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Maintaining cruise altitude while depressurised

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Maintaining cruise altitude while depressurised

Old 15th Mar 2016, 01:55
  #81 (permalink)  
 
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PFP,

Agreed but the certification standard does NOT anticipate the cabin getting above about 25,000' for long, if at all.

GF
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Old 15th Mar 2016, 03:23
  #82 (permalink)  
 
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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.
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Old 15th Mar 2016, 06:54
  #83 (permalink)  
 
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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.
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Old 15th Mar 2016, 09:27
  #84 (permalink)  
 
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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.
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Old 15th Mar 2016, 10:21
  #85 (permalink)  
 
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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.
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Old 15th Mar 2016, 13:10
  #86 (permalink)  
 
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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.
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Old 15th Mar 2016, 13:47
  #87 (permalink)  
 
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Originally Posted by 787 9 View Post
Its because it is so unbelivable that I cant tell you who it is, and it is a very reputable airline.
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.
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Old 15th Mar 2016, 15:42
  #88 (permalink)  
 
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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!
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Old 15th Mar 2016, 16:21
  #89 (permalink)  
 
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Does Draeger make PBE's for flightcrew use?

I couldn't find information ref PBE's with self-contained O2 provisions on their web site.
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Old 15th Mar 2016, 16:45
  #90 (permalink)  


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Question

"self contained" - Why?

The aircraft I worked on all had a separate supply of O2 for the flight deck
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Old 15th Mar 2016, 16:52
  #91 (permalink)  
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PBEs are essentially for use fighting fires or smoke. Empty positioning flights, cargo flights may require the pilots to do so.
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Old 15th Mar 2016, 17:29
  #92 (permalink)  
 
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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"?
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Old 15th Mar 2016, 18:36
  #93 (permalink)  
 
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Una Due Tfc


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.
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Old 16th Mar 2016, 09:46
  #94 (permalink)  
 
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Sunny,

The latest iteration of the B747 FCTM says, inter alia, for "rapid descent" squawk 7700 as soon as can be done after the memory items are completed.
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Old 16th Mar 2016, 10:17
  #95 (permalink)  
 
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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.
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Old 16th Mar 2016, 10:37
  #96 (permalink)  
 
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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.
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Old 16th Mar 2016, 16:42
  #97 (permalink)  
 
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Mustafagander and Wiggy


Thanks chaps. I see it disappeared from the checklist but has reappeared in the FCTM.
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Old 16th Mar 2016, 16:54
  #98 (permalink)  
 
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Changing squawk is a bit of a sticky one. That it alerts controllers of airspace below you is inits favour, but against it is the loss of the data block attached to your "echo", which was the reason given by several of my employers for retaining the given squawk code unless told to change to 7700. But the idea of staying at cruise level depressurised is utterly wrong, unjustifiable and should be ignored. Unfortunately, most airlines have good SOPs and bas, some more of one than the other. Those pilots that have been around a few employers and types, especially those that have a few interesting days out, will know when to ignore an SOP. It's much harder for folk in their first company, especially if that company has an over-onerous approach to SOP adherence.
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Old 17th Mar 2016, 07:02
  #99 (permalink)  
 
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In various airlines, when discussing delays in changing SOP's, we were told they required approval by local XAA's. If true then a local XAA has approved this and they should be questioned and asked for their reasoning in the approval.
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Old 17th Mar 2016, 08:30
  #100 (permalink)  
 
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My recollection from RAF days:

O2 required above 10,000ft; 100% O2 required above 25,000ft; Under pressure above 33,000ft.

Up to 41,000ft unpressurised for the duration of a 180 turn? If the anoxia doesn't get them, the cold will.
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