Narrative:

While working the final position at tpa I noticed two erroneous mode C readouts. The first one was on air carrier X on the tpa 002/7.69. I observed the mode C to be 999 for 1 sweep and then the aircraft went into CST for 1 sweep. The aircraft was in a descent when this occurred. This aircraft was around 3000 ft descending when this occurred. The second occurrence was with air carrier Y on the tpa 018/15.19 descending through 6000 ft. This aircraft was observed to be in a CST status for 2 sweeps.

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Original NASA ASRS Text

Title: MODE C READOUT ON AN ACR GOES TO 999 FOR ONE SWEEP OF THE RADAR ANTENNA, AND ANOTHER TARGET ON AN ACR GOES INTO COAST STATUS FOR TWO SWEEPS.

Narrative: WHILE WORKING THE FINAL POS AT TPA I NOTICED TWO ERRONEOUS MODE C READOUTS. THE FIRST ONE WAS ON ACR X ON THE TPA 002/7.69. I OBSERVED THE MODE C TO BE 999 FOR 1 SWEEP AND THEN THE ACFT WENT INTO CST FOR 1 SWEEP. THE ACFT WAS IN A DSCNT WHEN THIS OCCURRED. THIS ACFT WAS AROUND 3000 FT DSNDING WHEN THIS OCCURRED. THE SECOND OCCURRENCE WAS WITH ACR Y ON THE TPA 018/15.19 DSNDING THROUGH 6000 FT. THIS ACFT WAS OBSERVED TO BE IN A CST STATUS FOR 2 SWEEPS.

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.