Commercial Fixed Wing
Ground Event / Encounter Other / Unknown
Flight Crew Regained Aircraft Control
Aircraft; Airport
Flight arrived on the gate at approximately XA54. Once the aircraft was at the stop mark; the nose gear was chocked immediately; the Passenger Loading Bridge (PLB) was given a signal to approach; and the main gears were then chocked. Right after the main gears were chocked and as the PLB was a few feet away from the fuselage; the aircraft started to roll back with all the chocks sliding on the contaminated ramp surface. The aircraft rolled approximately three feet before it was apparently stopped by the flight crew with them re-applying the brakes. This is a problem that has occurred time after time here primarily when the ramp is contaminated; but it has also occurred when the ramp is dry. The common denominator in all events is the release of the aircraft brakes that allows the aircraft to roll backwards.
A ramp worker reports that at his location; because of ramp contamination that even after aircraft are chocked; aircraft roll backwards when the parking brake is released. The chocks merely slide along with the aft moving aircraft.