's somewhere in the neighborhood of 40 seconds.
More like 30 seconds ...
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More like 30 seconds ...
In a vacuum.
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(https://upload.wikimedia.org/wikipedia/commons/thumb/0/04/Aircraft_oxygen_generator_diagram.svg/617px-Aircraft_oxygen_generator_diagram.svg.png)
Interesting chemistry there in the "Chemical oxygen generator." The percussion cap starts the burning of Potassium Superoxide (KO2) in the canister which generates O2.
KO2 looks funny from a valence point of view but sort of makes sense from a complex structural point of view. Kind of. Meaning I can't figure it out from my 1950 AD chemistry.
Didn't want to delve into it too deeply. Just wanted a visual sense of what the generator in the planes looked like.
Terry
Pic in public domain
Nothing new under the sun.
These were always fun to use.
https://en.wikipedia.org/wiki/Oxygen_Breathing_Apparatushttps://en.wikipedia.org/wiki/Oxygen_Breathing_Apparatus (https://en.wikipedia.org/wiki/Oxygen_Breathing_Apparatushttps://en.wikipedia.org/wiki/Oxygen_Breathing_Apparatus)
Though it looks bulky and unwieldy it is a light and comfortable device to wear and does not much interfere with the user's freedom of movement
Somebody has a sense of humor
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:rofl:
Awwww, poor baby. >:D
Seven miles per second. "For a spherical chicken in a vacuum."
(But of course, sphericity doesn't matter in a vacuum.)
REF:
Hatcher's Notebook pp 517, 553 and surrounding.
Extracted quote from page 552:
"In high school physics we were taught that..."
(https://imgs.xkcd.com/comics/an_apple_for_a_dollar.png)
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....
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We can manually release the masks at any altitude from the cockpit and the flight attendants have a tool to pop the mask doors if needed.
The part I'm curious about is how much it costs to replace them all if you have an in flight deployment. I know they're not particularly cheap as one-off purchases, but I'd assume airlines get serious bulk discounts. Plus presumably (if it's otherwise airworthy) the plane can still be flown empty to the maintenance facility of choice with the pilots carrying portable oxygen (or just replacing the pilots' bottle(s)) for that flight.
Have they given you a "this costs $x if you do it unnecessarily, but not doing it when it is needed costs lives" talk about that particular system?
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I don’t know the costs. Since it is airplane related, I assume $$$!!!
FWIW, unused masks can be stuffed back in and closed up.
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I don’t know the costs. Since it is airplane related, I assume $$$!!!
FWIW, unused masks can be stuffed back in and closed up.
Sort of.
If I understand it, each "package" includes a group of two, three, or four masks, depending on how many seats in that bank. The masks are all fed from a common canister, and pulling the lanyard from any one of the masks fires up the generator and starts oxygen flowing to however many masks are in that group. So if I understand it correctly, you can only stuff the masks up and close the hatch if none of the masks in that group were activated.
And the way the airlines are cramming people into planes these days, the possibility of finding two, three, or four unused seats all together is between slim and none. (And Slim left town.)
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You are probably right. I don’t know enough about the system to contradict you. I was mainly refering to an accidental deployment. Or a test deployment, which must happen every so often.
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Sort of.
If I understand it, each "package" includes a group of two, three, or four masks, depending on how many seats in that bank. The masks are all fed from a common canister, and pulling the lanyard from any one of the masks fires up the generator and starts oxygen flowing to however many masks are in that group. So if I understand it correctly, you can only stuff the masks up and close the hatch if none of the masks in that group were activated.
And the way the airlines are cramming people into planes these days, the possibility of finding two, three, or four unused seats all together is between slim and none. (And Slim left town.)
The "give a sharp pull" is a very important part of making these things work so it is a possibility that there could be a group of several that don't understand because they didn't listen to the safety brief given by the passenger waitress as they were preparing to roll back from the dock. I mean, have you ever looked around during the safety brief, nobody and I mean nobody listens. I guess if you made a safety brief app it would work a little better. ;)
bob
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I mean, have you ever looked around during the safety brief, nobody and I mean nobody listens. I guess if you made a safety brief app it would work a little better. ;)
bob
I'm not sure if they were doing the aviation water survival training via the ASTC schools when you were in, but I can tell you, after I did that initial training at Lemoore, every time since that I have flown commercial, the first thing I do after I sit down is a 360 for exits and non-visibility reference points. :laugh:
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I'm not sure if they were doing the aviation water survival training via the ASTC schools when you were in, but I can tell you, after I did that initial training at Lemoore, every time since that I have flown commercial, the first thing I do after I sit down is a 360 for exits and non-visibility reference points. :laugh:
When I am in my seat, I count the number of seatbacks to the nearest fore and aft exit points. I figure that will make it easier when I am choking on smoke after the crash.
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When I am in my seat, I count the number of seatbacks to the nearest fore and aft exit points. I figure that will make it easier when I am choking on smoke after the crash.
Or else just:
https://youtu.be/4TuEWtXBT_0
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I'm not sure if they were doing the aviation water survival training via the ASTC schools when you were in, but I can tell you, after I did that initial training at Lemoore, every time since that I have flown commercial, the first thing I do after I sit down is a 360 for exits and non-visibility reference points. :laugh:
I did the full meal deal every four years whether I want to or not, the altitude chamber, other physiology stuff, water survival including the single dunker and helo dunker, The highlight of every trip was getting thrown into the ocean off of North Island in strings of 7 or 8 and bobbing around while waiting for the helo to come get you.
I have flown exactly two times since I retired from active duty, first because I had nowhere to go and then after 9-11 just because. I did have to get on a plane to get to Hawaii and back. I sure will be glad when they get that bridge built. ;)
bob
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I have flown exactly two times since I retired from active duty, first because I had nowhere to go and then after 9-11 just because. I did have to get on a plane to get to Hawaii and back. I sure will be glad when they get that bridge built. ;)
bob
Wait a minute. There's an Interstate Highway there already, Interstate H-1. Interstate H-1 is the busiest Interstate Highway in the US state of Hawaii.
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Wait a minute. Isn't there an Interstate Highway there already?
(https://upload.wikimedia.org/wikipedia/commons/thumb/e/e5/Interstate_H1_map.png/290px-Interstate_H1_map.png)
Hell, they have 4 of them now. H1, H2, H3 and H201. Anything to get those federal highway dollars. ;)
bob
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The "give a sharp pull" is a very important part of making these things work so it is a possibility that there could be a group of several that don't understand because they didn't listen to the safety brief given by the passenger waitress as they were preparing to roll back from the dock.
I've lost count of how many airlines I've flown on, but I'm quite certain that none have ever said to "give a sharp pull" when explaining the oxygen masks. I think the standard language is "pull the mask down and oxygen will begin to flow." I'm 74 years old, I've been flying since I was 6 months old, and I didn't know how those mask thingies work until I saw the illustration in this thread.
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I did have to get on a plane to get to Hawaii and back. I sure will be glad when they get that bridge built. ;)
Minor detour for an old joke:
A guy is walking on the beach alone, feeling sad because his girlfriend just broke up with him. He stubs his toe on something, looks down, and sees a bottle. He picks up the bottle, looks at it, rubs the sand off it, and when he removes the cork ... out pops a genie. The genie tells the guy he can have any wish he wants as a reward for having released the genie.
The guy says, "I thought I was supposed to get three wishes." The genie says, "No, that only happens in fairy tales. This is the real world, it's one wish per customer. What would you like?"
The guy thinks for a minute. "Anything at all?" he asks.
"Anything at all," replies the genie.
"Well," says the guy, "I've always wanted to see Hawaii, but I'm afraid of flying and I get seasick, so I can't go by plane and I can't go by ship. How about building me a bridge from California to Hawaii?"
"Whoa," says the genie. "You know, the bridge itself isn't a big deal. But it's 2500 miles from California to Hawaii. You can't drive that on one tank of gas, or in one day. That means I'll have to build service stations, hotels, and restaurants. And that means I'll have to create several islands to put all those service facilities on. And I'll have to find people to work in them all. That's really a tremendous undertaking."
The guy looks crestfallen. "You're right," he says. "I didn't think through all the implications. I'm sorry, that was too much to ask even of a genie. Tell you what -- how about if you can just make it so that I understand women?"
The genie looks at the guy for a few seconds, then he says, "Okay, then -- did you want that bridge to start in Oakland, or Los Angeles?"
We now return you to your regularly scheduled ... whatever.
(https://forum.m1911.org/images/smilies/bolt.gif)
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I've lost count of how many airlines I've flown on, but I'm quite certain that none have ever said to "give a sharp pull" when explaining the oxygen masks. I think the standard language is "pull the mask down and oxygen will begin to flow." I'm 74 years old, I've been flying since I was 6 months old, and I didn't know how those mask thingies work until I saw the illustration in this thread.
Back when I occasionally flew commercial that was a standard part of the safety brief, usually they said give a sharp tug or pull. Now it seems they just say pull down. I remember because once when I flew I asked why a sharp pull and they told me to initiate the canister. All I know is if all you do is gently place the mask on you won't be getting any O2.
bob
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'Tis possible that the lanyards on the masks are short enough that you have to pull and release the trigger before the mask will extend down to your face.
Dunno ... never had to use one, and I hope I never have to test it.
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'Tis possible that the lanyards on the masks are short enough that you have to pull and release the trigger before the mask will extend down to your face.
Dunno ... never had to use one, and I hope I never have to test it.
I have never had to use one on a commercial flight either, got a lot of use out of the O2 mask (technically a smoke mask, we didn't use O2 in the P3 except in an emergency or prior to landing at night) in the Navy though, especially after a rough night of carousing around Olongapo or Subic City!!! Suck down pure O2 for a while and you could actually focus. ;)
From looking at the pic posted earlier it looks like a very short lanyard so to get the mask to your face you would trigger it.
bob
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If there is a change in cabin pressure, four
oxygen masks will drop from overhead. Firmly
pull a mask towards you to start the flow of oxygen.
That is a direct quote of our safety briefing.
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I read that the Navy did not want to use KO2 for its oxygen supplies because of its highly exothermic reaction with water. Read "explosive" for "highly exothermic."
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I've lost count of how many airlines I've flown on, but I'm quite certain that none have ever said to "give a sharp pull" when explaining the oxygen masks. I think the standard language is "pull the mask down and oxygen will begin to flow." I'm 74 years old, I've been flying since I was 6 months old, and I didn't know how those mask thingies work until I saw the illustration in this thread.
You're welcome.
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I've lost count of how many airlines I've flown on, but I'm quite certain that none have ever said to "give a sharp pull" when explaining the oxygen masks. I think the standard language is "pull the mask down and oxygen will begin to flow." I'm 74 years old, I've been flying since I was 6 months old, and I didn't know how those mask thingies work until I saw the illustration in this thread.
Pretty much every safety briefing I remember on the airlines I've flown has the flight attendant demonstrating a quick, forceful pull of the mask. So even if they don't say it, if you watch them demo it, you can see the procedure.
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The highlight of every trip was getting thrown into the ocean off of North Island in strings of 7 or 8 and bobbing around while waiting for the helo to come get you.
Lemoore didn't have an ocean, so they had you jump in the training pool where they turned on some bajillion CFM fans aimed at the water and hit you with water monitors to simulate "stormy conditions" as they dropped the "helo hoist", basically the hoist attached to a crane contraption, for you to hook yourself up and get lifted.
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Lemoore didn't have an ocean, so they had you jump in the training pool where they turned on some bajillion CFM fans aimed at the water and hit you with water monitors to simulate "stormy conditions" as they dropped the "helo hoist", basically the hoist attached to a crane contraption, for you to hook yourself up and get lifted.
We had a swimmer (in training) come out of the helo to hook us up. Every time I went I used the school wetsuit except the last time. By then we were flying with those new fangled survival suits (big orange gumby) so I took one with me. They let me bob around for ever because they said they knew I wasn't getting cold, and I wasn't. That plus I was the first one they had seen so all of the swimmers had to take a turn hooking me up. :)
bob
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The real reason it's not been a good month to fly is because we've had a late "swap" season on the east coast. Cold fronts and thunderstorms have caused a pretty hefty number of delays into July.
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The real reason it's not been a good month to fly is because we've had a late "swap" season on the east coast. Cold fronts and thunderstorms have caused a pretty hefty number of delays into July.
Suck it bambi, and approve my requests pronto.
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I read that the Navy did not want to use KO2 for its oxygen supplies because of its highly exothermic reaction with water. Read "explosive" for "highly exothermic."
I wouldn't think our Navy was that forward thinking. After all, our old OBAs ran on KO2. (After briefly considering trolloing old people I will allow that stands for Oxygen Breathing Apparatus, our older firefighting air pack). We had storerooms full of the canisters. We stored our MK58 signal markers in saltwater sprinkler protected magazines. The MK58 is a saltwater activated very large flare. Our liquid oxygen shop was one wall away from where we stored the gasoline which in turn was downwind of the smoke pit... See where I'm going with this? Carrier life makes one kinda immune to senses of actual danger. It's normal to live in the middle of millions of gallons of fuel and thousands of bombs right?
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Suck it bambi, and approve my requests pronto.
Sorry, UAL promised I wouldn't get an ass beating next time I fly on them, so priority goes to UAL...
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French G said,
(After briefly considering trolling old people I will allow that ["OBA"]stands for Oxygen Breathing Apparatus, our older firefighting air pack).
Deference accepted, and thanks.
French G again:
I wouldn't think our Navy was that forward thinking. After all, our old OBAs ran on KO2.
From wiki on KO2:
Applications[edit]
The Russian Space Agency has had success using potassium superoxide in chemical oxygen generators for its spacesuits and Soyuz spacecraft. <> KO2 has also been used in canisters for rebreathers for fire fighting and mine rescue work, but had limited use in scuba rebreathers because of its dangerously explosive reaction with water; the Russian IDA71 rebreather was designed to be used with potassium hydroxide.
https://en.wikipedia.org/wiki/Potassium_superoxide#Applications
It's not clear at <> whether they finished talking about Russia or not, but I think that's where I got the idea that the (our) Navy did not like to use KO2. I also note that was with respect to rebreathers and not necessarily straight oxygen generators. So basically, I think I stand corrected, and again, thanks.
Terry
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But why is it sold in butt plugs?
https://www.alibaba.com/product-detail/potassium-superoxide-potassium-peroxide-KO2-powder_11693965.html
(https://sc02.alicdn.com/kf/UTB8jfsuj3QydeJk43PUq6AyQpXat/potassium-superoxide-potassium-peroxide-KO2-powder.jpg)
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Well, since you broke the ice, I started to wonder a couple of posts ago whether "give it a sharp pull" was changed because of the snickering of the ... less than clean... minds of some of the passengers.
Just an amusing thought, not really presented as a theory.
Terry