Flight Crew Air Transport Pilot (ATP)
Flight Crew Last 90 Days 100; Flight Crew Total 15000; Flight Crew Type 9000
Ground Event / Encounter Object
Human Factors
Upon initial taxi out; we received an ECAM HYD PTU (Power Transfer Unit) Fault message during the second engine start; we taxied to a holding area where we investigated the issue prior to take off. Following consultation with Maintenance Control; a return to the gate was coordinated with ZZZ Maintenance and Operations. The hydraulic PTU appeared to be inoperative and needed maintenance attention. Due to the late hour; Operations said the self-park system at gate X would be turned on and a ground crew would be coordinated. We taxied to the gate stop point under the automated guidance system and set the parking brake. The jetway was moved into position and the airplane door was opened to allow two awaiting maintenance technicians to board the aircraft and begin troubleshooting the hydraulic issue. The passengers remained onboard the aircraft. We remained in our seats as the technicians; on the flight deck behind us; followed their troubleshooting instructions they had brought with them. At some point in the procedures; the lead technician requested the parking brake to be released. He said we were chocked and I moved my seat forward to guard the brakes as I released the parking brake. No immediate movement was noted. The troubleshooting continued; for 5-10 minutes after the parking brake release; until it the airplane was noticed moving backwards. Then; the parking brake was immediately set. The movement wasn't noticed until the personnel on the jetway began yelling that the plane was moving. A maintenance supervisor was requested to inspect the airplane door as it appeared door 1L had come into contact with the jetway visor. The door was inspected and determined to not be damaged. Subsequently; the hydraulic PTU was determined to inoperative and needing repair. An aircraft swap was coordinated; the passengers offloaded and we moved to the newly assigned airplane.
[Report narrative contained no additional information.]
A319 flight crew reported that while troubleshooting a hydraulic power transfer unit fault maintenance requested the parking brake to be released; which caused the aircraft to roll backwards into the jetway. No damage was reported to either the aircraft door or the jetway.