E145 crew had an encounter with severe wake turbulence from a preceding B757-200 in C-90 class east.

Attributes
ACN	569105
Time
Date	200212
Day	Thu
Local Time Of Day	1201 To 1800
Place
Locale Reference	airport : ord.airport
State Reference	IL
Altitude	msl single value : 5000
Environment
Weather Elements	Rain other
Light	Daylight
Aircraft 1
Controlling Facilities	tracon : c90.tracon
Operator	common carrier : air carrier
Make Model Name	EMB ERJ 145 ER&LR
Operating Under FAR Part	Part 121
Navigation In Use	ils localizer & glide slope : 27l other
Flight Phase	descent : approach
Route In Use	approach : instrument precision arrival : on vectors
Flight Plan	IFR
Aircraft 2
Controlling Facilities	tracon : c90.tracon
Operator	common carrier : air carrier
Make Model Name	B757 Undifferentiated or Other Model
Operating Under FAR Part	Part 121
Flight Phase	descent : approach
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
ASRS Report	569105
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Events
Anomaly	inflight encounter : wake turbulence other anomaly
Independent Detector	other flight crewa other flight crewb
Resolutory Action	flight crew : exited adverse environment
Consequence	other
Miss Distance	horizontal : 30000
Supplementary
Problem Areas	FAA Environmental Factor Airspace Structure Weather
Primary Problem	Environmental Factor

Narrative:

We were being vectored to ord ILS runway 27L behind a B757. Although currently VMC, rain and mist had been a problem all day long. Chicago approach -- 128.45 -- gave us a final vector to join the localizer -- heading about 300 degrees, and at 5000 ft MSL. As I, the PNF, was responding to the clearance, the aircraft was suddenly and strongly rolled about 45 degrees angle of bank to the left, then 45 degrees angle of band right before we cleared the area of turbulence. The TCASII does not have a reliable scale for determining distance, but best guess is 5 NM or slightly closer.

Original NASA ASRS Text

Title: E145 CREW HAD AN ENCOUNTER WITH SEVERE WAKE TURB FROM A PRECEDING B757-200 IN C-90 CLASS E.

Narrative: WE WERE BEING VECTORED TO ORD ILS RWY 27L BEHIND A B757. ALTHOUGH CURRENTLY VMC, RAIN AND MIST HAD BEEN A PROB ALL DAY LONG. CHICAGO APCH -- 128.45 -- GAVE US A FINAL VECTOR TO JOIN THE LOC -- HDG ABOUT 300 DEGS, AND AT 5000 FT MSL. AS I, THE PNF, WAS RESPONDING TO THE CLRNC, THE ACFT WAS SUDDENLY AND STRONGLY ROLLED ABOUT 45 DEGS ANGLE OF BANK TO THE L, THEN 45 DEGS ANGLE OF BAND R BEFORE WE CLRED THE AREA OF TURB. THE TCASII DOES NOT HAVE A RELIABLE SCALE FOR DETERMINING DISTANCE, BUT BEST GUESS IS 5 NM OR SLIGHTLY CLOSER.

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.