B737-800
Flight Crew Air Transport Pilot (ATP)
Flight Crew Last 90 Days 169; Flight Crew Type 10000
Communication Breakdown; Situational Awareness
Deviation / Discrepancy - Procedural Published Material / Policy
Flight Crew Took Evasive Action
Airport; Company Policy; Procedure
When we parked at Gate XX; the Ramp Agent used hand signals to indicate the chocks were installed. I released the parking brake. The aircraft started to role; and the Ramp Agent immediately signaled to apply the brakes. The aircraft rolled aft approximately three to four inches. Upon speaking with the Ramp Crew; I was informed the ramp had installed the aft chock with it not flush against both nose tires. It was slanted to one side. When I released the brakes; the aircraft rolled aft; startling the Ramp Agent installing the nose wheel lockout pin; and the Marshaller. They told me that they had issues with Gates XX and YY that slope away from the terminal. They have issues with having to pull the aircraft forward to get the aft chock out from these two gates. They stated Gate XX was a particular problem; as if the brakes were released and the chock were to fail; the aircraft would role across the ramp. I suggested they file a safety report; and that I would do the same with Operations. I filed a report and am notifying Company and the FAA of a possibly safety issue at Gates XX and YY at ZZZ.Incorporate language into the ZZZ airport pages that Gates XX and YY slope aft; and that Flight Crews should keep the parking brake set at these gates until prepared to push.
B737-800 Captain reported that after the Marshaller indicated the chocks were installed; they released the brakes and began to roll backwards. The Captain would like to see warning publications regarding specific gates which have a slope.