About pressurisation on take/bumps etc,packs don't have much input on take off, The out flow valves controls this. as the aircraft depressurises with the rate set. Bumps after take off, on selecting packs can be ironed out by selecting each pack in turn with a pause. I know you have to get it all ready for coffee!!
Another thing it is cheaper to fix cold air units than to change engines early. As well should consider the extra fuel burn on take off etc.....
[ 10 November 2001: Message edited by: schit.furbraen ]