AN ACR BATP SUFFERED SOME DAMAGE WHEN THE GND CREW DISCONNECTED THE TUG WITHOUT TELLING THE FLC. THE ACFT COASTED FORWARD AND THE L PROP STRUCK THE TUG. FORTUNATELY; THE ENG WAS NOT RUNNING.

Narrative

THE INCIDENT OCCURRED WHILE PUSHING BACK AT ORD ON THE AIRLINE RAMP. FOLLOWING COMPANY-PROVIDED PROCS; WE HAD 1 PERSON DRIVING THE PUSHBACK; 1 WALKING ALONGSIDE; AND A WINGWALKER AT EACH WINGTIP. DURING THE PUSHBACK PROC; THE TUG STOPPED AND STARTED SEVERAL TIMES; JERKING THE ACFT EACH TIME. AT ONE POINT IN THE PROC; I LOST SIGHT OF BOTH THE TUG DRIVER AND PERSON WALKING ALONGSIDE THE TUG; AND ADVISED THE FO TO INFORM ME IF HE SAW EITHER RAMP WORKER GIVE THE SIGNAL TO SET THE BRAKES PRIOR TO THE TOWBAR BEING DISCONNECTED. NEITHER MY FO NOR MYSELF SAW OR ACKNOWLEDGED A SIGNAL BY THE GND CREW TO SET THE BRAKE. THE ACFT THEN BEGAN TO MOVE FORWARD AND THE FO; STILL BELIEVING THE ACFT WAS HOOKED TO THE TUG; ASKED ME WHERE I THOUGHT THEY WERE PULLING US TO NOW. I LOOKED TO MY R TO SEE IF THERE WAS A CONFLICT WITH ANOTHER ACFT CAUSING THE GND CREW TO NEED TO MOVE US FORWARD. I THEN LOOKED TO MY L; AND SAW THAT THE TUG WAS DISCONNECTED AND PULLING AWAY FROM THE ACFT. I REALIZED THAT WE WERE ROLLING FREELY FORWARD; AND THE TUG WAS MOVING TOWARD THE L ENG (WHICH WAS NOT RUNNING). I IMMEDIATELY APPLIED THE BRAKES; BUT WAS UNABLE TO STOP THE ACFT PRIOR TO THE L PROP HITTING THE TUG.