WAKE TURB BEHIND B757 AT HIGH ALT.

Narrative

THE MAIN PURPOSE OF THIS RPT IS TO PROVIDE FURTHER DATA FOR WAKE ENCOUNTERS WITH B757 ACFT FOR YOUR RECENT STUDY. OUR ACFT; AN MD80; WAS PASSING THROUGH FL327 TO LEVEL OFF AT FL330. WE ENCOUNTERED A MODERATE 'BUMP' AND THE ACFT IMMEDIATELY ROLLED INTO A 20-30 DEG L BANK; AND THEN ROLLED R SLIGHTLY PAST WING LEVEL. DURING THIS ENCOUNTER THE AUTOPLT KICKED OFF AND I ROLLED LEVEL AND LEVELED THE ACFT AT OUR ASSIGNED ALT OF 33000 FT. DURING THE ENCOUNTER WE HAD ASSOCIATED TURB THAT MADE US FEEL IT WAS A WAKE TURB PENETRATION. WE RPTED THE EVENT TO ATC AND ASKED WHAT THE TYPE OF ACFT WAS THAT WE WERE FOLLOWING; AND OUR DISTANCE. ATC REPLIED THAT IT WAS A B757 AT 5 1/2 MI AHEAD. WE COULD SEE HIM VISUALLY AT THIS POINT AND I BELIEVE HE WAS AT OUR ALT IN THE SAME DIRECTION. WHAT SURPRISED ME ABOUT THIS ENCOUNTER WAS THE ABRUPTNESS OF THE INDUCED ROLL (ENOUGH TO TRIP THE AUTOPLT); AND OUR DISTANCE FROM THE B757. IT WAS ALSO THE FIRST TIME I HAD ENCOUNTERED SUCH STRONG WAKE AT CRUISE ALT. YOU'D THINK 5-6 MI SEPARATION WOULD BE ENOUGH; BUT APPARENTLY NOT HERE. AFTER LEVEL OFF THE AUTOPLT WAS RE-CONNECTED AND NO FURTHER INCIDENT WAS EXPERIENCED. I FELT CERTAIN THAT THIS WAS A WAKE ENCOUNTER AS NO OTHER CHOP WAS PRESENT AT OUR ALT. I HAD ALSO NEVER REALLY FELT TURB TO INDUCE A ROLL LIKE THIS BEFORE. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: THIS CALLBACK IN CONJUNCTION WITH WAKE TURB INCIDENT CALLBACK QUESTIONNAIRE. RPTR WAS SURPRISED; FIRST IN ENCOUNTERING THE WAKE TURB AT HIGH ALT; THEN ALSO AT THE ABRUPTNESS AND STRENGTH OF IT; ESPECIALLY SINCE THEY WERE 6 MI IN TRAIL OF THE B757. IN THE FUTURE HE WILL BE MORE AWARE OF THE POTENTIAL OF WAKE TURB WHEN FOLLOWING A B757. HE WOULD LIKE FOR ATC TO PROVIDE MORE INFO WHEN FOLLOWING A B757.