Originally Posted by
stator vane
The chapter on the cabin altitude panel does not go any further than shown.
Thanks, Stator.
That cabin altitude/diff gauge is an interesting one.
I recall a 737 incident where they did a rapid depressurisation and emergency descent after a window crack, and subsequently found themselves at a low altitude with the cabin altitude above 40,000'.
Very confusing. Except that the cabin altitude wasn't above 40,000' of course, it was way below sea level. You see, they didn't actually have a rapid depressurisation. So they closed the outflow valve manually as per the checklist, descended as per the checklist, and consequently pressurised the cabin way below sea level. That gauge is capable of reading negative, but it doesn't have negative graduations. The needle just moves anti-clockwise until it shows a high cabin altitude. No mention of that in the manuals either. Hmmm.