Air carrier flight crew reported they lost control of the aircraft after releasing the parking brake as requested by the ground crew. The Captain applied the brakes to stop the aircraft.
Synopsis
Air carrier flight crew reported they lost control of the aircraft after releasing the parking brake as requested by the ground crew. The Captain applied the brakes to stop the aircraft.
Narrative
While parked at gate XX in ZZZ at scheduled departure time; the ground crew; in preparation for pushback; advised they were going to remove the chocks and requested that the parking brake be released to allow for tug capture. Then I clarified their request; and the ground crew confirmed they did want the parking brake released. Gate XX is positioned on a noticeable downward slope; and once the parking brake was released; the aircraft began to roll forward. I immediately reapplied the brake; bringing the aircraft to a stop.After the aircraft was secured; we debriefed with the ground crew; who informed us that during the brief forward roll; the nose gear tire made contact with the tug in the normal capture area slightly. We requested the jet bridge be reattached to the aircraft and called for maintenance to inspect the nose gear. Maintenance responded promptly; and along with myself conducted a thorough inspection. No damage was found. We were cleared to depart and left the gate shortly afterward.Cause: From our assessment; the aircraft's position on the sloped gate surface contributed to the forward movement upon brake release. It also appeared that full tug capture had not yet occurred at the time the ground crew requested the brake be released. Given that we were at departure time; it's reasonable to believe that pressure to meet an on-time block out may have influenced the timing of the ground crew's request.Suggestion: Ensure ground crew is not rushing in order to receive and on time block out; and proper phrasology is used.
Second reporter narrative
While parked at gate XX; after the before start checklist was completed and in preparation for pushback. The ground crew stated that they are going to remove the chocks and to release the parking brake for tug capture. The Captain confirmed and read back that he was releasing the parking brake.As it was released the aircraft started rolling forward; we quickly noticed that it was more than normal and so the Captain immediately reapplied the parking brake. After debriefing with the ground crew they informed us that the tire made contact with the tug. After discussing with the captain we decided it was best to get Mx (Maintenance) to inspect the aircraft to ensure a qualified individual inspected the nose gear.Cause: I believe the ground crew miss stated their directions and intended on the parking brake remaining engaged while the chocks where released; and or the ground handler making the request was unaware that gate XX is on a slope.Suggestion: Warnings of the slope at gate XX should be placed in front of the gate in plain view of ground handlers and flight crew. While also adding this warning into the company pages for ZZZ. Further more; training of ground crew on proper aircraft ground handling procedures and communication.
Source: NASA Aviation Safety Reporting System (public domain). Reports are voluntary submissions and are not verified by NASA.