Narrative:

While on approach to runway 10 at bwi, in very windy and gusty and turbulence conditions, the aircraft's navigational computer suddenly became unreliable and finally had failed altogether. The aircraft was approximately 1200 ft AGL and was showing to be exactly on course and GS. However, once the runway was in sight, it was clear that the aircraft was actually below the GS and left of course. The autoplt then disengaged on its own. It was apparent that the navigational capabilities of the aircraft were deteriorating rapidly. I was now flying the aircraft manually, fighting stiff winds and very turbulent conditions. I knew without question that I did not want to take the aircraft back into the IFR conditions and proceed to the alternate, as I was convinced that the navigational capabilities of the aircraft were now totally unreliable. I therefore decided to land the aircraft at bwi, even though the winds were very turbulent and gusty, possibly exceeding the company recommended crosswind 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 aircraft. It was a very smooth and normal landing. I then taxied the aircraft to the gate, and handed it over to maintenance personnel, who then made the necessary repairs to the navigational computers. My concern is that the aircraft was left of course on approach, and that I found it necessary to land in the windy conditions. Again, the aircraft suffered a malfunction of its navigational capabilities and I felt I had no alternative but to land the aircraft as soon as possible. Bwi tower made no comments as to the approach. I believe it was within limits, but I just want to make sure and explain the sequence of events which caused the deviation.

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Original NASA ASRS Text

Title: 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.

Data retrieved from NASA's ASRS site as of July 2007 and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.