Narrative:

The controller put us 2 1/2 - 3 mi behind a B757 without cautioning us. We asked his aircraft type and controller said 'air carrier X B727.' the air carrier X replied 'B757.' then our aircraft began an uncontrolled left roll to approximately 45-60 degrees. The autoplt disengaged and we recovered to straight and level. Callback conversation with reporter revealed the following information: reporter participated in the wake turbulence callback study. Reporter was close to the preceding aircraft. He thought it was a B727 until the pilot of the aircraft reported it to be a B757. At that time he was only 2 1/2 - 3 mi behind. When he encountered the wake he described it as the most frightening experience he has ever had flying anything. The bank roll went to 45 degrees, disengaging the autoplt. He had partial control and was able to right the aircraft. A go around was performed to get out of the wake. During flight crew/ATC review, supervisor stated the controller would receive additional training. Supplemental information from acn 427256: the captain made visual contact with the preceding aircraft and this prompted him to have me ask approach what type of aircraft we were following. The approach controller replied, 'air carrier X B727.' shortly after, a voice with a spanish accent responded, 'B757.' within a few seconds, the aircraft, which was on autoplt and coupled to the localizer, began an uncommanded left bank exceeding 45-50 degrees of bank. The autoplt disengaged and the captain recovered heading 250 degrees and climbing to 5000 ft while executing a go around/missed approach. The controller noticed this and confirmed our go around, assigning us a new heading. I then questioned ATC to verify what we were following and he said 'B757.' we then landed with no further incident.

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Original NASA ASRS Text

Title: A CL65 ENCOUNTERS WAKE TURB BEHIND A B757 DURING APCH AT ORD.

Narrative: THE CTLR PUT US 2 1/2 - 3 MI BEHIND A B757 WITHOUT CAUTIONING US. WE ASKED HIS ACFT TYPE AND CTLR SAID 'ACR X B727.' THE ACR X REPLIED 'B757.' THEN OUR ACFT BEGAN AN UNCTLED L ROLL TO APPROX 45-60 DEGS. THE AUTOPLT DISENGAGED AND WE RECOVERED TO STRAIGHT AND LEVEL. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: RPTR PARTICIPATED IN THE WAKE TURB CALLBACK STUDY. RPTR WAS CLOSE TO THE PRECEDING ACFT. HE THOUGHT IT WAS A B727 UNTIL THE PLT OF THE ACFT RPTED IT TO BE A B757. AT THAT TIME HE WAS ONLY 2 1/2 - 3 MI BEHIND. WHEN HE ENCOUNTERED THE WAKE HE DESCRIBED IT AS THE MOST FRIGHTENING EXPERIENCE HE HAS EVER HAD FLYING ANYTHING. THE BANK ROLL WENT TO 45 DEGS, DISENGAGING THE AUTOPLT. HE HAD PARTIAL CTL AND WAS ABLE TO RIGHT THE ACFT. A GAR WAS PERFORMED TO GET OUT OF THE WAKE. DURING FLC/ATC REVIEW, SUPVR STATED THE CTLR WOULD RECEIVE ADDITIONAL TRAINING. SUPPLEMENTAL INFO FROM ACN 427256: THE CAPT MADE VISUAL CONTACT WITH THE PRECEDING ACFT AND THIS PROMPTED HIM TO HAVE ME ASK APCH WHAT TYPE OF ACFT WE WERE FOLLOWING. THE APCH CTLR REPLIED, 'ACR X B727.' SHORTLY AFTER, A VOICE WITH A SPANISH ACCENT RESPONDED, 'B757.' WITHIN A FEW SECONDS, THE ACFT, WHICH WAS ON AUTOPLT AND COUPLED TO THE LOC, BEGAN AN UNCOMMANDED L BANK EXCEEDING 45-50 DEGS OF BANK. THE AUTOPLT DISENGAGED AND THE CAPT RECOVERED HDG 250 DEGS AND CLBING TO 5000 FT WHILE EXECUTING A GAR/MISSED APCH. THE CTLR NOTICED THIS AND CONFIRMED OUR GAR, ASSIGNING US A NEW HDG. I THEN QUESTIONED ATC TO VERIFY WHAT WE WERE FOLLOWING AND HE SAID 'B757.' WE THEN LANDED WITH NO FURTHER INCIDENT.

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.