NAV EMER DECLARED AFTER THE LOSS OF THE SECOND OMEGA.

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DISPATCHED WITH 1 OMEGA INOP: I AM WRITING THIS RPT BECAUSE I DISAGREE WITH THE WAIVER ALLOWED TO ACR'S TO OPERATE CARIBBEAN RTES WITH 1 LONG RANGE NAV SYS INOP; AND TO POINT OUT THAT MY ACR'S AVIONIC MAINT IS VERY POOR. THE BASIS OF THIS WAIVER; APPARENTLY; IS THAT FLTS ARE NOT OUT OF RADAR COVERAGE LONGER THAN 2 HRS; AND DEAD RECKONING CAN BE USED WITH THE COMPUTER FLT PLAN INFO; IE MH; FORECAST WIND; TIME FIX; ETC. SHORTLY AFTER TKOF ANTIGUA; FLT WAS RERTED DUE TO WATERS AGREEMENT FROM A312/523 TO A632. #2 OMEGA FAILED ABOUT 20 MINS AFTER LOSING RADAR CONTACT WITH ZSU. RPTED NAV EQUIP FAILURE TO NY AND DECLARED NAV EMER TO LAND BDA. THE FLT PLAN IN THIS CASE WAS PRETTY MUCH USELESS FOR DR NAV; AS CHK POINTS; COURSE; MAGNETIC HDG; DID NOT APPLY. AS THE FAILURE OCCURRED ON THE SOUTHERN EDGE OF A W TO E JET STREAM (150 AT CORE); WE MADE HDG ADJUSTMENT SIMILAR TO FLT PLAN XWIND TRACK CORRECTION OF ADDITIONAL 10 DEG LONGITUDE; R DRIFT. AT THE BERMUDA FIR; 45 MINS LATER; ACFT WAS 40 MI E OF COURSE. IN THE MEANTIME; DID SOME TROUBLE SHOOTING AND RESTORED PWR TO #2 OMEGA. ACCOMPLISHED PRECISION UPDATES AT BDA AND TARGA AND CONTINUED FLT NORMALLY. MAINT WRITE UP DECLARED THE ACFT UNSAFE FOR FURTHER FLT OVER WATER WITHOUT REPAIRING BOTH NAV SYS AND FLT CHKING SAME OVER LAND. FOLLOWING DAY; WE WERE ASSIGNED SAME ACFT TO FLY SAME TRIP; #1 OMEGA STILL INOP; #2 OMEGA SIGNED OFF 'SUSPECT CAUSE OF PWR LOSS IN RPU; REPLACED; CHKED OK ON TAXI DURING REPOSITION FROM HANGAR.' SINCE WE WERE THE LAST CREW TO FLY THE ACFT; WE FOUND IT UNUSUAL THAT OUR MAINT GRIPE OF #2 OMEGA WAS NOT IN THE FRONT OF THE LOGBOOK. IN FACT; IT WAS PLACED IN A POUCH SLIGHTLY OUT OF ORDER SO THAT IT WOULD NOT APPEAR TO BE FROM PREVIOUS DAY FLYING. A NEW CREW (UNSUSPECTING) COULD HAVE VERY EASILY MISSED MY NOTATION OF A NEED TO FLT CHK OMEGAS. REFUSED ACFT FOR OVERWATER FLT UNTIL FLT CHKED!