What was found
AT FL280 LANDING CONFIGURATION INDICATION APPEARED AND ACFT NOSED OVER AND BACKUP. FLAP DEGRADE STATUS MSG APPEARED. PERFORMED FLAP FAULT ISOLATION PER AMM 27-50-00 WHICH INDICATED A FAULT WITH SKEW DETECTION SYS. PERFORMED TEST OF SDS SYS PER FIM. NO FAULTS INDICATED. PERFORMED FECU TEST PER AMM 27-51-05 AND CONTROL UNIT FAILED. PER MX CNTRL, DEACTIVATE SDS SYS PER MEL 27-51-03 AND RETEST FECU. DEACTIVATION OF SDS, THE FECU TEST OK PER AMM 27-51-05. FLAPS OPS TEST GOOD PER AMM 27-54-00-710-801. HORIZ STAB CONTROL SYS ALSO TEST OK PER AMM 27-41-00. REPLACED SDU PER AMM 27-51-15. REACTIVATED SKEW DETECTION SYSTEM PER AWAC SUPP 06-076A. SYSTEM TESTS GOOD. OK FOR SERVICE.