B737-300 encountered wake turbulence; rolling aircraft into approximately 35 degrees angle of bank.

Attributes
ACN	757405
Time
Date	200710
Local Time Of Day	1201 To 1800
Place
Locale Reference	airport : ord.airport
State Reference	IL
Altitude	msl single value : 5000
Environment
Flight Conditions	Marginal
Aircraft 1
Controlling Facilities	tracon : c90.tracon
Operator	common carrier : air carrier
Make Model Name	B737-300
Operating Under FAR Part	Part 121
Flight Phase	descent : intermediate altitude
Route In Use	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 : intermediate altitude
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Experience	flight time last 90 days : 88 flight time total : 14000 flight time type : 5500
ASRS Report	757405
Events
Anomaly	inflight encounter : wake turbulence other anomaly
Independent Detector	other flight crewa
Resolutory Action	flight crew : regained aircraft control
Supplementary
Problem Areas	Environmental Factor ATC Human Performance
Primary Problem	Environmental Factor

Narrative:

On downwind for runway 4R ILS at 5000 ft autoplt on aircraft began sudden bank to approximately 35 degrees due to wake turbulence; autoplt disengaged and unusual attitude recovery accomplished with little or no loss of altitude. ATC advised of wake turbulence encounter. They replied that they had a B757 in front of us that they had descended to 4000 ft. Approach and landing was normal without further incident. Winds were relatively calm and it appears that ATC is vectoring aircraft too close together.

Original NASA ASRS Text

Title: B737-300 ENCOUNTERED WAKE TURB; ROLLING ACFT INTO APPROX 35 DEGS ANGLE OF BANK.

Narrative: ON DOWNWIND FOR RWY 4R ILS AT 5000 FT AUTOPLT ON ACFT BEGAN SUDDEN BANK TO APPROX 35 DEGS DUE TO WAKE TURBULENCE; AUTOPLT DISENGAGED AND UNUSUAL ATTITUDE RECOVERY ACCOMPLISHED WITH LITTLE OR NO LOSS OF ALTITUDE. ATC ADVISED OF WAKE TURBULENCE ENCOUNTER. THEY REPLIED THAT THEY HAD A B757 IN FRONT OF US THAT THEY HAD DESCENDED TO 4000 FT. APCH AND LNDG WAS NORMAL WITHOUT FURTHER INCIDENT. WINDS WERE RELATIVELY CALM AND IT APPEARS THAT ATC IS VECTORING ACFT TOO CLOSE TOGETHER.

Data retrieved from NASA's ASRS site as of January 2009 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.