Rumours & News Reporting Points that may affect our jobs or lives as professional pilots. Also, items that may be of interest to professional pilots.

B787 O2 supply

Old 8th Nov 2019, 10:47
  #61 (permalink)  
 
Join Date: Apr 2019
Location: Earth
Posts: 16
Likes: 0
Received 0 Likes on 0 Posts
Originally Posted by Flight Alloy
our lung muscles have very limited overcapacity
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.
Surlybonds is offline  
Old 8th Nov 2019, 16:51
  #62 (permalink)  
 
Join Date: Apr 2019
Location: Earth
Posts: 16
Likes: 0
Received 0 Likes on 0 Posts
Originally Posted by Flight Alloy
...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?
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.
Surlybonds is offline  
Old 8th Nov 2019, 16:59
  #63 (permalink)  
 
Join Date: Jul 2019
Location: STR
Posts: 5
Likes: 0
Received 0 Likes on 0 Posts
Originally Posted by Surlybonds
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.
Fully agreed in the case you specify here. That's why I specifically stated in my case a continuous flow over-pressure mask that would pressurize the lungs, as to illustrate the fact that both 'lung muscles' and the lungs themselves have a capacity limit that when reached results in bad things. I hope we can leave it there.
Flight Alloy is offline  
Old 9th Nov 2019, 08:33
  #64 (permalink)  
Pegase Driver
 
Join Date: May 1997
Location: Europe
Age: 73
Posts: 3,671
Likes: 0
Received 0 Likes on 0 Posts
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..
ATC Watcher is online now  
Old 9th Nov 2019, 08:49
  #65 (permalink)  
 
Join Date: Dec 2013
Location: Weltschmerz-By-The-Sea, Queensland, Australia
Posts: 1,364
Received 77 Likes on 34 Posts
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.
Australopithecus is offline  
Old 9th Nov 2019, 09:00
  #66 (permalink)  
 
Join Date: Sep 2019
Location: Outer ring of HEL
Posts: 1,682
Received 337 Likes on 110 Posts
Originally Posted by Australopithecus
Maybe thatís because the pax O2 worked for more than 75% of the passengers.

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.
Beamr is online now  
Old 9th Nov 2019, 09:33
  #67 (permalink)  
 
Join Date: May 2006
Location: UK, South East
Posts: 79
Likes: 0
Received 0 Likes on 0 Posts
Originally Posted by ATC Watcher
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..
On the 787, assuming no structural damage and increasing the speed to Vmo/Mmo in descent from 41,000í it takes about 3 1/2 mins to 10,000í. If you leave the speed where it is at .84 and donít increase it assuming structural damage it takes about 5 1/2 mins for the descent. Thatís with full speed brakes obviously.
Jumpjim is offline  
Old 9th Nov 2019, 10:57
  #68 (permalink)  
 
Join Date: Mar 2019
Location: On the Ground
Posts: 155
Likes: 0
Received 0 Likes on 0 Posts
Originally Posted by Jumpjim
in descent from 41,000í it takes about 3 1/2 mins to 10,000í.
8,800 fpm.

Takwis is offline  
Old 9th Nov 2019, 11:22
  #69 (permalink)  
 
Join Date: Mar 2002
Location: EU
Posts: 644
Likes: 0
Received 0 Likes on 0 Posts
Originally Posted by Australopithecus
Maybe thatís 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.
Exactly! The whole point is that Boeing, instead of sticking to the proven system, applied some new technology which got certificated by the FAA.
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. Doesnít exactly return my faith in Boeing and FAA..
golfyankeesierra is offline  
Old 9th Nov 2019, 11:25
  #70 (permalink)  
 
Join Date: Mar 2014
Location: Sydney, Australia
Posts: 3
Likes: 0
Received 0 Likes on 0 Posts
Originally Posted by ATC Watcher
Helios and various Lear jets..
If we add 'King Air' to your 'Lear Jet' example, there's definitely a pun there somewhere...

(Certain variants of Beech' King Air are known for their propensity to decompress very slooooowly and head off on cross-country ghost flights)
vhogb is offline  
Old 9th Nov 2019, 13:10
  #71 (permalink)  
 
Join Date: Dec 2014
Location: Uk
Posts: 4
Likes: 0
Received 0 Likes on 0 Posts
Originally Posted by fab777
At VMO, gear extended and in a side slip, maybe. So definitely not realistic in the real life. 4000 is a correct figure.
rubbish, easily done ,

and I really wouldnít extend the gear at VMO or do a side slip in a big jet.....back to flightsim for you.
Meester proach is offline  
Old 9th Nov 2019, 13:16
  #72 (permalink)  
Pegase Driver
 
Join Date: May 1997
Location: Europe
Age: 73
Posts: 3,671
Likes: 0
Received 0 Likes on 0 Posts
Originally Posted by Takwis
8,800 fpm.
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...
ATC Watcher is online now  
Old 9th Nov 2019, 23:56
  #73 (permalink)  
 
Join Date: Mar 2019
Location: On the Ground
Posts: 155
Likes: 0
Received 0 Likes on 0 Posts
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.
Takwis is offline  
Old 10th Nov 2019, 02:39
  #74 (permalink)  
 
Join Date: May 2011
Location: NEW YORK
Posts: 1,352
Likes: 0
Received 1 Like on 1 Post
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..
etudiant is offline  
Old 10th Nov 2019, 04:30
  #75 (permalink)  
 
Join Date: Jul 2007
Location: Auckland, NZ
Age: 79
Posts: 721
Likes: 0
Received 0 Likes on 0 Posts
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?
FlightlessParrot is offline  
Old 10th Nov 2019, 07:49
  #76 (permalink)  
 
Join Date: Feb 2001
Location: The Winchester
Posts: 6,548
Received 5 Likes on 5 Posts
Originally Posted by FlightlessParrot
Do all other passenger aircraft use oxygen generators instead of bottles?
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.

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.
wiggy is offline  
Old 10th Nov 2019, 10:07
  #77 (permalink)  
 
Join Date: Feb 2018
Location: Devon
Posts: 11
Likes: 0
Received 0 Likes on 0 Posts
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.


Viscount Way is offline  
Old 10th Nov 2019, 10:36
  #78 (permalink)  
 
Join Date: Feb 2001
Location: The Winchester
Posts: 6,548
Received 5 Likes on 5 Posts
Which aircraft still operate with a ring main system?
Certainly some (?all) 744s, certainly some (?all) 777s operate a ring main system (though some T7s I know of use generators in one of the cabin crew crew rest areas).

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.
Looks like must vary from operator to operator - FWIW where I am we are certainly allowed to tap into the ring main for medical cases if it looks like the passenger is going to need supplementary oxygen for an extended period, regardless of whether it's a pre-notified case or the crew are dealing with somebody who has fallen ill on the flight.

Last edited by wiggy; 10th Nov 2019 at 10:54.
wiggy is offline  
Old 10th Nov 2019, 12:11
  #79 (permalink)  
 
Join Date: Jul 2019
Location: STR
Posts: 5
Likes: 0
Received 0 Likes on 0 Posts
The ring main system sounds like it has some controlability at every station, does it have extra plugs for medical masks and manual activation valves for such uses?
Flight Alloy is offline  
Old 11th Nov 2019, 00:44
  #80 (permalink)  
 
Join Date: Sep 2017
Location: Europe
Posts: 1,674
Likes: 0
Received 0 Likes on 0 Posts
Originally Posted by Australopithecus
Maybe thatís 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.
Precisely.

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?
Rated De is offline  

Thread Tools
Search this Thread

Contact Us - Archive - Advertising - Cookie Policy - Privacy Statement - Terms of Service

Copyright © 2024 MH Sub I, LLC dba Internet Brands. All rights reserved. Use of this site indicates your consent to the Terms of Use.