Narrative:

On final approach to runway 01 at sdf wind approximately 190 degrees at 20 KTS at the OM (claw) and 190 degrees at 08 KTS at 300 ft AGL. We were following another B757. At 300-400 ft and 1/2 DOT high (to compensate for possible wake turbulence) we encountered a slight indication of wake turbulence. At about 100 ft AGL the indication became a little more pronounced. At approximately 40 ft the aircraft made an uncommanded role to the left, and an increasing rate of descent. A go around was executed the aircraft contacted the ground became airborne, normal control was regained and the go around was completed without incident. An air carrier B727 following behind us also executed a go around due to wake turbulence. I was not able to ascertain the severity of his encounter. On our next approach we followed a DC8 with the atmospheric conditions approximately similar. At 300-400 ft we encountered similar wake turbulence indications and indicated a go around. We requested a landing on runway 29 or not to follow another heavy or B757. The request for runway 29 was denied but, we were vectored to follow a B727. The subsequent landing was uneventful. Callback conversation with reporter revealed the following information: reporter participated in the structured wake turbulence callback program. Reporter was following a B757 and flew a half a DOT high on the GS just to avoid any wake. He also planned to touchdown a little longer than usual just to avoid any wake close to the runway. There was a quartering tailwind that moved the wake farther down the runway. Reporter encountered wake 50 ft above the runway. The wake rolled the reporter's aircraft sharply to the left, to a 30 degree bank, dropped the pitch, and the aircraft struck the runway. Reporter immediately applied power and executed a go around. Making another approach behind a dc-8, the reporter encountered more light turbulence such as preceded their last encounter, so they executed another go around. After being vectored to follow a B-727 the next approach resulted in an uneventful landing. When the aircraft struck the runway, no damage to the aircraft resulted. However, it did affect the reporter in that every time he goes back into the same airport, it causes anxiety that is very disturbing to the reporter. He recalls the suddenness, sharpness, and loss of control that forced him to the runway. Reporter feels that landing with a tailwind moved the wake to a point that affects all aircraft trying to avoid any wake.

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Original NASA ASRS Text

Title: WAKE TURB ENCOUNTERED OVER RWY TOUCHDOWN ZONE.

Narrative: ON FINAL APCH TO RWY 01 AT SDF WIND APPROX 190 DEGS AT 20 KTS AT THE OM (CLAW) AND 190 DEGS AT 08 KTS AT 300 FT AGL. WE WERE FOLLOWING ANOTHER B757. AT 300-400 FT AND 1/2 DOT HIGH (TO COMPENSATE FOR POSSIBLE WAKE TURB) WE ENCOUNTERED A SLIGHT INDICATION OF WAKE TURB. AT ABOUT 100 FT AGL THE INDICATION BECAME A LITTLE MORE PRONOUNCED. AT APPROX 40 FT THE ACFT MADE AN UNCOMMANDED ROLE TO THE L, AND AN INCREASING RATE OF DSCNT. A GAR WAS EXECUTED THE ACFT CONTACTED THE GND BECAME AIRBORNE, NORMAL CTL WAS REGAINED AND THE GAR WAS COMPLETED WITHOUT INCIDENT. AN ACR B727 FOLLOWING BEHIND US ALSO EXECUTED A GAR DUE TO WAKE TURB. I WAS NOT ABLE TO ASCERTAIN THE SEVERITY OF HIS ENCOUNTER. ON OUR NEXT APCH WE FOLLOWED A DC8 WITH THE ATMOSPHERIC CONDITIONS APPROX SIMILAR. AT 300-400 FT WE ENCOUNTERED SIMILAR WAKE TURB INDICATIONS AND INDICATED A GAR. WE REQUESTED A LNDG ON RWY 29 OR NOT TO FOLLOW ANOTHER HVY OR B757. THE REQUEST FOR RWY 29 WAS DENIED BUT, WE WERE VECTORED TO FOLLOW A B727. THE SUBSEQUENT LNDG WAS UNEVENTFUL. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: RPTR PARTICIPATED IN THE STRUCTURED WAKE TURB CALLBACK PROGRAM. RPTR WAS FOLLOWING A B757 AND FLEW A HALF A DOT HIGH ON THE GS JUST TO AVOID ANY WAKE. HE ALSO PLANNED TO TOUCHDOWN A LITTLE LONGER THAN USUAL JUST TO AVOID ANY WAKE CLOSE TO THE RWY. THERE WAS A QUARTERING TAILWIND THAT MOVED THE WAKE FARTHER DOWN THE RWY. RPTR ENCOUNTERED WAKE 50 FT ABOVE THE RWY. THE WAKE ROLLED THE RPTR'S ACFT SHARPLY TO THE L, TO A 30 DEG BANK, DROPPED THE PITCH, AND THE ACFT STRUCK THE RWY. RPTR IMMEDIATELY APPLIED PWR AND EXECUTED A GAR. MAKING ANOTHER APCH BEHIND A DC-8, THE RPTR ENCOUNTERED MORE LIGHT TURB SUCH AS PRECEDED THEIR LAST ENCOUNTER, SO THEY EXECUTED ANOTHER GAR. AFTER BEING VECTORED TO FOLLOW A B-727 THE NEXT APCH RESULTED IN AN UNEVENTFUL LNDG. WHEN THE ACFT STRUCK THE RWY, NO DAMAGE TO THE ACFT RESULTED. HOWEVER, IT DID AFFECT THE RPTR IN THAT EVERY TIME HE GOES BACK INTO THE SAME ARPT, IT CAUSES ANXIETY THAT IS VERY DISTURBING TO THE RPTR. HE RECALLS THE SUDDENNESS, SHARPNESS, AND LOSS OF CTL THAT FORCED HIM TO THE RWY. RPTR FEELS THAT LNDG WITH A TAILWIND MOVED THE WAKE TO A POINT THAT AFFECTS ALL ACFT TRYING TO AVOID ANY WAKE.

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.