Narrative:

Inbound to clt on unarm arrival. Expect ILS 18R. Both navigation radios on clt VOR at approximately 4 DME told to fly heading for vector to ILS backcourse runway 23. Copilot flying. He set 053 and ILS frequency. After crossing the airfield (we could see it through broken deck as ceiling and visibility were better than reported), there were thunderstorms north through south on the east side of clt; however, none in the approach sector. Unknown to me, the copilot switched from the backcourse frequency back to the or (he said later to keep his relationship and distance to the field), even though I was on the VOR for DME. He did this while I was looking out for traffic and building cumulus. We were turned south to intercept the backcourse and cleared for the approach; 2300' till lecar (7.1 DME clt). When inbound at 2300' approach said they showed us left of course. I looked at coplts display and he showed on course. I told approach we showed 'on' still, not realizing copilot had switched frequency to VOR and wasn't on localizer frequency. Copilot started down out of 2300' at what he thought was lecar intersection. I was still looking out for traffic and we were VMC. Approach called us and said they showed us left of course and below our altitude outside lecar. I said we showed past lecar and on course. I looked back outside and saw the field to our right front and told approach we had the field. I looked down then and realized copilot did not have localizer frequency tuned anymore.

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Original NASA ASRS Text

Title: ACR MLG MADE LOCALIZER BACK COURSE APCH WITH NAVIGATION RADIO TUNED TO VOR FREQ.

Narrative: INBND TO CLT ON UNARM ARR. EXPECT ILS 18R. BOTH NAV RADIOS ON CLT VOR AT APPROX 4 DME TOLD TO FLY HDG FOR VECTOR TO ILS BACKCOURSE RWY 23. COPLT FLYING. HE SET 053 AND ILS FREQ. AFTER XING THE AIRFIELD (WE COULD SEE IT THROUGH BROKEN DECK AS CEILING AND VISIBILITY WERE BETTER THAN RPTED), THERE WERE TSTMS N THROUGH S ON THE E SIDE OF CLT; HOWEVER, NONE IN THE APCH SECTOR. UNKNOWN TO ME, THE COPLT SWITCHED FROM THE BACKCOURSE FREQ BACK TO THE OR (HE SAID LATER TO KEEP HIS RELATIONSHIP AND DISTANCE TO THE FIELD), EVEN THOUGH I WAS ON THE VOR FOR DME. HE DID THIS WHILE I WAS LOOKING OUT FOR TFC AND BUILDING CUMULUS. WE WERE TURNED S TO INTERCEPT THE BACKCOURSE AND CLRED FOR THE APCH; 2300' TILL LECAR (7.1 DME CLT). WHEN INBND AT 2300' APCH SAID THEY SHOWED US LEFT OF COURSE. I LOOKED AT COPLTS DISPLAY AND HE SHOWED ON COURSE. I TOLD APCH WE SHOWED 'ON' STILL, NOT REALIZING COPLT HAD SWITCHED FREQ TO VOR AND WASN'T ON LOC FREQ. COPLT STARTED DOWN OUT OF 2300' AT WHAT HE THOUGHT WAS LECAR INTXN. I WAS STILL LOOKING OUT FOR TFC AND WE WERE VMC. APCH CALLED US AND SAID THEY SHOWED US LEFT OF COURSE AND BELOW OUR ALT OUTSIDE LECAR. I SAID WE SHOWED PAST LECAR AND ON COURSE. I LOOKED BACK OUTSIDE AND SAW THE FIELD TO OUR RIGHT FRONT AND TOLD APCH WE HAD THE FIELD. I LOOKED DOWN THEN AND REALIZED COPLT DID NOT HAVE LOC FREQ TUNED ANYMORE.

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.