What was found
DURING CLIMBOUT, THE FIRST OFFICER'S GROUND PROXIMITY SYSTEM, ALTIMETER, ALTITUDE ALERT SYSTEM (AUTO-PILOT AND NR 2 NAV SYSTEM) BECAME INOPERATIVE. FLIGHT RETURNED TO ORIGINATION AND LANDED WITHOUT INCIDENT. ON FINAL APPROACH TO LANDING, FLIGHT CREW NOTED THAT ALL INSTRUMENTS BECAME OPERABLE. MAINTENANCE REPLACED THE NR 2 AIR DATA COMPUTER, OPERATIONAL CHECK NORMAL.