Cabin Pressurisation
Guys, it is all pretty simple. Normal practice would be to set the CABIN ALTITUDE SELECTOR to destination airfield elevation at TOD, and RATE at desired RATE OF CHANGE. Usually for pax comfort, the RATE OF CHANGE OF CABIN ALTITUDE ON DESCENT, would be a maximum of 300 FPM based on normal rate of descent of the aircraft. So if the cabin altitude at cruise was, say, 3000' the normal rate of descent of the aircraft would need to be no more than would allow at least 10 mins for the cabin to come down from 3000' to Zero. ANY GREATER RATE OF DESCENT OF THE AIRCRAFT WILL RESULT IN THE CABIN ALTITUDE BECOMING THE SAME AS AIRCRAFT ALTITUDE BEFORE THE AIRCRAFT HAS COMPLETED THE DESCENT AND THUS THE AIRCRAFT ALTITUDE AND THE CABIN ALTITUDE WILL DESCEND AT THE SAME RATE FROM THAT POINT. Not exactly rocket science.