Wearing my beancounter/management hat I have the following suggestion:
1) Both packs OFF til 10,000 ft, that should save a kg of fuel or two, whilst taking the strain off the engines IAW power-by-the-hour or wotever.
2) First pack ON @ 10,000 ft, this would avoid the erroneoues flap retraction risk as by then I'd hope they were safely tucked away. The reduced air density would lessen the "submarine" effect compared with sea level compression.
3) Second pack on at 25,000 ft, save more kgs of fuel and protect against the effects of losing the 1st pack, 1 pack flight up to FL250 apparently OK according to DDGs various.
4) One pack off in descent through FL250, save fuel and pack wear and tear, maybe swop which pack like engine ignitors to even out the wear and increase the chances of both failing at the same time, just like the ignitors did on me years ago.
5) Leave the remaining pack ON til touchdown as a gesture to the SLF that we really do care about their comfort.
Another advantage of the reduced packs climb is it would accelerate the expulsion of gases from the body cavities of both SLF and crew, clearing the mucus from the sinuses and blowing the plugs out of the eustacion tubes, thereby making for an easier and less painful descent.
Should any airline management adopt these procedures, I will of course expect a cut of the savings which could be considrable?!
