A319
Flight Crew Multiengine; Flight Crew Instrument; Flight Crew Air Transport Pilot (ATP)
Flight Crew Last 90 Days 199.23; Flight Crew Total 14535.50; Flight Crew Type 5213.35
Workload; Distraction
Aircraft Equipment Problem Critical; Deviation - Altitude Excursion From Assigned Altitude; Deviation / Discrepancy - Procedural Clearance
Air Traffic Control Provided Assistance; Flight Crew Overcame Equipment Problem; Flight Crew Regained Aircraft Control; Flight Crew Requested ATC Assistance / Clarification; Flight Crew FLC Overrode Automation; Flight Crew Became Reoriented
Aircraft
Cruising at [Flight Level] 360 with AP2 engaged (this was the First Officer's leg and he was returning to his seat from a lav break). FMGC2 screen blanked and the AP commanded an aggressive descent as if it was attempting to catch a descent path. I disconnected the AP/AT and leveled off at 34;800 [feet]; the First Officer notified ATC of our altitude [and] we were re-cleared to climb to [Flight Level] 360. We reengaged AP1 and AT and climbed back to [Flight Level] 360. FMGC2 screen blanked out numerous times after this; we considered it unreliable and continued on AP1. After determining that we were still legal for RVSM we confirmed with ATC that we could continue at [Flight Level] 360. We talked with the flight attendants and there were no injuries or further concerns in the cabin. Dispatch queried us [because] the aircraft TAPS reported severe turbulence (the ride was smooth). Dispatch and [Maintenance Control] were notified and then briefed verbally once on the ground.
A319 Captain reported an excursion from assigned altitude due to a failed/malfunctioning FMGC2.