(...)every takeoff with the Pack's OFF. They are selected off just before line up and they are put back on after reduction to climb thrust (1500 ft AGL) with a 10 second interval to soften the blast for the benifit of the PAX. This is a fuel saving SOP and has been standard in the company for a few years. I think there are a few other BUS operators that use this SOP.
Been there, done that (CFM-56-5A and Bs). After a while, more frequent pack valve replacements caught up with fuel and engine life savings. We don't do that anymore. Now packs off only in very limiting conditions - short rwy, hot, high, heavy. Otherwise Tflx-5.
@antic81
CFM powered 319/320: no, no, yes. We always check go-around gradient requirements and climb performance with packs on. Only occasionaly we have to turn them off - in the sim, never in actual flying but then we don't fly to Kathmandu.