The Boeing 777 has fore and aft pressurisation switches (see example here). If the aft switch was forgotten on takeoff, could this cause a loss of cabin pressurisation when the aircraft reaches altitude?

  • $\begingroup$ My question was edited and the point of it is now lost. My basic idea is: Is there any MISTAKE the pilots could have made that would have done in all the rest of the pasengers without the pilots noticing it until it was too late? The rest of the flight characteristics would then make sense.... $\endgroup$ – vas Mar 17 '14 at 0:24
  • $\begingroup$ There would most certainly be a visible alert on the screen that it had been left in the close position, since this is not the normal configuration, and the pilots would have seen that. Otherwise, they would also have gotten plenty of warnings about cabin pressure had it been too low. $\endgroup$ – Thunderstrike Mar 17 '14 at 20:13
  • $\begingroup$ So it can't be pressure. What about the air conditioning? Somewhere in the "Source" document, I read that passengers are airconditioned from both sides but the flight deck just from one (I think that it was the left). $\endgroup$ – vas Mar 17 '14 at 22:20
  • $\begingroup$ if it was unintentional, any deviation from the normal operation of the pressurization the pilots would have been alerted about problems on multiple levels. This was most probably a deliberate act by the pilots, where they might or might not have switched off the pressurization entirely. $\endgroup$ – Thunderstrike Mar 17 '14 at 22:34

From my previous source in that incapacitation question:

Two outflow valves are installed: one forward and one aft. Normally, most of the outflow is through the aft outflow valve. This improves ventilation and smoke removal. Cabin altitude and full ventilation rates can be maintained by either valve. Source


There is only one pressurization system for the whole aircraft. The two outflow valves regulate the airflow moving through the cockpit and cabin respectively, the intake air comes from engine bleed air, which is quite hot, and is mixed with outside ambient air to regulate the temperature through two or more heat exchangers, depending on the make and size of the aircraft. If there were two pressurization systems, one for the cockpit and one for the cabin, there would have to be a pressure bulkhead between the cockpit and the cabin, and there isn't.


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