LOSS OF COM WITH THE GND CREW DURING PUSHBACK LEADS TO A HAZARDOUS SIT WHEN IT IS NOT APPARENT TO THE CAPT WHETHER OR NOT THE TUG HAS BEEN DISCONNECTED OR WHETHER OR NOT BRAKES SHOULD BE SET.

Narrative

PUSHBACK FROM GATE; THE ACFT STOPPED. HEADSET COM FROM GND HAD BEEN GOOD; BUT UPON STOP; THE GND PERSONNEL MADE A XMISSION WHICH WAS WEAK AND GARBLED. I SAID 'YOU'RE COMING IN WEAK; SAY AGAIN.' NO RESPONSE. I ASKED 'DO YOU WANT THE PARKING BRAKE SET?' HE RESPONDED; BUT WAS SO WEAK AND GARBLED I COULDN'T UNDERSTAND HIM. I REPEATED THAT I COULDN'T COPY; AND ASKED IF HE WANTED THE PARKING BRAKE SET. NO RESPONSE. I HEARD HIM BANGING ON THE NOSE GEAR WHILE I WAS CHKING MY AUDIO PANEL. I LOOKED UP AND SAW THE ACFT AND THE TUG BOTH MOVING FORWARD IN UNISON; BUT THE GND MARSHALLER HAD THE WANDS UP AND CROSSED; INDICATING STOP. THE BROKEN COMS; AND THE BANGING ON THE NOSE GEAR MADE ME REALIZE THAT HE MAY HAVE DISCONNECTED WITHOUT EVER CONFIRMING WHETHER THE PARKING BRAKE HAD BEEN SET. I HAD TO CHOOSE; QUICKLY; WHETHER TO TAKE A CHANCE ON BREAKING THE NOSE GEAR PIN IF WE WERE BEING TOWED FORWARD; STILL CONNECTED; OR RUNNING OVER SOMEBODY IF WE WERE NOT. WE DID HAVE ENGS RUNNING AT THIS TIME. I GENTLY EASED THE BRAKE ON; AND SAW THE TUG PULL AWAY. WE WERE ABOUT TO RUN OVER THEM. THE HEADSET OPERATOR HAD UNPLUGGED; PROBABLY TO GET OUT OF THE WAY. THE GND CREW HAD DISCONNECTED THE TOWBAR WITHOUT CONFIRMING THE PARKING BRAKE WAS SET. BAD MOVE. IN THE FUTURE: HEADSETS WILL FAIL. IF COM IS COMPROMISED; THEY SHOULD CONFIRM WITH HAND SIGNALS THAT THE PARKING BRAKE IS SET BEFORE DISCONNECTING. SUPPLEMENTAL INFO FROM CAN 622318: NO DAMAGE TO EQUIP OR PERSONNEL WERE NOTED. I BELIEVE THIS COULD HAVE BEEN AVOIDED IF THE GND CREW HAD STAYED ON THE HEADSETS TO CONFIRM THE 'PARKING BRAKE SET' COMS AND HAD STAYED ON THE HEADSET UNTIL CLRED OFF.