So klappt's:
import fl.transitions.*;
import fl.transitions.easing.*;
//Einblenden:
TransitionManager.start(img1_mc, {type:Fade, direction:Transition.OUT, duration:9, easing:Strong.easeOut});
//Ausblenden:
TransitionManager.start(img1_mc, {type:Fade, direction:Transition.OUT, duration:9, easing:Strong.easeOut});