Maintaining cruise altitude while depressurised
Join Date: Mar 2014
Location: Maine USA
Age: 82
Posts: 199
Likes: 0
Received 0 Likes
on
0 Posts
I may have missed it, but has anyone so far pointed out the other problems that a loss of pressurization, especially an RD or ED, involves? Bends, chokes, trapped-gas dysbarisms, CNS.... taking a few hundred people, not all of them healthy, from 3000ft to 40,000 feet in a few seconds is going to create all kinds of physiological havoc that calls for descending to a lower altitude ASAP.
Join Date: Jan 2006
Location: Ijatta
Posts: 435
Likes: 0
Received 0 Likes
on
0 Posts
UDT,
Ref your remarks...
Our transponders should automatically squak 77**, (I don't think the last two digits matter), once a loss of cabin pressure greater than 10,000ft is detected.
Ref your remarks...
Our transponders should automatically squak 77**, (I don't think the last two digits matter), once a loss of cabin pressure greater than 10,000ft is detected.
Join Date: Jan 2006
Location: Ijatta
Posts: 435
Likes: 0
Received 0 Likes
on
0 Posts
PFP,
Your point is valid.
In the pressure chamber (actually negative pressure chamber) training that I remember, we were all instructed to open our mouths before they conducted the explosive decompression demonstration. "What the hell was that!!!"
LOUD bang...Immediate fog...Instant cold...
Some participants had their fillings pop out.
The flatulent smell was pungent.
We all had a "bloated" sensation as the air rushed out of our lungs.
Your point is valid.
In the pressure chamber (actually negative pressure chamber) training that I remember, we were all instructed to open our mouths before they conducted the explosive decompression demonstration. "What the hell was that!!!"
LOUD bang...Immediate fog...Instant cold...
Some participants had their fillings pop out.
The flatulent smell was pungent.
We all had a "bloated" sensation as the air rushed out of our lungs.
Last edited by wanabee777; 15th Mar 2016 at 12:16.
Join Date: Sep 2013
Location: UK
Posts: 730
Likes: 0
Received 0 Likes
on
0 Posts
The chart showing effective altitudes for different mask types is disingenuous. It assumes a rapid descent from those altitudes, not sustained flight at them; the masks will significantly retard the onset of hypoxia, giving a much increased time of useful conciousness at those levels, but will certainly not prevent hypoxia if the level is maintained.
Join Date: Mar 2014
Location: australia
Age: 81
Posts: 207
Likes: 0
Received 0 Likes
on
0 Posts
12 Minutes Passenger Oxygen in an NGX.
4 minutes holding level does not leave much for descent.
And a lot of people with slightly decreased lung function (older passengers) would have been pushed well into the O2 desaturation curve.
4 minutes holding level does not leave much for descent.
And a lot of people with slightly decreased lung function (older passengers) would have been pushed well into the O2 desaturation curve.
Igni
Window failures are fortunately rare. As I understand it, that is the design case for certification, see the small windows on Concorde.
Door seals leaking is usually more a problem of acoustics than pressurisation.
Window failures are fortunately rare. As I understand it, that is the design case for certification, see the small windows on Concorde.
Door seals leaking is usually more a problem of acoustics than pressurisation.
Join Date: Jul 2002
Location: LHS
Posts: 70
Likes: 0
Received 0 Likes
on
0 Posts
At Vietnam Airlines it is no problem: Maintenance screwed up the MEL, the crew took off and recognized the A350 wasn't pressurizing passing FL140, no problem they continued to climb to cruise altitude. Once level they decided to descend.
Person from Porlockis right. You should minimise any time above 25000 - above that there is a real and serious riskof decompression sickness. Any subaqua divers around? They'll tell us all about bends, chokes, creeps, staggers etc caused as the N2 in the blood comes out of solution on depressurisation.
The only time I did a chamber run above 25000, we prebreathed 100% O2 for 60 minutes to purge N2.
You really don't want to be mucking around up there.
The only time I did a chamber run above 25000, we prebreathed 100% O2 for 60 minutes to purge N2.
You really don't want to be mucking around up there.
I confess to you that it is very hard for me to grasp that a serious company in this industry would have such a practice or SOP. There is so much information and info on best practices on that matter that it just doesn't make sense to me, particularly as it relates to both passenger health/risk and crew health/risk.
Join Date: Jan 2005
Location: Mid Wales
Age: 63
Posts: 4
Likes: 0
Received 0 Likes
on
0 Posts
Hypoxia, and the lack of practical training received by our contractor pilots, is one of our biggest Risks to Life (RtL). Consequently, we recently went to RAF Henlow to receive some excellent training. I haven't done this level of training since leaving the RAF over 12 years ago, and I would thoroughly recommend it to those with a need and a budget. Furthermore, they have a part-task trainer, so you don't even have to go into a hypobaric chamber anymore.
The advice to stay at height - especially if the cabin alt is above 25,000 ft - is unwise. The RAF use 25,000ft as a cut off for pressure sickness, with 10,000 ft being the safe altitude before the risk of hypoxia increases significantly.
Pressure breathing is vastly different to having an over-pressure. Draegar Hoods are not effective above a cabin alt of 25,000 ft.
Aviate, navigate and communicate while you can. That should call for an immediate, controlled descent to below 10,000 ft, depending on the SALT.
The SAMs may get a 'cheap kill', but lack of oxygen will certainly send you to 'the great bar in the sky'. And debating about what to do in such a situation won't help your cause.
Fly safely!
The advice to stay at height - especially if the cabin alt is above 25,000 ft - is unwise. The RAF use 25,000ft as a cut off for pressure sickness, with 10,000 ft being the safe altitude before the risk of hypoxia increases significantly.
Pressure breathing is vastly different to having an over-pressure. Draegar Hoods are not effective above a cabin alt of 25,000 ft.
Aviate, navigate and communicate while you can. That should call for an immediate, controlled descent to below 10,000 ft, depending on the SALT.
The SAMs may get a 'cheap kill', but lack of oxygen will certainly send you to 'the great bar in the sky'. And debating about what to do in such a situation won't help your cause.
Fly safely!
Sims Fly Virtually
Join Date: Jun 2001
Location: Used to be 3rd Sand Dune from the Left - But now I'm somewhere else somewhere else.
Posts: 704
Likes: 0
Received 0 Likes
on
0 Posts
"self contained" - Why? 
The aircraft I worked on all had a separate supply of O2 for the flight deck
The aircraft I worked on all had a separate supply of O2 for the flight deck
Gender Faculty Specialist
PBEs are essentially for use fighting fires or smoke. Empty positioning flights, cargo flights may require the pilots to do so.
Join Date: Jun 2000
Location: last time I looked I was still here.
Posts: 4,507
Likes: 0
Received 0 Likes
on
0 Posts
I confess to you that it is very hard for me to grasp that a serious company in this industry would have such a practice or SOP. There is so much information and info on best practices on that matter that it just doesn't make sense to me, particularly as it relates to both passenger health/risk and crew health/risk.
So there you are; a seasoned captain, perhaps via a few airlines and perhaps even military. You've spent your whole life training and practicing Emergency Descents and Pressurisation problems. They've all been to the common standard of descent without unnecessary delay. I didn't say rush.
Now you end up at an airline with this as an SOP, and the worse happens. What are you going to do? It is your own life at stake + all the pax. You have more than enough O2, but they............Could this be the time to enforce "deviation from SOP for flight safety reasons SOP"?
So there you are; a seasoned captain, perhaps via a few airlines and perhaps even military. You've spent your whole life training and practicing Emergency Descents and Pressurisation problems. They've all been to the common standard of descent without unnecessary delay. I didn't say rush.
Now you end up at an airline with this as an SOP, and the worse happens. What are you going to do? It is your own life at stake + all the pax. You have more than enough O2, but they............Could this be the time to enforce "deviation from SOP for flight safety reasons SOP"?
Join Date: Jan 2008
Location: United Kingdom
Posts: 274
Likes: 0
Received 0 Likes
on
0 Posts
Una Due Tfc
Over the years we have had the debate of whether we should squawk 7700 when making an emergency descent. This has varied from yes we should squawk 7700 to alert ATC or no we shouldn't as ATC will lose all screen data on us, aircraft type, callsign etc. Generally we understand the preference to be not to squawk 7700 unless ATC request it or if we are unable to contact them. Consequently to squawk 7700 in emergency descent was removed from the checklist a while ago.
Your squawking 77 overrides all those filters and sets off audio alarms in both Shannon and Dublin. Everyone in every sector sees your mode c rolling like a slot machine and starts moving traffic in their sectors out of your way.
Over the years we have had the debate of whether we should squawk 7700 when making an emergency descent. This has varied from yes we should squawk 7700 to alert ATC or no we shouldn't as ATC will lose all screen data on us, aircraft type, callsign etc. Generally we understand the preference to be not to squawk 7700 unless ATC request it or if we are unable to contact them. Consequently to squawk 7700 in emergency descent was removed from the checklist a while ago.
FWIW whilst our 777 QRH and FCTM is silent on the issue our Ops Manual specifically states 7700 should be squawked in the event of an emergency descent to ensure the aircraft is "visible" to the controller(s) of lower sectors.
Join Date: Jan 2008
Location: london
Posts: 246
Likes: 0
Received 0 Likes
on
0 Posts
To me, the last five pages of posts serve as a chilling reminder of a very good reason why it's not a good idea to overfly a war zone at any altitude.
I'm now wondering how many commercial routes involve flight above terrain where the MSA is above FL250.
I'm now wondering how many commercial routes involve flight above terrain where the MSA is above FL250.