OMEGAS DRIFTED ACFT 34 MI OFF COURSE. HDG TRACK POS DEV.

Narrative

AFTER OUR DEP FROM SEATTLE IN THE DC-10 WE WERE CLRED DIRECT TO OUR OCEANIC GATEWAY; HEMLO. TO GET A MORE PRECISE POS I ELECTED TO FLY THE PUBLISHED RADIAL TO THE GATEWAY INSTEAD OF USING THE OMEGA. I CHOSE THE #2 VOR. THE #1 VOR CDI INDICATED THE RADIAL TO BE 4 DEGS TO THE L; WITHIN TOLERANCE FOR THE VORS. AS IT TURNED OUT IT WAS PROBABLY CORRECT; AND SO; WE WERE ABOUT 9 MI OFF TO START WITH. BOTH OMEGAS SHOWED A DISPARITY AT HEMLO. I PERFORMED A PRECISION UPDATE WHILE THE CAPT ELECTED TO LEAVE HIS ALONE. I CONTINUED TO NAV USING THE #2 OMEGA. UPON OBTAINING RADAR CONTACT; ZHN NOTIFIED US THAT WE WERE 34 MI OFF COURSE. SHORTLY THEREAFTER MY OMEGA SHOWED AN AMBIGUITY. THE JAPAN STATION HAS BEEN OFF THE AIR FOR MAINT DURING OCT. THIS DEFINITELY HAD AN EFFECT ON MY UNITS; AS THE GEOMETRY OF THE REMAINING STATIONS IS POOR; AND WE HAD BEEN HAVING OMEGA PROBS ALL MONTH LONG. IN REALITY I DON'T THINK IT IS POSSIBLE TO NAV RELIABLY ALONG THE SEA-HNL RTE WITH JAPAN OTS; USING OMEGAS ONLY. SOME DAYS ARE BETTER THAN OTHERS; WITH SUCH THINGS AS SOLAR ACTIVITY; TIME OF DAY; AND ANTENNA CONDITION AFFECTING PERFORMANCE. EVEN IF WE HAD 'SPLIT THE DIFFERENCE' BTWN THE OMEGAS; THE PLT'S TIME HONORED METHOD OF DEALING WITH SUCH PROBS; WE WOULD HAVE STILL BEEN 28 MI OFF; SINCE THE #1 OMEGA WAS 20 MI IN ERROR AS WELL. PERHAPS THE BEST COURSE OF ACTION WOULD HAVE BEEN TO BE RERTED TO A MORE SOUTHERLY TRACK; WHERE PATTERN GEOMETRY IS BETTER; OR TO TURN BACK. WITHOUT 2 GOOD OMEGAS WE PROBABLY SHOULDN'T BE OUT IN OCEANIC AIRSPACE. GOING 'BY THE BOOK' WOULD HAVE PREVENTED THE PROB IN THIS CASE.