B777-200 CAPT BECAME AWARE THE ACFT HAD ROLLED AFTER THE PARKING BRAKE WAS SET.

Narrative

AFTER COMPLETION OF PARKING CHKLIST; I WAS OUT OF MY CAPT'S SEAT PUTTING ON MY COAT AND GATHERING MY SUITCASE WHEN I FELT THE ACFT MOVE SLIGHTLY -- AS IF THE CATERERS HAD BUMPED THE ACFT. SHORTLY; I HEARD A LOUD CLICK AND LOOKED DOWN TO SEE THAT THE PARKING BRAKE HAD RELEASED ITSELF. BY THE TIME THAT I WAS IN THE SEAT TRYING TO FIGURE OUT WHAT HAD HAPPENED; MAINT CAME ON AND SAID THAT THE ACFT HAD ROLLED BACKWARDS AND HAD TO BE DOUBLECHOCKED. THEIR THEORY WAS THAT THE CARGO HAD BEEN REMOVED CAUSING THE PARKING BRAKE TO KICK OFF. THIS DIDN'T SOUND RIGHT TO ME; SO I CALLED THE CHIEF PLT WHEN I CAME HOME AND ASKED HIS OPINION. HE ALSO FELT IT WAS AN ODD OCCURRENCE AND THAT I SHOULD SUBMIT A RPT TO LET THE FLT DEPT KNOW THAT THIS HAD HAPPENED AND MAYBE THERE MIGHT BE A PROB WITH THE PARKING BRAKE ASSEMBLY AND SHOULD BE MONITORED ON THIS PARTICULAR ACFT. I WANTED TO WRITE THE OCCURRENCE IN THE ACFT LOGBOOK; BUT MAINT SAID THAT THEY WERE AWARE OF THE PROB AND THAT THEY WERE IN A HURRY TO GET THE AIRPLANE READY FOR AN OUT OF COUNTRY FLT. I WISH NOW THAT I HAD GONE AHEAD AND WRITTEN IT UP SO THAT THE NEXT CAPT WOULD BE AWARE OF THE PROB IN CASE IT SHOULD HAPPEN TO HIM OR FUTURE CAPTS ON THIS SHIP.