AN ACR ACFT MOVES WHEN THE PARKING BRAKE IS RELEASED DURING AN ANTI-SKID TEST AT THE GATE. THE CHOCKS WERE NOT PROPERLY PLACED TO PREVENT MOVEMENT.

Narrative

THE EVENT OCCURRED DURING AN ORIGINATION PREFLT INSPECTION AT THE GATE. THE FO RELEASED THE PARKING BRAKE IN ORDER TO PERFORM THE ANTI-SKID TEST. AS THE BRAKES WERE RELEASED THE ACFT ROLLED ABRUPTLY BACKWARD ABOUT 6-8 INCHES BEFORE THE BRAKES COULD BE REAPPLIED. EARLIER; DURING THE EXTERIOR SAFETY INSPECTION; IT WAS OBSERVED THAT GEAR CHOCKS WERE INSTALLED FORWARD AND AFT OF THE L MAIN LNDG GEAR. ON REINSPECTION OF THE L MAIN LNDG GEAR IT WAS APPARENT THAT THE AFT CHOCK HAD NOT BEEN PLACED IMMEDIATELY BEHIND; IN CONTACT WITH; THE GEAR. THIS INCIDENT; WHILE UNEVENTFUL; COULD HAVE CAUSED ACFT DAMAGE OR BODILY INJURY TO GND CREW. THE LESSON LEARNED BY THE FO IS TO ENSURE THE GEAR IS 'FIRMLY' CHOCKED. THIS LESSON WAS LOST ON THE GND CREW WHO FELT THE PARKING BRAKES SHOULD NEVER BE RELEASED AT THE GATE AND SEEMED TO DOUBT THAT THE DC9 OPERATING MANUAL ACTUALLY CALLS FOR THE PARKING BRAKES TO BE RELEASED DURING THE ANTI-SKID TEST; (ON A CHOCKED ACFT.) CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: THE COMPANY MANUAL COVERING CHOCK PLACEMENT REQUIRES THEM TO BE PLACED IMMEDIATELY BEHIND THE WHEEL. THE PROC FOR TESTING THE ANTI-SKID REQUIRES THAT THE PARKING BRAKE BE RELEASED TO COMPLETE THE CHK; BUT THE BRAKES MAY BE KEPT SET TO PREVENT MOVEMENT OF THE ACFT IF CHOCKS ARE NOT INSTALLED.