Narrative:

Aircraft was parked, engine shut down, chocks placed and brakes released in accordance with SOP. After the first officer and I performed the parking checklist, I left my seat to use the lavatory and then stood at the flight deck door to bid passenger good-bye. When approximately half of the cabin had deplaned, I heard the first officer mention 'gate hold' and as I turned to him, the FM yelled 'the plane is moving.' before I could get to my seat or the first officer could stop writing clearance and get his feet on the brakes, the aircraft had stopped moving. This was 7-10 mins after block in, it required another 2-3 mins to determine whether aircraft had moved or the jetway. We were able to determine that only one chock had been placed behind one nosewheel on top of a bare steel ground service cover (18 inches diameter). The uphill slope and slight movements of passenger deplaning and cargo unloading allowed the nosewheel to push chock aside and allow aircraft to roll aft. L1 door and escape slide caught jetway canopy structure bringing aircraft to slow stop. No injuries and minor cosmetic damage.

Google
 

Original NASA ASRS Text

Title: A B737-500 PARKED ON A GATE INCURRED SLIGHT DAMAGE WHEN THE ACFT ROLLED BACKWARDS DUE TO FAULTY NOSE CHOCK PLACEMENT.

Narrative: ACFT WAS PARKED, ENG SHUT DOWN, CHOCKS PLACED AND BRAKES RELEASED IN ACCORDANCE WITH SOP. AFTER THE FO AND I PERFORMED THE PARKING CHKLIST, I LEFT MY SEAT TO USE THE LAVATORY AND THEN STOOD AT THE FLT DECK DOOR TO BID PAX GOOD-BYE. WHEN APPROX HALF OF THE CABIN HAD DEPLANED, I HEARD THE FO MENTION 'GATE HOLD' AND AS I TURNED TO HIM, THE FM YELLED 'THE PLANE IS MOVING.' BEFORE I COULD GET TO MY SEAT OR THE FO COULD STOP WRITING CLRNC AND GET HIS FEET ON THE BRAKES, THE ACFT HAD STOPPED MOVING. THIS WAS 7-10 MINS AFTER BLOCK IN, IT REQUIRED ANOTHER 2-3 MINS TO DETERMINE WHETHER ACFT HAD MOVED OR THE JETWAY. WE WERE ABLE TO DETERMINE THAT ONLY ONE CHOCK HAD BEEN PLACED BEHIND ONE NOSEWHEEL ON TOP OF A BARE STEEL GND SVC COVER (18 INCHES DIAMETER). THE UPHILL SLOPE AND SLIGHT MOVEMENTS OF PAX DEPLANING AND CARGO UNLOADING ALLOWED THE NOSEWHEEL TO PUSH CHOCK ASIDE AND ALLOW ACFT TO ROLL AFT. L1 DOOR AND ESCAPE SLIDE CAUGHT JETWAY CANOPY STRUCTURE BRINGING ACFT TO SLOW STOP. NO INJURIES AND MINOR COSMETIC DAMAGE.

Data retrieved from NASA's ASRS site as of July 2007 and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.