DEV FROM CLRNC RTE. ACR CREW ALLOWS ACFT TO DRIFT OFF COURSE WHEN OMEGA NAV EQUIP MALFUNCTIONS EVEN THOUGH THE PROPER COURSE IS DISPLAYED ON THE VHF NAV RADIO.

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WE LEFT ORD FOR LGA BY ROUTING OUT J146. I WAS BEING GIVEN A LINE CHK BY A CHK AIRMAN. AS WE LEFT ORD I DID AN ACCURACY CHK OF OUR OMEGA AND COUPLED IT TO THE AUTOPLT. AS WE CROSSED GIPER (GIJ). I DID A POS CHK AND SET THE VORS TO THE OUTBOUND RADIAL (089 DEGS) TOWARD OUR NEXT FIX OF IDEAS. AS WE PROCEEDED OUTBOUND; WE NOTICED THE OMEGA TAKING US N OF J146. NOTING THE DISCREPANCY; WE BEGAN TO CHK COORDINATES AND PROPER ROUTING. WHILE TROUBLE-SHOOTING THE OMEGA POS AND ACCURACY; WE SELECTED A 110 DEG HDG TO REINTERCEPT THE AIRWAY. ATC CALLED SHORTLY THEREAFTER AND SUGGESTED A 120 DEG HDG TO REINTERCEPT; AND STATED THAT WE WERE 7 MI N OF CTRLINE. THE ONLY DISCREPANCY NOTED WAS AN OMEGA WIND RPT OF 358 DEGS AT 107 KTS. WE FEEL THE WIND WAS ERRONEOUS; AND THE OMEGA COMPUTED A TRACK ANGLE BASED ON WRONG INFO. SHORTLY AFTER OUR INTERCEPT; THE OMEGA SHOWED WINDS AT 40 KTS. NO CONFLICT WAS RPTED EITHER BY ATC OR TCASII. AS THE DEV HAPPENED RATHER QUICKLY; WE FEEL THE WIND RPT IN THE OMEGA GENERATED THE ERROR. AS IT WAS A LINE CHK; THERE WAS MUCH DISCUSSION ON THE FLT DECK. BRIEFINGS SHOULD BE LEFT FOR AFTER THE TRIP; AND NOT DURING IT.