Narrative:

We were cruising down J174 at 2400. TCASII issued a TA and displayed a target at 11-12 O'clock and about 8 mi. We were IMC at the time and could not visually identify the target. Then TCASII issued a descend command. It was now a RA and the target was coming straight at us and only 300 ft above us. We descended to 23500, asked ATC if he had traffic for us at 12 O'clock. ATC said there was no one there and TCASII issued a clear of conflict so we went back up to 24000. We later called center when we reached rdu. Talked to the supervisor who said they saw no traffic and that it was a phantom target most likely! I'll tell you what...it sure looked real to me!

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Original NASA ASRS Text

Title: FLC OF MLG AT FL240 HAD TCASII RA INTRUDER DEAD AHEAD 300 FT ABOVE. EVASIVE ACTION TO FL235 CLRED RA. CENTER ADVISED NO TFC.

Narrative: WE WERE CRUISING DOWN J174 AT 2400. TCASII ISSUED A TA AND DISPLAYED A TARGET AT 11-12 O'CLOCK AND ABOUT 8 MI. WE WERE IMC AT THE TIME AND COULD NOT VISUALLY IDENT THE TARGET. THEN TCASII ISSUED A DSND COMMAND. IT WAS NOW A RA AND THE TARGET WAS COMING STRAIGHT AT US AND ONLY 300 FT ABOVE US. WE DSNDED TO 23500, ASKED ATC IF HE HAD TFC FOR US AT 12 O'CLOCK. ATC SAID THERE WAS NO ONE THERE AND TCASII ISSUED A CLR OF CONFLICT SO WE WENT BACK UP TO 24000. WE LATER CALLED CENTER WHEN WE REACHED RDU. TALKED TO THE SUPVR WHO SAID THEY SAW NO TFC AND THAT IT WAS A PHANTOM TARGET MOST LIKELY! I'LL TELL YOU WHAT...IT SURE LOOKED REAL TO ME!

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.