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Concorde Depressurisation systems

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Concorde Depressurisation systems

Old 10th Feb 2006, 19:01
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Concorde Depressurisation systems

What procedures did Concorde have in place in the event of rapid depressuriation at 60000ft, were all passengers and crew doomed?

I've looked on the net and the only things I have found were that the windows were built smaller to avoid air escaping and that pilots and crew would have used pressure breathing but I don't know if any of that is correct.

As the time to unconciousness at 35000ft is a matter of seconds - would it have been likely there could have ever been any survivors. I seem to recall that in 1977 one had an engine failure and dropped from 60000 to 30000ft in 3 minutes.

Does anyone know or could point me in the right direction?
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Old 10th Feb 2006, 23:04
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I can tell you the British Airways procedures for the unlikely event
of rapid decompression: They were pretty standard other than O2 pressures and fuel xfer for CG purposes.

Cut the warning bell
Crew O2 maks on and @ 100%
Switch Comms mike to mask
Confirm Warning
O2 showing deployed for cabin

If no pressurization control possible then the ops manual calls for:
Emerg Descent
Fuel Xfer (FWD) on override (CG issues)
.........
...............

The PAX O2 regulator goes to 90 psi above FL180.

The above is reference the BA Concorde AFM.

It would be very interesting to hear about actual experiences on this event.
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Old 11th Feb 2006, 05:19
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ask26

…Concorde… in the event of rapid depressuriation at 60000ft, were all passengers and crew doomed?…

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 be 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 all 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.


… What procedures did Concorde have in place in the event of rapid depressuriation at 60000ft…


Just as on subsonic jets, the crew would have been:
  • 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.
  • If control of the cabin had been irretrievably lost….initiating an emergency descent.
Starting from FL600, the initial rate of descent would have been around 12,000 - 15,000 fpm, reducing on passing through FL500 and increasing again on passing through FL400.

On Concorde, once below FL500 an emergency descent also became a deceleration manoeuvre, which brought with it the necessity to move fuel forward rapidly to keep the CG within limits as the aircraft Mach number decreased.

Various emergency descent profiles were tried during test flying. The one that was finally adopted for line operations gave an average rate of descent of around 7,000 fpm, and kept the CG within limits throughout.


…As the time to unconciousness at 35000ft is a matter of seconds - would it have been likely there could have ever been any survivors…

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.


…the only things I have found were that the windows were built smaller to avoid air escaping…

Correct. The windows on the production aircraft were smaller than on the original test aircraft for that reason.


…and that pilots and crew would have used pressure breathing…

Only the flight deck crew had pressure breathing masks.


Regards

Bellerophon
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Old 11th Feb 2006, 10:11
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Originally Posted by Bellerophon
ask26
…Concorde… in the event of rapid depressuriation at 60000ft, were all passengers and crew doomed?…
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 be 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 all aircraft types, the aircraft did not instantly depressurise to ambient atmospheric pressure, even if it may have felt like it to the occupants.
There have, however, been a few disastrous decompressions.

A Boeing 747 had a cargo door come open over the Pacific.

The air pressure broke the cabin floor above the cargo hold and 9 seats were blown out of the floor underneath, with their occupants. However, the plane remaining continued to fly and eventually landed safely.

A DC-10 also had a cargo door opening when climbing out of Paris, and again seats, this time 6, were blown out of floor. But that time, the remaining airframe also crashed.

A Boeing 747 had a rear pressure bulkhead breaking. No one was sucked out, and the plane initially continued to fly - poorly, so it flew about an hour and eventually crashed.

A Boeing 737 had a large stretch of entire upper fuselage blown away when climbing over the Pacific. One woman was sucked out - a stewardess standing in the aisle. But the plane continued to fly and landed safely... all passengers survived, even those facing the slipstream at cruise speed in their window seats that no longer had windows, or any sidewall at all.
Originally Posted by Bellerophon
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.
… What procedures did Concorde have in place in the event of rapid depressuriation at 60000ft…
Just as on subsonic jets, the crew would have been:
  • 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.
  • If control of the cabin had been irretrievably lost….initiating an emergency descent.
Starting from FL600, the initial rate of descent would have been around 12,000 - 15,000 fpm, reducing on passing through FL500 and increasing again on passing through FL400.
On Concorde, once below FL500 an emergency descent also became a deceleration manoeuvre, which brought with it the necessity to move fuel forward rapidly to keep the CG within limits as the aircraft Mach number decreased.
Various emergency descent profiles were tried during test flying. The one that was finally adopted for line operations gave an average rate of descent of around 7,000 fpm, and kept the CG within limits throughout.
…As the time to unconciousness at 35000ft is a matter of seconds - would it have been likely there could have ever been any survivors…
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.
OK, how would passengers have been affected by facing slipstream at Mach 2?
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Old 11th Feb 2006, 10:58
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Originally Posted by chornedsnorkack
OK, how would passengers have been affected by facing slipstream at Mach 2?
Chorned ... if you actually read what Bellerophon said it would probably answer your question. He should know - he was a Concorde pilot, and said ...
Question…Concorde… in the event of rapid depressuriation at 60000ft, were all passengers and crew doomed?…
Answer. 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.
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Old 11th Feb 2006, 12:10
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Decompression

Well, I have pointed at several examples of subsonic pressurized airplanes undergoing rather rapid decompression without immediately breaking up in flight. Some of the planes (a 737 and a 747) eventually managed to perform descent and land.

15 000 fpm from FL600 to FL500 is 40 seconds, correct? And 12 000 fpm is 50 seconds. FL500 to FL400 was a deceleration maneuver, slower. So, you get 1,5 to 2 minutes before the plane is below FL400. Or more?

250 feet per second or 75 metres per second descent cannot itself be achieved at once - if the wing is completely unloaded, it takes 8 seconds of free fall. Plus, before the descent is even initiated, the crew must put on their own masks.

Are a few seconds of useful consciousness at 60 000 feet cabin/cockpit altitude enough to put on pressurized oxygen?

If the crew could put on their masks then so could the passengers. The difference being the passenger masks had unpressurized oxygen. This is not enough to fly a plane and make sensitive decisions at FL600. But would the passengers who put on their masks have stayed conscious a few seconds longer than those who did not?

Of course assuming they had masks and the PSU-s were not blown away, as they were in a famous 737.

Also, if the plane reached more breathable air at FL 400, or FL300 or FL200 a few minutes later, were the passengers supposed to wake up from unconsciousness, or be already dead and stay that way?
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Old 11th Feb 2006, 15:34
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Chorned

As the proverb goes, 'you can lead a horse to water, bu you can't make it drink'.....
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