Cabin Pressurisation
I am unable to understand why in cases such as the Helios B737 loss that (1), neither pilot understood the Cabin Altitude Aural warning as indicated by FGD135 and (2), that having failed to recognize such warning that no action was taken when the emergency masks deployed, if they did as they should have, when the cabin altitude reached approximately 14000 feet. Neither pilot should have been hypoxic at that stage. That, again as cited by FGD135, the engineering department could not guide the pilots is hard to comprehend.