What was found
SHORTLY BEFORE THE DESCENT PHASE OF THE FLIGHT LDG ALT WAS DISPLAYED ON FO PFD. THEN THE AUTOPILOT REVERTED TO CWS P/R THEN MAP WAS DISPLAYED FO SIDE. GROUNDED-YES. DFCS BITE, PER B737-900 FIM 22-11 TASK 801 SHOWED 9 FAULTS ON FCC-A AND 24 FAULTS ON FCC-B FOR LEG 3-ALL RELATED TO RIGHT FMC FAILURE. FMCS BITE FOR LEG 3 SHOWED EACH FMC FAULTING THE OTHER FMC FOR "PRES POS LAT RATE" AND "ALREADY SINGLE", BUT NO OTHER FAULTS AND NO CURRENT FAULTS. DURING T/S, RIGHT FMC DROPPED OFF LINE MOMENTARILY WITH NO FAULTS LOGGED BY EITHER FMC. REMOVED AND REPLACED RIGHT FLIGHT MANAGEMENT COMPUTER, PER B737-900 AMM 34-61-02-000-801/AMM 34-62-02-400-801. VIA CROSSLOAD, PER AMM 34-61-00-470-806. LOADED FMC OPS SOFTWARE 559775-001, MEDB SOFTWARE BCG01TA0, OPC SOFTWARE BCG01T61, LDDB SOFTWARE 557362-004, ADDB SOFTWARE ASA1007A, AND NDB ASA1201401. ACCOMPLISHED PERFORMANCE FACTORS ADJUSTMENT, PER AMM 34-61-00-800-801 AND FMCS OPERATIONAL TEST PER AMM 34-61-00-710-801, ALL TESTS PASS.