Narrative:

On first call to ZHN, at position duffe on route R576, I advised ATC that I wasn't exactly sure of my position as I had an approximately 25 mi sep in the dual omega system we were using for navigation. When we were finally picked up on radar, by the air force according to ATC, we were more than 200 mi off course. I have no explanation for this, in that according to the TRACON units the most we could have been off course was 25 mi depending on which of the 2 units I believed to have been correct. Upon landing in hnl the gross error check on the 2 units showed the #1 omega was 268.6 mi off with a 321 degree bearing. The #2 omega was 299.2 mi off with a 312 degree bearing I have no immediate explanation as to why these omega units went so far aria during our trip from lax to hnl on airlines flight on 11/mon/88. Callback conversation with reporter revealed the following: reporter claimed did not have opportunity to check omega accuracy against VOR/DME until over ingress gateway. At that time it checked well within tolerance. Neither set was giving a wind update from takeoff to top of climb, so wind was not valid and crew manually entered winds from forecasts and flight plan for entire flight. At all fixes along track both navigation sets stayed reasonably close together with biggest deviation being 20 NM crosstrack and 48 NM along track, and times and fuel burn were reasonable over every chkpoint, so crew had no reason to suspect error until hnl ARTCC radar unable to pick up flight at egress gateway. Center then asked air force to check for flight on their long range radar and that was when they discovered 200 NM off course. Crew thinks omega sets flew great circle route all way from ingress gateway to point where radar picked them up. Claims ADF were tuned, but were no good, but at time picked up on radar were ready to turn south as ADF was now homing. Stated does not think maintenance very good as this aircraft navigation sets had been written up 8 times with write off being cleaned cannon plugs. FAA still investigating incident and threatening action. Knew navigation sets not accurate but did not advise ATC until VHF contact with hnl. Supplemental information from acn 97726: at the gateway and before ATC contact, captain determined there was a problem because there was no VOR DME information on radar contours of the islands. The captain then asked me to check the overhead magnetic compass, which was found to be accurate with the captain's and first officer's D/G. Supplemental information from acn 97812: after passing airway gateway outbnd (from lax) omegas began drifting apart. It became obvious that something was wrong. Manual wind information had to be inserted to the computers. We used flight plan winds and actual reported winds (from other reporting aircraft) captain opted to 'split the difference' between omegas and continue to use them for navigation. 'Navigation unreliability' was not declared. Approaching hnl, center radar was not able to locate aircraft. We missed inbound gateway in excess of 200 NM.

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Original NASA ASRS Text

Title: ACR HVT GROSS NAVIGATION ERROR PACIFIC.

Narrative: ON FIRST CALL TO ZHN, AT POS DUFFE ON ROUTE R576, I ADVISED ATC THAT I WASN'T EXACTLY SURE OF MY POS AS I HAD AN APPROX 25 MI SEP IN THE DUAL OMEGA SYS WE WERE USING FOR NAV. WHEN WE WERE FINALLY PICKED UP ON RADAR, BY THE AIR FORCE ACCORDING TO ATC, WE WERE MORE THAN 200 MI OFF COURSE. I HAVE NO EXPLANATION FOR THIS, IN THAT ACCORDING TO THE TRACON UNITS THE MOST WE COULD HAVE BEEN OFF COURSE WAS 25 MI DEPENDING ON WHICH OF THE 2 UNITS I BELIEVED TO HAVE BEEN CORRECT. UPON LNDG IN HNL THE GROSS ERROR CHK ON THE 2 UNITS SHOWED THE #1 OMEGA WAS 268.6 MI OFF WITH A 321 DEG BEARING. THE #2 OMEGA WAS 299.2 MI OFF WITH A 312 DEG BEARING I HAVE NO IMMEDIATE EXPLANATION AS TO WHY THESE OMEGA UNITS WENT SO FAR ARIA DURING OUR TRIP FROM LAX TO HNL ON AIRLINES FLT ON 11/MON/88. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING: RPTR CLAIMED DID NOT HAVE OPPORTUNITY TO CHK OMEGA ACCURACY AGAINST VOR/DME UNTIL OVER INGRESS GATEWAY. AT THAT TIME IT CHKED WELL WITHIN TOLERANCE. NEITHER SET WAS GIVING A WIND UPDATE FROM TKOF TO TOP OF CLB, SO WIND WAS NOT VALID AND CREW MANUALLY ENTERED WINDS FROM FORECASTS AND FLT PLAN FOR ENTIRE FLT. AT ALL FIXES ALONG TRACK BOTH NAV SETS STAYED REASONABLY CLOSE TOGETHER WITH BIGGEST DEVIATION BEING 20 NM CROSSTRACK AND 48 NM ALONG TRACK, AND TIMES AND FUEL BURN WERE REASONABLE OVER EVERY CHKPOINT, SO CREW HAD NO REASON TO SUSPECT ERROR UNTIL HNL ARTCC RADAR UNABLE TO PICK UP FLT AT EGRESS GATEWAY. CENTER THEN ASKED AIR FORCE TO CHK FOR FLT ON THEIR LONG RANGE RADAR AND THAT WAS WHEN THEY DISCOVERED 200 NM OFF COURSE. CREW THINKS OMEGA SETS FLEW GREAT CIRCLE ROUTE ALL WAY FROM INGRESS GATEWAY TO POINT WHERE RADAR PICKED THEM UP. CLAIMS ADF WERE TUNED, BUT WERE NO GOOD, BUT AT TIME PICKED UP ON RADAR WERE READY TO TURN S AS ADF WAS NOW HOMING. STATED DOES NOT THINK MAINT VERY GOOD AS THIS ACFT NAV SETS HAD BEEN WRITTEN UP 8 TIMES WITH WRITE OFF BEING CLEANED CANNON PLUGS. FAA STILL INVESTIGATING INCIDENT AND THREATENING ACTION. KNEW NAV SETS NOT ACCURATE BUT DID NOT ADVISE ATC UNTIL VHF CONTACT WITH HNL. SUPPLEMENTAL INFO FROM ACN 97726: AT THE GATEWAY AND BEFORE ATC CONTACT, CAPT DETERMINED THERE WAS A PROB BECAUSE THERE WAS NO VOR DME INFO ON RADAR CONTOURS OF THE ISLANDS. THE CAPT THEN ASKED ME TO CHK THE OVERHEAD MAGNETIC COMPASS, WHICH WAS FOUND TO BE ACCURATE WITH THE CAPT'S AND F/O'S D/G. SUPPLEMENTAL INFO FROM ACN 97812: AFTER PASSING AIRWAY GATEWAY OUTBND (FROM LAX) OMEGAS BEGAN DRIFTING APART. IT BECAME OBVIOUS THAT SOMETHING WAS WRONG. MANUAL WIND INFO HAD TO BE INSERTED TO THE COMPUTERS. WE USED FLT PLAN WINDS AND ACTUAL RPTED WINDS (FROM OTHER RPTING ACFT) CAPT OPTED TO 'SPLIT THE DIFFERENCE' BTWN OMEGAS AND CONTINUE TO USE THEM FOR NAV. 'NAV UNRELIABILITY' WAS NOT DECLARED. APCHING HNL, CENTER RADAR WAS NOT ABLE TO LOCATE ACFT. WE MISSED INBND GATEWAY IN EXCESS OF 200 NM.

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.