CAPT EXPERIENCING DIFFICULTY IN B-747 HOLDING AIRSPD AND ALT. ALTDEV ALT EXCURSION; HDG TRACK DEV DURING APCH INTO AMS.

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LOST CAPT'S #1 INS ON APCH. I WAS HAND FLYING AND THE #1 INS FAILED GRADUALLY. TURB WAS MODERATE; MAKING HAND FLYING DIFFICULT TO START WITH; BUT IT SEEMED TO BE GETTING INCREASINGLY HARD TO HOLD ALT AND SPD WHERE I WANTED IT. FINALLY GOT A 'GYRO' FLAG WHEN INS INPUTS GOT BAD ENOUGH. GAVE ACFT TO FO SINCE THE SO CONFIRMED THAT FO'S INSTS APPEARED TO BE THE CORRECT ONES. WE DRIFTED TO THE R OF THE LOC AND WENT FROM OUR ASSIGNED ALT OF 2000 FT UP TO 2500 FT BEFORE GETTING THINGS BACK UNDER CTL. TO COMPLICATE MATTERS; ONCE INSIDE THE MARKER; THE TWR RPTED WINDS NOW GUSTING AT OUR MAX XWIND LIMIT; BUT I DECIDED WE WOULD BE BETTER OFF LNDG NOW THAT WE WERE IN VMC; SINCE OUR INST SIT WAS NOT GOOD. FO COMPLETED LNDG AND DID A FINE JOB. MY OBSERVATIONS: GRADUAL INST FAILURES CAN BE INSIDIOUS. I SHOULD HAVE XCHKED INSTS INITIALLY WHEN I NOTICED IT GETTING HARDER TO HOLD ALTS AND SPDS. HAVING A GOOD CREW THAT WORKS WELL TOGETHER IS EXTREMELY IMPORTANT IN A SIT LIKE THIS. THE SO DID A GREAT JOB OF PINPOINTING THE PROB FROM HIS VANTAGE POINT. I FEEL I DID THE CORRECT THING BY TRANSFERRING FLYING DUTIES TO THE FO AND THE FO DID AN EXCELLENT JOB UNDER TRYING CIRCUMSTANCES. I AM DUAL-QUALIFIED (CAPT B-747 AND CAPT A-320). I SPEND MUCH MORE TIME FLYING THE A-320 THAN THE 747. THIS GREATLY CONTRIBUTES TO LOSS OF HAND FLYING AND INST SCAN HABIT PATTERNS; AND ADDS TO THE LEVEL OF DIFFICULTY ENCOUNTERED IN HANDLING ABNORMAL SITS LIKE THIS ONE IN 'STEAM GAUGE' (OLD TECHNOLOGY) ACFT. I FEEL THAT DUAL-QUALIFICATION SHOULD ONLY BE DONE ON 2 GLASS AIRPLANES; OR 2 STEAM-GAUGE AIRPLANES; NOT ONE OF EACH! I HAVE NO CTL OVER THIS; MY COMPANY ESSENTIALLY CHOOSES THE 2. SUPPLEMENTAL INFO FROM ACN 292241: THE STRANGEST PART OF THE SIT IS THAT WE DID NOT GET A GYRO FLAG UNTIL WE WERE WELL INTO AN UNUSUAL SIT. WINDS APPROX 230 DEGS AT ABOUT 30 KTS WITH GUSTS TO 45 KTS. CONSIDERING THE GYRO PROBS ONCE THE RWY WAS VISUALLY ACQUIRED THE DECISION TO LAND WAS MADE EVEN WITH WINDS NEAR MAX XWIND LIMITS. SUPPLEMENTAL INFO FROM ACN 292133: HOWEVER; WITH THE LOSS OF THE INS; THE CAPT'S ATTITUDE INDICATOR FAILED. THE FAILURE OF THE CAPT'S GYRO (ATTITUDE INDICATOR) PRECEDED THE INS. WE RECEIVED NO INST WARNING.