Narrative:

Upon listening to ykm ATIS, ATIS said airport was using ILS approach 27. In our descent to 9000' and 30 NM from VOR, we were switched to ykm approach control. Told to expect localizer/DME backcourse 09, although wind was 220 degrees at 6 KTS. At this point the first officer began getting setup for the approach, and upon contacting ykm approach 20 NM, we were cleared for the localizer/DME backcourse 09. We had to join a 16 DME arc, which at that position was the IAF. Copilot incorrectly interpreted approach plate and we subsequently descended through 7000' (to 6500') before I realized he had made a mistake. We climbed back to proper altitude (7000') for that portion of the arc. All other procedures were going as should be, until we broke out at about 3200' and the runway was way off to our right, although the CDI on the his was centered. At that point, the first officer had realized he set in the VOR frequency for the localizer approach and we subsequently had flown the VOR radial on the approach. Luckily the VOR was farther away from the airport and all altitudes were descended to about 5 mi later than would have been on the localizer course. We also broke out of IMC and were able to proceed visually to land at that point. No abnormal descent was needed, only a modified turn to the final approach course to reintercept. This is the first time in 4500 hours I have ever shot an almost complete INS approach on the wrong navigation frequency. On looking back, we were both amazed we could have been so stupid and felt lucky no accident occurred. (On our 'course' there were 2 hills at 1400' and 1300' marked on the INS approach plate.) had dscnts to out altitudes not been delayed or had we not been able to break out.

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Original NASA ASRS Text

Title: AFTER FLT CREW BROKE OUT OF OVERCAST ON A LOCALIZER BACKCOURSE APCH THEY REALIZED THEY HAD MADE THE APCH ON THE VOR FREQ AND RADIAL.

Narrative: UPON LISTENING TO YKM ATIS, ATIS SAID ARPT WAS USING ILS APCH 27. IN OUR DSNT TO 9000' AND 30 NM FROM VOR, WE WERE SWITCHED TO YKM APCH CTL. TOLD TO EXPECT LOC/DME BACKCOURSE 09, ALTHOUGH WIND WAS 220 DEGS AT 6 KTS. AT THIS POINT THE F/O BEGAN GETTING SETUP FOR THE APCH, AND UPON CONTACTING YKM APCH 20 NM, WE WERE CLRED FOR THE LOC/DME BACKCOURSE 09. WE HAD TO JOIN A 16 DME ARC, WHICH AT THAT POS WAS THE IAF. COPLT INCORRECTLY INTERPRETED APCH PLATE AND WE SUBSEQUENTLY DSNDED THROUGH 7000' (TO 6500') BEFORE I REALIZED HE HAD MADE A MISTAKE. WE CLBED BACK TO PROPER ALT (7000') FOR THAT PORTION OF THE ARC. ALL OTHER PROCS WERE GOING AS SHOULD BE, UNTIL WE BROKE OUT AT ABOUT 3200' AND THE RWY WAS WAY OFF TO OUR RIGHT, ALTHOUGH THE CDI ON THE HIS WAS CENTERED. AT THAT POINT, THE F/O HAD REALIZED HE SET IN THE VOR FREQ FOR THE LOC APCH AND WE SUBSEQUENTLY HAD FLOWN THE VOR RADIAL ON THE APCH. LUCKILY THE VOR WAS FARTHER AWAY FROM THE ARPT AND ALL ALTS WERE DSNDED TO ABOUT 5 MI LATER THAN WOULD HAVE BEEN ON THE LOC COURSE. WE ALSO BROKE OUT OF IMC AND WERE ABLE TO PROCEED VISUALLY TO LAND AT THAT POINT. NO ABNORMAL DSNT WAS NEEDED, ONLY A MODIFIED TURN TO THE FINAL APCH COURSE TO REINTERCEPT. THIS IS THE FIRST TIME IN 4500 HRS I HAVE EVER SHOT AN ALMOST COMPLETE INS APCH ON THE WRONG NAV FREQ. ON LOOKING BACK, WE WERE BOTH AMAZED WE COULD HAVE BEEN SO STUPID AND FELT LUCKY NO ACCIDENT OCCURRED. (ON OUR 'COURSE' THERE WERE 2 HILLS AT 1400' AND 1300' MARKED ON THE INS APCH PLATE.) HAD DSCNTS TO OUT ALTS NOT BEEN DELAYED OR HAD WE NOT BEEN ABLE TO BREAK OUT.

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.