not for fuel saving but for increasing flex temp to reduce the possibility of an engine failure. also reducing maintenance costs. packs on apu or off increases flex temp around 3 degrees. I donīt know how long the rwy is but I allways try to have a flex of 40 or more. Off course you can also switch the packs off without apu running but packs on increases cabin ventilation in addition to the cabin fans which are anyways too loud in the flight deck.
Edit: Just checked rwy length and calculated performance: rwy around 2100 meters long gives me following data for an A320 ZFW around 58000 and 8 tons of fuel for a two hours flight, wind calm: 134, 134, 137 with config 2 and flex 36.
So packs off or on APU is a good idea in my opinion.
Last edited by herbert23; 20th Jan 2009 at 12:48.