AN ACR B727 CAPT RELEASED HIS PARKING BRAKES WHILE IN THE CHOCKS. A MECH WAS STARTLED AND SLIGHTLY INJURED WHEN THE BRAKES WERE RELEASED.

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OUR FLT MANUAL FOR THE B727 REQUIRES BRAKE RELEASE AFTER PARKING AT THE GATE IF THE INBOUND LNDG WT WAS HIGH ENOUGH TO EXCEED THE 'MAX WT FOR QUICK TURNAROUND.' PRIOR TO BRAKE RELEASE; THE STATION GND CREW IS REQUIRED TO CHOCK THE WHEELS TO PREVENT ACFT MOVEMENT. ON ARR; I SIGNALED THE MECH WITH HAND SIGNALS OF MY DESIRE TO RELEASE THE PARKING BRAKE. HE SHOOK HIS HEAD INDICATING TO ME HE WASN'T READY. SOME MINS LATER; I SAW 2 FLT OFFICERS DOING AN OUTSIDE PREFLT OF OUR ACFT. I OPENED THE WINDOW AND ASKED IF WHEELS WERE CHOCKED. ON THEIR VERBAL AFFIRMATIVE; I RELEASED THE BRAKES. MECH ARRIVED SHORTLY AFTER AND SAID HE FELT BRAKE RELEASE WAS UNNECESSARY AND DANGEROUS AS ACFT COULD MOVE SLIGHTLY EVEN WITH CHOCKS IN PLACE. LATER I LEARNED HE HAD RPTED TO THE COMPANY THAT THE BRAKE RELEASE HAD STARTLED HIM WHILE HE WAS CHKING THE WHEEL TEMPS AND HE HAD SCRATCHED HIS ARM ON LNDG GEAR DOOR IN RESPONSE TO BEING STARTLED. HE HAD NOT TOLD ME OF THIS AT THE TIME. SUGGESTION: FLT MANUAL AND MAINT MANUALS NEED TO AGREE ON PROPER PROCS TO BE FOLLOWED WHILE PARKING. DISAGREEMENT OVER THIS LED MECH TO BELIEVE BRAKE RELEASE NOT NECESSARY AND PLT TO BELIEVE THAT VERIFYING CHOCKS IN PLACE COULD BE DONE WITH SOMEONE OTHER THAN THE MECH.