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There are several documented occurrences of "ghost flights" where the cockpit crew have succumbed to anoxia as a result of cabin depressurization, and the autopilot has kept the plane on course until it ran out of fuel and spun in, typically with the loss of all on board.
Pressurization (or oxygen)
is needed for the non-acclimatised above about 5000m AMSL (acclimatised individuals can cope at considerably higher altitudes, up to 10000m).
There aren't many bits of your planet above 5000m, so it would be safe enough to link the cabin pressurization warning system to the autopilot. When the pressurization alarm sounds, if there is no "override" action within a set period, the altitude setting automatically defaults to 5000m. The aircraft makes a controlled descent to denser air where (hopefully) the crew will recover, and take appropriate action.
There is a risk that the aircraft might fly into terrain. But if something isn't done before the fuel is exhausted, that's going to happen anyway, so the risk is justified in this special circumstance.
Ghost Plane
http://en.wikipedia..._Airways_Flight_522
[bs0u0155, Oct 22 2013]
Chilling effects of hypoxia
http://youtu.be/_IqWal_EmBg
[Klaatu, Oct 24 2013]
[link]
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Seems like this ought to be fairly obvious. Are we sure that modern systems don't do something like this already? I guess maybe the actual occurance of this is farely rare, so most pilots/airlines don't see a good cost/benefit ratio. |
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// Are we sure that modern systems don't do something like this already? // |
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Yes. It's not implemented in the Die-By-Wire software on any extant commercial transport, and definitely not on older airframes, although it would be a fairly simple autopilot mod. |
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I'm pretty sure the flying-into-mountains part could
be avoided as well. |
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//I'm pretty sure the flying-into-mountains part could
be avoided as well.// |
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Absolutely. Don't let the South Americans,
Pakistanis, Chinese or Nepalese have aircraft. The
one or two remaining peaks over 5000m can be
considered concentration aids. |
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Given that there appear to be maybe a hundred
points in the world above 5000m, I would have to
agree. Admittedly, you're probably going to want to
remain in the 4900-5000 meter range, since dropping
below that increases the number of peaks greatly. |
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Of course, if the autopilot is smart enough to do
that, can't it just signal the nearest airport with long
enough runways and an autoland system, and bring
itself down? |
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// if the autopilot is smart enough to do that // |
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The whole point about this is that it isn't smart at all. It's extremely dumb and simple. |
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//Of course, if the autopilot is smart enough to do
that, can't it just signal the nearest airport with long
enough runways and an autoland system, and bring
itself down// |
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Or, first class passengers may select their preferred
terrain to fly into. |
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I like this idea. It seems simple to implement. Yet I could
see a malfunctioning cabin pressure sensor, a
malfunctioning altimeter, and pilots confused by the alarm
resulting in controlled flight into terrain. I have no idea
how these things are guarded against and no idea how
rapid a descent would be needed to arrive at 5000 in time
to prevent death/brain damage. |
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The big risk is from subtle incapacitation. |
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Explosive depressurization is hard to miss, what with all the symptoms - bleeding from the eyes and ears, loss of bowel control due to expanding intestinal gas, etc. and the flight crew are provided with oxygen masks. |
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However, a systems failure that drops the pressure slowly without generating an immediate alert is more dangerous. The pilots are deprived of oxygen before the alarm goes off; their decision-making capacity is impaired and their thinking processes slowed. When the alarm does trigger, they spend time trying to find out what's wrong instead of immediately going onto supplementary oxygen, and then pass out before disconnecting the autopilot. |
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You don't need a rapid descent. A 500 ft per minute glideslope from FL350 will put you back into "breathable" air where the crew have a good chance of spontaneous recovery in 20 minutes, and the moment the descent starts the air quality improves. 1000 fpm would be better, easily achieved without any aerobatics, just a matter of throttling back and dropping the nose slightly. |
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Slow depressurization with the wrong switch thrown
was the culprit here <link>. |
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I think they've fixed the problem now. |
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Write a letter to Boeing or Airbus. And Ask |
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I recently thought of a way to save one of your airplanes (and most of the people on board) . In a nutshell.... |
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//...bleeding from the eyes and ears, loss of bowel control due to expanding intestinal gas, etc...// |
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I'm guessing it happens the other way around, if holiday dinners at my house are any indication. Most of us would happily choose the mountain after that... [+] |
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//it's extremely dumb and simple// [8th], I think
you're forgetting (I know you know this stuff better
than me) the minimum complexity of modern FBW
systems. |
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A global digital elevation map of the necessary
resolution (100m vertical, 1 degree horizontal) will
fit in 64k of memory. You could literally do this off
an 8048 microprocessor - that's the one which runs
your keyboard - and have it take position data from
best of
[GPS | dead reckoning]. |
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The FBW is *far* more complicated than that; if it
fails, you're doomed to be a blood/aluminum/dirt
mixture anyway. |
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//The FBW is *far* more complicated than that; if it
fails, you're doomed to be a blood/aluminum/dirt
mixture anyway// |
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The new generation of jets is changing all that
though.... now there's slightly less fuel and a whole
load of composites in there too! |
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Yes, wonderful isn't it ? The gut-wrenching terror of dying because of an avionics system failure has now been knocked off top spot by that old favourite Catastrophic Structural Failure aided and abetted by In-Flight Fire. Makes the concerns about Pilot Error and ATC incompetence fade into the background by comparison ... |
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// "Dear Mr. Boeing: I recently thought of a way to save one of your airplanes (and most of the people on board) . In a nutshell.... // |
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"Dear Mr Aircraft Manufacturer, |
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We've been busily reverse-engineering the software in your flight control systems with a view to turning a civil airliner into a precision guided munition, when we had an idea ..." |
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