Narrative:

At about 1500 ft AGL on final for runway 35R at dfw we encountered severe wake turbulence from a B757 4-5 mi ahead of us. We had an immediate loss of approximately 30-40 KTS and a left roll of about 60 degrees. We also got the stick shaker at this point. I had to unload the jet and use right rudder to get us back upright while executing a go around. Winds were particularly calm and the B757 had made a high steep approach in front of us. Our speed was approximately 145 KTS and decreased to about 120 KTS and then back to 165 after unloading. We made an uneventful go around and landing. Also of interest one of the flight attendants had delayed taking her seat and ended up on the lap of a passenger while walking the isle. Suggest a reminder to flight attendants about sitting down promptly after the prepare for landing PA would be helpful. Finally a deadheading first officer reported that he saw the wingtip pointing at the ground during the event. Callback conversation with reporter revealed the following information: the reporter was flying a fokker F10 behind a company B757-200 in calm wind conditions. The aircraft wind readout was 0/0 and the flight crew commented on this unusual condition as they entered the pattern at dfw. The captain first saw the B757 as both aircraft rolled out on parallel base legs. The F10 was about 10 mi from touchdown and the B757 was about 5 mi inside of him. The controller gave the flight crew the standard wake turbulence caution, but the crew realized that due to the high, close-in situation of the B757 that he would be making an above the GS approach, at least initially. The captain said that he also stayed above the GS initially, but as he approached the runway he began to close on to the GS. At the time of the encounter he was about 1/3 to 1/2 a DOT high. There were no nibbles or any other normal warnings before the event. At onset the aircraft rolled to the left very rapidly to about 30 degrees even though he had full aileron input to the right. After the craft finally rolled upright there was another left roll to about 60 degrees with full aileron input and this recovery was managed using full right aileron and almost full right rudder. The reporter said that his aerobatic training helped him survive this encounter. He also said that non-trained pilots do not appear to understand the requirement for rapid correct flight control inputs in this situation. As it were the pilot does not think that he would have been successful if he had been at a lower altitude such as over the approach lights.

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Original NASA ASRS Text

Title: ACR F10 ENCOUNTERS THE WAKE OF A PRECEDING B757 AND HAS 2 UNCOMMANDED ROLLS WITH ACTIVATION OF THE STALL WARNING BOTH TIMES.

Narrative: AT ABOUT 1500 FT AGL ON FINAL FOR RWY 35R AT DFW WE ENCOUNTERED SEVERE WAKE TURB FROM A B757 4-5 MI AHEAD OF US. WE HAD AN IMMEDIATE LOSS OF APPROX 30-40 KTS AND A L ROLL OF ABOUT 60 DEGS. WE ALSO GOT THE STICK SHAKER AT THIS POINT. I HAD TO UNLOAD THE JET AND USE R RUDDER TO GET US BACK UPRIGHT WHILE EXECUTING A GAR. WINDS WERE PARTICULARLY CALM AND THE B757 HAD MADE A HIGH STEEP APCH IN FRONT OF US. OUR SPD WAS APPROX 145 KTS AND DECREASED TO ABOUT 120 KTS AND THEN BACK TO 165 AFTER UNLOADING. WE MADE AN UNEVENTFUL GAR AND LNDG. ALSO OF INTEREST ONE OF THE FLT ATTENDANTS HAD DELAYED TAKING HER SEAT AND ENDED UP ON THE LAP OF A PAX WHILE WALKING THE ISLE. SUGGEST A REMINDER TO FLT ATTENDANTS ABOUT SITTING DOWN PROMPTLY AFTER THE PREPARE FOR LNDG PA WOULD BE HELPFUL. FINALLY A DEADHEADING FO RPTED THAT HE SAW THE WINGTIP POINTING AT THE GND DURING THE EVENT. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: THE RPTR WAS FLYING A FOKKER F10 BEHIND A COMPANY B757-200 IN CALM WIND CONDITIONS. THE ACFT WIND READOUT WAS 0/0 AND THE FLC COMMENTED ON THIS UNUSUAL CONDITION AS THEY ENTERED THE PATTERN AT DFW. THE CAPT FIRST SAW THE B757 AS BOTH ACFT ROLLED OUT ON PARALLEL BASE LEGS. THE F10 WAS ABOUT 10 MI FROM TOUCHDOWN AND THE B757 WAS ABOUT 5 MI INSIDE OF HIM. THE CTLR GAVE THE FLC THE STANDARD WAKE TURB CAUTION, BUT THE CREW REALIZED THAT DUE TO THE HIGH, CLOSE-IN SIT OF THE B757 THAT HE WOULD BE MAKING AN ABOVE THE GS APCH, AT LEAST INITIALLY. THE CAPT SAID THAT HE ALSO STAYED ABOVE THE GS INITIALLY, BUT AS HE APCHED THE RWY HE BEGAN TO CLOSE ON TO THE GS. AT THE TIME OF THE ENCOUNTER HE WAS ABOUT 1/3 TO 1/2 A DOT HIGH. THERE WERE NO NIBBLES OR ANY OTHER NORMAL WARNINGS BEFORE THE EVENT. AT ONSET THE ACFT ROLLED TO THE L VERY RAPIDLY TO ABOUT 30 DEGS EVEN THOUGH HE HAD FULL AILERON INPUT TO THE R. AFTER THE CRAFT FINALLY ROLLED UPRIGHT THERE WAS ANOTHER L ROLL TO ABOUT 60 DEGS WITH FULL AILERON INPUT AND THIS RECOVERY WAS MANAGED USING FULL R AILERON AND ALMOST FULL R RUDDER. THE RPTR SAID THAT HIS AEROBATIC TRAINING HELPED HIM SURVIVE THIS ENCOUNTER. HE ALSO SAID THAT NON-TRAINED PLTS DO NOT APPEAR TO UNDERSTAND THE REQUIREMENT FOR RAPID CORRECT FLT CTL INPUTS IN THIS SIT. AS IT WERE THE PLT DOES NOT THINK THAT HE WOULD HAVE BEEN SUCCESSFUL IF HE HAD BEEN AT A LOWER ALT SUCH AS OVER THE APCH LIGHTS.

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.