What was found
AFTER TAKE OFF, BOTH CA & FO LOST BOTH HEADING AND LATERAL INDICATIONS, FO DATA CAME BACK. ACP DCFS BITE, BPCS, GCU 1 & 2, NO FAULTS. LT ADIRU HAS ENTER HEADING FAULT ON LAST LEG MAIT MESSAGE 34-21009 FIM 34-21 TASK 808 INITIAL EVALUATION SHOWED NO CURRENT FAULTS IAW ADIRS BITE FIM 34-21 TASK 801. PERFORMED FIM 34-21 TASK 808, WIRING CHECKS OUTLINED BETWEEN THE LT ADIRU & THE MSU CHECKED GOOD. REMOVED AND REPLACED LT ADIRU IAW AMM 34-21-01/401, AS A PRECAUTION. . ADIRU INSTALLATION TESTS PASSED. FLAGGED FOR CAT LAND TEST.