TheSonntag
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Would People Survive A Decompression On Concorde?

Wed Nov 23, 2005 8:09 am

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?
 
Espion007
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RE: Would People Survive A Decompression On Concorde?

Wed Nov 23, 2005 8:15 am

Thats the reason behind the tiny windows. It was done that way to minimilize the dangerous of a high altitude decompression.
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DeskPilot
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RE: Would People Survive A Decompression On Concorde?

Wed Nov 23, 2005 12:06 pm

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?
 
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Starlionblue
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RE: Would People Survive A Decompression On Concorde?

Wed Nov 23, 2005 12:29 pm

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." - John Ringo
 
Fly2HMO
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RE: Would People Survive A Decompression On Concorde?

Wed Nov 23, 2005 12:37 pm

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
 
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Starlionblue
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RE: Would People Survive A Decompression On Concor

Wed Nov 23, 2005 12:43 pm

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." - John Ringo
 
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HAWK21M
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RE: Would People Survive A Decompression On Concorde?

Wed Nov 23, 2005 5:11 pm

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
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Bellerophon
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RE: Would People Survive A Decompression On Concorde?

Wed Nov 23, 2005 5:58 pm

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
 
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RE: Would People Survive A Decompression On Concorde?

Wed Nov 23, 2005 6:15 pm

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
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TheSonntag
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RE: Would People Survive A Decompression On Concorde?

Wed Nov 23, 2005 8:20 pm

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?
 
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TripleDelta
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RE: Would People Survive A Decompression On Concor

Wed Nov 23, 2005 10:24 pm

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?
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Bellerophon
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RE: Would People Survive A Decompression On Concorde?

Wed Nov 23, 2005 10:42 pm

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
 
David L
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RE: Would People Survive A Decompression On Concorde?

Wed Nov 23, 2005 10:57 pm

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
 
mirrodie
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RE: Would People Survive A Decompression On Concorde?

Thu Nov 24, 2005 12:00 am

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
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RE: Would People Survive A Decompression On Concorde?

Thu Nov 24, 2005 1:06 am

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 
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vc10
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RE: Would People Survive A Decompression On Concorde?

Thu Nov 24, 2005 1:47 am

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
 
undehoulli
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RE: Would People Survive A Decompression On Concorde?

Thu Nov 24, 2005 2:09 am

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.
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RE: Would People Survive A Decompression On Concorde?

Thu Nov 24, 2005 2:21 am

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

Does a Concorde engineer count ?

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Jetlagged
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RE: Would People Survive A Decompression On Concorde?

Thu Nov 24, 2005 2:27 am

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.
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RE: Would People Survive A Decompression On Concorde?

Thu Nov 24, 2005 2:30 am

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...
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TripleDelta
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RE: Would People Survive A Decompression On Concorde?

Thu Nov 24, 2005 3:56 am

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.
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GDB
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RE: Would People Survive A Decompression On Concorde?

Thu Nov 24, 2005 4:28 am

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.
 
vc10
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RE: Would People Survive A Decompression On Concorde?

Thu Nov 24, 2005 4:34 am

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
 
airfoilsguy
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RE: Would People Survive A Decompression On Concorde?

Thu Nov 24, 2005 6:50 am

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?
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FlyingColours
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RE: Would People Survive A Decompression On Concorde?

Thu Nov 24, 2005 8:52 am

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
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David L
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RE: Would People Survive A Decompression On Concorde?

Thu Nov 24, 2005 9:17 am

Quoting GDB (Reply 21):
the cabin pressure on Concorde was indeed lower that conventional airliners

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 lower than on conventional airliners? A lower cabin pressure would make sense to this layman, due to the lower external pressure at FL600, but that would make the Champagne go flat sooner, which doesn't make any sense at all.  Sad
 
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Starlionblue
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RE: Would People Survive A Decompression On Concorde?

Thu Nov 24, 2005 10:06 am

Quoting Jwenting (Reply 8):
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?

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 talking about. Ok no more brown nosing  Wink

Quoting HiFi (Reply 14):
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.

Granted, but even so there are significant safety margins.
"There are no stupid questions, but there are a lot of inquisitive idiots." - John Ringo
 
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HAWK21M
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RE: Would People Survive A Decompression On Concorde?

Thu Nov 24, 2005 11:53 am

Quoting Vc10 (Reply 15):
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.

How does this logic work out.Isn't the MOFV near closed position in cruise.

Quoting Wrighbrothers (Reply 17):
Does a Concorde engineer count

Were you in Concorde Mx.
regds
MEL
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HiFi
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RE: Would People Survive A Decompression On Concorde?

Thu Nov 24, 2005 10:44 pm

Quoting Starlionblue (Reply 26):
Granted, but even so there are significant safety margins.

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 aspects, not only decompression  Wink
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sudden
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RE: Would People Survive A Decompression On Concorde?

Thu Nov 24, 2005 11:05 pm

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

For you who doesn't know, and his modesty to not write it,
Bellerophon was flying the Concorde.

Aim for the sky!
Sudden
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jush
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RE: Would People Survive A Decompression On Concorde?

Thu Nov 24, 2005 11:28 pm

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 stop flying supersonic. Would it be possible that the Concorde didn't manage to find a suitable airport for emergency landing or was did they have this in mind when planning. I certainly hope so.
Would be a horror to survive the decompression and then dive the thing into water before the coast of either Europe or America because of fuel starvation.

Regds
jush
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TheSonntag
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RE: Would People Survive A Decompression On Concorde?

Thu Nov 24, 2005 11:55 pm

Quoting Jush (Reply 30):
Would be a horror to survive the decompression and then dive the thing into water before the coast of either Europe or America because of fuel starvation.

Well, just imagine Concorde ditching and sinking to ground the same place where Titanic hit an iceberg, with many celebrities on board... Would've been terrible but somehow ironic.

But I guess Kevlavik, Shannon, the Azores, Gander are not that far away from each other so that Concorde might have reached them, but I leave it for the experts to determine that...
 
jush
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RE: Would People Survive A Decompression On Concorde?

Fri Nov 25, 2005 1:17 am

Quoting TheSonntag (Reply 31):
But I guess Kevlavik, Shannon, the Azores, Gander are not that far away from each other so that Concorde might have reached them, but I leave it for the experts to determine that...

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 operations ceased it's purely hypothetical.

Regds
jush
There is one problem with airbus. Though their products are engineering marvels they lack passion, completely.
 
vc10
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RE: Would People Survive A Decompression On Concorde?

Fri Nov 25, 2005 1:53 am

Hawk21M,
In answer to your query [reply27 ] , the outflow valves would be at their control position during cruise which is a variable depending on
Cabin height selected , aircraft height , amount of incoming air etc but this position under normal conditions was far from closed and approximately their total area equaled the area of two cabin windows
Now there was no recirculation cabin air on Concorde and the rate of air change was twice that of a conventional jet as the airflow was also required to keep the cabin cool during supersonic flight, and with a nose skin temp during cruise of anything up to 127 degs C then this airflow was quite important and resulted in the outflow valves being more open than you might expect.

Be happy little vc10
 
GDB
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RE: Would People Survive A Decompression On Concorde?

Fri Nov 25, 2005 2:00 am

Jush, though I'm sure Bellerphon can elaborate, flight planning was based around such contingencies.

But the point about modern safety standards had resonance, one reason why AF, inevitably followed by BA, retired the fleet was a rash of new requirements, meaning an extra £40 Million of extra maintenance costs, over 2 years, above what had already been budgeted for.
Including work on fuel tanks due to TWA800 aging aircraft issues, a new EGPWS, just to name two, these were to keep the fleet current with evolving
airworthiness requirements.

David L, to clarify, cabin altitude was lower.
 
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HAWK21M
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RE: Would People Survive A Decompression On Concorde?

Fri Nov 25, 2005 2:08 am

Quoting VC10 (Reply 33):
Cabin height selected , aircraft height , amount of incoming air etc but this position under normal conditions was far from closed and approximately their total area equaled the area of two cabin windows

What Delta P was the Cabin Pressurised till.
regds
MEL
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David L
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RE: Would People Survive A Decompression On Concorde?

Fri Nov 25, 2005 2:14 am

Quoting GDB (Reply 34):
David L, to clarify, cabin altitude was lower.

Cheers.
 
Bellerophon
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RE: Would People Survive A Decompression On Concorde?

Fri Nov 25, 2005 2:53 am

Jush

Concorde would have flown safely to a suitable airfield (not necessarily the intended destination) and landed, with normal fuel reserves still remaining, following a:

  • Total Decompression
  • Single Engine Failure
  • Double Hydraulic System Failure
  • Triple Generator Failure
which occurred at the most remote point along her intended track.

Out of interest, she would also have flown safely to a suitable airfield and landed following a Double Engine Failure which occurred at the most remote point along her intended track.

Unlike any of the twin-engined aircraft currently flying across the World's oceans. Big grin


HiFi

I wonder if perhaps you may be confusing aircraft altitude and cabin altitude when you say that Concorde would have to get down from FL600 to FL250 in two minutes.

There is no such requirement, even if she were to be certificated under FARs, which, being a European aircraft, not American, she would not be.

Under FARs, Concorde would be required to show that, following an improbable failure (not an extremely improbable failure, which may be ignored) occupants would never be exposed to:
  • A cabin altitude in excess of 40,000 ft.
  • A cabin altitude in excess of 25,000 ft, but below 40,000 ft, for more than 2 minutes.
To do this, she would have had to prove she could:
  • Descend from FL600 to FL400 before the cabin altitude climbed to 40,000 ft.
  • Descend to FL250 in under two minutes from the time that the cabin altitude reached 40,000 ft.
Both of which, I believe, she would have done with ease. I stand by my earlier post and say that it is highly unlikely, following any probable or improbable failure, that the cabin would ever have got above 20,000 ft.

There could be areas where she might struggle with modern certification under FARs, principally noise requirements, but personally I don't think that pressurisation would be an issue.


Best regards to both

Bellerophon
 
HiFi
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RE: Would People Survive A Decompression On Concorde?

Fri Nov 25, 2005 4:31 am

Bellerophon,
Great to have such accurate information about Concorde!
But I'll still question some of your points...  duck 

Quoting Bellerophon (Reply 37):
I wonder if perhaps you may be confusing aircraft altitude and cabin altitude when you say that Concorde would have to get down from FL600 to FL250 in two minutes

We both know that when decompression occurs, equalization is not instantaneous. It can take more or less time, depending on the size of the damage to the structure or to pressurization systems.
You are right in your statement, Concorde would not necessarily have to descend to 25000ft in less than 2min. Nevertheless, pressure will equalize, and in some cases that will take less than 2min (from 5000 to 25000ft if the info in here is correct about concorde's cabin alt).

Only extremely improbable failure conditions are excluded from this analysis.. Rotor bursts have a global probability of 10e-6 (this number is for modern engines).. Depending on the debri angles intersecting the cabin (which are pretty big with concorde's engines under the fuselage), you have the risk of a pretty serious (and rapid) decompression qualified as improbable (10e-7 > probability > 10e-9), for example.
Please correct me if my reasoning is forgetting something.. I have no factual data, this is just based on experience with other airliners (I do know that Concorde is THE unique airliner  Smile).

Quoting Bellerophon (Reply 37):
There is no such requirement, even if she were to be certificated under FARs, which, being a European aircraft, not American, she would not be

The concorde didn't need FAA certification because it wasn't a commercial success... Anyway, JARs have also evolved (there is also a JAR 25.1309, that didn't exist at the time, if I remember correctly).

Quoting Bellerophon (Reply 37):
Under FARs, Concorde would be required to show that, following an improbable failure (not an extremely improbable failure, which may be ignored) occupants would never be exposed to

Extremely improbable failures may not be ignored.. they need to be proved extremely improbable  scared 
If you have a failure condition that involves decompression and, for example, reduced airbraking capability (then assuming the a/c would not be able to make the emergency descent in the time required), you have to prove it to be extremely improbable (probability < 10e-9).

Quoting Bellerophon (Reply 37):
Descend to FL250 in under two minutes from the time that the cabin altitude reached 40,000 ft

"from the time cabin altitude reached 25000ft"  Wink
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jush
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RE: Would People Survive A Decompression On Concorde?

Fri Nov 25, 2005 4:47 am

Quoting Bellerophon (Reply 37):

Thanks very much indeed for that detailed answer.

Regds
jush
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Bellerophon
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RE: Would People Survive A Decompression On Concorde?

Fri Nov 25, 2005 5:18 am

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 that!


...Nevertheless, pressure will equalize,...

No, not necessarily. It would have depended entirely on the particular failure, and for many foreseeable failures, Concorde would have remained pressurised, albeit sometimes to a higher cabin altitude.


...and in some cases that will take less than 2min (from 5000 to 25000ft if the info in here is correct about concorde's cabin alt)...

What cases are you thinking of, and what evidence is this based on?

Without going into laborious detail, Concorde's cabin was very well protected, from over-pressurisation as well as de-pressurisation, by various design features, secondary systems and systems redundancy.

Whilst obviously not impossible for the cabin to climb at 10,000+ fpm, I can't think of any cases that don't fall into the catastrophic / extremely improbable category, common to most aircraft types.


...Extremely improbable failures may not be ignored.. they need to be proved extremely improbable...

And once they have been, they are, by definition, extremely improbable and therefore may be ignored.

Which is what I said.  Wink


...If you have a failure condition that involves decompression and, for example, reduced airbraking capability...

Not a problem on Concorde. No airbrakes, speedbrakes, slats or flaps!


..."from the time cabin altitude reached 25000ft"...

Oooops!  Embarrassment

You are right! It should read "From the time the cabin altitude first exceeded 25,000 ft" but for some reason I can't seem to edit that post to correct it.

Concorde may have had some weak areas which might have caused problems if undergoing present day certification, but, in my view, the pressurisation system was not one of them.


Best Regards

Bellerophon
 
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RE: Would People Survive A Decompression On Concorde?

Fri Nov 25, 2005 5:59 am

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 reservations about the design and a time scale was given for these modifications to be done to to meet FAA pertinent requirements . Braniff ceased operations with Concorde before the end date came about and not all the modifications were incorporated.

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TheSonntag
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RE: Would People Survive A Decompression On Concorde?

Fri Nov 25, 2005 7:44 am

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 seconds) if a window was "blown out" (which, itself, is almost impossible anyway).

So thank you all, especially Bellerophon, for these replies.

Which areas would cause problems for certification today? Noise, of course, even though it might be impossible to design quiet supersonic designs, it is highly unlikely that 119.5EPNdB could be called quiet enough for modern certification standards.

But what else (assuming the modifications on the fuel tanks have been incorporated) would be problematic?
 
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RE: Would People Survive A Decompression On Concorde?

Fri Nov 25, 2005 9:36 am

Quoting Bellerophon (Reply 40):
What cases are you thinking of, and what evidence is this based on?

Without going into laborious detail, Concorde's cabin was very well protected, from over-pressurisation as well as de-pressurisation, by various design features, secondary systems and systems redundancy.

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 subsequent decompression might not be extremely improbable.. But anyways, to further speculate would not be a profitable discussion unless I looked much deeper into Concorde's design.

I learned a lot about Concorde in this thread and I'll take your word for structural integrity of the cabin  bigthumbsup  (RUed you, btw)

Quoting TheSonntag (Reply 42):
Which areas would cause problems for certification today?

Main concern would be fire protection, in my opinion. You can never be too careful with fire.

The TWA 800 crash originated SFAR 88 (sorry, I just know the FARs better, JARs aren't free.. but I'd bet there's an European equivalent regulation). The fuel tanks would have to be modified, as already stated, but that's only 1 of the problems.
The engines are located just underneath the fuel tanks. This would be very difficult to accept, due to fuel leakage hazards.
Due to fuel tank dimensions, other issues should also be checked.. fuel spillage on hot breaks (landing or RTO) or on high temperature bleed lines (if any), for example.

For the pilots here: how would Concorde behave with a perforated wing and 1 engine out (or 2 engines out, since they're adjacent) on the same side, while in low subsonic regime? Yes, I'm thinking rotor burst, again, or FOD, and I'm thinking about 'sufficient rate of climb' (assuming flight controls remained 100% available, which is not necessarily true  Wink).

I don't know Concorde enough to speculate about what the impact of AC/AMJ 25.1309 - Arsenal Revised would be (although not mandatory).. But, summarizing, Concorde's configuration is inherently exposed to several risks.

I'm not judging whether the a/c is safe or not, but in my view, certification would be quite a challenge nowadays, although it's an absolute engineering marvel..
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Starlionblue
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RE: Would People Survive A Decompression On Concorde?

Fri Nov 25, 2005 10:24 am

Quoting Bellerophon (Reply 37):
Out of interest, she would also have flown safely to a suitable airfield and landed following a Double Engine Failure which occurred at the most remote point along her intended track.

Unlike any of the twin-engined aircraft currently flying across the World's oceans.

Cue the Flying Beard: "4 Engines 4 Long Haul!" (NB: This doesn't mean I wanted him to "get Concorde").

Quoting Bellerophon (Reply 40):
but for some reason I can't seem to edit that post to correct it.

That would be the 30 minute rule on the forums. Didn't you study it in Flight School?

Quoting TheSonntag (Reply 42):
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 seconds) if a window was "blown out" (which, itself, is almost impossible anyway).

Watching too many movies. Unless there's a rather catastrophic failure (like Aloha 737, UA 747) it might get uncomfortable but normally nowhere near howling hurricane. And note that even the examples I cited led to very little loss of life and both aircraft made it to the runway in one piece.

Quoting TheSonntag (Reply 42):
But what else (assuming the modifications on the fuel tanks have been incorporated) would be problematic?

As HiFi mentions, there are risks inherent in the configuration. One is due to the fact that the engines are right next to each other as opposed to separate nacelles. So it's easier for a blade failure or other high-energy event in one engine to affect it's neighbor.
"There are no stupid questions, but there are a lot of inquisitive idiots." - John Ringo
 
David L
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RE: Would People Survive A Decompression On Concorde?

Fri Nov 25, 2005 7:08 pm

Quoting HiFi (Reply 43):
how would Concorde behave with a perforated wing and 1 engine out (or 2 engines out, since they're adjacent)



Quoting Starlionblue (Reply 44):
One is due to the fact that the engines are right next to each other as opposed to separate nacelles. So it's easier for a blade failure or other high-energy event in one engine to affect it's neighbor.

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 adjecent engines.
 
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RE: Would People Survive A Decompression On Concorde?

Fri Nov 25, 2005 7:59 pm

Quoting David L (Reply 45):

Quoting Starlionblue (Reply 44):
One is due to the fact that the engines are right next to each other as opposed to separate nacelles. So it's easier for a blade failure or other high-energy event in one engine to affect it's neighbor.

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 adjecent engines.

I was in fact aware of the wall. But authorities would probably take a very close look at this.
"There are no stupid questions, but there are a lot of inquisitive idiots." - John Ringo
 
David L
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RE: Would People Survive A Decompression On Concorde?

Sat Nov 26, 2005 3:13 am

Quoting Starlionblue (Reply 46):
I was in fact aware of the wall. But authorities would probably take a very close look at this.

That wasn't aimed at you, honest. But you know what some people here are like.  Smile
 
GDB
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RE: Would People Survive A Decompression On Concorde?

Sat Nov 26, 2005 7:02 am

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, (turned out to be a one off manufacturing fault with that particular engine).
The aircraft diverted to SNN I believe.
The engine next to the failed one operated OK through all this.
That thick titanium wall and the inherent redundancy of the design was well proven that day.
 
HiFi
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RE: Would People Survive A Decompression On Concorde?

Mon Nov 28, 2005 11:45 pm

Quoting GDB (Reply 48):
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, (turned out to be a one off manufacturing fault with that particular engine).
The aircraft diverted to SNN I believe.
The engine next to the failed one operated OK through all this.
That thick titanium wall and the inherent redundancy of the design was well proven that day

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 titanium wall solution.. some of the certification criteria for an uncontained engine failure rely on 'infinite energy' models... meaning the titanium wall wouldn't be of much use.
Modern engines usually carry some protection to try to contain failures, particularly for the fan blades (a reinforced kevlar ring is quite common, for example), but the analyses cannot take credit of these. I understand the titanium wall is not part of the engine, and wouldn't qualify as the same kind of protection, but I believe the Concorde would still have some difficulties.

Great discussion going on here..  Smile
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