Narrative:

Den TRACON cleared my aircraft for a visual approach to runway 35R to follow a B757 turning right base to final -- also on a visual approach. Our separation from the B757 was 6 mi as reported by the approach controller. I briefed my copilot regarding my intentions to avoid the vortices of the B757 -- we would maintain a glide path at least 1 DOT above the GS and fly an airspeed of vref plus 15 KTS. After the briefing, approach control issued instructions for me to maintain an airspeed of 180 KTS to the OM. I complied with the instruction and observed the B757 fly what appeared to be a visual approach that was on the GS. His touchdown point on the runway was between the 1000 ft and 1500 ft markers. I continued my approach and maintained a flight path 1-2 dots above the GS. At approximately 350 ft AGL, my aircraft encountered the wake vortices of the B757. 3 rapid full aileron deflections were made (r-l-right) to regain control of my aircraft. This action was followed by an immediate missed approach with an uneventful landing made on runway 26. Den tower reported wind was 170 degrees at 5 KTS when we reported in on the visual approach to runway 35R. Callback conversation with reporter revealed the following information: callback in conjunction with wake turbulence incident callback questionnaire. Reporter says the most significant cause of the wake turbulence encounter was the ATC instructions to maintain 180 KTS to the marker. Initially, the separation from the B757 was 6 mi, but when it slowed at the marker and reporter was holding 180 KTS, the separation rapidly decreased to within reporter estimated 3 mi when encounter occurred. Reporter also thinks the tailwind causes an aberration in the dissipation of vortices and that the tailwind may tend to keep the vortices at altitude longer rather than dissipate downward. He says that in the future he will be very wary of following a B757 on approach and would definitely not accept a higher approach speed when behind a 757.

Related reports:

Google
 

Original NASA ASRS Text

Title: WAKE TURB ON APCH BEHIND B757.

Narrative: DEN TRACON CLRED MY ACFT FOR A VISUAL APCH TO RWY 35R TO FOLLOW A B757 TURNING R BASE TO FINAL -- ALSO ON A VISUAL APCH. OUR SEPARATION FROM THE B757 WAS 6 MI AS RPTED BY THE APCH CTLR. I BRIEFED MY COPLT REGARDING MY INTENTIONS TO AVOID THE VORTICES OF THE B757 -- WE WOULD MAINTAIN A GLIDE PATH AT LEAST 1 DOT ABOVE THE GS AND FLY AN AIRSPD OF VREF PLUS 15 KTS. AFTER THE BRIEFING, APCH CTL ISSUED INSTRUCTIONS FOR ME TO MAINTAIN AN AIRSPD OF 180 KTS TO THE OM. I COMPLIED WITH THE INSTRUCTION AND OBSERVED THE B757 FLY WHAT APPEARED TO BE A VISUAL APCH THAT WAS ON THE GS. HIS TOUCHDOWN POINT ON THE RWY WAS BTWN THE 1000 FT AND 1500 FT MARKERS. I CONTINUED MY APCH AND MAINTAINED A FLT PATH 1-2 DOTS ABOVE THE GS. AT APPROX 350 FT AGL, MY ACFT ENCOUNTERED THE WAKE VORTICES OF THE B757. 3 RAPID FULL AILERON DEFLECTIONS WERE MADE (R-L-R) TO REGAIN CTL OF MY ACFT. THIS ACTION WAS FOLLOWED BY AN IMMEDIATE MISSED APCH WITH AN UNEVENTFUL LNDG MADE ON RWY 26. DEN TWR RPTED WIND WAS 170 DEGS AT 5 KTS WHEN WE RPTED IN ON THE VISUAL APCH TO RWY 35R. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: CALLBACK IN CONJUNCTION WITH WAKE TURB INCIDENT CALLBACK QUESTIONNAIRE. RPTR SAYS THE MOST SIGNIFICANT CAUSE OF THE WAKE TURB ENCOUNTER WAS THE ATC INSTRUCTIONS TO MAINTAIN 180 KTS TO THE MARKER. INITIALLY, THE SEPARATION FROM THE B757 WAS 6 MI, BUT WHEN IT SLOWED AT THE MARKER AND RPTR WAS HOLDING 180 KTS, THE SEPARATION RAPIDLY DECREASED TO WITHIN RPTR ESTIMATED 3 MI WHEN ENCOUNTER OCCURRED. RPTR ALSO THINKS THE TAILWIND CAUSES AN ABERRATION IN THE DISSIPATION OF VORTICES AND THAT THE TAILWIND MAY TEND TO KEEP THE VORTICES AT ALT LONGER RATHER THAN DISSIPATE DOWNWARD. HE SAYS THAT IN THE FUTURE HE WILL BE VERY WARY OF FOLLOWING A B757 ON APCH AND WOULD DEFINITELY NOT ACCEPT A HIGHER APCH SPD WHEN BEHIND A 757.

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.