DISTR CREW OF WDB FAILS TO TURN AT WAYPOINT DEPARTING NRT.

Narrative

ON CLBOUT FROM AN INTL ARPT; WE FAILED TO MAKE A 42 DEG L TURN TO MAINTAIN THE ATC CLRED RTE. CAPT WAS USING 'HDG SELECT' ON THE AUTOPLT. I WAS DOING A COAST OUT ACCURACY CHK OF INS SYS PRIOR TO LOSS OF NAVAIDS. FOLLOW-ON POINT COORDINATES WERE CHKED AND I PRESSED HOLD ON MY INS TO CHK PRESENT POS. THE LEG ADVANCED AND I WENT BACK TO MY ACCURACY CHK. I MISSED THE FACT THAT THE PF FAILED TO TURN AND ZERO OUT THE 'TRACK ANGLE ERROR' AND 'XTRACK' (AUTOPLT NOT COUPLED TO INS THUS REQUIRING PLT MANIPULATION VERSUS MONITORING). ATC INQUIRED ON OUR TRACK TO THE FOLLOW-ON POINT AND I LOOKED AT THE PF'S INS AND SAW THE PROPER 'FROM/TO' WAYPOINTS. I ANSWERED 'YES' TO ATC'S QUERY OF 'PROCEEDING TO PABBA?' SHORTLY THEREAFTER; ATC GAVE US A VECTOR AND I CHKED MY INS AND SAW WE WERE 18 MI R OF TRACK. AT THE SAME TIME; WE HAD REQUESTED FL310 INSTEAD OF THE ORIGINAL CLRNC OF FL350. ATC GAVE US FL310 AND I CONFIRMED IT AGAIN. WE LEVELED AT FL310 AND ATC CALLED AND SAID THEY WANTED US AT FL350 AND TO EXPEDITE. WE WERE STILL UNDER RADAR AND THIS MAY HAVE BEEN DUE TO THE EXTRA TIME IT TOOK US TO GET TO PABBA. AS FAR AS THE OFF COURSE GOES; I SHOULD HAVE PRIORITIZED THE COMPLETION OF COURSE INTERCEPTION RATHER THAN THE ACCURACY CHK. THE INS'S GOT US TO KAGIS -- THEY WERE OBVIOUSLY OK. I HAVE BUILT A HABIT OF CAREFULLY DOCUMENTING THE ACCURACY CHK AS OUR OLD NAV SYS (DELCO CAROUSEL IV VERSUS LITTON) WERE MUCH MORE PRONE TO DRIFT. DOING THE CHK AT A RADIAL DME CHK POINT IS CONVENIENT; BUT SHOULD NOT TAKE PRIORITY OVER 'WAYPOINT PASSING' PROCS. WITH REGARD TO THE ALT; I'M SOMEWHAT AT A LOSS UNLESS THE EXTRA TIME IT TOOK TO GET TO PABBA CAUSED THE PROB. CLRNC; READBACK/RECONFIRMATION SOMEHOW FAILED IN THIS CASE. I WILL MAKE A COURTESY CALL A HABIT WHEN LEVELING AT AN ALT LOWER THAN PREVIOUSLY CLRED.