KrisJ wrote on Jan 11^th, 2010 at 9:01pm:

And where the real 727 pilots assign this button...? I very much like CS 727 product but i believe there should be no such gaps on "PRO" products like this. I guess avionics are available as soon as you start battery / source power and this should be reflected.

this is an FSX limitation, not the fault of CS. Many third party add-ons have this, ranging from CS to the little pipers by Carenado (excuse me for using the name of another dev here)... If the presaved flight was made using the default Cessna, and turning everything off, you'll encounter this problem with any aircraft that doesn't have a master avionics switch.
And these are many, as most only have the battery switch.