A319
Flight Crew Air Transport Pilot (ATP)
Situational Awareness
Aircraft Equipment Problem Less Severe; Ground Event / Encounter Other / Unknown
Flight Crew Became Reoriented; Flight Crew Overcame Equipment Problem
Human Factors; Aircraft
We came to a stop at the gate after a single engine taxi in; I set the parking brake handle; turned off the seat belt sign; and was about to turn off the fuel pumps when I noticed that it appeared that the jetway was moving to the plane much faster than usual.  I looked out the window and saw that we were rolling forward; and applied the brake pedals immediately; resulting some noises of surprise from the cabin.  I checked the parking brake handle and it was set; and the pressure indicator showed brake pressure above 2000psi on both sides.  After verifying the signal from the ground crew that the chocks were in from the ground crew; I started the APU so that we could shut down the engine without waiting for ground power.  While still holding the brakes with my feet; I released the parking brake; and the pressure dropped to zero; with no movement from the aircraft.  I turned the brake handle on again and the pressure stayed at zero.  I held the brakes until the engine start switch was selected off; at which point I noticed that the brake pressure had returned to normal.  We tried to duplicate the failure again; but the brakes worked normally after that.  The aircraft had rolled forward approximately 9 feet from the A320 parking markings.  As nearly as I can determine; this is the one situation (parking with one engine running) where I am not consistently checking the brake pressure after setting the brake.  In the future; I will make sure that I check the pressure after parking.  Given the immediate heads-down attention of both the captain and first officer after parking the aircraft at the gate; combined with the close proximity of people and equipment; the FOM should be modified to require both the captain and first officer to check for brake pressure after parking at the gate; and after completion of pushback.
Arrived at gate captain set brake. I put head down to input FMS felt movement looked at brake; brake was on; looked at brake pressure indicated green captain simultaneously applied manual brakes. Aircraft appeared to have rolled while brake on.Captain wrote brakes up in logbook
A319 flight crew reported the aircraft moved about nine feet after setting the brakes at the gate. Crew reported brake pressure was in the green when the brakes were set.