Narrative:

I issued aircraft Y an approach clearance. When he did not read it back; I sought confirmation of the clearance from the pilot. He acknowledged the clearance but never began the descent. I took evasive action with aircraft X to maintain separation. Upon reviewing the tapes; it became apparent that aircraft Y never read back the descent portion of the clearance.

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Original NASA ASRS Text

Title: ZMA CTLR EXPERIENCED OPERROR AT 3000 FT WHEN INCOMPLETE READBACK WAS NOT RECOGNIZED.

Narrative: I ISSUED ACFT Y AN APCH CLRNC. WHEN HE DID NOT READ IT BACK; I SOUGHT CONFIRMATION OF THE CLRNC FROM THE PLT. HE ACKNOWLEDGED THE CLRNC BUT NEVER BEGAN THE DSCNT. I TOOK EVASIVE ACTION WITH ACFT X TO MAINTAIN SEPARATION. UPON REVIEWING THE TAPES; IT BECAME APPARENT THAT ACFT Y NEVER READ BACK THE DSCNT PORTION OF THE CLRNC.

Data retrieved from NASA's ASRS site as of January 2009 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.