|37000 Feet||Browse and search NASA's
Aviation Safety Reporting System
|Local Time Of Day||0601 To 1200|
|Locale Reference||atc facility : sju|
|Altitude||msl bound lower : 37000|
msl bound upper : 37000
|Controlling Facilities||artcc : zma|
|Operator||common carrier : air carrier|
|Make Model Name||Widebody, Low Wing, 3 Turbojet Eng|
|Navigation In Use||Other|
|Flight Phase||cruise other|
|Route In Use||enroute airway : g431|
|Affiliation||company : air carrier|
|Function||flight crew : captain|
oversight : pic
|Qualification||pilot : atp|
|Experience||flight time total : 12500|
|Affiliation||government : faa|
|Function||controller : radar|
|Qualification||controller : radar|
|Anomaly||non adherence : clearance|
other spatial deviation
|Independent Detector||other controllera|
|Resolutory Action||controller : issued new clearance|
flight crew : returned to intended course or assigned course
|Primary Problem||Flight Crew Human Performance|
|Air Traffic Incident||Pilot Deviation|
Both omegas #1 and #2 had functioned normally throughout the trip (including pre and postdep checks) up to a point between tooms and elmuc on G431 under ZMA radar coverage. At this point the omegas began to diverge with near nominal wind readouts and no failure or malfunction indication. They had diverged by approximately 8 NM when we were advised by ZMA that we were 26 NM north of course. Very shortly the dr light on the #1 omega illuminated with a status of 03 (no malfunction code). This was followed by an ambiguity light with a status of 01. When it later appeared that the unit was within 15 NM of the correct position the 'clear ambiguity procedure' was followed. Although the ambiguity light disappeared the navigation error persisted until landing. A post-flight check showed a radial position error of 27 NM on omega #1 and a 12 NM error on omega #2. The #1 unit accepted a precision update on the ramp and appeared to then function nominally. After ZMA initially advised us of the cross track error we were given a heading to re-intercept the arwy. We were then given a frequency change for sjc center which proved to be an incorrect frequency. When communication was established with sju we were again shown to be 25 NM north of course and given vectors. After landing I advised dispatch of the above and I contacted coast guard duty officer of the facility assigned to maintain the omega stations. He referenced the recent solar flare activity and the current omega status report which refers to polar cap disturbances and he advised that there have been a number of such incidents, not persistent in a given area, but rather brief and at random location, consistent with what we experienced.
Original NASA ASRS Text
Title: ACR WDB DEVIATED FROM CLRNC ROUTE BETWEEN JFK AND SJU.
Narrative: BOTH OMEGAS #1 AND #2 HAD FUNCTIONED NORMALLY THROUGHOUT THE TRIP (INCLUDING PRE AND POSTDEP CHKS) UP TO A POINT BTWN TOOMS AND ELMUC ON G431 UNDER ZMA RADAR COVERAGE. AT THIS POINT THE OMEGAS BEGAN TO DIVERGE WITH NEAR NOMINAL WIND READOUTS AND NO FAILURE OR MALFUNCTION INDICATION. THEY HAD DIVERGED BY APPROX 8 NM WHEN WE WERE ADVISED BY ZMA THAT WE WERE 26 NM N OF COURSE. VERY SHORTLY THE DR LIGHT ON THE #1 OMEGA ILLUMINATED WITH A STATUS OF 03 (NO MALFUNCTION CODE). THIS WAS FOLLOWED BY AN AMB LIGHT WITH A STATUS OF 01. WHEN IT LATER APPEARED THAT THE UNIT WAS WITHIN 15 NM OF THE CORRECT POS THE 'CLEAR AMBIGUITY PROC' WAS FOLLOWED. ALTHOUGH THE AMB LIGHT DISAPPEARED THE NAV ERROR PERSISTED UNTIL LNDG. A POST-FLT CHK SHOWED A RADIAL POS ERROR OF 27 NM ON OMEGA #1 AND A 12 NM ERROR ON OMEGA #2. THE #1 UNIT ACCEPTED A PRECISION UPDATE ON THE RAMP AND APPEARED TO THEN FUNCTION NOMINALLY. AFTER ZMA INITIALLY ADVISED US OF THE CROSS TRACK ERROR WE WERE GIVEN A HDG TO RE-INTERCEPT THE ARWY. WE WERE THEN GIVEN A FREQ CHANGE FOR SJC CENTER WHICH PROVED TO BE AN INCORRECT FREQ. WHEN COM WAS ESTABLISHED WITH SJU WE WERE AGAIN SHOWN TO BE 25 NM N OF COURSE AND GIVEN VECTORS. AFTER LNDG I ADVISED DISPATCH OF THE ABOVE AND I CONTACTED COAST GUARD DUTY OFFICER OF THE FAC ASSIGNED TO MAINTAIN THE OMEGA STATIONS. HE REFERENCED THE RECENT SOLAR FLARE ACTIVITY AND THE CURRENT OMEGA STATUS RPT WHICH REFERS TO POLAR CAP DISTURBANCES AND HE ADVISED THAT THERE HAVE BEEN A NUMBER OF SUCH INCIDENTS, NOT PERSISTENT IN A GIVEN AREA, BUT RATHER BRIEF AND AT RANDOM LOCATION, CONSISTENT WITH WHAT WE EXPERIENCED.
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.