Date: 201304
Local time of day: 1801-2400
Location: ZZZZ.Airport, FO
Flight conditions: VMC
Light: Night
Aircraft: B747 Undifferentiated or Other Model
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Mission: Passenger
Flight phase: Parked
ATC / advisory: Ramp ZZZZ
Aircraft component: Parking Brake
Component problem: Malfunctioning
Reporter organization: Air Carrier
Reporter function: Pilot Not Flying; First Officer
Human factors: Distraction; Situational Awareness; Workload
Second reporter function: Captain; Pilot Flying
Anomaly: Aircraft Equipment Problem Less Severe; Deviation / Discrepancy - Procedural Published Material / Policy; Ground Event / Encounter Loss Of Aircraft Control
Detector: Person Flight Crew
When detected: Aircraft In Service At Gate
Result: Aircraft Aircraft Damaged; Flight Crew Took Evasive Action
Contributing factors: Procedure; Aircraft; Human Factors
Primary problem: Ambiguous

Narrative: Our approach; landing and taxi were all normal. After being directed to stop using the Self-Parking System at the gate; I observed the Captain set the parking break. I watched as he took his hand away to make certain the parking brake handle remained up. I then observed out the right window that there was no aircraft movement indicated. We then proceeded with the remaining 'after parking flows' which are required prior to reading the Parking Checklist of which there are several items to include engine shutdown. As I was nearly finished with my items; the Captain indicated that it appeared that we were moving as he simultaneously applied the brakes. This happened at the same moment the left wing came in contact with the jet bridge. The Captain re-engaged the parking brake until a tug was able to push the aircraft back to the original spot. It was actually very difficult to tell we had impacted the bridge due to the slow movement of the aircraft and the fact that the brakes were applied at the same moment. There were no injuries to crew; passengers or ground personnel and the passengers were eventually deplaned via stairs at door 1R. During our delay after the event; the Captain and I tried to make sense of what had happened and could not understand how the brakes could have been disengaged after being verified set. The only thing I can deduce is that the parking brake did disengage and until the engines were shut down; not more than a few seconds after the setting of the parking break; they provided enough thrust to give the aircraft forward momentum. During my 'after parking flows;' I did not observe any aircraft movement. Some possibly useful information could be derived from our pushback from the gate at the departure airport; the flight's origin. After pushback from the gate; the Captain set the brakes and both he and I observed the handle not stay up but release as his hand was removed. He immediately reapplied the parking brake and they held normally with proper indications. This did not seem at all abnormal as I know a certain amount of initial pedal pressure is required for the parking brake to engage. The Captain concurred with this analysis during our 'post event' discussions.


Second narrative: Aircraft arrived at the gate and the parking brake was set. Both pilots remember seeing the parking brake set indication on the IECAS screen as well as the handle in the up position and the aircraft appeared stopped when looking out. We then proceeded to do our parking flows. After bringing the APU online and turning the seatbelt sign off; I realized that the plane had begun moving. I reapplied the brake pedals as soon as I realized we were moving and the aircraft stopped. The stop came at the same time that the aircraft came in contact with the jet bridge. After completing our flows and running the parking checklist; the co-pilot brought up the fact that the parking break came off the first time it was set after we were pushed back out of the gate in and ready to start our engines. At that time I did not think anything about it and reset the brakes believing that I had not held the brakes hard enough when I set them the first time. This second event was more subtle because we were occupied with our other flows and did not notice the brake release.


Synopsis: A B747 parking break did not fully engage after parking at the gate and as the engines were shut down; it rolled forward striking the jetway.