Originally Posted by
JohnMcGhie
Why is this system not fully automatic?
If the FADEC has full authority over the engine, why doesn't the environmental control system have full authority over the cabin pressure?
Surely Mr. Boeing has some kind of a warning: "Excuse me, you're climbing without cabin pressure, have you forgotten something?"
Surely there is a serious warning on the flight deck long before the rubber jungle?
It certainly is automatic, but just as the FADEC can't control a non running engine if you haven't given it any fuel the pressurisation system has nothing to control if you leave the bleed switch off and give it no air.
Warning? You bet there's a warning! A loud and very insistent intermittent horn but as said above it's the same as the t/o config warning and can result in a usually fairly short conversation that begins with "Why is the config warning going off at this altitude?" and ends rather abruptly with a scatalogical exclamation shortly thereafter. It doesn't give you a lot of time though, iirc the horn goes off at 10,000ft and the rubber jungle deploys at 14,000. Plenty of time for most crew to remember the other meaning of the config horn, something that is drilled into every 737 pilot.
It isn't a system failure, the systems all worked just fine as they were supposed to. The only thing that needs fixing is a crew who make a critical mistake, fail to spot it and additionally forget critical technical knowledge at the critical moment when the machine is urgently trying to tell them something. The usual fix is rockets of variable size inserted in the fundament with variable degrees of empathy.
I agree you would think that both the cabin crew and the pilots would notice the unusual ear sensations but the cc may be reluctant to call the flight deck for various reasons (ie below 10,000ft if that's SOP, or simply a steep authority gradient in the company/culture in question).