Narrative:

While being vectored for an approach to msp we experienced what I believe was severe wake turbulence. We were on an assigned heading at 11000 ft and assigned speed of 250 KTS. It started with maybe 5 seconds of steady but very light turbulence. I commented on the strange feel to the PNF. As I said that, the airplane rolled into a 90 degree bank to the right instantly. I disengaged the autoplt and recovered by hand flying the airplane. By the time the wings were level we had lost 700 ft of altitude. The PNF called approach control to tell him what had happened. The controller said that we were 8 mi in trail of a B757. I called both the tower and TRACON after landing and talked further with them. Given the speed of the B757 and our airplane (250 KTS) the controllers were surprised that the wake turbulence was so severe. They stated that usually that severe of turbulence is associated with slower speeds and the associated drag from flaps, etc. There was 1 passenger on board. There were no injuries to crew or passenger. Our passenger was scared but otherwise unharmed. Callback conversation with reporter revealed the following information: reporter states that his review with ATC brought added questions since the B757 was clean and at 250 KTS. Both aircraft were on radar vectors and on the exact same flight path and speeds. The in trail separation should have been ample to avoid such a wake turbulence encounter. Reporter was surprised when autoplt was disengaged that there was no control input already active. Inquiring of the manufacturer they learned that in extreme control changes the autoplt goes into a coast mode until it can determine if the extreme is a false input or not. The autoplt then responds with correct input. Reporter says you learn something new all the time. In his 23 yrs of flying he has never experienced anything as severe as this. The aircraft was a hawker 700.

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Original NASA ASRS Text

Title: FLC OF A HAWKER 700 EXPERIENCES SEVERE WAKE TURB 8 MI IN TRAIL OF A B757 ON STEPDOWN DSCNT VECTOR.

Narrative: WHILE BEING VECTORED FOR AN APCH TO MSP WE EXPERIENCED WHAT I BELIEVE WAS SEVERE WAKE TURB. WE WERE ON AN ASSIGNED HDG AT 11000 FT AND ASSIGNED SPD OF 250 KTS. IT STARTED WITH MAYBE 5 SECONDS OF STEADY BUT VERY LIGHT TURB. I COMMENTED ON THE STRANGE FEEL TO THE PNF. AS I SAID THAT, THE AIRPLANE ROLLED INTO A 90 DEG BANK TO THE R INSTANTLY. I DISENGAGED THE AUTOPLT AND RECOVERED BY HAND FLYING THE AIRPLANE. BY THE TIME THE WINGS WERE LEVEL WE HAD LOST 700 FT OF ALT. THE PNF CALLED APCH CTL TO TELL HIM WHAT HAD HAPPENED. THE CTLR SAID THAT WE WERE 8 MI IN TRAIL OF A B757. I CALLED BOTH THE TWR AND TRACON AFTER LNDG AND TALKED FURTHER WITH THEM. GIVEN THE SPD OF THE B757 AND OUR AIRPLANE (250 KTS) THE CTLRS WERE SURPRISED THAT THE WAKE TURB WAS SO SEVERE. THEY STATED THAT USUALLY THAT SEVERE OF TURB IS ASSOCIATED WITH SLOWER SPDS AND THE ASSOCIATED DRAG FROM FLAPS, ETC. THERE WAS 1 PAX ON BOARD. THERE WERE NO INJURIES TO CREW OR PAX. OUR PAX WAS SCARED BUT OTHERWISE UNHARMED. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: RPTR STATES THAT HIS REVIEW WITH ATC BROUGHT ADDED QUESTIONS SINCE THE B757 WAS CLEAN AND AT 250 KTS. BOTH ACFT WERE ON RADAR VECTORS AND ON THE EXACT SAME FLT PATH AND SPDS. THE IN TRAIL SEPARATION SHOULD HAVE BEEN AMPLE TO AVOID SUCH A WAKE TURB ENCOUNTER. RPTR WAS SURPRISED WHEN AUTOPLT WAS DISENGAGED THAT THERE WAS NO CTL INPUT ALREADY ACTIVE. INQUIRING OF THE MANUFACTURER THEY LEARNED THAT IN EXTREME CTL CHANGES THE AUTOPLT GOES INTO A COAST MODE UNTIL IT CAN DETERMINE IF THE EXTREME IS A FALSE INPUT OR NOT. THE AUTOPLT THEN RESPONDS WITH CORRECT INPUT. RPTR SAYS YOU LEARN SOMETHING NEW ALL THE TIME. IN HIS 23 YRS OF FLYING HE HAS NEVER EXPERIENCED ANYTHING AS SEVERE AS THIS. THE ACFT WAS A HAWKER 700.

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.