MLG HAD NAV COMPUTER FAILURE IN HIGH GUSTY XWINDS. ENTERS VFR ON DSCNT; CORRECT APCH POS AND LANDS MANUALLY.

Narrative

WHILE ON APCH TO RWY 10 AT BWI; IN VERY WINDY AND GUSTY AND TURB CONDITIONS; THE ACFT'S NAVIGATIONAL COMPUTER SUDDENLY BECAME UNRELIABLE AND FINALLY HAD FAILED ALTOGETHER. THE ACFT WAS APPROX 1200 FT AGL AND WAS SHOWING TO BE EXACTLY ON COURSE AND GS. HOWEVER; ONCE THE RWY WAS IN SIGHT; IT WAS CLR THAT THE ACFT WAS ACTUALLY BELOW THE GS AND L OF COURSE. THE AUTOPLT THEN DISENGAGED ON ITS OWN. IT WAS APPARENT THAT THE NAVIGATIONAL CAPABILITIES OF THE ACFT WERE DETERIORATING RAPIDLY. I WAS NOW FLYING THE ACFT MANUALLY; FIGHTING STIFF WINDS AND VERY TURBULENT CONDITIONS. I KNEW WITHOUT QUESTION THAT I DID NOT WANT TO TAKE THE ACFT BACK INTO THE IFR CONDITIONS AND PROCEED TO THE ALTERNATE; AS I WAS CONVINCED THAT THE NAVIGATIONAL CAPABILITIES OF THE ACFT WERE NOW TOTALLY UNRELIABLE. I THEREFORE DECIDED TO LAND THE ACFT AT BWI; EVEN THOUGH THE WINDS WERE VERY TURBULENT AND GUSTY; POSSIBLY EXCEEDING THE COMPANY RECOMMENDED XWIND LIMIT. I FELT I HAD NO CHOICE. I WAS COMFORTABLE WITH THE WX CONDITIONS AT HAND AND MY ABILITY TO COMPENSATE FOR THE WINDS AND LAND THE ACFT. IT WAS A VERY SMOOTH AND NORMAL LNDG. I THEN TAXIED THE ACFT TO THE GATE; AND HANDED IT OVER TO MAINT PERSONNEL; WHO THEN MADE THE NECESSARY REPAIRS TO THE NAVIGATIONAL COMPUTERS. MY CONCERN IS THAT THE ACFT WAS L OF COURSE ON APCH; AND THAT I FOUND IT NECESSARY TO LAND IN THE WINDY CONDITIONS. AGAIN; THE ACFT SUFFERED A MALFUNCTION OF ITS NAVIGATIONAL CAPABILITIES AND I FELT I HAD NO ALTERNATIVE BUT TO LAND THE ACFT AS SOON AS POSSIBLE. BWI TWR MADE NO COMMENTS AS TO THE APCH. I BELIEVE IT WAS WITHIN LIMITS; BUT I JUST WANT TO MAKE SURE AND EXPLAIN THE SEQUENCE OF EVENTS WHICH CAUSED THE DEV.