B737-800 captain reported that after the marshaller indicated the chocks were installed; they releas...

Narrative:

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.

Original NASA ASRS Text

Title: 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.

Narrative: 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.

Data retrieved from NASA's ASRS site 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.

Attributes
ACN	1419062
Time
Date	201701
Local Time Of Day	0601-1200
Place
Locale Reference	ZZZ.Airport
State Reference	US
Environment
Light	Daylight
Aircraft 1
Make Model Name	B737-800
Operating Under FAR Part	Part 121
Flight Phase	Taxi
Flight Plan	IFR
Person 1
Function	Captain Pilot Flying
Qualification	Flight Crew Air Transport Pilot (ATP)
Experience	Flight Crew Last 90 Days 169 Flight Crew Type 10000
Events
Anomaly	Deviation - Procedural Published Material / Policy

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.