Narrative:

While being vectored for a localizer approach to knoxville downtown island I thought I heard the controller issue a descent clearance to us to descend from 4000 to 3100' MSL. I read the clearance back (my copilot heard me), received no response and started to descend. As we descended out of the clouds we observed 3 large radio towers 1 mi off our right wing. Approach called and told us we should be at 4000'. I told him I heard a clearance to 3100' and read it back. We requested a visibility as we were VFR and landed west/O further incident. When the controller talked to us he did so hurriedly. Although our assigned frequency was quiet I feel that he was working other positions and did not hear me read back the descent clearance to 3100', which was probably for another aircraft due to his working other frequencys. What did you say about hearback?

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Original NASA ASRS Text

Title: CPR SMT ACCEPTED A CLRNC TO DESCEND BELOW THE INTERCEPT ALT FOR LOCALIZER APCH INTO DKX. CTLR SAID THE CLRNC WAS FOR ANOTHER ACFT.

Narrative: WHILE BEING VECTORED FOR A LOC APCH TO KNOXVILLE DOWNTOWN ISLAND I THOUGHT I HEARD THE CTLR ISSUE A DESCENT CLRNC TO US TO DSND FROM 4000 TO 3100' MSL. I READ THE CLRNC BACK (MY COPLT HEARD ME), RECEIVED NO RESPONSE AND STARTED TO DSND. AS WE DSNDED OUT OF THE CLOUDS WE OBSERVED 3 LARGE RADIO TWRS 1 MI OFF OUR RIGHT WING. APCH CALLED AND TOLD US WE SHOULD BE AT 4000'. I TOLD HIM I HEARD A CLRNC TO 3100' AND READ IT BACK. WE REQUESTED A VIS AS WE WERE VFR AND LANDED W/O FURTHER INCIDENT. WHEN THE CTLR TALKED TO US HE DID SO HURRIEDLY. ALTHOUGH OUR ASSIGNED FREQ WAS QUIET I FEEL THAT HE WAS WORKING OTHER POSITIONS AND DID NOT HEAR ME READ BACK THE DSCNT CLRNC TO 3100', WHICH WAS PROBABLY FOR ANOTHER ACFT DUE TO HIS WORKING OTHER FREQS. WHAT DID YOU SAY ABOUT HEARBACK?

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.