AN ACR MLG CAPT RPTS THAT HIS ACFT CREPT FORWARD AND STRUCK A TUG AFTER PUSHBACK. THE GND PERSON HAD TO USE HAND SIGNALS AS THERE WAS NO HEADSET.

Narrative

WE RECEIVED A CLRNC FOR PUSHBACK FROM SFO GND CTL. THE TUG OPERATOR/PUSHBACK CREW HAD INOP HEADSETS; SO WE USED HAND SIGNALS. THE PUSHBACK APPEARED NORMAL AS OUR ACFT CAME TO A STOP ON TXWY A. I WAS LOOKING AT THE RAMPER FOR A HAND SIGNAL TO 'SET PARKING BRAKES.' I BRIEFLY GLANCED INSIDE AT THE COCKPIT ENG GAUGES AS I HEARD MY FO CLICK ON THE FUEL LEVER(S) FOR ENG START. A MOMENT LATER; I GLANCED BACK OUT AT THE RAMPER AND HE WAS RAPIDLY GIVING ME THE 'SET BRAKES' SIGNAL. I PROMPTLY SET THE BRAKES. I THEN NOTICED THE RAMPER WAS POINTING TO THE NOSE OF THE ACFT. I OPENED MY WINDOW AND THOUGHT I HEARD HIM SAY 'DAMAGE; BACK TO GATE;' SO WE RECEIVED CLRNC TO GET A TUG BACK TO THE GATE. I SAW A LARGE HOLE IN THE NOSE OF ACFT -- IT HAD CREPT FORWARD VERY SLOWLY AND IMPACTED THE TUG CAB. THE MAIN REASON FOR THIS MISHAP WAS THE PUSHBACK CREW DISCONNECTED THE TUG FROM THE ACFT BEFORE COMMANDING ME TO SET MY PARKING BRAKE. THEY SHOULD HAVE STOPPED THE TUG/ACFT; COMMANDED ME TO PARK MY BRAKES AND THEN DISCONNECTED THE TUG.