A B777 AFTER ENG START AND WITH NO GND TO COCKPIT COM THE GND CREW DISCONNECTED THE TUG AND TOWBAR. THE AIRPLANE ROLLED FORWARD ENDANGERING THE GND CREW.

Narrative

WAS THE RELIEF PLT ON FLT ABC; ZZZ TO ZZZ1. WHILE AT THE GATE; THE GND CREW TRIED TO MOTION TO THE CAPT THAT THEY HAD NO HEADSET FOR ENG START AND THAT THEY WANTED TO USE HAND SIGNALS. THE CAPT REFUSED AND TOLD THEM TO FIND AN OPERATIVE HEADSET. AFTER SOME SEARCH; GND CREW RETURNS AND SAYS HE HAS ONE THAT HE THINKS WILL WORK. AS WE PUSH BACK; HE CLRS US TO START. THE AUTOSTART FUNCTION ON THE L ENG FAILS ALMOST IMMEDIATELY AS WE ATTEMPT TO START BOTH ENGS SIMULTANEOUSLY. WE NOTIFY THE GND PERSONNEL OF THIS AND TELL HIM TO NOT DISCONNECT BECAUSE WE HAVE A PROB. HE SAYS FINE. ABOUT THIS TIME WE HAVE FINISHED OUR PUSHBACK AND ARE STILL CONNECTED TO THE TUG. WE REFER TO THE MANUAL ENG START CHKLIST AND THE L ENG STARTS NORMALLY. AT THIS TIME; WE NOTIFY THE GND PERSONNEL THAT WE HAVE 2 NORMAL STARTS AND THAT HE IS CLRED TO DISCONNECT. HE REPLIED HE'D SEE US OUT FRONT. THE NEXT THING WE REALIZE IS THAT THE AIRPLANE IS ROLLING FORWARD AND THAT THE GND CREW HAD IN FACT DISCONNECTED THE TUG WITHOUT EVER TELLING US TO SET THE PARKING BRAKE. ALTHOUGH NOTHING OCCURRED; THERE WAS A TREMENDOUS OPPORTUNITY FOR AN ACCIDENT TO HAPPEN; TO EITHER THE GND PERSONNEL OR THE ACFT SHOULD HAVE CONTACTED EITHER THE GND PERSONNEL OR THE TUG; AS THE ACFT ROLLED FORWARD.