I have noticed on the TAKEOFF page (TO/APPR key) that the packs are listed as off. Does this mean they are currently off, will automatically be turned off during takeoff, or that they need to be turned off now for takeoff? TOPCAT indicates a difference of a couple of hundred feet in takeoff roll at at about max TOGW depending upon whether the packs are on or off.Thank youMichael Cubine

I have noticed on the TAKEOFF page (TO/APPR key) that the packs are listed as off. Does this mean they are currently off, will automatically be turned off during takeoff, or that they need to be turned off now for takeoff? TOPCAT indicates a difference of a couple of hundred feet in takeoff roll at at about max TOGW depending upon whether the packs are on or off.Thank youMichael Cubine

Hi!They are temp. disengaged when start of engine, after full start on all engines you should turn them off./ Leffe

Hi!They are temp. disengaged when start of engine, after full start on all engines you should turn them off./ Leffe

No need to turn them off in normal operations, anyway the purpose of the FMC option is it's fully automatic. Upon application of T/O thrust the Packs switch themselves off. And switch back on after thrust reduction or acceleration altitude

Thanks a lot for the information.Michael Cubine

Hi All,Sorry to disagree.The FMC page with packs on or off option is for thrust calculations.Normal use is a packs on take-off, but at high altitude airfields or extreme temperatures combined with a maximum take-off weight the packs are switched off.You tell the FMC this and before t/o you switch packs off and during initial climb you switch them back on.Sincerly,Bob

Hey Bob.Whatever the normal use is.The PMDG MD11 will temp. turn off the packs when T/O thrust is applied and PACKS OFF was selected in the FMC.Cheers

Bob,you're incorrect here. Packs off is the normal procedure, that's why the air system controller does this automatically.Cheers,Markus