B787 O2 supply
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I'd love for you to point out on an anatomical diagram where you think the lung muscles are... There ain't no such animal.
Chest muscles, and Diaphragm muscle, yep, but neither of those have a "capacity" as such, the chest cavity can expand by up to 1.5 to 2 litres from maximum exhalation to maximum inhalation.
Chest muscles, and Diaphragm muscle, yep, but neither of those have a "capacity" as such, the chest cavity can expand by up to 1.5 to 2 litres from maximum exhalation to maximum inhalation.
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...Now at external pressure that is lower than internal lung pressure, which are being pressurized by, for sake of argument, a continuous air supply, our lungs are inflated like a balloon. This force could be multiples of the normal inspiration force that is normal. Our lungs have a limited expansion capacity before injury occurs, linings are torn, intricate alveoli and arteries ripped, they explode, baro-trauma?
If you manually ventilate a patient in respiratory arrest - where the diaphragm and intercostal muscles are dormant - you can feel when you have met the elastic limit of the lungs, and any excess volume will be expelled round the seal of the mask. But even in a fully intubated patient using an automatic ventilator, you would be unlikely to cause any baro-trauma.
To try and drag this discussion back to some sort of relevance, the purpose of the passenger air masks is not to ventilate the patient, but simply to increase the partial pressure of oxygen within the mask, and therefore the lungs, to the point where anoxia does not occur.
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Even in a decompressed aircraft, the pressure differential between the external environment and the internal lung pressure is not going to be anywhere near enough to cause damage. We are talking about low flow rate supplementary oxygen, maybe 10 litres/min, not connecting the patient to a high pressure air-line. Baro-trauma is usually the result of being too near the shockwave of an explosion, or other such high pressure events.
If you manually ventilate a patient in respiratory arrest - where the diaphragm and intercostal muscles are dormant - you can feel when you have met the elastic limit of the lungs, and any excess volume will be expelled round the seal of the mask. But even in a fully intubated patient using an automatic ventilator, you would be unlikely to cause any baro-trauma.
To try and drag this discussion back to some sort of relevance, the purpose of the passenger air masks is not to ventilate the patient, but simply to increase the partial pressure of oxygen within the mask, and therefore the lungs, to the point where anoxia does not occur.
If you manually ventilate a patient in respiratory arrest - where the diaphragm and intercostal muscles are dormant - you can feel when you have met the elastic limit of the lungs, and any excess volume will be expelled round the seal of the mask. But even in a fully intubated patient using an automatic ventilator, you would be unlikely to cause any baro-trauma.
To try and drag this discussion back to some sort of relevance, the purpose of the passenger air masks is not to ventilate the patient, but simply to increase the partial pressure of oxygen within the mask, and therefore the lungs, to the point where anoxia does not occur.
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I find this medical discussion fascinating, and educative, but very theoretical.
In my 35 years as a radar controller controlling mostly upper airspace, I had to witness a few emergency descent myself, and saw a lot more on replay.
On the ROD : except from very old types like CV990 which could put 4 reverses in flight and could go down with 10.000 ft/min, the DC8 which could put the inboards in reverse and do 6000 ft/min , most of the others did around 4000 .I never seen a 787 doing one , left before they arrived.
After the incidents occurred , except from some minor injuries ,I cannot recall anyone killed or being permanently brain damaged. I have never read anything like this on incidents reports from rest of the world either. People sucked out if seated besides the hole.. yes, but Dead by hypoxia during a descent ? But maybe someone here can find references. .
And I mean hypoxia during an emergency descent, not slow ones or staying at altitude , e.g. Helios and various Lear jets..
In my 35 years as a radar controller controlling mostly upper airspace, I had to witness a few emergency descent myself, and saw a lot more on replay.
On the ROD : except from very old types like CV990 which could put 4 reverses in flight and could go down with 10.000 ft/min, the DC8 which could put the inboards in reverse and do 6000 ft/min , most of the others did around 4000 .I never seen a 787 doing one , left before they arrived.
After the incidents occurred , except from some minor injuries ,I cannot recall anyone killed or being permanently brain damaged. I have never read anything like this on incidents reports from rest of the world either. People sucked out if seated besides the hole.. yes, but Dead by hypoxia during a descent ? But maybe someone here can find references. .
And I mean hypoxia during an emergency descent, not slow ones or staying at altitude , e.g. Helios and various Lear jets..
Maybe that’s because the pax O2 worked for more than 75% of the passengers.
This issue breaks down into a discussion when really it should be about the aircraft's ability to meet the regulations and moral imperatives to supply 100% of the iccupants with reliable O2 supply. This is just the Titanic revisited: Insufficient lifeboats=insufficienct O2 reliability.
This issue breaks down into a discussion when really it should be about the aircraft's ability to meet the regulations and moral imperatives to supply 100% of the iccupants with reliable O2 supply. This is just the Titanic revisited: Insufficient lifeboats=insufficienct O2 reliability.
Interesting enough, in many of the pictures/videos that have appeared in social media from airplanes with launched masks, relatively high percentage of PAX seems to either wear the mask incorrectly or not wearing it at all. Without getting to the root of this phenomenon, I believe the situation has been the same in times prior to everyone having a smart phone at hand. Considering that for average joe the situation probably comes as a surprise, they've never even seen the mask live, they've never paid attention to safety briefs and then they should assist the children, too, I reckon that during all these years and all the emergencies world wide there would've been even one case of hypoxia related death during emergency decent.
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I find this medical discussion fascinating, and educative, but very theoretical.
In my 35 years as a radar controller controlling mostly upper airspace, I had to witness a few emergency descent myself, and saw a lot more on replay.
On the ROD : except from very old types like CV990 which could put 4 reverses in flight and could go down with 10.000 ft/min, the DC8 which could put the inboards in reverse and do 6000 ft/min , most of the others did around 4000 .I never seen a 787 doing one , left before they arrived.
After the incidents occurred , except from some minor injuries ,I cannot recall anyone killed or being permanently brain damaged. I have never read anything like this on incidents reports from rest of the world either. People sucked out if seated besides the hole.. yes, but Dead by hypoxia during a descent ? But maybe someone here can find references. .
And I mean hypoxia during an emergency descent, not slow ones or staying at altitude , e.g. Helios and various Lear jets..
In my 35 years as a radar controller controlling mostly upper airspace, I had to witness a few emergency descent myself, and saw a lot more on replay.
On the ROD : except from very old types like CV990 which could put 4 reverses in flight and could go down with 10.000 ft/min, the DC8 which could put the inboards in reverse and do 6000 ft/min , most of the others did around 4000 .I never seen a 787 doing one , left before they arrived.
After the incidents occurred , except from some minor injuries ,I cannot recall anyone killed or being permanently brain damaged. I have never read anything like this on incidents reports from rest of the world either. People sucked out if seated besides the hole.. yes, but Dead by hypoxia during a descent ? But maybe someone here can find references. .
And I mean hypoxia during an emergency descent, not slow ones or staying at altitude , e.g. Helios and various Lear jets..
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Maybe that’s because the pax O2 worked for more than 75% of the passengers.
This issue breaks down into a discussion when really it should be about the aircraft's ability to meet the regulations and moral imperatives to supply 100% of the iccupants with reliable O2 supply. This is just the Titanic revisited: Insufficient lifeboats=insufficienct O2 reliability.
This issue breaks down into a discussion when really it should be about the aircraft's ability to meet the regulations and moral imperatives to supply 100% of the iccupants with reliable O2 supply. This is just the Titanic revisited: Insufficient lifeboats=insufficienct O2 reliability.
But contrary to everything we do in aviation, this cannot checked or tested. It is a lifesaver! How could this have passed certification?
And now apparently it has been tested, only 75% works. Doesn’t exactly return my faith in Boeing and FAA..
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very Impressive indeed . Descending at Vmo? , the leveling off must be interesting , especially for the pax. .
@ vhogb : not many Kings in the airspace I controlled back then , but yes, heard the stories..
I was on duty in the 80s when a German Lear 25 overflew my sector at 430 , intercepted by F4s which reported an empty cockpit.. it crashed in the Atlantic when It ran out of fuel .Left an imprint in my memory...
@ vhogb : not many Kings in the airspace I controlled back then , but yes, heard the stories..
I was on duty in the 80s when a German Lear 25 overflew my sector at 430 , intercepted by F4s which reported an empty cockpit.. it crashed in the Atlantic when It ran out of fuel .Left an imprint in my memory...
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I should have clarified. I thought lots of other pilots would chime in and say, "no way". But no one did. So I will.
No Way. 4000fpm is realistic. 8800 fpm is ludicrous, for an airliner.
No Way. 4000fpm is realistic. 8800 fpm is ludicrous, for an airliner.
It might be helpful if Boeing were to address this O2 system issue directly by actually testing it on one of the airline 787s. It would cost a little money, but would also show that Boeing actually is sensitive to passenger safety issues again.
Moreover, if the test is a dud, it saves Boeing from the disaster that an in flight failure would have been, allowing them to solve the problem in peacetime, as it were..
Moreover, if the test is a dud, it saves Boeing from the disaster that an in flight failure would have been, allowing them to solve the problem in peacetime, as it were..
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Not wanting to be insistent, but may I ask again if this problem is unique to Boeing, or indeed the 787? I assume the devices come from a third-party supplier. Do all other passenger aircraft use oxygen generators instead of bottles? Is it known what the normal failure rate is?
From a users POV in the Long Haul arena they have at least a couple of possible advantages over generator systems:
1. If post decompression you end up in a brief cruise just above 10,000 feet (e.g; at say 12 000' for terrain reasons) you can selectively turn off/on supply to individual seats, thereby saving what's left in the tanks for those who are deemed to still need breathing assistance (not everybody will).
2. On a more routine basis if you have a passenger with a medical problem who needs oxygen for a considerable period of time ( and on a long haul flight it can sometimes be hours) you can supply him/her with a mask plugged into the oxygen ring main system rather than use up all your portable walk around bottles..
Last edited by wiggy; 10th Nov 2019 at 08:05.
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PulsOx Emergency O2 System
[QUOTE=wiggy;10615215]Can't comment of the specifics of the 787 but there certainly are other large passenger aircraft around that use gaseous oxygen/"ring main" systems.
The 787 and certain A350's, are equipped with the Collins Aerospace (that's UTC now) PulsOx system. New technology indeed which introduces lightweight O2 cylinders along with complex, electronically controlled pyrotechnic supply valves. (the ones in question) . Operation is driven by a pcb at each seat set. This system is said to reduce system weight compared to a ring main installation. Strangely, Collins make no weight comparison with the widely used O2 generator system.
The main attraction of the O2 generator is its simplicity. Oxygen is provided by the action of the user pulling the mask downward, withdrawing a safety pin to activate the chemical reaction. Maintenance is simple; confined to checking the serviceability of the panel latches and confirming that the generator has not reached its expiry date. That very check prompted an FAA/EASA scare in 2017 when it was found that a batch of life expired generators would not work when attempts were made to dispose of them.
Most aircraft in my experience have chemical O2 generators. They seemed to have been introduced with DC10's way back when. The L1011 from the same era came with the ring main though. Which aircraft still operate with a ring main system?
Wiggy, in my old outfit it was forbidden to tap into the ring main for planned medical cases. The Stretcher Kit came complete with sufficient Therapeutic Bottles for the whole trip.
The 787 and certain A350's, are equipped with the Collins Aerospace (that's UTC now) PulsOx system. New technology indeed which introduces lightweight O2 cylinders along with complex, electronically controlled pyrotechnic supply valves. (the ones in question) . Operation is driven by a pcb at each seat set. This system is said to reduce system weight compared to a ring main installation. Strangely, Collins make no weight comparison with the widely used O2 generator system.
The main attraction of the O2 generator is its simplicity. Oxygen is provided by the action of the user pulling the mask downward, withdrawing a safety pin to activate the chemical reaction. Maintenance is simple; confined to checking the serviceability of the panel latches and confirming that the generator has not reached its expiry date. That very check prompted an FAA/EASA scare in 2017 when it was found that a batch of life expired generators would not work when attempts were made to dispose of them.
Most aircraft in my experience have chemical O2 generators. They seemed to have been introduced with DC10's way back when. The L1011 from the same era came with the ring main though. Which aircraft still operate with a ring main system?
Wiggy, in my old outfit it was forbidden to tap into the ring main for planned medical cases. The Stretcher Kit came complete with sufficient Therapeutic Bottles for the whole trip.
Which aircraft still operate with a ring main system?
Wiggy, in my old outfit it was forbidden to tap into the ring main for planned medical cases. The Stretcher Kit came complete with sufficient Therapeutic Bottles for the whole trip.
Last edited by wiggy; 10th Nov 2019 at 10:54.
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Maybe that’s because the pax O2 worked for more than 75% of the passengers.
This issue breaks down into a discussion when really it should be about the aircraft's ability to meet the regulations and moral imperatives to supply 100% of the iccupants with reliable O2 supply. This is just the Titanic revisited: Insufficient lifeboats=insufficienct O2 reliability.
This issue breaks down into a discussion when really it should be about the aircraft's ability to meet the regulations and moral imperatives to supply 100% of the iccupants with reliable O2 supply. This is just the Titanic revisited: Insufficient lifeboats=insufficienct O2 reliability.
Into every crevice at Boeing crawled the business school MBA.
Slashing with reckless abandon, never striking the vital artery, they achieved personal enrichment.
How could a proud company be denigrated to such a state where forums discuss the availability of supplemental breathing oxygen in the event of loss of cabin pressure?
Just what do these educated fools actually know?