The Mystery of Missing Malaysia Airlines 370

[Ed Anger]

Plus, Asians have poor eyesight.

[OttoVonBismarck]

I thought about that possibility too, but it doesn't seem to work unless pilots can manually depressurize the cabin separately from the cockpit, or else the locked-out pilot could warn people what was going on and I would think someone would have made calls/sent texts about the situation.  I don't know if it's possible to control cabin pressure in that way.

Yes, you can definitely intentionally depressurize the cabin. Read about Helios Airways Flight 522, it was accidentally depressurized because the pilots missed that the pressurization system was set to manual and one of the outflow valves had been left open, so essentially that flight as it got to cruising altitude everyone on the plane was rendered unconscious, including the pilots. The Greeks even did a flyby with a fighter jet and got visual on the copilot slumped over in his chair and the pilot not visible (ostensibly fell over into the floor.) Near the very end somehow a flight attendant was spotted climbing into the controls and trying to do something, but that happened right as the plane was flying into a mountain due to having no fuel left.

So anyway, a pilot could just lock the door, depressurize and go to 45,000 ft and good night passengers. It wouldn't necessarily kill them but it would incapacitate them for sure. We did hear rumors that the plane went up to 45,000 ft (but like CdM with his trust in the Malaysians I don't trust a lot of the various/contradictory technical stories we've heard), and the only reason you'd do that is to make the incapacitation happen more rapidly in my opinion. At regular cruising altitude it's theoretically possible for someone to be conscious for awhile, especially if they have some training. For example the famous Everest "zone of death" is only that "with caveats." People who have trained themselves can and have actually summited and gone all the way through the death zone without using portable oxygen bottles.

[OttoVonBismarck]

Oh, and "separately from the cockpit" doesn't matter. In my scenario the cockpit would be depressurized as well, however the pilot would have put an oxygen mask on in preparation. Much of the passengers would probably fail to secure  their oxygen masks in time (you only have a few seconds.) Further, those things aren't portable, the passengers aren't going to be able to storm the cockpit. There are a few portable oxygen masks on the plane for flight attendants, if anyone could get to it in time.

Additionally the oxygen mask the pilot gets has more oxygen in it and is designed to last for a longish time (like maybe 30 minutes), for passengers they're just there for dire emergencies where during a theoretical brief moment when the plane loses pressurization but before the pilot gets them down to lower altitude (which he'd be doing very rapidly in such a scenario.) So the passengers would run out of oxygen long before the pilot did.

[grumbler]

I would be astonished if the pilot could flip a switch and depressurize the cabin.  The Helios Airways incident happened because the ground crew disabled the door seal system in order to test it, but they did that at the door.  I can see no utility for a cockpit switch that could, by being accidentally and unknowingly triggered, kill or incapacitate the passengers and crew.

[OttoVonBismarck]

I would be astonished if the pilot could flip a switch and depressurize the cabin.  The Helios Airways incident happened because the ground crew disabled the door seal system in order to test it, but they did that at the door.  I can see no utility for a cockpit switch that could, by being accidentally and unknowingly triggered, kill or incapacitate the passengers and crew.

It's not a single switch, but it's definitely controllable in cockpit. First you set the pressurization system to manual, then you open one of the outflow valves.

[OttoVonBismarck]

That's actually what happened on the Helios flight by the way. The maintenance crew was indeed investigating reported strange sounds and etc that lead the previous pilots on the aircraft to believe there were problems with some seals or something, and that is why they had set the system to manual and had one of the outflow valves opened--was part of their testing.

During pre-flight one of the steps is to verify that the pressurization system is set to auto, and another step is to verify that all of the outflow valves are closed. The pilots of the Helios 552 missed both steps (there is a record of them going through those steps, but they checked them off apparently without actually being certain--probably because the outflow valves are almost always closed and the pressurization system is almost always pre set to auto so they just rushed through it.) That's really exactly what you'd do to depressurize a plane in mid-flight, just set it to manual and open a valve.

On Flight 552 what instead happened is they took off that way. But there are still safe guards, for example an alarm goes off telling you the pressure is dangerously low, at which point they should have aborted their climb. Instead, the pilots mistook the alarm for something else and ignored it, continuing to climb. They eventually realized something was wrong and radioed for help, but they were clearly disoriented and confused and kept repeating confused diagnosis of what was going on before they stopped responding--because that's typical of how your brain works when you've subjected it to a low oxygen environment.

[Caliga]

Yeah, I'm familiar with the Helios incident (I mentioned it earlier in this thread), and I also knew pilots have control over pressurization because in the case of the Helios flight, at one point when the crew was in touch with ATC they mentioned having a problem, and the ground tech who worked on the flight prior to departure actually asked them to check the pressurization control, but they either didn't understand him or didn't hear him, because obviously they didn't do that in time.

[derspiess]

I can't believe it's gone unmentioned thus far, but everyone should read up on what happened with Helios Airways Flight 522.

[Razgovory]

Has someone brought up the Helios flight yet?

[grumbler]

Yeah, I'm familiar with the Helios incident (I mentioned it earlier in this thread), and I also knew pilots have control over pressurization because in the case of the Helios flight, at one point when the crew was in touch with ATC they mentioned having a problem, and the ground tech who worked on the flight prior to departure actually asked them to check the pressurization control, but they either didn't understand him or didn't hear him, because obviously they didn't do that in time.

I am aware that the pilots can change the pressure control to manual from the cockpit, but I'd be astonished if they could flip a switch to open the outlet valves, whose only purpose would be to kill the passengers.  However, further investigation shows that the cabin loses enough pressure naturally that this wouldn't be an issue.

So, never mind!

[OttoVonBismarck]

My non-pilot's understanding of the outflow valves is they are (when pressure control is set to manual) being partially opened and partially closed all the time to help create air flow and regulate cabin pressure. The only scenario I've been able to look up where it really makes 'sense' to manually control them involves setting the system to manual and closing them 100%, which you would do if you were ditching in water. It probably wouldn't make a huge difference, but all things being equal it would slow the rate at which water flooded the plane and you want the fuselage to sink below the surface as slowly as possible. Although most likely if you do a successful water ditching you'll have more than enough time to get everyone out of the cabin, and if you don't the fuselage is going to have broken apart as it hit the water so it's a moot point.

[Razgovory]

I would be astonished if the pilot could flip a switch and depressurize the cabin.  The Helios Airways incident happened because the ground crew disabled the door seal system in order to test it, but they did that at the door.  I can see no utility for a cockpit switch that could, by being accidentally and unknowingly triggered, kill or incapacitate the passengers and crew.

There's all kinds of weird switches and buttons on airplanes.

[Ed Anger]

Raz wins with the Far Side.

[Queequeg]

 

[Caliga]

Good one, Raz.