Concorde Depressurisation systems

[chornedsnorkack]

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?