Narrative:

Aircraft en route bermuda-ewr on B24 flann direct bergh A300 owenz direct coyle direct mcguire direct robbinsville V213 ward direct ewr. This crew flew aircraft from charleston to bermuda using omega navigation. Arrived priss (bma TCA) with 2 and 3 mi error on #1 and #2 omega. Wind readout on this trip averaged 200 degree/100 K. On departure bermuda we deviated approximately 60 mi east for WX then reintercepted B24 prior to targa but not enough time to get an accurate crab angle for wind. Omega 1 had 6 mi distance error and 3 mi x-track error at targa. #2 omega position froze just prior. Position updated both omegas and targa, 2 still frozen. Proceeded toward flann using #1 omega which checked normal. Heading was normal for the wind which indicated 205 degree/115 (varied to 125 K). Attempted to reinstate 2 omega including turning off air cooling then reinitializing. Unable to reinstate #2, #1 omega wind increased to 205/230 K. At that time due to obvious #1 error used dead reckoning heading for flann. Flann ETA corresponded with the distance to go. At this time (known #1 unreliability) we were within 2-3 mins of flann and were sent to dca center. They cleared us direct coyle, 310 degree heading until receiving. They then advised we were 55 mi southwest flann. Rechecked waypoint entry and compared position with center radar position. Omega position showed us on course. Radar position showed us southwest of course. In hindsight it appears that the winds aloft forecast was much more accurate than the omega wind readout, even on the outbnd leg when they were navigating properly. The reliance on the validity of the omega wind readout caused the aircraft heading to appear accurate and the drift angle to appear accurate. At the same time the deviation southwest of course put us too far away to pick up nantucket VOR for additional position check. The aircraft autoplt was inoperative and this also added to the workload which reduced the amount of attention the pilot flying could give to solving the navigation problem. The trip was released over the phone without a computer flight plan. This also increased the flight planning workload when revised clrncs were issued. Callback conversation with reporter revealed the following: reporter stated that the particular omegas in this aircraft and the installation/maintenance procedures were not legal for overwater operation and the operations specifications allowing or disallowing this had been changed by the FAA the previous march. Flight dispatch and the flight crew all missed this bulletin and operations specifications change. Flight operated on #1 omega which developed a wind error. This threw the aircraft off track. The actual winds were more like 205 degree at 30 KTS. Omega used winds of 205 degree at 120 KTS. The resultant increased left correction placed aircraft southwest of desired point. The reason there was no computer flight plan was that a new destination was decided on for reason of us customs clearance. Jfk was changed to ewr. This made a manual flight plan necessary, creating another factor for error. Crew's deviation for WX short cut their company procedure of getting an accurate drift angle check on the initial leg. Flight crew also deviated from ICAO procedures in not advising ATC that they were operating on only one navigation system. They hesitated to tell ATC their problems as they were at FL390 and knew there was no conflict with any traffic.

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Original NASA ASRS Text

Title: OCEANIC FLT REPORTED TO BE 55 MILES SOUTHWEST OF REQUIRED REPORTING POINT APCHING UNITED STATES MAINLAND. POSITION DEVIATION.

Narrative: ACFT ENRTE BERMUDA-EWR ON B24 FLANN DIRECT BERGH A300 OWENZ DIRECT COYLE DIRECT MCGUIRE DIRECT ROBBINSVILLE V213 WARD DIRECT EWR. THIS CREW FLEW ACFT FROM CHARLESTON TO BERMUDA USING OMEGA NAV. ARRIVED PRISS (BMA TCA) WITH 2 AND 3 MI ERROR ON #1 AND #2 OMEGA. WIND READOUT ON THIS TRIP AVERAGED 200 DEG/100 K. ON DEP BERMUDA WE DEVIATED APPROX 60 MI E FOR WX THEN REINTERCEPTED B24 PRIOR TO TARGA BUT NOT ENOUGH TIME TO GET AN ACCURATE CRAB ANGLE FOR WIND. OMEGA 1 HAD 6 MI DISTANCE ERROR AND 3 MI X-TRACK ERROR AT TARGA. #2 OMEGA POSITION FROZE JUST PRIOR. POSITION UPDATED BOTH OMEGAS AND TARGA, 2 STILL FROZEN. PROCEEDED TOWARD FLANN USING #1 OMEGA WHICH CHECKED NORMAL. HDG WAS NORMAL FOR THE WIND WHICH INDICATED 205 DEG/115 (VARIED TO 125 K). ATTEMPTED TO REINSTATE 2 OMEGA INCLUDING TURNING OFF AIR COOLING THEN REINITIALIZING. UNABLE TO REINSTATE #2, #1 OMEGA WIND INCREASED TO 205/230 K. AT THAT TIME DUE TO OBVIOUS #1 ERROR USED DEAD RECKONING HDG FOR FLANN. FLANN ETA CORRESPONDED WITH THE DISTANCE TO GO. AT THIS TIME (KNOWN #1 UNRELIABILITY) WE WERE WITHIN 2-3 MINS OF FLANN AND WERE SENT TO DCA CENTER. THEY CLRED US DIRECT COYLE, 310 DEG HDG UNTIL RECEIVING. THEY THEN ADVISED WE WERE 55 MI SW FLANN. RECHECKED WAYPOINT ENTRY AND COMPARED POSITION WITH CENTER RADAR POSITION. OMEGA POSITION SHOWED US ON COURSE. RADAR POSITION SHOWED US SW OF COURSE. IN HINDSIGHT IT APPEARS THAT THE WINDS ALOFT FORECAST WAS MUCH MORE ACCURATE THAN THE OMEGA WIND READOUT, EVEN ON THE OUTBND LEG WHEN THEY WERE NAVIGATING PROPERLY. THE RELIANCE ON THE VALIDITY OF THE OMEGA WIND READOUT CAUSED THE ACFT HDG TO APPEAR ACCURATE AND THE DRIFT ANGLE TO APPEAR ACCURATE. AT THE SAME TIME THE DEVIATION SW OF COURSE PUT US TOO FAR AWAY TO PICK UP NANTUCKET VOR FOR ADDITIONAL POSITION CHECK. THE ACFT AUTOPLT WAS INOPERATIVE AND THIS ALSO ADDED TO THE WORKLOAD WHICH REDUCED THE AMOUNT OF ATTN THE PLT FLYING COULD GIVE TO SOLVING THE NAV PROBLEM. THE TRIP WAS RELEASED OVER THE PHONE WITHOUT A COMPUTER FLT PLAN. THIS ALSO INCREASED THE FLT PLANNING WORKLOAD WHEN REVISED CLRNCS WERE ISSUED. CALLBACK CONVERSATION WITH REPORTER REVEALED THE FOLLOWING: REPORTER STATED THAT THE PARTICULAR OMEGAS IN THIS ACFT AND THE INSTALLATION/MAINT PROCS WERE NOT LEGAL FOR OVERWATER OPERATION AND THE OPERATIONS SPECS ALLOWING OR DISALLOWING THIS HAD BEEN CHANGED BY THE FAA THE PREVIOUS MARCH. FLT DISPATCH AND THE FLT CREW ALL MISSED THIS BULLETIN AND OPS SPECS CHANGE. FLT OPERATED ON #1 OMEGA WHICH DEVELOPED A WIND ERROR. THIS THREW THE ACFT OFF TRACK. THE ACTUAL WINDS WERE MORE LIKE 205 DEG AT 30 KTS. OMEGA USED WINDS OF 205 DEG AT 120 KTS. THE RESULTANT INCREASED LEFT CORRECTION PLACED ACFT SW OF DESIRED POINT. THE REASON THERE WAS NO COMPUTER FLT PLAN WAS THAT A NEW DEST WAS DECIDED ON FOR REASON OF U.S. CUSTOMS CLRNC. JFK WAS CHANGED TO EWR. THIS MADE A MANUAL FLT PLAN NECESSARY, CREATING ANOTHER FACTOR FOR ERROR. CREW'S DEVIATION FOR WX SHORT CUT THEIR COMPANY PROC OF GETTING AN ACCURATE DRIFT ANGLE CHECK ON THE INITIAL LEG. FLT CREW ALSO DEVIATED FROM ICAO PROCS IN NOT ADVISING ATC THAT THEY WERE OPERATING ON ONLY ONE NAVIGATION SYSTEM. THEY HESITATED TO TELL ATC THEIR PROBLEMS AS THEY WERE AT FL390 AND KNEW THERE WAS NO CONFLICT WITH ANY TFC.

Data retrieved from NASA's ASRS site as of August 2007 and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.