A321
Flight Crew Air Transport Pilot (ATP)
Workload; Troubleshooting; Situational Awareness; Confusion; Human-Machine Interface
Aircraft Equipment Problem Less Severe; Inflight Event / Encounter Weather / Turbulence
Flight Crew Took Evasive Action; Flight Crew Diverted; Flight Crew Landed As Precaution; General Maintenance Action
Aircraft
Enroute; in cruise at FL340 First Officer's (F/O's) ND route display blank and 'Map not Available' warning displayed. GPS warning displayed. Attempted to reset using QRH procedures. Discovered F/O's MCDU completely locked. I.e. would not accept any push button commands. Captain remained as pilot flying. Directed F/O to contact dispatch using cockpit phone. Conference between Dispatch and Maintenance (MTC). Cockpit phone either quit working or dropped call. Contacted dispatch again through Airinc. Received further reset procedures pulling 2 circuit breakers. FMCG #2 and MCDU #2. Resets failed. Reviewed weather at our destination. At time of discovery information special observation. Winds 03014G22. 1 1/2 -SN OVC008 M01/M02. Continued toward the destination. Switched to Approach. Descent to 12;000 ft. Had approach read current weather and verified information 05016G22. 1 1/4 -SN BR BKN008. Weather deteriorating forecast to further deteriorate. Elected to divert to flight plan alternate. Weather at the alternate was approximately 8-9000 OVC visibility 8+SM. Activated and confirmed approach. At LOC and glideslope intercept F/O's PFD dropped all indications of speed reference. No bug speed displayed. Turned Flight directors off autopilot off and hand flew visual approach from 2500 ft. to landing. APPR push button inop. In addition; at gate attempted full alignment of ADIRS' and initially all appeared normal. Then failures occurred after about 15 minutes. GPS primary display disappeared from ND display. Confusion as to which system was inop.   Multiple unknown failures in navigation systems. After landing and shutdown contract MTC met the aircraft. He determined conflicting indications with test diagnostic readouts were beyond his capability. With concurrence of MTC Control flight was cancelled and subsequent cancelled ferry flight to a maintenance station. At this time I have no idea what the ultimate cause(s) of the malfunction(s) will be determined. Too much conflicting information to decipher. It was noted enroute #2 MCDU appeared to locked between FMG and ATSU systems. Then locked completely. At first we thought it was a stuck 2L push button that caused the MCDU lock up. We never were able to recover map display and GPS primary indication.   There are no suggestions to Nav system to pass along. At time of departure; climb and level off in cruise; all systems normal. The only thing I could suggest is to find a better inflight phone system. Losing contact with dispatch and MTC due to dropped call was a problem trying to work the problem.
An A321 First Officer's FMGC and MCDU locked up in flight causing multiple NAV failures. The flight diverted to the filed alternate because of poor destination airport weather.