Narrative:

On a visual approach to msp, we were being vectored off the localizer at 4000 ft for spacing on traffic ahead. While on a 310 degree heading and level at 4000 ft we encountered the wake of a 757 ahead. The aircraft rolled violently to left (approximately 120 degree bank) and entered a rapid descent. The aircraft was completely out of control for several seconds. We regained control at approximately 2500 ft MSL (1700 ft AGL) and advised ATC of our encounter. We climbed and took a few mins to clean up the cockpit. In this violent nature of this upset, various objects became flying objects. My flight bag (between the seats) flew up and tipped upside down and landed on the floor. A metal 'can' for maintenance forms hit me in the head as did an 8 1/2 inch by 11 inch folder used for the deferral log documentation. In the cabin, the wingspar cover came off and hit the rear bulkhead. Fortunately, no injuries were sustained by either crew or passenger. After reporting incident to management a radar trace was obtained. At the time of our visual approach clearance, we were only 3 1/2 mi behind the 757 and were 1000 ft below and downwind of the 757's flight path. We were vectored below, downwind and behind the 757. Several problems are involved here. Turboprops can routinely descend faster and easier than jets, yet we are always below the jets on arrival procedures and approach. Metal objects and other potential projectiles should be secured in both cockpit and cabin and finally ATC needs to be more aware of wake turbulence. Had this been an IMC encounter, I firmly believe the outcome would have been disastrous (our aircraft was a BA3100 jetstream). At the point of encounter, we were almost exactly 2 mins behind the 757, 1000 ft below his flight path at the same position relative to runway. Aircraft rolled violently left so we must have entered his right wingtip vortex. Radar trace showed a distance of 3 1/2 - 4 mi between us and at time of visual approach clearance we were 3 1/2 mi behind. Callback conversation with reporter revealed the following information: reporter further stated that the turbulence started lightly. In his words, 'like light chop.' as the aircraft began to roll the flight crew applied opposite aileron to the roll, as the roll increased to 120 degrees, full aileron was held in place to oppose the roll, but the full deflection of aileron did nothing to dampen or stop the roll, after the roll reached the 120 degree point the flight controls began to regain control and roll the aircraft back upright. Altitude loss during this event was 600 ft. The whole event from first signs of turbulence to recovering back to level flight is estimated to be from 6-10 seconds. Reporter felt there was an excellent chance they would strike the ground.

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Original NASA ASRS Text

Title: WAKE TURB BEHIND A B757.

Narrative: ON A VISUAL APCH TO MSP, WE WERE BEING VECTORED OFF THE LOC AT 4000 FT FOR SPACING ON TFC AHEAD. WHILE ON A 310 DEG HDG AND LEVEL AT 4000 FT WE ENCOUNTERED THE WAKE OF A 757 AHEAD. THE ACFT ROLLED VIOLENTLY TO L (APPROX 120 DEG BANK) AND ENTERED A RAPID DSCNT. THE ACFT WAS COMPLETELY OUT OF CTL FOR SEVERAL SECONDS. WE REGAINED CTL AT APPROX 2500 FT MSL (1700 FT AGL) AND ADVISED ATC OF OUR ENCOUNTER. WE CLBED AND TOOK A FEW MINS TO CLEAN UP THE COCKPIT. IN THIS VIOLENT NATURE OF THIS UPSET, VARIOUS OBJECTS BECAME FLYING OBJECTS. MY FLT BAG (BTWN THE SEATS) FLEW UP AND TIPPED UPSIDE DOWN AND LANDED ON THE FLOOR. A METAL 'CAN' FOR MAINT FORMS HIT ME IN THE HEAD AS DID AN 8 1/2 INCH BY 11 INCH FOLDER USED FOR THE DEFERRAL LOG DOCUMENTATION. IN THE CABIN, THE WINGSPAR COVER CAME OFF AND HIT THE REAR BULKHEAD. FORTUNATELY, NO INJURIES WERE SUSTAINED BY EITHER CREW OR PAX. AFTER RPTING INCIDENT TO MGMNT A RADAR TRACE WAS OBTAINED. AT THE TIME OF OUR VISUAL APCH CLRNC, WE WERE ONLY 3 1/2 MI BEHIND THE 757 AND WERE 1000 FT BELOW AND DOWNWIND OF THE 757'S FLT PATH. WE WERE VECTORED BELOW, DOWNWIND AND BEHIND THE 757. SEVERAL PROBS ARE INVOLVED HERE. TURBOPROPS CAN ROUTINELY DSND FASTER AND EASIER THAN JETS, YET WE ARE ALWAYS BELOW THE JETS ON ARR PROCS AND APCH. METAL OBJECTS AND OTHER POTENTIAL PROJECTILES SHOULD BE SECURED IN BOTH COCKPIT AND CABIN AND FINALLY ATC NEEDS TO BE MORE AWARE OF WAKE TURB. HAD THIS BEEN AN IMC ENCOUNTER, I FIRMLY BELIEVE THE OUTCOME WOULD HAVE BEEN DISASTROUS (OUR ACFT WAS A BA3100 JETSTREAM). AT THE POINT OF ENCOUNTER, WE WERE ALMOST EXACTLY 2 MINS BEHIND THE 757, 1000 FT BELOW HIS FLT PATH AT THE SAME POS RELATIVE TO RWY. ACFT ROLLED VIOLENTLY L SO WE MUST HAVE ENTERED HIS R WINGTIP VORTEX. RADAR TRACE SHOWED A DISTANCE OF 3 1/2 - 4 MI BTWN US AND AT TIME OF VISUAL APCH CLRNC WE WERE 3 1/2 MI BEHIND. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: RPTR FURTHER STATED THAT THE TURB STARTED LIGHTLY. IN HIS WORDS, 'LIKE LIGHT CHOP.' AS THE ACFT BEGAN TO ROLL THE FLC APPLIED OPPOSITE AILERON TO THE ROLL, AS THE ROLL INCREASED TO 120 DEGS, FULL AILERON WAS HELD IN PLACE TO OPPOSE THE ROLL, BUT THE FULL DEFLECTION OF AILERON DID NOTHING TO DAMPEN OR STOP THE ROLL, AFTER THE ROLL REACHED THE 120 DEG POINT THE FLT CTLS BEGAN TO REGAIN CTL AND ROLL THE ACFT BACK UPRIGHT. ALT LOSS DURING THIS EVENT WAS 600 FT. THE WHOLE EVENT FROM FIRST SIGNS OF TURB TO RECOVERING BACK TO LEVEL FLT IS ESTIMATED TO BE FROM 6-10 SECONDS. RPTR FELT THERE WAS AN EXCELLENT CHANCE THEY WOULD STRIKE THE GND.

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.