B777 OVERSHOT ITS ALT WHEN THE DATA BASE DOES NOT SWITCH OVER TO ITS UNITED STATES DOMESTIC SENSING OF TRANSITION LEVEL OF 18000 FT. THE DATA BASE WAS 'STUCK' AT THE 6000 FT TRANSITION LEVEL AS UTILIZED IN THE UNITED KINGDOM; THE ACFT'S DEP POINT. ACFT LEVELED OFF SOME 600 FT BELOW ASSIGNED ALT. PIC HAD THIS OCCUR BEFORE; RECOGNIZED THE PROB AND RESET THE VNAV CLB DATA BASE TO 18000 FT.

Narrative

CLRED TO DSND FROM FL200 TO 17000 FT MSL. SET 17000 FT IN MODE CTL PANEL. AS ACFT DSNDED THROUGH 18000 FT I TRIED TO SET ALTIMETER TO 29.52 MB. ALT INDICATOR WENT YELLOW TO ALERT US TO AN ALTIMETER PROB. ACFT LEVELED OFF AT 17000 FT INDICATED. ALTIMETER INDICATION STILL YELLOW; SELECTED VNAV CLB PAGE ON CDU AND DISCOVERED DATA BASE HAD NOT AUTOMATICALLY SWITCHED FROM TRANSITION ALT OF 6000 FT FOR LONDON TO 18000 FT FOR UNITED STATES AIRSPACE. ENTERED '18000 FT;' ALTIMETER WENT TO NORMAL INDICATION AND INDICATED WE WERE AT ABOUT 16400 FT. IMMEDIATELY STARTED CLB BACK TO 17000 FT; ZNY REQUESTED OUR INDICATED ALT; WE REPLIED WE WERE HAVING AN ALTIMETER PROB WITH OUR AUTOMATION AND WERE CLBING TO 17000 FT. I HAVE PREVIOUSLY EXPERIENCED THIS PROB IN THE B777; BUT IT HAS NEVER BEFORE INTERFERED WITH ALTIMETRY; THE DATA BASE SHOULD NOT MAINTAIN 6000 FT TRANSITION ALT IN THE UNITED STATES; PERIOD. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: RPTR'S INCIDENT OCCURRED ON THE ONE AND ONLY B777 IN THE FLEET THAT HAS EXHIBITED THIS CHARACTERISTIC. DURING DSCNT THE CLB PAGE STICKS AND STAYS IN CLB INSTEAD OF SHIFTING TO THE DSCNT MODE PAGE. THE FLT HAD BEEN AT FL200 AND WAS RECLRED TO 17000 FT. THE ALTIMETER DISPLAY GAVE A YELLOW WARNING OF 'ALT NOT SET CORRECTLY' INDICATION WHEN GOING THROUGH FL180. THE ALTIMETER WOULDN'T RESET. THE PIC WENT INTO THE CLB PAGE AND RESET THAT PAGE TO 18000 FT. HE THEN GOT A NORMAL INDICATION ON HIS ALTIMETERS. HE HAD DSNDED TO 16500 FT BEFORE ATC ASKED HIM ABOUT HIS PROB. THIS HAS OCCURRED NUMEROUS TIMES AND ENTERED INTO THE LOGBOOK EACH AND EVERY TIME. HE DOESN'T NOW WHAT HIS COMPANY IS DOING ABOUT IT.