Narrative:

I was pilot of an LR45 landing at stp runway 32 ILS in VMC conditions. About 1/2 way down the GS we noticed a seaplane paralleling our course. Suddenly he turned 90 degrees towards us and crossed the final approach course approximately 1000 ft horizontally and 200-300 ft under us. We experienced an RA advising check descent. We leveled off momentarily and avoided him. Tower at stp says they were not talking to him; but would try to see if approach control could track him. If there are issues with seaplanes on the river; someone should fix the problem.

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Original NASA ASRS Text

Title: LR45 PLT WITH LCL CTLR EXPERIENCED TCAS RA WITH UNRPTED TFC WHILE ON ILS TO STP.

Narrative: I WAS PLT OF AN LR45 LNDG AT STP RWY 32 ILS IN VMC CONDITIONS. ABOUT 1/2 WAY DOWN THE GS WE NOTICED A SEAPLANE PARALLELING OUR COURSE. SUDDENLY HE TURNED 90 DEGS TOWARDS US AND CROSSED THE FINAL APCH COURSE APPROX 1000 FT HORIZLY AND 200-300 FT UNDER US. WE EXPERIENCED AN RA ADVISING CHK DSCNT. WE LEVELED OFF MOMENTARILY AND AVOIDED HIM. TWR AT STP SAYS THEY WERE NOT TALKING TO HIM; BUT WOULD TRY TO SEE IF APCH CTL COULD TRACK HIM. IF THERE ARE ISSUES WITH SEAPLANES ON THE RIVER; SOMEONE SHOULD FIX THE PROB.

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.