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Philipvv
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Concorde cruise alt & Armstrong limit.

Wed Apr 18, 2018 9:47 am

Dear A'netters,

I was wondering what would have happened if Concorde would have had an explosive decrompression or very fast, immediate decompression at cruise altitude ( 60.000 ft ? ).

I am quite curious given the fact that aircraft like SR-71 & U2 who would operate at at least a similar altitude ( usually higher up probably ) but nevertheless those pilots are dressed in some kind of space suits, which would protect their blood from boiling in case of pressure loss at those altitudes.

The Armstrong line somewhat corresponds (give & take and according to wikipedia ) to 60.000ft let's say, so if pressure was lost, the concorde's passengers glasses of champagne and their bodily fluids would start to boil ? Besides losing consciousness almost immediately.

Of course the pilots will descend rapidly, so time spent at 60k won't be very long, nevertheless, not a fun thought losing pressure at 60000ft

thanks
best regards
PVV.
 
flipdewaf
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Re: Concorde cruise alt & Armstrong limit.

Wed Apr 18, 2018 10:05 am

It was my understanding that one of the reasons that Concorde's cabin windows were so small is that because of the issues you describe the systems have to be capable of maintaining a suitable pressure even with a (multiple?) window(s) blown.

Fred
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mmo
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Re: Concorde cruise alt & Armstrong limit.

Wed Apr 18, 2018 12:10 pm

IIRC, the max FL was 600, so that is right at the lower edge of where the Armstrong limit is. Also, the Concorde was designed to lose two windows in the cabin and still be able to maintain a cabin pressure of 15,000'. So, the risk of any effect from the Armstrong limit is very low.

Just for perspective, the U2/SR fly above FL700. At those levels the U2 cabin is around 29,000'.
If we weren't all crazy we'd all go insane!
 
cpd
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Re: Concorde cruise alt & Armstrong limit.

Wed Apr 18, 2018 1:21 pm

Philipvv wrote:
Dear A'netters,

I was wondering what would have happened if Concorde would have had an explosive decrompression or very fast, immediate decompression at cruise altitude ( 60.000 ft ? ).

I am quite curious given the fact that aircraft like SR-71 & U2 who would operate at at least a similar altitude ( usually higher up probably ) but nevertheless those pilots are dressed in some kind of space suits, which would protect their blood from boiling in case of pressure loss at those altitudes.

The Armstrong line somewhat corresponds (give & take and according to wikipedia ) to 60.000ft let's say, so if pressure was lost, the concorde's passengers glasses of champagne and their bodily fluids would start to boil ? Besides losing consciousness almost immediately.

Of course the pilots will descend rapidly, so time spent at 60k won't be very long, nevertheless, not a fun thought losing pressure at 60000ft

thanks
best regards
PVV.


Aside from what the others have already said, it was set up for an emergency descent so that this could be initiated very fast. This set up including things like the load limit controllers. And it could descend very fast if needed.
 
RetiredWeasel
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Re: Concorde cruise alt & Armstrong limit.

Wed Apr 18, 2018 2:23 pm

mmo wrote:
Just for perspective, the U2/SR fly above FL700. At those levels the U2 cabin is around 29,000'.


I believe all U-2s now have had the 'Cabin Altitude Reduction Effort' mod which increases cabin pressure in high altitude cruise. According to this article, that mod keeps the cabin pressure around 15,000 ft.
http://www.af.mil/News/Article-Display/Article/467537/u-2-modifications-reduce-decompression-sickness/
 
mmo
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Re: Concorde cruise alt & Armstrong limit.

Wed Apr 18, 2018 2:25 pm

It's been a while!!! Thanks.
If we weren't all crazy we'd all go insane!
 
Max Q
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Re: Concorde cruise alt & Armstrong limit.

Wed Apr 18, 2018 11:46 pm

Concorde was certified to use reverse thrust in flight (there were no spoilers installed)


I don’t know if these would be used in an emergency descent but, as stated it could come down very quickly if needed
The best contribution to safety is a competent Pilot.


GGg
 
cpd
Posts: 6462
Joined: Sat Jun 28, 2008 4:46 am

Re: Concorde cruise alt & Armstrong limit.

Thu Apr 19, 2018 9:09 am

Max Q wrote:
Concorde was certified to use reverse thrust in flight (there were no spoilers installed)


I don’t know if these would be used in an emergency descent but, as stated it could come down very quickly if needed



However, remember you cannot just throttle the engines all the way back at those altitudes, so idle reverse on the inboard engines wouldn't have worked.

That's from my now fuzzy memory.

Concorde did in testing go higher than 60000ft. AXDN did so and I seem to remember that F-WTSB also went very high.

The Washington descent was one way of descending very fast in a short distance, but in a decompression incident I'm unsure if it'd be used.
 
GalaxyFlyer
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Re: Concorde cruise alt & Armstrong limit.

Thu Apr 19, 2018 2:41 pm

Also, the certification isn’t based on the cabin instantly equalizing with the aircraft altitude. IIRC, it’s not supposed, or only rarely, exceed F250 during the emergency descent. The point of “4 minutes to 10,000’” is that the ascending cabin leak rate is contained to a rate that the cabin and the plane equalize below F250. There are tolerances and an allowance for reaction, donning masks by the crew and beginning the descent.

GF
 
kurtverbose
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Re: Concorde cruise alt & Armstrong limit.

Thu Apr 19, 2018 7:02 pm

cpd wrote:
Concorde did in testing go higher than 60000ft. AXDN did so and I seem to remember that F-WTSB also went very high.


From some forum: -

here is some information from Andr Turcat's book "Concorde essais d'hier, batailles d'aujourd'hui" on that subject:
March, 16th, 1973: ...They wore pressure suits, flew horizontally on 001 at Mach2, 56000 feet. Then Turcat pulled up and Concorde reached over 68000 feet (French: Au sommet, nous avions dpass 68000 pieds...) for a short time and went down again.... He noted that the production series, although more powerful were now limited to 63000 feet.
(translated from his book, page 229)
 
cpd
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Re: Concorde cruise alt & Armstrong limit.

Fri Apr 20, 2018 3:49 am

kurtverbose wrote:
cpd wrote:
Concorde did in testing go higher than 60000ft. AXDN did so and I seem to remember that F-WTSB also went very high.


From some forum: -

here is some information from Andr Turcat's book "Concorde essais d'hier, batailles d'aujourd'hui" on that subject:
March, 16th, 1973: ...They wore pressure suits, flew horizontally on 001 at Mach2, 56000 feet. Then Turcat pulled up and Concorde reached over 68000 feet (French: Au sommet, nous avions dpass 68000 pieds...) for a short time and went down again.... He noted that the production series, although more powerful were now limited to 63000 feet.
(translated from his book, page 229)


Thanks. :)

So:

001 F-WTSS: 68,000ft+ (Source: Andre Turcat)
101 G-AXDN: 63,700ft / M2.23 / Tangier
201 F-WTSB: 68,000ft / M2.22 / June 1973 / 75,459ft (unknown date)
202 G-BBDG: unknown / M2.21 (source: Brian Trubshaw)
216 G-BFKX: unknown / M2.19?

Another reliable source for 201 claims 23,000m was achieve by 201, this is nearly 75,500ft!? I can only imagine that was in a controlled pitch up (manual pitch hold using the datum adjust).
 
Bellerophon
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Re: Concorde cruise alt & Armstrong limit.

Sun Apr 22, 2018 5:02 pm

Philipvv

…I was wondering what would have happened if Concorde would have had an explosive decrompression or very fast, immediate decompression at cruise altitude ( 60.000 ft ? )…

This topic recurs every few years, however, for some reason - probably senility - I'm unable to post a link to my earlier replies, so permit me to re-hash some posts I made several years ago:


In the event of a total and near-instantaneous decompression to 60,000 ft, then the ramifications would have been very serious. Passengers exposed to atmospheric pressure at FL600 for any appreciable length of time would have had only a few seconds of consciousness followed by a merciful lapse into unconsciousness. However, the sort of damage or failures necessary to have caused this would have brought with them a whole host of other problems, making it highly likely that the aircraft would have ceased to be a viable flying machine - the early Comet accidents being a case in point.

What we have learnt is that in the overwhelming majority of decompressions, experienced over many years, on all aircraft types, the aircraft did not explosively 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 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.


…I am quite curious given the fact that aircraft like SR-71 & U2 who would operate at at least a similar altitude ( usually higher up probably ) but nevertheless those pilots are dressed in some kind of space suits, which would protect their blood from boiling in case of pressure loss at those altitudes...

I suspect this may have something to do with the fact that the pilots went into hostile airspace and were strapped into an ejection seat or system. Pulling an ejection handle, or receiving a missile strike, are among the fastest known ways of equalising cabin pressure with ambient pressure! :o


…The Armstrong line somewhat corresponds (give & take and according to wikipedia ) to 60.000ft let's say, so if pressure was lost, the concorde's passengers glasses of champagne and their bodily fluids would start to boil ? Besides losing consciousness almost immediately….

Dr Harry Armstrong did a lot of pioneering work into aircraft pressurisation at Wright Field, in the USA, in the late 1930’s. It was there he discovered, amongst other things, that at 63,000 feet pressure altitude, blood will boil at body temperature, an altitude limit know to this day as the Armstrong Line.

A point I would like to emphasise is that if we are to talk about TUC or damage to bodily fluids, then these effects are dependent, at least initially, upon the cabin altitude at which the problem occurs, not the aircraft cruise altitude. 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.


…Of course the pilots will descend rapidly, so time spent at 60k won't be very long, nevertheless, not a fun thought losing pressure at 60000ft…

Correct, and in most scenarios the predicted cabin altitude would never have got above 20,000 ft, and the overwhelming majority of these scenarios, though alarming, would have been highly survivable for all occupants. The possibility of passengers ever being exposed to atmospheric pressure at FL600 was considered to be extremely remote.

Best Regards

Bellerophon
 
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Semaex
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Re: Concorde cruise alt & Armstrong limit.

Mon Apr 23, 2018 8:33 am

Thanks all for your knowledgeable replies. If I may add a question:
I have heard of the theory that Concorde could sustain a suitable cabin pressure with 2 windows blown out on any point of the aircraft - but I highly doubt it could sustain 5000ft.
So which altitude would the cabin be able to hold, and also how much time would it take for the cabin to climb to this altitude?
I'm guessing that even though the possibility of a positive outcome of such a situation is mathematically possible, I expect this to be a "pain in the ear" for all aboard nonetheless.

Regards,
// You know you're an aviation enthusiast if you look at your neighbour's cars and think about fleet commonality.
 
mmo
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Re: Concorde cruise alt & Armstrong limit.

Mon Apr 23, 2018 9:34 am

Semaex wrote:
Thanks all for your knowledgeable replies. If I may add a question:
I have heard of the theory that Concorde could sustain a suitable cabin pressure with 2 windows blown out on any point of the aircraft - but I highly doubt it could sustain 5000ft.
So which altitude would the cabin be able to hold, and also how much time would it take for the cabin to climb to this altitude?
I'm guessing that even though the possibility of a positive outcome of such a situation is mathematically possible, I expect this to be a "pain in the ear" for all aboard nonetheless.

Regards,


As I previously wrote, the Concorde was certified with the ability to maintain a cabin of 15,000' with the loss of two windows. Depending on the severity of the cabin pressure fault, it could be almost instantaneous. It just depends if it's a slow leak or an actual window let go. How long is a piece of string?????
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