Narrative:

I was inbound to runway 10 at stt from the south. I had been given radar vectors to be sequenced behind a B757; who was inbound from the north. As I was receiving vectors at 1500ft that took me slightly north of the localizer (and slightly downwind of the jet's position); the jet was on the localizer ahead of me; coming through my altitude on the glideslope. The sju approach controller advised 'caution wake turbulence' and had me switch over to tower. At this point I am below and a little downwind of the jet; and behind by what I'd estimate to be about 3-4 miles. I decided to go to in-range power at this point to put a little more distance between me and the B757. I would much rather be above the wake than below it; but I knew in order to safely get above it; I'd have to get upwind of it (right and south of localizer course). As I started to make my way to that side of the course; I felt a sharp shake of the airplane and then a quick snap roll to the left; close to 90 degrees of bank. I regained control of the airplane and brought it back to level flight using aileron and rudder. I checked all gauges and looked around the visible surfaces of the airplane and noted everything was working the way it should. I turned around and gave the 6 passengers a questionary 'thumbs up' and received thumbs up back. I turned back around and continued to fly. The plane did not fly any differently after this event; so I continued the VFR approach; 2 dots above the glideslope until I landed without incident. Upon arriving at the gate and after shutdown; I asked all the passengers if they were ok and apologized for the event. Everyone seemed fine and I only received one question asking what that big bump was. I explained in simple terms what happened and everyone proceeded to deplane. I take full responsibility for this wake turbulence event. Even though ATC vectored me below and downwind of the B757; it is my responsibility as PIC to avoid wake turbulence. I should have either asked for an avoidance deviation or just deviated and explained later. Visualizing where you think the wake is either drifting or not drifting (based on winds) to is also important.

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Original NASA ASRS Text

Title: C402C Pilot reported encountering wake turbulence that resulted in a 90 degree bank on approach to STT in trail of a B757.

Narrative: I was inbound to RWY 10 at STT from the south. I had been given radar vectors to be sequenced behind a B757; who was inbound from the north. As I was receiving vectors at 1500ft that took me slightly north of the localizer (and slightly downwind of the jet's position); the jet was on the localizer ahead of me; coming through my altitude on the glideslope. The SJU Approach Controller advised 'caution wake turbulence' and had me switch over to Tower. At this point I am below and a little downwind of the jet; and behind by what I'd estimate to be about 3-4 miles. I decided to go to in-range power at this point to put a little more distance between me and the B757. I would much rather be above the wake than below it; but I knew in order to safely get above it; I'd have to get upwind of it (right and south of localizer course). As I started to make my way to that side of the course; I felt a sharp shake of the airplane and then a quick snap roll to the left; close to 90 degrees of bank. I regained control of the airplane and brought it back to level flight using aileron and rudder. I checked all gauges and looked around the visible surfaces of the airplane and noted everything was working the way it should. I turned around and gave the 6 passengers a questionary 'thumbs up' and received thumbs up back. I turned back around and continued to fly. The plane did not fly any differently after this event; so I continued the VFR approach; 2 dots above the glideslope until I landed without incident. Upon arriving at the gate and after shutdown; I asked all the passengers if they were OK and apologized for the event. Everyone seemed fine and I only received one question asking what that big bump was. I explained in simple terms what happened and everyone proceeded to deplane. I take full responsibility for this wake turbulence event. Even though ATC vectored me below and downwind of the B757; it is my responsibility as PIC to avoid wake turbulence. I should have either asked for an avoidance deviation or just deviated and explained later. Visualizing where you think the wake is either drifting or not drifting (based on winds) to is also important.

Data retrieved from NASA's ASRS site 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.