Narrative:

After receiving two reports of the airway between hinchinbrook and ocean cape NDB's not coinciding with the published airway on the alaska L-1, I was tasked by the military to verify the route. After flying the casel 3 departure, I directed my co-pilot to intercept the 079 bearing from hbk to fly the A1 airway. As he was flying the route using our AFD, I was backing it up by observing our deviation from an RNAV flight plan consisting of the following routing: intercept the track from gcr to corva direct corva direct ataga direct capem direct occ. As we turned on the 079 bearing from hbk, I observed our track to be 2.4 NM north of the A1 airway and diverging towards terrain. At this point, I verified the left/left's of hbk, corva, and capem to ensure that our RNAV flight plan was correctly entered. I also checked our RNAV system (embedded GPS/INS) and observed an estimated horizontal error of 8 yards and a figure of merit of 1 (the best fom achievable). After observing a 6 degree divergence from the course, I plotted a new waypoint offset from hbk on the 085 bearing from at 94 NM. This new wp coincided exactly with capem intersection. Per my observations, the course on the A1 airway should now be the 085 bearing from hbk. If you were to fly the A1 as published without RNAV back up, you would impact terrain at the MEA. At capem, you would be 9.4 NM north of the track, well outside the lateral limits of the airway. I don't know if the NDB airway system is still updated, but if it isn't, the A1 airway should be deleted from the en route low structure. The center will still clear aircraft on this route, and if radar services aren't available, a fatality could occur. After further conversations with the local FSDO, I believe that this problem is endemic in alaska. Apparently, the courses defining the LF airways are not being updated to reflect annual changes in magnetic variation. This results in significant course deviations. The course defining the A1 airway was last aligned in the 70's when the NAVAID was installed. This problem has gone unnoticed due to a procedural anomaly in the FAA flight check protocol. Flight check is entering the historic magnetic variation for the installation date of the NDB's into their navigation system. This results in an incorrect verification of the ground track when the raw data is used for navigation. The large annual changes in magnetic variation, in concert with the proximity to terrain along many of these airways create a very hazardous situation, especially in a non-radar environment. Exacerbating this problem is the fact that many of these airways have lower MEA's than nearby victor airways, making these rtes preferable during IMC conditions, as they keep low en route traffic in airspace less likely to have icing problems. Callback conversation with reporter stated that zan ARTCC contacted the military to perform a check on the A1 airway because a few aircraft have been noticed off course. The helicopter used has a RNAV system that uses military GPS and INS to get the most accurate position. The pilot noticed a 6 degree error by setting one side of the cockpit with only an ADF tracking the NDB off of hbk. The other side used the RNAV. The pilot noticed in the alaska supplemental chart that the hbk NDB has had no magnetic variation change to it in 30 years. The reporter also talked about the potential for two aircraft to be holding over the same location due to magnetic variation when one aircraft is at casel and the other is at corva. The reporter said that there are about 10 NDB's that he knows about throughout alaska that have at least a 4 degree variation. He noted that the A1 airway between hbk and occ had a new MEA of 10000, which will protect aircraft from terrain. However, this will not protect aircraft from being off course due to the variation and coming in conflict with V319.

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Original NASA ASRS Text

Title: A MIL HELI PLT DISCOVERED THAT THE A1 AIRWAY PREDICATED OFF THE HBK NDB AND OCC NBD HAS A 6 DEG DEV WHICH COULD ENABLE AN ACFT TO BE WELL OFF COURSE.

Narrative: AFTER RECEIVING TWO RPTS OF THE AIRWAY BETWEEN HINCHINBROOK AND OCEAN CAPE NDB'S NOT COINCIDING WITH THE PUBLISHED AIRWAY ON THE ALASKA L-1, I WAS TASKED BY THE MIL TO VERIFY THE RTE. AFTER FLYING THE CASEL 3 DEP, I DIRECTED MY CO-PLT TO INTERCEPT THE 079 BEARING FROM HBK TO FLY THE A1 AIRWAY. AS HE WAS FLYING THE RTE USING OUR AFD, I WAS BACKING IT UP BY OBSERVING OUR DEV FROM AN RNAV FLT PLAN CONSISTING OF THE FOLLOWING ROUTING: INTERCEPT THE TRACK FROM GCR TO CORVA DIRECT CORVA DIRECT ATAGA DIRECT CAPEM DIRECT OCC. AS WE TURNED ON THE 079 BEARING FROM HBK, I OBSERVED OUR TRACK TO BE 2.4 NM NORTH OF THE A1 AIRWAY AND DIVERGING TOWARDS TERRAIN. AT THIS POINT, I VERIFIED THE L/L'S OF HBK, CORVA, AND CAPEM TO ENSURE THAT OUR RNAV FLT PLAN WAS CORRECTLY ENTERED. I ALSO CHECKED OUR RNAV SYSTEM (EMBEDDED GPS/INS) AND OBSERVED AN ESTIMATED HORIZONTAL ERROR OF 8 YARDS AND A FIGURE OF MERIT OF 1 (THE BEST FOM ACHIEVABLE). AFTER OBSERVING A 6 DEG DIVERGENCE FROM THE COURSE, I PLOTTED A NEW WAYPOINT OFFSET FROM HBK ON THE 085 BEARING FROM AT 94 NM. THIS NEW WP COINCIDED EXACTLY WITH CAPEM INTERSECTION. PER MY OBSERVATIONS, THE COURSE ON THE A1 AIRWAY SHOULD NOW BE THE 085 BEARING FROM HBK. IF YOU WERE TO FLY THE A1 AS PUBLISHED WITHOUT RNAV BACK UP, YOU WOULD IMPACT TERRAIN AT THE MEA. AT CAPEM, YOU WOULD BE 9.4 NM NORTH OF THE TRACK, WELL OUTSIDE THE LATERAL LIMITS OF THE AIRWAY. I DON'T KNOW IF THE NDB AIRWAY SYSTEM IS STILL UPDATED, BUT IF IT ISN'T, THE A1 AIRWAY SHOULD BE DELETED FROM THE ENRTE LOW STRUCTURE. THE CTR WILL STILL CLEAR ACFT ON THIS ROUTE, AND IF RADAR SERVICES AREN'T AVAILABLE, A FATALITY COULD OCCUR. AFTER FURTHER CONVERSATIONS WITH THE LOCAL FSDO, I BELIEVE THAT THIS PROB IS ENDEMIC IN ALASKA. APPARENTLY, THE COURSES DEFINING THE LF AIRWAYS ARE NOT BEING UPDATED TO REFLECT ANNUAL CHANGES IN MAGNETIC VARIATION. THIS RESULTS IN SIGNIFICANT COURSE DEVIATIONS. THE COURSE DEFINING THE A1 AIRWAY WAS LAST ALIGNED IN THE 70'S WHEN THE NAVAID WAS INSTALLED. THIS PROB HAS GONE UNNOTICED DUE TO A PROCEDURAL ANOMALY IN THE FAA FLT CHECK PROTOCOL. FLT CHECK IS ENTERING THE HISTORIC MAGNETIC VARIATION FOR THE INSTALLATION DATE OF THE NDB'S INTO THEIR NAV SYSTEM. THIS RESULTS IN AN INCORRECT VERIFICATION OF THE GND TRACK WHEN THE RAW DATA IS USED FOR NAVIGATION. THE LARGE ANNUAL CHANGES IN MAGNETIC VARIATION, IN CONCERT WITH THE PROXIMITY TO TERRAIN ALONG MANY OF THESE AIRWAYS CREATE A VERY HAZARDOUS SIT, ESPECIALLY IN A NON-RADAR ENVIRONMENT. EXACERBATING THIS PROB IS THE FACT THAT MANY OF THESE AIRWAYS HAVE LOWER MEA'S THAN NEARBY VICTOR AIRWAYS, MAKING THESE RTES PREFERABLE DURING IMC CONDITIONS, AS THEY KEEP LOW ENRTE TFC IN AIRSPACE LESS LIKELY TO HAVE ICING PROBS. CALLBACK CONVERSATION WITH RPTR STATED THAT ZAN ARTCC CONTACTED THE MIL TO PERFORM A CHECK ON THE A1 AIRWAY BECAUSE A FEW ACFT HAVE BEEN NOTICED OFF COURSE. THE HELI USED HAS A RNAV SYSTEM THAT USES MIL GPS AND INS TO GET THE MOST ACCURATE POSITION. THE PLT NOTICED A 6 DEG ERROR BY SETTING ONE SIDE OF THE COCKPIT WITH ONLY AN ADF TRACKING THE NDB OFF OF HBK. THE OTHER SIDE USED THE RNAV. THE PLT NOTICED IN THE ALASKA SUPPLEMENTAL CHART THAT THE HBK NDB HAS HAD NO MAGNETIC VARIATION CHANGE TO IT IN 30 YEARS. THE RPTR ALSO TALKED ABOUT THE POTENTIAL FOR TWO ACFT TO BE HOLDING OVER THE SAME LOCATION DUE TO MAGNETIC VARIATION WHEN ONE ACFT IS AT CASEL AND THE OTHER IS AT CORVA. THE RPTR SAID THAT THERE ARE ABOUT 10 NDB'S THAT HE KNOWS ABOUT THROUGHOUT ALASKA THAT HAVE AT LEAST A 4 DEG VARIATION. HE NOTED THAT THE A1 AIRWAY BETWEEN HBK AND OCC HAD A NEW MEA OF 10000, WHICH WILL PROTECT ACFT FROM TERRAIN. HOWEVER, THIS WILL NOT PROTECT ACFT FROM BEING OFF COURSE DUE TO THE VARIATION AND COMING IN CONFLICT WITH V319.

Data retrieved from NASA's ASRS site as of July 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.