B-767-300 CAPTURES FALSE LOC AND GS.

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ON JAN/XX/95 I WAS PF; FLT BACKUP; FLT X FROM JFK TO BRU. WE WERE BEING VECTORED FOR THE ILS RWY 25L APCH. WX CONDITIONS AT THE TIME WERE VMC. BRU APCH GAVE US A HDG TO INTERCEPT THE LOC THEN CLRED US FOR THE APCH. THE CTR AUTOPLT WAS ON AND APCH MODE ARMED. LOC AND GS CAPTURED WHILE IN THE TURN. AIRPLANE BEGAN A DSCNT ON AUTOPLT. HOWEVER; RAW DATA SHOWED US RIGHT OF COURSE AND BELOW GS. FO CALLED OUT ALT AT ABOUT THE SAME TIME BRU APCH QUERIED OUR ALT. CAPT DIRECTED ME TO CLB. AT THAT POINT THE FLT DIRECTOR WAS UNRELIABLE; COMMANDING A TURN AWAY FROM THE LOC AND A DSCNT AWAY FROM GS; I DISCONNECTED THE AUTOPLT AND AUTOTHROTTLE THEN CORRECTED ONTO THE ILS RWY 25L USING RAW DATA. REMAINDER OF FLT WAS UNEVENTFUL. SUPPLEMENTAL INFO FROM ACN 295045: AT APPROX XA20Z; FLT BACKUP WAS FLYING ACFT WITH AUTOPLT ON; IN GND CONTACT; AT 2000 FT MSL; IN R DOWNWIND TO BRU RWY 25L. 5 NM SHORT OF BUN; APCH INSTRUCTED US TO TURN R TO 220 DEGS; AND CLRED US FOR THE ILS RWY 25L. FLT BACKUP SET HDG SELECT 220 AND ARMED APCH. WE WERE R OF LOC AND BELOW GS. LOC CAPTURE OCCURRED IN THE TURN AND AUTOPLT CONTINUED TURN TOWARD THE 253 DEG RWY HDG. GS CAPTURED DURING THE TURN; AND AUTOPLT BEGAN A DSCNT BELOW 2000 FT. RAW DATA INDICATED WE WERE R OF LOC. THE PNF FO CALLED 'ALT' AND I DIRECTED THE FLT BACKUP TO CLB. AT THIS POINT; THE RWY WAS IN SIGHT. FLT BACKUP DISCONNECTED THE AUTOPLT; AUTOTHROTTLES; AND BEGAN A CLB TOWARD THE GS AND A SLIGHT L TURN TOWARD THE LOC. APCH CTL QUESTIONED OUR ALT AND THEN HANDED US OVER TO TWR. BOTH FLT DIRECTORS WERE COMMANDING A R TURN AWAY FROM THE LOC; AND A DSCNT AWAY FROM THE GS. I CYCLED BOTH FLT DIRECTORS OFF THEN ON; AND ARMED THE APCH MODE. THE REMAINDER OF THE FLT WAS UNEVENTFUL WITH NORMAL FLT DIRECTOR INDICATIONS. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: THE CAPT STATES HE WAS IN THE COPLT SEAT OF THE B-767-300; THE RELIEF PLT DOING THE FLYING IN THE CAPT'S SEAT. THE LOC HAD NOT LEFT THE FULL DISPLACEMENT WHEN THE ACFT STARTED TO TURN. THE HDG BUG AUTOMATICALLY ALIGNED WITH THE ILS AND THE AUTOPLT CAPTURED A FALSE LOC AND COMMENCED DSCNT ON A FALSE GS. (ON APR/XX/95 A CAUTION WAS SENT TO THE COMPANY PLTS REGARDING NUMEROUS FALSE CAPTURES AT BRUSSELS AND TORONTO.) THE CAPT SWITCHED OFF THE AUTOPLT; AUTOTHROTTLE; AND FLT DIRECTOR AND REARMED THE FLT DIRECTOR WHICH THEN INDICATED NORMALLY. THE AIRPLANE; HOWEVER; WAS HAND FLOWN TO THE LNDG WITH THE FLT DIRECTOR INDICATING NORMALLY. DURING THE FALSE CAPTURE THE RAW DATA WAS INDICATING CORRECTLY AS OBSERVED VISUALLY WITH THE ARPT IN SIGHT WHILE THE FLT DIRECTOR AND AUTOPLT WERE CHASING A FALSE CAPTURE TO THE R OF AND BELOW COURSE. THE 3 IRU'S ALIGNMENTS WERE ACCURATE THROUGHOUT THE APCH AND DURING THE FALSE CAPTURE. INDUSTRY PROC IS TO ARM THE APCH AT THE CUE 'CLRED FOR THE APCH' AS WAS DONE IN THIS CASE. THIS CAPT ARMS THE APCH WHEN HE IS FLYING WHEN HE SEES THE RAW DATA LOC MOVE ACROSS THE CASE FINESSING WITH HDG SELECT TO A MODERATE INTERCEPT ANGLE. HE SUGGESTS THIS PROC MAY HAVE PRECLUDED THIS FALSE CAPTURE AND MIGHT BE CONSIDERED A BETTER PROC INDUSTRY WIDE. HE FINDS THIS ESPECIALLY USEFUL IN SOUTH AMERICA WHERE FACILITY SURVEYS ARE LESS ACCURATE.