A B757-200 PLT RPTS TRACKING AN FMS COURSE ON THE CRI 223 DEG RADIAL; BUT WHEN QUESTIONED BY NY TRACON; CREW DISCOVERED AN 8 DEG HDG ERROR FROM RAW DATA.

Narrative

CLR NIGHT WITH EXCELLENT VISIBILITY. CLRED FOR VOR 13L AT JFK VIA VECTORED HDG TO INTERCEPT 223 DEG HDG OFF CANARSIE (CRI) VOR. LNAV INTERCEPT COURSE BUT ATC QUESTIONED IF WE WERE ON 223 DEG RADIAL CRI. AS JUST REACHING INITIAL APCH FIX; HAD YET TO PLACE ONE VOR/EHSI ON RAW DATA. WE DID SO AND FOUND APPROX 8 DEGS N OF CRI 223 DEG RADIAL. CORRECTED VIA RAW DATA AND FLEW REMAINDER OF APCH TOTALLY RAW DATA. ONCE ON GND; ATC REQUESTED WE CALL NY JFK APCH. DOING SO; CONSTRUCTIVE CHAT WITH SUBJECT AS TO OUR DATABASE/FMS; ETC. SEEMS SIMILAR PROBS ENCOUNTERED ON SAME APCH WITH OTHER AIRLINES AND ACFT. FIGURED OUR DEV AND ONE MILE AT MAX POINT. FAA HAD 'RTE CHKED' APCH PREVIOUSLY AND IT CHKED NORMAL. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: RPTR DID NOT KNOW OF ANY CHANGES IN THE NY AREA NAVAIDS. HOWEVER; AFTER TALKING WITH THE TRACON SUPVR; QUESTIONED THE SOURCE OF THE ERROR. HE SUGGESTED TALKING WITH OTHER ACRS IN THE AREA TO COMPARE BETWEEN GPS EQUIPPED ACFT; FMS; AND ACFT FLYING PURE RAW DATA. THE FACT THAT THIS HAD BEEN RTE CHKED MAKES THE ACFT SUSPECT.