GLF2 CREW WAS 700 MI OFF COURSE AND LOST IN THE PACIFIC.

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FLT FROM WEWAK; PNG; TO MAJURO; RMI ON JUL/THU/01. RTE OF FLT WAS: AYWK DIRECT WK DIRECT ISMAR DIRECT AGERA DIRECT PALAN DIRECT TOK DIRECT CHG DIRECT BUK B589 DIRECT PKMJ. WE CRUISED AT MACH .80 AT FL410. THE TRIP BEGAN ROUTINELY EXCEPT IT WAS DIFFICULT TO ESTABLISH AND MAINTAIN COMS WITH MADANG AND PORT MORESBY CTRS; ON BOTH VHF AND HF FREQS. ONCE ESTABLISHED ON B589; THE FLT CONTINUED ROUTINELY. PASSING INTO NAURU FIR AT TASAK FIX (S01 26.5-E160 00.0) WE ESTABLISHED COMS WITH ZOA THROUGH COMMERCIAL RADIO. FROM THAT POINT ON WE HAD RELIABLE COMS WITH ATC. SHORTLY AFTER REACHING THE ELNUR FIX (N03 30.0-E166 30.5) AND RPTING POS; BOTH FMS UNITS WENT TO THE DEAD RECKONING MODE AND OUR INS ALSO FAILED. IT IS IMPORTANT TO NOTE THAT ALL 3 LONG RANGE NAV SYS FAILED SIMULTANEOUSLY. AFTER IT FAILED; THE INS INDICATED A POS MORE THAN 300 MI AWAY FROM OUR LAST KNOWN POS BASED ON GPS SENSORS IN BOTH FMS UNITS. WE WERE TOPPING AND CIRCUMNAVING AROUND NUMEROUS TSTMS AT THE TIME. THERE WAS ALSO NO VISUAL CONTACT WITH THE SURFACE. WE SELECTED NAURU NDB/DME; BUT WERE UNABLE TO IDENT THE STATION AND ESTABLISH A RELIABLE POS BASED ON THAT NAVAID. WE WERE ALSO UNABLE TO ESTABLISH ANY COM WITH NAURU RADIO ON ANY PUBLISHED FREQ TO VERIFY NAVAID OP. WE DID HAVE OUR LAST KNOWN POS AND HDG TO REACH MAJURO; AS WELL AS SUFFICIENT FUEL TO REACH MAJURO; AS WELL AS MAJURO'S WX FORECAST; WHICH WAS GOOD. SO WE DECIDED TO HOLD OUR HDG (043 DEGS) TO REACH DEST AT ETA. WE ALSO KNEW WE WOULD BE ABLE TO RECEIVE MAJURO NDB AND DME APPROX 200 MI OUT. WITH THE HELP OF KWAJALEIN RADAR AND WITH OUR PREVIOUS EXPERIENCE AND FAMILIARITY WITH FLYING TO AND FROM MAJURO; WE DECIDED TO CONTINUE ON TO MAJURO. AT THIS POINT WE DESELECTED INERTIAL MODE FROM THE FMS UNITS AND TURNED EACH FMS UNIT OFF; THEN BACK ON. WE DID THIS TWICE; BUT WERE UNABLE TO REGAIN NAV CAPABILITIES. THE WX GOT WORSE AND WE HAD TO DEVIATE AROUND MORE SEVERE STORMS. BUT WE ALWAYS RETURNED TO OUR DEAD RECKONING HDG OF 043 DEGS. GETTING CLOSE TO OUR ETA; WE WERE UNABLE TO NEITHER RECEIVE MAJURO NDB/DME; NOR CONTACT MAJURO RADIO ON 123.6 VHF OR ACR OPS ON 1XX.0 VHF; OUR HANDLER AT ZZZ. HVY WX ALSO PREVENTED US FROM IDENTING MAJURO ATOLL WITH OUR WX RADAR IN GND MAP MODE. WE ALSO TRIED NUMEROUS TIMES TO TUNE IN AND IDENT BUCHOLZ NDB AS WELL AS CONTACT BUCHOLZ RADAR APCH AT KWAJALEIN; BUT TO NO AVAIL. UNABLE TO ESTABLISH COMS WITH ATC; WE ASKED FOR HELP FROM ANY FLT ON THE INTL GUARD FREQ; 121.5 VHF. FORTUNATELY; ACR FLT YYY RESPONDED AND WE EXPLAINED OUR PROB. THEY OFFERED AS MUCH HELP AS THEY POSSIBLY COULD AND NOTIFIED ZOA THROUGH COMMERCIAL RADIO OF OUR PREDICAMENT. IN THE MEANTIME; AFTER CONSIDERING THE LIKELY POSSIBILITY WE HAD ALREADY PASSED MAJURO; WE OPTED TO REVERSE COURSE AND FLY 223 DEGS. WE BEGAN TO TUNE IN ANY AND ALL NDB'S WE COULD FIND PUBLISHED ON THE ENRTE CHART. YYY SUGGESTED TRYING WAKE NDB AS WELL AS WAKE RADIO VHF. IT CAME AS MUSIC TO OUR EARS WHEN WE HEARD THE WAKE ISLAND RADIO OPERATOR TALKING TO BOTH US AND YYY. SOON; WE HAD WAKE NDB AND DME TUNED IN AND DETERMINED OUR POS AS 200 MI S OF WAKE ISLAND. WE TURNED TO FLY DIRECT TO WAKE AND MADE VISUAL CONTACT 80 MI OUT. WE THEN MADE A NORMAL VISUAL APCH AND LANDED; WITH MINIMAL RESERVE FUEL. AFTER SHUTTING DOWN ALL SYS; WE THEN STARTED UP AND REINITIALIZED BOTH THE INERTIAL AND THE FMS'S AND THERE WERE NO FURTHER PROBS. WE WERE BACK TO NORMAL OP ON THE GND AT WAKE ISLAND. OUR FLT PROCEEDED SMOOTHLY FROM THERE TO HNL; HI. AT HNL; A TECHNICIAN FROM A CERTIFIED FAA REPAIR STATION RAMP TESTED OUR #1 AND #2 FMS UNITS; AS WELL AS THE INS UNIT; BUT DID NOT FIND ANY EVIDENCE OF A LIGHTNING STRIKE. ALL SYS CHKED NORMAL. I HAVE NO LOGICAL EXPLANATION AS TO WHAT CAUSED ALL OUR LONG RANGE NAV SYS TO FAIL AT THE SAME TIME; AND WHY WE ENDED UP SO FAR OFF COURSE. BUT WE FEEL STRONGLY THAT WE FLEW INTO AN ELECTROMAGNETIC FIELD; PROBABLY COMING FROM HIGH PWRED DEFENSE RADARS AT KWAJALEIN. THIS MORE THAN LIKELY DISABLED OUR LONG RANGE NAV CAPABILITY; ASWELL AS GAVE US ERRONEOUS HDG INFO. HOW THIS ALL COULD HAVE BEEN PREVENTED WE REALLY CAN'T SAY. BUT WE ADVISE ANYONE USING LONG RANGE NAV EQUIP LIKE OURS TO EXERCISE EXTRA VIGILANCE AS TO POS AWARENESS; AT ALL TIMES. THIS IS ESPECIALLY TRUE IN THE WEST CENTRAL AND SOUTH PACIFIC. THIS MEANS CHKING AND XCHKING POS WITH WHATEVER MEANS AVAILABLE; DME; ADF; AIRBORNE RADAR AND VISUAL CONTACT WHENEVER POSSIBLE. AND NEVER BE RELUCTANT TO ASK FOR HELP. THANKS TO ALL OUR FELLOW AVIATION PROFESSIONALS WHO MONITOR 121.5! CALLBACK INFO FROM RPTR REVEALED THE FOLLOWING INFO: CREW WAS FLYING A GULFSTREAM G2. IT WAS EQUIPPED WITH DUAL GPS SYS AND A SINGLE INS UNIT. THE ACFT WAS NOT EQUIPPED WITH A MOVING MAP. POS INFO THEN IS FED INTO THE DUAL FMC'S WHICH PROVIDE NAV FOR THE ACFT. THE FMC ALSO RECEIVE NAV INFO FROM DUAL DME; VOR-DME AND VOR-VOR IF RECEIVED. IN THIS CASE; THE GPS WAS THE ONLY EXTERNAL NAV SOURCE. THE RPTR STILL DOESN'T UNDERSTAND HOW THEY GOT SO FAR OFF COURSE.