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Would People Survive A Decompression On Concorde?  
User currently offlineTheSonntag From Germany, joined Jun 2005, 3570 posts, RR: 29
Posted (8 years 9 months 1 week 4 days 8 hours ago) and read 4770 times:

Fortunately this never happened, but what would have happened if Concorde had a rapid decompression at Mach2 and cruise level? Would this have been survivable? Which measures were taken to prevent that?

57 replies: All unread, showing first 25:
 
User currently offlineEspion007 From Denmark, joined Dec 2003, 1691 posts, RR: 0
Reply 1, posted (8 years 9 months 1 week 4 days 8 hours ago) and read 4768 times:

Thats the reason behind the tiny windows. It was done that way to minimilize the dangerous of a high altitude decompression.


Snakes on a Plane!
User currently offlineDeskPilot From Australia, joined Apr 2004, 767 posts, RR: 0
Reply 2, posted (8 years 9 months 1 week 4 days 4 hours ago) and read 4693 times:

Quoting Espion007 (Reply 1):
dangerous of a high altitude decompression.

I don't understand - how ?



By the way, is there anyone on board who knows how to fly a plane?
User currently offlineStarlionblue From Greenland, joined Feb 2004, 17028 posts, RR: 67
Reply 3, posted (8 years 9 months 1 week 4 days 4 hours ago) and read 4686 times:

The higher you are, the larger the pressure differential between the outside and inside.

To counteract this, the smaller the window, the less air can escape in a given amount of time. The Concorde pilots on the board can probably answer this better, but the aircraft was certified to the same standard as any other airliner, so I assume it had to be able to maintain (some) pressure even with a window "popped". It would not have been certified if decompression->automatic doom.



"There are no stupid questions, but there are a lot of inquisitive idiots."
User currently offlineFLY2HMO From , joined Dec 1969, posts, RR:
Reply 4, posted (8 years 9 months 1 week 4 days 4 hours ago) and read 4683 times:

Quoting Starlionblue (Reply 3):
The Concorde pilots on the board can probably answer this better,

We have Concorde pilots in here!?!?!  eyepopping 

I want your autographs!!! Big grin


User currently offlineStarlionblue From Greenland, joined Feb 2004, 17028 posts, RR: 67
Reply 5, posted (8 years 9 months 1 week 4 days 3 hours ago) and read 4677 times:

Quoting FLY2HMO (Reply 4):
Quoting Starlionblue (Reply 3):
The Concorde pilots on the board can probably answer this better,

We have Concorde pilots in here!?!?! eyepopping

I want your autographs!!! Big grin

Either that, or they're very good posers

But you know, they still put their pants on one leg at a time.... just very very fast... supersonically one might even say.

[Edited 2005-11-23 04:55:26]


"There are no stupid questions, but there are a lot of inquisitive idiots."
User currently offlineHAWK21M From India, joined Jan 2001, 31679 posts, RR: 56
Reply 6, posted (8 years 9 months 1 week 3 days 23 hours ago) and read 4624 times:

Quoting Starlionblue (Reply 3):
To counteract this, the smaller the window, the less air can escape in a given amount of time

How much of a difference would that make.
regds
MEL



Think of the brighter side!
User currently offlineBellerophon From United Kingdom, joined May 2002, 583 posts, RR: 59
Reply 7, posted (8 years 9 months 1 week 3 days 22 hours ago) and read 4614 times:

TheSonntag

... what would have happened if Concorde had a rapid decompression at Mach2 and cruise level?...

To answer your question, we first need to know just how rapid the rapid decompression was.

A near-instantaneous decompression at 60,000 ft would have been very serious. Passengers exposed to atmospheric pressure at that height for any appreciable length of time would have had only a few seconds of awareness followed by a merciful lapse into unconsciousness.

The sort of damage necessary to have caused this would have brought with it a whole host of other problems, and probably the aircraft would have ceased to have been a viable flying machine - the early Comet accidents being a case in point.

However, in the overwhelming majority of decompressions, experienced over many years on other aircraft types, the aircraft did not instantly depressurise to ambient atmospheric pressure, even if it may have felt like it to the occupants.

Whether due to pressurisation system failure, discharge valve failure, a small hull breach, a door or window blow-out, or just plain human error, the cabin took time to decompress, often a considerable amount of time.

It is this time, the time the cabin takes to climb which provides the flight crew with a safety margin, precious seconds in which to act to protect passengers and crew from extreme cabin altitudes.

On Concorde, this involved the crew in protecting themselves (pressurised O2 masks) analysing the situation (what warnings?, what cabin rate-of-climb?) rectifying if possible (re-instating packs, selecting alternate systems, closing errant valves manually) or, if control of the cabin had been irretrievably lost, initiating an emergency descent.

The cabin altitude on Concorde was typically around 5,000 ft in the cruise, and in common with most commercial aircraft, various flight deck warnings would occur as the cabin altitude rose through 10,000 ft, and again passing through 14,000 ft, to alert the crew to any problem, assuming their own eyes, ears, sinuses and lower intestines had not already done so!

There were also many protection devices fitted to Concorde to ensure that the cabin altitude never exceeded 14,000 ft, however, even had they all failed and the cabin had been climbing at 5,000 fpm, it would still have taken 36 seconds before the cabin altitude exceeded 8,000 ft.

It would have taken 108 seconds before it exceeded 14,000 ft and around 3 minutes for the cabin to exceed 20,000 ft, by which time the aircraft would have been well on its way down to safety in an emergency descent.

In most cases, the cabin altitude would never have got above 20,000 ft, and the overwhelming majority of these incidents, though alarming, would have been highly survivable for all occupants. The chances of passengers ever being exposed to atmospheric pressure at FL600 was an extremely remote possibility.

It never even came close to happening, during 27 years of commercial service.


Regards

Bellerophon


User currently offlineJwenting From Netherlands, joined Apr 2001, 10213 posts, RR: 18
Reply 8, posted (8 years 9 months 1 week 3 days 22 hours ago) and read 4604 times:

Quoting Starlionblue (Reply 5):
Either that, or they're very good posers

You mean like the guys in the chatroom a few years back claiming to be A380 pilots for Qantas? Big grin



I wish I were flying
User currently offlineTheSonntag From Germany, joined Jun 2005, 3570 posts, RR: 29
Reply 9, posted (8 years 9 months 1 week 3 days 20 hours ago) and read 4557 times:

Quoting Bellerophon (Reply 7):

Thank you for your insights. How long would it take to decelerate from Mach 2 and 60000feet to 15000 feet and a speed where you can fly at this altitude?


User currently onlineTripleDelta From Croatia, joined Jul 2004, 1123 posts, RR: 7
Reply 10, posted (8 years 9 months 1 week 3 days 18 hours ago) and read 4535 times:
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Quoting Starlionblue (Reply 3):
The higher you are, the larger the pressure differential between the outside and inside.

To counteract this, the smaller the window, the less air can escape in a given amount of time.

There's another reason as well - every window is basically a hole in the plating. Every hole reduces the local structure strength, possibly leading to a structural failure around the hole (because of the lower number of structural elements and stress distribution - what happened in the first Comet I disaster if I'm not wrong).

In a normal airliner, the pressure differential at its cruise altitude dictates one window size. On the Concorde, the higher pressure differential requires a smaller one, since the stress it produces on the airframe is greater. Reducing the size of the window - that is, reducing the hole and the number of "missing" structural elements - would also reduce the chances of a structural failure around the window, since more structural elements are opposing the greater stress.

But I wonder: the Concorde was built with better hermetisation than an ordinary airliner - to reduce the amount of air flowing out. The engine compressors are not as effective up around FL600 as they are at FL300, which would mean a lower amount of air flowing into the cabin at lower pressure. However, how would Concorde's speed influence this? Less air flowing into the compressor (in terms of volume), but at a higher speed?



No plane, no gain.
User currently offlineBellerophon From United Kingdom, joined May 2002, 583 posts, RR: 59
Reply 11, posted (8 years 9 months 1 week 3 days 18 hours ago) and read 4523 times:

TheSonntag

...How long would it take to decelerate from Mach 2 and 60000feet to 15000 feet and a speed where you can fly at this altitude?...

It would have taken around 160 nm and 14 minutes to decel/descend from FL600 and Mach 2.0 down to FL150 and 350 kts, in ISA conditions with zero wind.


Regards

Bellerophon


User currently offlineDavid L From United Kingdom, joined May 1999, 9524 posts, RR: 42
Reply 12, posted (8 years 9 months 1 week 3 days 17 hours ago) and read 4514 times:

Quoting Bellerophon (Reply 7):
The cabin altitude on Concorde was typically around 5,000 ft in the cruise

That's a lower altitude than on most subsonic airliners, I believe. This was to keep the Champagne bubbly for longer?  Smile


User currently offlineMirrodie From United States of America, joined Apr 2000, 7443 posts, RR: 62
Reply 13, posted (8 years 9 months 1 week 3 days 16 hours ago) and read 4490 times:
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has someone been reading MAYDAY? Sounds like a question spured by that book and film.

Quoting Bellerophon (Reply 7):
followed by a merciful lapse into unconsciousness.

Only Bellerophon can make disaster sound so poetic!  Wink



Forum moderator 2001-2010; He's a pedantic, pontificating, pretentious bastard, a belligerent old fart, a worthless st
User currently offlineHiFi From Brazil, joined Apr 2005, 192 posts, RR: 0
Reply 14, posted (8 years 9 months 1 week 3 days 15 hours ago) and read 4453 times:

Quoting Starlionblue (Reply 3):
It would not have been certified if decompression->automatic doom.

The concorde probably wouldn't be certified by nowadays safety standards.

In case of a cabin decompression, an airliner must be able to descend to 25000 ft in less than 2min (unless decompression is very slow):

"FAR 25.841
(a) Pressurized cabins and compartments to be occupied must be equipped to provide a cabin pressure altitude of not more than 8,000 feet at the maximum operating altitude of the airplane under normal operating conditions.

(1) If certification for operation above 25,000 feet is requested, the airplane must be designed so that occupants will not be exposed to cabin pressure altitudes in excess of 15,000 feet after any probable failure condition in the pressurization system.

(2) The airplane must be designed so that occupants will not be exposed to a cabin pressure altitude that exceeds the following after decompression from any failure condition not shown to be extremely improbable:

(i) Twenty-five thousand (25,000) feet for more than 2 minutes; or

(ii) Forty thousand (40,000) feet for any duration.

(3) Fuselage structure, engine and system failures are to be considered in evaluating the cabin decompression."



In case it could not be proven that the Concorde was able to make an emergency descent from FL600 to FL250 in less than 2min (Bellerophon, could the concorde make it?), they would have to PROVE that decompression is extremely improbable, meaning that its probability of occurence is inferior to 10e-9. That's not at all easy to do, not even for sudden decompression.

In fact, for the Concorde, item (a)(2)(ii) means that sudden decompression must be extremely improbable from the start.

And cabin decompression isn't the only issue that would jeopardize an updated concorde certification.. just think 'engine position', for example!  no 



no commercial potential
User currently offlineVc10 From United Kingdom, joined Nov 2001, 1408 posts, RR: 16
Reply 15, posted (8 years 9 months 1 week 3 days 14 hours ago) and read 4437 times:

The size of Concorde's windows are such that would allow a blowout of two windows without the aircraft's pressurization being compromised severely. The reason for this is the area of two windows roughly equals the total area of the open controlling outflow valves, so if the windows went the outflow valves would close and the pressure would remain roughly equal.

Now I am not saying the crew would carry on serving the dinner if this happened as it would be noisy and dangerous for anybody near those windows, and the cabin height might climb , but not at a catastrophic rate.

Anyway I always thought the small windows were handy as there was one for each eye

Do Not worry little vc10  Smile


User currently offlineUndehoulli From , joined Dec 1969, posts, RR:
Reply 16, posted (8 years 9 months 1 week 3 days 14 hours ago) and read 4420 times:

I certainly wouldn't want to be exposed to conditions like that at 60,000 feet! I lasted about 3 minutes at 25,000 feet (in the altitude chamber at school) before someone had to help me with my mask.

User currently offlineWrighbrothers From United Kingdom, joined Jul 2005, 1875 posts, RR: 9
Reply 17, posted (8 years 9 months 1 week 3 days 14 hours ago) and read 4410 times:

Quoting FLY2HMO (Reply 4):
We have Concorde pilots in here!?!?!

Does a Concorde engineer count ?

Wrighbrothers



Always stand up for what is right, even if it means standing alone..
User currently offlineJetlagged From United Kingdom, joined Jan 2005, 2546 posts, RR: 24
Reply 18, posted (8 years 9 months 1 week 3 days 14 hours ago) and read 4402 times:

Quoting TripleDelta (Reply 10):
The engine compressors are not as effective up around FL600 as they are at FL300, which would mean a lower amount of air flowing into the cabin at lower pressure.

You don't need high pressure air to pressurise a cabin. In fact it only needs to be just above the target cabin pressure. Part of the function of a pack is to reduce bleed air pressure to a level at which it can be used.

As far as compressor efficiency goes, they are still efficianet at FL600 in terms of pressure ratio. Also you are forgetting that in supersonic cruise, most of the compression comes from the intake. There's plenty of airflow and certainly sufficient pressure.



The glass isn't half empty, or half full, it's twice as big as it needs to be.
User currently offlineWingscrubber From UK - England, joined Sep 2001, 848 posts, RR: 0
Reply 19, posted (8 years 9 months 1 week 3 days 14 hours ago) and read 4400 times:

The noise/shockwaves generated in a possible supersonic de-compression would probably burst eardrums and cause a variety of injuries to crew and passengers akin to those suffered when caught in a bomb blast I'd imagine...


Resident TechOps Troll
User currently onlineTripleDelta From Croatia, joined Jul 2004, 1123 posts, RR: 7
Reply 20, posted (8 years 9 months 1 week 3 days 12 hours ago) and read 4364 times:
AIRLINERS.NET CREW
PHOTO SCREENER

Quoting Jetlagged (Reply 18):
You don't need high pressure air to pressurise a cabin. In fact it only needs to be just above the target cabin pressure. Part of the function of a pack is to reduce bleed air pressure to a level at which it can be used.

Yes, you're correct, I had a conceptual error in my head  banghead 

Quoting Jetlagged (Reply 18):
As far as compressor efficiency goes, they are still efficianet at FL600 in terms of pressure ratio. Also you are forgetting that in supersonic cruise, most of the compression comes from the intake. There's plenty of airflow and certainly sufficient pressure.

So the pressurisation system is then much like the one on a normal airliner, right? Taking air directly from behind the intake, just before the first compressor stage would be an unnecessary complication in that case I guess, as it would only be used in the supersonic region.



No plane, no gain.
User currently offlineGDB From United Kingdom, joined May 2001, 13191 posts, RR: 77
Reply 21, posted (8 years 9 months 1 week 3 days 12 hours ago) and read 4346 times:

Mirrodie, I read Mayday around 1982!

Bellerphon was a BA Concorde pilot, until October 2003, since (like me) he does not choose to have his name on here, it's not for me to bandy it around, though I worked out who it was.
He also makes valuable contributions to the forums on www.concordesst.com

I was in Engineering on the type from only 1997 to the very end.
VC-10 was on the fleet too, earlier in it's life at BA, I suspect rather more in depth too.

As has been noticed by one poster, the cabin pressure on Concorde was indeed lower that conventional airliners.


User currently offlineVC10 From United Kingdom, joined Nov 2001, 1408 posts, RR: 16
Reply 22, posted (8 years 9 months 1 week 3 days 12 hours ago) and read 4342 times:

The pressurization air source on Concorde is a bleed from the engines compressor, just like many other aircraft.
Now there is an air bleed from the top of the intake area and forward of the compressor, known as the secondary air bleed. This air source is available when the "Secondary Air Doors" open above 220 kts, however this air is used to cool the outer case of the engine during the flight, and has nothing to do with the pressurization system .

little vc10


User currently offlineAirfoilsguy From , joined Dec 1969, posts, RR:
Reply 23, posted (8 years 9 months 1 week 3 days 9 hours ago) and read 4287 times:

What causes such rapid lose of consciousness at high flight levels? Shouldn't time to lose of consciousness be dictated by how long you can hold your breath? I know air would be forced out your lungs at low air pressure but shouldn't you be able to last more then a few seconds?

User currently offlineFlyingColours From United Kingdom, joined Dec 2003, 2315 posts, RR: 10
Reply 24, posted (8 years 9 months 1 week 3 days 7 hours ago) and read 4249 times:

Quoting Airfoilsguy (Reply 23):

Its Hypoxia, its kind of like being somewhat very drunk and happy. We were always taught to look for signs in other people (as you can't detect it in yourself that much). Its the lack of oxygen that makes everyone feel very happy and eventually everyone just falls unconscious and thats it.

Luckily they never forced us into pressure chambers, so we just got to watch the US Armed Forces (not sure which area) video instead.

An intresting topic, I'm just glad we will never find out the answer for sure now, just a shame why.

Phil
FlyingColours



Lifes a train racing towards you, now you can either run away or grab a chair & a beer and watch it come - Phil
25 Post contains images David L : I think some here don't realise how easily I can be confused - can we just clarify whether it was the cabin pressure or the cabin altitude which was
26 Post contains images Starlionblue : Hehe. Just for the record, I don't think Bellerophon, GDB et.al. are posers. IMHO they are valuable contributors to the board and know what they are
27 HAWK21M : How does this logic work out.Isn't the MOFV near closed position in cruise. Were you in Concorde Mx. regds MEL
28 Post contains images HiFi : I agree.. I'm just saying that it wouldn't meet the updated regulations.. And in that statement you quoted I was also refering to other certification
29 Sudden : For you who doesn't know, and his modesty to not write it, Bellerophon was flying the Concorde. Aim for the sky! Sudden
30 Jush : My question is now. If that would've happened over the Atlantic half way through the journey. They made anemergency descent to a safe altitude and sto
31 TheSonntag : Well, just imagine Concorde ditching and sinking to ground the same place where Titanic hit an iceberg, with many celebrities on board... Would've be
32 Jush : Right i forgot about that they're flying NAT routes. So i guess you're right. There might always be something near to land the bird. But as operation
33 VC10 : Hawk21M, In answer to your query [reply27 ] , the outflow valves would be at their control position during cruise which is a variable depending on Cab
34 GDB : Jush, though I'm sure Bellerphon can elaborate, flight planning was based around such contingencies. But the point about modern safety standards had r
35 HAWK21M : What Delta P was the Cabin Pressurised till. regds MEL
36 David L : Cheers.
37 Post contains images Bellerophon : Jush Concorde would have flown safely to a suitable airfield (not necessarily the intended destination) and landed, with normal fuel reserves still re
38 Post contains images HiFi : Bellerophon, Great to have such accurate information about Concorde! But I'll still question some of your points... We both know that when decompressi
39 Jush : Thanks very much indeed for that detailed answer. Regds jush
40 Post contains images Bellerophon : HiFi ...You are right in your statement, Concorde would not necessarily have to descend to 25000ft in less than 2min. .. Good, I'm glad we agree on th
41 VC10 : Just a short addition when Concorde flew with Braniff it was put on the American register and was approved by the FAA. Now they did have a few reserva
42 TheSonntag : Wow, when I started this thread I didn't expect to get such great replies. I always thought that decompression would happen much faster (within second
43 Post contains images HiFi : I mentioned rotor burst, as that kind of event has the potential to make quite a damage to the a/c's structure and, depending on engine position, a s
44 Starlionblue : Cue the Flying Beard: "4 Engines 4 Long Haul!" (NB: This doesn't mean I wanted him to "get Concorde"). That would be the 30 minute rule on the forums
45 David L : But not as easy as one might think. I'm sure Bellerophon and GDB will be able to provide, for example, details of the titanium wall between the adjec
46 Starlionblue : I was in fact aware of the wall. But authorities would probably take a very close look at this.
47 Post contains images David L : That wasn't aimed at you, honest. But you know what some people here are like.
48 GDB : Well before my time, around 1981, and I've only seen the photos, of when an engine (on G-BOAF IIRC) had a major failure, virtually was sheared in two,
49 Post contains images HiFi : I'm not trying to prove the concorde was unsafe.. I'm discussing certification requirements.. And certain authorities would not be at ease with a tit
50 GDB : I should perhaps point out that having the engines so close together, meant that Concorde was maintained to ETOPS requirements.
51 VC10 : I think there are pro's and con's to be said for closely positioned engines but it has to said that this type of engine arrangement does suffer from t
52 GDB : Thanks for the update VC-10, it was before my time, I was still at school then! I was told by one of those who went to fit a new engine, that the adja
53 Art : I'm a bit baffled why it would take much time at all to lose altitude. If you are 12 miles up and travelling at 10+ miles a minute horizontally, why s
54 Starlionblue : I haven't tried to replicate your arithmetic but my guess is this entail overspeed.
55 Post contains links B2707SST : That, and the G-forces exerted on the airframe and passengers would probably be excessively high. Several Concorde books also mention that the engine
56 Post contains images Bellerophon : B2707SSR ...know if this procedure was waived during an emergency descent (i.e. flight idle thrust immediately)?... Yes. For an emergency descent, fli
57 B2707SST : Ah, thanks for the clarification. Fascinating machines, these! --B2707SST
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