Narrative:

I was hand-flying visual approach to runway 17C at dfw at night with good WX with a computer wind on navigation display showing a left quartering tailwind of around 010/09 KTS at 3000 ft. Approach asked us our ground speed numerous times and kept slowing us and said winds were real weird that night. We were following traffic about 4 mi ahead. We were cleared for approach and went to tower. Tower cleared us to land, and surface winds were reported light out of the south. Approach was smooth with no turbulence. At about 300 ft AGL, aircraft began an uncommanded roll to the right. I tried to compensate, but roll continued. Aircraft then began to snap back in the other direction. It felt like a classic wake vortex roll. I immediately applied go around power and climbed out of the wake. We went straight ahead, climbed out, and returned for another approach. Approach asked us if we would then land behind a B757 on runway 17C and we politely said no thanks. We took runway 17L and landed normally. We do not know if the traffic we were following originally was an S80 or a B757 -- but an uncommanded roll at 200-300 ft, it didn't really make any difference -- a go around was the only option. I will certainly take heed when approach and tower are reporting so called weird winds, even though surface winds are light and seemingly benign. We never were below the GS. So where these vortices came from, I will never know.

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Original NASA ASRS Text

Title: AN AIRLINE FOKKER F100 CREW HIT WAKE TURB, OF UNKNOWN ORIGIN, WHILE ON SHORT FINAL APCH. THE CREW PERFORMED A GAR THEN RETURNED FOR A SUCCESSFUL LNDG.

Narrative: I WAS HAND-FLYING VISUAL APCH TO RWY 17C AT DFW AT NIGHT WITH GOOD WX WITH A COMPUTER WIND ON NAV DISPLAY SHOWING A L QUARTERING TAILWIND OF AROUND 010/09 KTS AT 3000 FT. APCH ASKED US OUR GND SPD NUMEROUS TIMES AND KEPT SLOWING US AND SAID WINDS WERE REAL WEIRD THAT NIGHT. WE WERE FOLLOWING TFC ABOUT 4 MI AHEAD. WE WERE CLRED FOR APCH AND WENT TO TWR. TWR CLRED US TO LAND, AND SURFACE WINDS WERE RPTED LIGHT OUT OF THE S. APCH WAS SMOOTH WITH NO TURB. AT ABOUT 300 FT AGL, ACFT BEGAN AN UNCOMMANDED ROLL TO THE R. I TRIED TO COMPENSATE, BUT ROLL CONTINUED. ACFT THEN BEGAN TO SNAP BACK IN THE OTHER DIRECTION. IT FELT LIKE A CLASSIC WAKE VORTEX ROLL. I IMMEDIATELY APPLIED GAR PWR AND CLBED OUT OF THE WAKE. WE WENT STRAIGHT AHEAD, CLBED OUT, AND RETURNED FOR ANOTHER APCH. APCH ASKED US IF WE WOULD THEN LAND BEHIND A B757 ON RWY 17C AND WE POLITELY SAID NO THANKS. WE TOOK RWY 17L AND LANDED NORMALLY. WE DO NOT KNOW IF THE TFC WE WERE FOLLOWING ORIGINALLY WAS AN S80 OR A B757 -- BUT AN UNCOMMANDED ROLL AT 200-300 FT, IT DIDN'T REALLY MAKE ANY DIFFERENCE -- A GAR WAS THE ONLY OPTION. I WILL CERTAINLY TAKE HEED WHEN APCH AND TWR ARE RPTING SO CALLED WEIRD WINDS, EVEN THOUGH SURFACE WINDS ARE LIGHT AND SEEMINGLY BENIGN. WE NEVER WERE BELOW THE GS. SO WHERE THESE VORTICES CAME FROM, I WILL NEVER KNOW.

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.